CA1316310C - Polyhedron cell structure and method of making same - Google Patents
Polyhedron cell structure and method of making sameInfo
- Publication number
- CA1316310C CA1316310C CA 536960 CA536960A CA1316310C CA 1316310 C CA1316310 C CA 1316310C CA 536960 CA536960 CA 536960 CA 536960 A CA536960 A CA 536960A CA 1316310 C CA1316310 C CA 1316310C
- Authority
- CA
- Canada
- Prior art keywords
- cell
- ratio
- open
- negative poisson
- ribs
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/56—After-treatment of articles, e.g. for altering the shape
- B29C44/5627—After-treatment of articles, e.g. for altering the shape by mechanical deformation, e.g. crushing, embossing, stretching
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/35—Component parts; Details or accessories
- B29C44/355—Characteristics of the foam, e.g. having particular surface properties or structure
- B29C44/357—Auxetic foams, i.e. material with negative Poisson ratio; anti rubber; dilatational; re-entrant
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/56—After-treatment of articles, e.g. for altering the shape
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/56—After-treatment of articles, e.g. for altering the shape
- B29C44/5627—After-treatment of articles, e.g. for altering the shape by mechanical deformation, e.g. crushing, embossing, stretching
- B29C44/5636—After-treatment of articles, e.g. for altering the shape by mechanical deformation, e.g. crushing, embossing, stretching with the addition of heat
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/36—After-treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
- B29K2105/045—Condition, form or state of moulded material or of the material to be shaped cellular or porous with open cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S521/00—Synthetic resins or natural rubbers -- part of the class 520 series
- Y10S521/918—Physical aftertreatment of a cellular product
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24273—Structurally defined web or sheet [e.g., overall dimension, etc.] including aperture
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
- Y10T428/249962—Void-containing component has a continuous matrix of fibers only [e.g., porous paper, etc.]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
- Y10T428/249967—Inorganic matrix in void-containing component
- Y10T428/24997—Of metal-containing material
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
- Y10T428/249975—Void shape specified [e.g., crushed, flat, round, etc.]
Abstract
POLYHEDRON CELL STRUCTURE AND METHOD OF MAKING SAME
ABSTRACT OF THE DLSCLOSURE
An open cell foam structure that has a negative Poisson's ratio. Structure can be created by triaxially compressing a conventional open-cell foam material and heating the compressed structure beyond the softening point to produce a permanent deformation in the structure of the material. The structure thus produced has cells whose ribs protrude into the cell resulting in unique properties for materials of this type.
ABSTRACT OF THE DLSCLOSURE
An open cell foam structure that has a negative Poisson's ratio. Structure can be created by triaxially compressing a conventional open-cell foam material and heating the compressed structure beyond the softening point to produce a permanent deformation in the structure of the material. The structure thus produced has cells whose ribs protrude into the cell resulting in unique properties for materials of this type.
Description
POI,YH~DRON C~ LL STI~U ,TUI_:E' A~D ME'I'HOD OF' MAKING SA~E
BACI~GROUND Or T~E INVENTION
1 3 I h3 1 n Low density foarned polyhedron cell structures are well known. The conventionalopen-cell foam structure consists o~
a plurality of inter-connected, three dimensional cells which are generally convex. In a conventional open-cell structure, all or a portion of the cell faces may be absent, but the cells are intercommunicating and the cellular structure is retained.
Depending upon the molecular structure of the material, a foamed cellular material may range from quite rigid to a material that is soft and flexible. The flexible foamed cellular structures are resilient and recover their original shape after deformation.
All known engineering materials including open-cell foam cellular structures have a positive Poisson's ratio and thus contract laterally when stretched and expand laterally when compressed. Also, bent beams of conventional materials which have a positive Poisson's ratio display the conventional cross-sectional configuration known as "anticlastic curvature".
There are known techniques for modifying the compress/deflection characteristics of certain types of open-cell foam materials. One of these techniques is described in U.S. Patent No. 3,025,200 issued on March 13, 1962 for an invention by William R. Powers entitled "Celliform Structure and Method of Making Same". This paten~s teaches that if a foam material is permanently compressed, its properties can be changed so that the material responds with linear strain when linear stress is applied. Conventional untreated materials produce non-linear response. However, the teaching of the foregoing patent is the application of compression in one direction only, and the resulting material has a positive Poisson's ratio.
If an open-cell foam material could be produced with the property of a negative Poisson's ratio, there would ~e ~umero~s possible applications such as fasteners, gaskets and other seals, as well as applications ~or shock absorbing and cushioning materials. There is there~ore a need ~or an improved material .; :
of the open-cell Eoam -type having a negative Poisson's ratio. There is specially a need in rnany applications for such a material if such material could be produced by a simple and inexpensive method.
S SUMMARY OF THE IN~ENTION
In lts broader aspects, the invention comprehends a method of making an open-cell isotropic material having a negative Poisson's ratio comprising the steps of restraining the material from three orthogonal directions during the formation of the material and allowing the material to cool while maintaining the restraint.
The invention also comprehends an isotropic open-cell material having a negative Poisson's ratio, the material comprising a plurality of interconnected spaced-apart ribs defining a plurality of cells, the ribs in the cells protruding inwardly.
More particularly, a conventional open-cell foam material o~ relatively low density is compressed in three orthogonal directions, and while so compressed, the material is heated to a temperaturewhich slightly exceeds the softening temperature of the material. The material is then cooled to room temperature, so as to permanently set the structure of the cells. The resulting material has a cell ~ .
:
.. ... .. .
structure in which the ribs of the cells protrude into the cell. This permanent deformation of the cells results in a material that has a negative Poisson's ratio.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an illustration of the cell structure in a conventional open-cell foam material;
Fig. 2 is an illustration of the cell structure after transformation according to the principles of the invention;
Fig. 3 is a schematic view of an idea] cell structure after transformation according to the principles of the invention; and Figs. 4a and 4b compare the curvature of a bent beam before and after transformation.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The invention relates to modification of an open-cell foam structure so as to produce a material with a negative Poisson's ratio. Poisson's ratio is defined in terms of the strains which occur when material is stretched and is equal to minus the transverse strain divided by the axial strain in the direction of stretch. With one possible exception, all known materials contract laterally when stretched and expand : '' :
la~erally w~cn compressed, an~ therefore ~oisson's rati~ for such material is positive. For e~arnple, positive Poisson's ratios for various materials are 0.3 for steel, 0.5 for rubber, 0.1 to 0.4 for typical polymer foams and almosc 0 for cork.
Because cork has a positive Poisson's ratio just slightly above 0, an ideal practical application for cork is in sealing a wine bo~tle. In this application, the cork can be easily inserted and removed, yet it withstands the pressure from within the bottle. Rubber, with a Poisson's ratio of positive 0.5, could not be used for this purpose because it would expand when compressed for insertion into the neck of the bottle and therefore would jam.
Although negative Poisson's ratios are theoretically possible, they have generally not been observed in any known materials.
In a Treatise entitled "Foundations of Solid Mechanics" (Prentice Hall 1968) Y. C. Fung indicates that in an isotropic material the allowable range of Poisson's ratio is from negative 1.0 ~o positive 0.~ based on energetic considerations in the theory of elasticity. However, Fung states that materials with negative values of Poisson's ratio are unknown. On the other hand, A. E. H. Love in "A Treatise on.the Mathematical Theory of . Elasticity" (Dover 4th Ed. 1944) presents a single example of single crystal pyrite as having a negative Poisson's ratio of 0.14. However, such a crystal is cubic rather than isotropic.
The structure of a conventional open-cell foam material is shown in Fig. 1 in whlch each cell is defined by a plurality of ribs that define a polyhedron structure with the cells being interconnected, thus forming a three dimensional network of ribs or strands. The spaces between the ribs are open, and thus the individual cells are open. This is in contrast to - a cell structure in which the ribs would define walls of a cell, which walls would enclose the cell to form a closed-cell structure.
Preferably, the starting material is an open-cell foam ; 35 structure as indicated which has a low density. Such a material would have, relatively speaking, a larger space between the ribs of each cell than would a high density material. Also, - 1 31 631 (J
regardless o~ chc number o' ribs ~orming the polyhcdron cell structure, the cells should be col)vex in configur.ltion, and the material shou1d have sufficient resilience lo recover i~s original shape after deformation. I have found, for example, chat a polyester foam material marketecl by Scot~ Paper Company as "Scott Industrial Foa~" is a suitable low-density ma~erial that has a convex polyhedron open-cell structure of the general type illustrated in Fig. 1.
Force is then applied to the selected material in each of three orthogonal directions or triaxially to compress the material. This triaxial compression causes the ribs of the cells to buckle inwardly into a "re-entrant" structure. The compressed material is then placed in a mold or is otherwise held in the compressed state and heat is applied to the material by heating the mold or in any other suitable manner urtil the temperature of the material slightly exceeds the softening temperature of the foam material. I have found that a temperature in the range of 163 to 171 ~entigrade was effective. The mold containing the compressed material is then allowed to cool to room temperature, and the material removed from the mold. The triaxial compression and heating to the correct temperature produces permanent transformation of the cell structure in which the ribs protrude into the cell as illustrated in Fig. 2. This transformed structure of an open-cell foam I
have termed a "re-entrant" structure, and in Fig. 3 there is illustrated an ideal re-entrant foam structure for a single cell that has been triaxially compressed. Note in Fig. 3 that the ribs or struts in each face of the cell protrude into the cell. Although it is not strictly necessary for the permanent deformation from the triaxial compression to be the same in each of the three directions, theoverall deformation should be of the correct order of magnitude since too little permanent deformation results in failure to create re-entrant structure.
On the other hand, if the deformation is excessive, portions of the structure may become intertwlned and not produce the deslred result of a Degative Poisson's ratio.
*Trademark . .:
1 31 63 1 r) ~ lso, ~hc temperature se1c~e(l to brillg about ttle permanent deformation wil1 ~epend, of course, upon the material being treated The temperature must be slightly above the temperature at which the material becomes soft, but if too low a temperature is used, the material will not be permanently deformed. On ~he other hand, if too high a temperature is used, the material may actually turn into a liquid or semi-liquid state and flow toge~her and not produce the desired result.
In an actual test using a polyester foam marketed by Scott Paper Company and identified as "Scott Industrial Foam", the material was compressed triaxially to 60-80% of its original dimension in each of the three directions. As previously described, the material was then placed in a mold and heated to a temperature in the range of 163 to 171~ centigrade, held at that temperature for minutes and then allowed to cool to room temperature. After the cooled material was removed from the mold, the mechanical properties of the transformed material were measured. The Scott Industrial Foam prior to transformation had a density of 0.03 gm/cm3. After being transformed, the density was measured to be 0.12 gm/cm . Before the transformation, the foam material had a Young's modulus in tension of 71kPa (10 PSI) whereas after transformation, Young's modulus was measured to be 72 kPa (10 PSI). The significant change however was in Poisson's ratio. Prior to the transformation, the foam material had a positive Poisson's ratio of 0.4, whereas after transformation, the material had a negative Poisson's ratio of 0.7. The cutability of the material also changed in that the material was easily cut with a sharp blade prior to transformation, whereas after transformation it was much more difficult to cut the material.
As a further illustration of the effects of the change ; from a positive to a negative Poisson's ratio, a piece of foam material both before and after transformation was cut into he shape of an elongated rectangular beam, The material was then bent transversely to its longitudinal axis in the direction of the short side of the rectangular cross-section. Wllen the material before and after transformation was compared in a bent condition, the cross-section of the material after trans-formation displayed a curvature opposite to the principal curvature ' , -~-~ 131631(~
in rhe direcsion of bending. This is known as "anticlastic curvature" and is predictable by the cheory of elasticity when Poisson's ratio is positive, which is the case for ordinary ma~erials, In Fig. 4a there is illustrated the anticlastic curvature of ordinary material having a positive Poisson's ratio. By contrast, Fig. 4b shows the material with a negative Poisson's ratio, and it is clear that the curvature is in the direetion opposite to material with a positive Poisson's ratio.
This can be referred to as "synclastic curvature", and this phenomenon has not to my knowledge been reported anywhere, although according to the theory of elasticity, synclastic curvature would be consistent with a negative Poisson's ratio.
Although I have deseribed only a preferred embodiment of the invention, the method and the resulting properties of open-foam material is not restricted to polymeric foams. For example, an open-eell metallic foam might be used as a starting material for the transformation process. The temperature required for the transformation of a metallic foam could be expected to be a significant fraction of the melting temperature for the metal. Also, metal foams are obviously much more rigid than polymeric foams of comparable structure, since homogenous metals have a mueh higher modulus of elastieity than polymers.
A re-entrant strueture for an open-eell metallie foam may also be produeed by irreversibly (plastieally) deforming the foam at room temperature, deformation being accomplished by sequentially and incrementally appLying force in each of three perpendicular directions.
Also, ereating an open-cell foam material with a negative Poisson's ratio has been described as using an existing open-cell material and transforming it by the deseribed method steps.
- However, a material having the same property of a negative Poisson's ratio could be produeed during the initial forming process by restraining the material as it is formed thereby causing the ribs or struts forming the eells to buckle inwardly and then allowing the material to eool and harden under restraint.
There are numerous potential applLeations for a material of the type deseribed herein having a negative Poisson's ratio.
1 31 6 ~1 (J
, . , For e:-:ample, sincc ~1 Im~terial wi~ll a ne~,ativc l'oi-,.sor)'s r.s~:io e;pands la~cr,llly when stre~ched, a cylindrical plu~ of fo.llll material could be used as a fastener by press-f:itting it into a cvlindrical cavi.ty. Attempts to remove the plug would result in its laceral e~pansion against the walls of the cylindrical cavity. This would have numerous fastening applications in the manufacture of products where it was either impossible or e~pedient not to use two-piece fasteners to join two components together.
Conventional polymeric foams are also often used as a cushioning or shock absorbing material. The compliance of such a foam material is controlled by its density, and in conventional foam structures the modulus of elasticity (the inverse of the compliance) is proportional to the square of the density. Therefore, low density is associated with a compliant foam, but low ~ensity foams are also weak and easily abraded. The transformed foam material of the invention i5 compliant but it is also relatively dense, and therefore would be more advantageous than conventional foam materials in applications where superior strength and abrasion resistance are desired along with a compliant foam.
Polymeric foams are also currently used in a wide variety of applications for air filters, shoe soles, sandwich panels, ; humidifier belts, sound absorbers, sponges, gaskets and in medical supplies. In any of these situations in which a combination of compliance and strength is required, the transformed foam having a negative Poisson's ratio would be far superior. Further e~amples in the medical field would be as a cushioning material for individuals who are immobilized for long periods of time.
Such persons frequently develop pressure sores or "bed sores"
due to the effects of prolonged pressure on the blood vessels : of the skin and underlying tissues. The transformed foam material oE the invention would be useful in preventing these pressure sores.
A thin layer of transformed Eoam of the invention could be used as a replacement for the conventional ankle or elbow wrap since the foam would be less likely to become loose during physical activity because of the negative Poisson's ratio.
.
~ -8-1 31 63 1 ~) In ilno~ r m~c~ical ~Ippli~ ion, ~rtifioi.ll bloo~ vess~ls .Ire typically mad~ of .I Dacron*fabric which has a positive Poisson's r;ltio. The interstices in the fabric allow the body to ~enerate a new lining for the vessel. A porous material having a ne~ltiv~ Poisson's ratio would be advantageous in this application in that the stresses at the interface with the natural vessel may be reduced, thus improving the reliability of the graft. In addition, a superior match between resilience of the graft and that of the natural vessel may be achievable with material having a negative Poisson's ratio, resulting in a graft that would be likely to cause clotting of blood near the interface.
In current applications where conventional foams are used as filters, the filters obviously can become clogged with filtrate, increasing the pressure in the system. When this occurs, the pressure difference across the filter can collapse the pores, further hamperlng and retarding flow through the filter. A
filter made of material that has a negative Poisson's ratio would be advantageous since a bulging of the filter element would tend to open rather than close the pores. This would help to maintain flow in the system without affec~ing the ability of~the material to perform its function of retaining the filtrate.
Althoagh the invention has been described only'in connection with the preferred embodiment of it, it will be evident to ~
those skilled in the art that various revisions and modifications can be made to the~described method and material without departing `~ Erom the splrit and scope of th~ invention. It is further evident that the principles of the invention are applicable ~ to a variety of materials used in a variety of applicatlons.
; 30 ~ It is my~intent~on however that all such revisions and modifications, and~the varloù:s materials and their uses and applications will be included within the scope of the following claims.
*Trddemark _9_ ' ` ' , .
BACI~GROUND Or T~E INVENTION
1 3 I h3 1 n Low density foarned polyhedron cell structures are well known. The conventionalopen-cell foam structure consists o~
a plurality of inter-connected, three dimensional cells which are generally convex. In a conventional open-cell structure, all or a portion of the cell faces may be absent, but the cells are intercommunicating and the cellular structure is retained.
Depending upon the molecular structure of the material, a foamed cellular material may range from quite rigid to a material that is soft and flexible. The flexible foamed cellular structures are resilient and recover their original shape after deformation.
All known engineering materials including open-cell foam cellular structures have a positive Poisson's ratio and thus contract laterally when stretched and expand laterally when compressed. Also, bent beams of conventional materials which have a positive Poisson's ratio display the conventional cross-sectional configuration known as "anticlastic curvature".
There are known techniques for modifying the compress/deflection characteristics of certain types of open-cell foam materials. One of these techniques is described in U.S. Patent No. 3,025,200 issued on March 13, 1962 for an invention by William R. Powers entitled "Celliform Structure and Method of Making Same". This paten~s teaches that if a foam material is permanently compressed, its properties can be changed so that the material responds with linear strain when linear stress is applied. Conventional untreated materials produce non-linear response. However, the teaching of the foregoing patent is the application of compression in one direction only, and the resulting material has a positive Poisson's ratio.
If an open-cell foam material could be produced with the property of a negative Poisson's ratio, there would ~e ~umero~s possible applications such as fasteners, gaskets and other seals, as well as applications ~or shock absorbing and cushioning materials. There is there~ore a need ~or an improved material .; :
of the open-cell Eoam -type having a negative Poisson's ratio. There is specially a need in rnany applications for such a material if such material could be produced by a simple and inexpensive method.
S SUMMARY OF THE IN~ENTION
In lts broader aspects, the invention comprehends a method of making an open-cell isotropic material having a negative Poisson's ratio comprising the steps of restraining the material from three orthogonal directions during the formation of the material and allowing the material to cool while maintaining the restraint.
The invention also comprehends an isotropic open-cell material having a negative Poisson's ratio, the material comprising a plurality of interconnected spaced-apart ribs defining a plurality of cells, the ribs in the cells protruding inwardly.
More particularly, a conventional open-cell foam material o~ relatively low density is compressed in three orthogonal directions, and while so compressed, the material is heated to a temperaturewhich slightly exceeds the softening temperature of the material. The material is then cooled to room temperature, so as to permanently set the structure of the cells. The resulting material has a cell ~ .
:
.. ... .. .
structure in which the ribs of the cells protrude into the cell. This permanent deformation of the cells results in a material that has a negative Poisson's ratio.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an illustration of the cell structure in a conventional open-cell foam material;
Fig. 2 is an illustration of the cell structure after transformation according to the principles of the invention;
Fig. 3 is a schematic view of an idea] cell structure after transformation according to the principles of the invention; and Figs. 4a and 4b compare the curvature of a bent beam before and after transformation.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
The invention relates to modification of an open-cell foam structure so as to produce a material with a negative Poisson's ratio. Poisson's ratio is defined in terms of the strains which occur when material is stretched and is equal to minus the transverse strain divided by the axial strain in the direction of stretch. With one possible exception, all known materials contract laterally when stretched and expand : '' :
la~erally w~cn compressed, an~ therefore ~oisson's rati~ for such material is positive. For e~arnple, positive Poisson's ratios for various materials are 0.3 for steel, 0.5 for rubber, 0.1 to 0.4 for typical polymer foams and almosc 0 for cork.
Because cork has a positive Poisson's ratio just slightly above 0, an ideal practical application for cork is in sealing a wine bo~tle. In this application, the cork can be easily inserted and removed, yet it withstands the pressure from within the bottle. Rubber, with a Poisson's ratio of positive 0.5, could not be used for this purpose because it would expand when compressed for insertion into the neck of the bottle and therefore would jam.
Although negative Poisson's ratios are theoretically possible, they have generally not been observed in any known materials.
In a Treatise entitled "Foundations of Solid Mechanics" (Prentice Hall 1968) Y. C. Fung indicates that in an isotropic material the allowable range of Poisson's ratio is from negative 1.0 ~o positive 0.~ based on energetic considerations in the theory of elasticity. However, Fung states that materials with negative values of Poisson's ratio are unknown. On the other hand, A. E. H. Love in "A Treatise on.the Mathematical Theory of . Elasticity" (Dover 4th Ed. 1944) presents a single example of single crystal pyrite as having a negative Poisson's ratio of 0.14. However, such a crystal is cubic rather than isotropic.
The structure of a conventional open-cell foam material is shown in Fig. 1 in whlch each cell is defined by a plurality of ribs that define a polyhedron structure with the cells being interconnected, thus forming a three dimensional network of ribs or strands. The spaces between the ribs are open, and thus the individual cells are open. This is in contrast to - a cell structure in which the ribs would define walls of a cell, which walls would enclose the cell to form a closed-cell structure.
Preferably, the starting material is an open-cell foam ; 35 structure as indicated which has a low density. Such a material would have, relatively speaking, a larger space between the ribs of each cell than would a high density material. Also, - 1 31 631 (J
regardless o~ chc number o' ribs ~orming the polyhcdron cell structure, the cells should be col)vex in configur.ltion, and the material shou1d have sufficient resilience lo recover i~s original shape after deformation. I have found, for example, chat a polyester foam material marketecl by Scot~ Paper Company as "Scott Industrial Foa~" is a suitable low-density ma~erial that has a convex polyhedron open-cell structure of the general type illustrated in Fig. 1.
Force is then applied to the selected material in each of three orthogonal directions or triaxially to compress the material. This triaxial compression causes the ribs of the cells to buckle inwardly into a "re-entrant" structure. The compressed material is then placed in a mold or is otherwise held in the compressed state and heat is applied to the material by heating the mold or in any other suitable manner urtil the temperature of the material slightly exceeds the softening temperature of the foam material. I have found that a temperature in the range of 163 to 171 ~entigrade was effective. The mold containing the compressed material is then allowed to cool to room temperature, and the material removed from the mold. The triaxial compression and heating to the correct temperature produces permanent transformation of the cell structure in which the ribs protrude into the cell as illustrated in Fig. 2. This transformed structure of an open-cell foam I
have termed a "re-entrant" structure, and in Fig. 3 there is illustrated an ideal re-entrant foam structure for a single cell that has been triaxially compressed. Note in Fig. 3 that the ribs or struts in each face of the cell protrude into the cell. Although it is not strictly necessary for the permanent deformation from the triaxial compression to be the same in each of the three directions, theoverall deformation should be of the correct order of magnitude since too little permanent deformation results in failure to create re-entrant structure.
On the other hand, if the deformation is excessive, portions of the structure may become intertwlned and not produce the deslred result of a Degative Poisson's ratio.
*Trademark . .:
1 31 63 1 r) ~ lso, ~hc temperature se1c~e(l to brillg about ttle permanent deformation wil1 ~epend, of course, upon the material being treated The temperature must be slightly above the temperature at which the material becomes soft, but if too low a temperature is used, the material will not be permanently deformed. On ~he other hand, if too high a temperature is used, the material may actually turn into a liquid or semi-liquid state and flow toge~her and not produce the desired result.
In an actual test using a polyester foam marketed by Scott Paper Company and identified as "Scott Industrial Foam", the material was compressed triaxially to 60-80% of its original dimension in each of the three directions. As previously described, the material was then placed in a mold and heated to a temperature in the range of 163 to 171~ centigrade, held at that temperature for minutes and then allowed to cool to room temperature. After the cooled material was removed from the mold, the mechanical properties of the transformed material were measured. The Scott Industrial Foam prior to transformation had a density of 0.03 gm/cm3. After being transformed, the density was measured to be 0.12 gm/cm . Before the transformation, the foam material had a Young's modulus in tension of 71kPa (10 PSI) whereas after transformation, Young's modulus was measured to be 72 kPa (10 PSI). The significant change however was in Poisson's ratio. Prior to the transformation, the foam material had a positive Poisson's ratio of 0.4, whereas after transformation, the material had a negative Poisson's ratio of 0.7. The cutability of the material also changed in that the material was easily cut with a sharp blade prior to transformation, whereas after transformation it was much more difficult to cut the material.
As a further illustration of the effects of the change ; from a positive to a negative Poisson's ratio, a piece of foam material both before and after transformation was cut into he shape of an elongated rectangular beam, The material was then bent transversely to its longitudinal axis in the direction of the short side of the rectangular cross-section. Wllen the material before and after transformation was compared in a bent condition, the cross-section of the material after trans-formation displayed a curvature opposite to the principal curvature ' , -~-~ 131631(~
in rhe direcsion of bending. This is known as "anticlastic curvature" and is predictable by the cheory of elasticity when Poisson's ratio is positive, which is the case for ordinary ma~erials, In Fig. 4a there is illustrated the anticlastic curvature of ordinary material having a positive Poisson's ratio. By contrast, Fig. 4b shows the material with a negative Poisson's ratio, and it is clear that the curvature is in the direetion opposite to material with a positive Poisson's ratio.
This can be referred to as "synclastic curvature", and this phenomenon has not to my knowledge been reported anywhere, although according to the theory of elasticity, synclastic curvature would be consistent with a negative Poisson's ratio.
Although I have deseribed only a preferred embodiment of the invention, the method and the resulting properties of open-foam material is not restricted to polymeric foams. For example, an open-eell metallic foam might be used as a starting material for the transformation process. The temperature required for the transformation of a metallic foam could be expected to be a significant fraction of the melting temperature for the metal. Also, metal foams are obviously much more rigid than polymeric foams of comparable structure, since homogenous metals have a mueh higher modulus of elastieity than polymers.
A re-entrant strueture for an open-eell metallie foam may also be produeed by irreversibly (plastieally) deforming the foam at room temperature, deformation being accomplished by sequentially and incrementally appLying force in each of three perpendicular directions.
Also, ereating an open-cell foam material with a negative Poisson's ratio has been described as using an existing open-cell material and transforming it by the deseribed method steps.
- However, a material having the same property of a negative Poisson's ratio could be produeed during the initial forming process by restraining the material as it is formed thereby causing the ribs or struts forming the eells to buckle inwardly and then allowing the material to eool and harden under restraint.
There are numerous potential applLeations for a material of the type deseribed herein having a negative Poisson's ratio.
1 31 6 ~1 (J
, . , For e:-:ample, sincc ~1 Im~terial wi~ll a ne~,ativc l'oi-,.sor)'s r.s~:io e;pands la~cr,llly when stre~ched, a cylindrical plu~ of fo.llll material could be used as a fastener by press-f:itting it into a cvlindrical cavi.ty. Attempts to remove the plug would result in its laceral e~pansion against the walls of the cylindrical cavity. This would have numerous fastening applications in the manufacture of products where it was either impossible or e~pedient not to use two-piece fasteners to join two components together.
Conventional polymeric foams are also often used as a cushioning or shock absorbing material. The compliance of such a foam material is controlled by its density, and in conventional foam structures the modulus of elasticity (the inverse of the compliance) is proportional to the square of the density. Therefore, low density is associated with a compliant foam, but low ~ensity foams are also weak and easily abraded. The transformed foam material of the invention i5 compliant but it is also relatively dense, and therefore would be more advantageous than conventional foam materials in applications where superior strength and abrasion resistance are desired along with a compliant foam.
Polymeric foams are also currently used in a wide variety of applications for air filters, shoe soles, sandwich panels, ; humidifier belts, sound absorbers, sponges, gaskets and in medical supplies. In any of these situations in which a combination of compliance and strength is required, the transformed foam having a negative Poisson's ratio would be far superior. Further e~amples in the medical field would be as a cushioning material for individuals who are immobilized for long periods of time.
Such persons frequently develop pressure sores or "bed sores"
due to the effects of prolonged pressure on the blood vessels : of the skin and underlying tissues. The transformed foam material oE the invention would be useful in preventing these pressure sores.
A thin layer of transformed Eoam of the invention could be used as a replacement for the conventional ankle or elbow wrap since the foam would be less likely to become loose during physical activity because of the negative Poisson's ratio.
.
~ -8-1 31 63 1 ~) In ilno~ r m~c~ical ~Ippli~ ion, ~rtifioi.ll bloo~ vess~ls .Ire typically mad~ of .I Dacron*fabric which has a positive Poisson's r;ltio. The interstices in the fabric allow the body to ~enerate a new lining for the vessel. A porous material having a ne~ltiv~ Poisson's ratio would be advantageous in this application in that the stresses at the interface with the natural vessel may be reduced, thus improving the reliability of the graft. In addition, a superior match between resilience of the graft and that of the natural vessel may be achievable with material having a negative Poisson's ratio, resulting in a graft that would be likely to cause clotting of blood near the interface.
In current applications where conventional foams are used as filters, the filters obviously can become clogged with filtrate, increasing the pressure in the system. When this occurs, the pressure difference across the filter can collapse the pores, further hamperlng and retarding flow through the filter. A
filter made of material that has a negative Poisson's ratio would be advantageous since a bulging of the filter element would tend to open rather than close the pores. This would help to maintain flow in the system without affec~ing the ability of~the material to perform its function of retaining the filtrate.
Althoagh the invention has been described only'in connection with the preferred embodiment of it, it will be evident to ~
those skilled in the art that various revisions and modifications can be made to the~described method and material without departing `~ Erom the splrit and scope of th~ invention. It is further evident that the principles of the invention are applicable ~ to a variety of materials used in a variety of applicatlons.
; 30 ~ It is my~intent~on however that all such revisions and modifications, and~the varloù:s materials and their uses and applications will be included within the scope of the following claims.
*Trddemark _9_ ' ` ' , .
Claims (7)
1. The method of making a composition of matter having a negative Poisson's ratio comprising the steps of producing a starting material having an open-cell foam structure with each cell being defined by a plurality of ribs; applying sufficient force to the starting material in each of three orthogonal directions simultaneously to compress the ribs of the cells inwardly; raising the temperature of the material above the softening temperature of the material while maintaining the material in the compressed state; cooling the material below the softening temperature while continuing to maintain the material in the compressed state; and releasing the applied force once the material has cooled below the softening temperature.
2. The method of Claim 1 in which the starting material is an open-cell foam structure which has a low density.
3. The method of Claim 2 in which the starting material is an open-cell isotropic structure.
4. A material having a negative Poisson's ratio produced by the method of Claim 1.
5. A method of making an open-cell isotropic material having a negative Poisson's ratio comprising the steps of restraining the material from three orthogonal directions during the formation of the material and allowing the material to cool while maintaining the restraint.
6. A material having a negative Poisson's ratio produced by the method of Claim 5.
7. An isotropic open-cell material having a negative Poisson's ratio, said material comprising a plurality of inter-connected spaced-apart ribs defining a plurality of cells, the ribs in the cells protruding inwardly.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US886,833 | 1986-07-18 | ||
US06/886,833 US4668557A (en) | 1986-07-18 | 1986-07-18 | Polyhedron cell structure and method of making same |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1316310C true CA1316310C (en) | 1993-04-20 |
Family
ID=25389875
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA 536960 Expired - Lifetime CA1316310C (en) | 1986-07-18 | 1987-05-12 | Polyhedron cell structure and method of making same |
Country Status (7)
Country | Link |
---|---|
US (1) | US4668557A (en) |
EP (1) | EP0328518B1 (en) |
JP (1) | JPH02500894A (en) |
KR (1) | KR910006378B1 (en) |
AU (1) | AU610505B2 (en) |
CA (1) | CA1316310C (en) |
WO (1) | WO1988000523A1 (en) |
Families Citing this family (125)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6171338B1 (en) * | 1988-11-10 | 2001-01-09 | Biocon, Oy | Biodegradable surgical implants and devices |
GB8916231D0 (en) * | 1989-07-14 | 1989-08-31 | Evans Kenneth E | Polymeric materials |
GB2235650A (en) * | 1989-07-14 | 1991-03-13 | Nat Res Dev | Curvable core layers |
US5035713A (en) * | 1990-02-12 | 1991-07-30 | Orthopaedic Research Institute, Inc. | Surgical implants incorporating re-entrant material |
US5296182A (en) * | 1992-05-28 | 1994-03-22 | Creme Art Corporation | Method for making formed laminate |
US5273698A (en) * | 1992-05-28 | 1993-12-28 | Creme Art Corporation | Method for shaping cover materials |
AT401268B (en) * | 1992-10-15 | 1996-07-25 | Greiner & Soehne C A | FOAM ELEMENT, ESPECIALLY MOLDED PART FROM ONE OR MORE PLATES OF FOAM, AND METHOD FOR THE PRODUCTION THEREOF |
GB9607815D0 (en) * | 1995-05-03 | 1996-06-19 | Taylor David G | Synthetic closure device for containers |
GB9723140D0 (en) * | 1997-11-04 | 1998-01-07 | British Nuclear Fuels Plc | Improvements in and relating to material separations |
AU1461799A (en) * | 1997-11-19 | 1999-06-07 | Wisconsin Alumni Research Foundation | Scale-up of negative poisson's ratio foams |
GB9805619D0 (en) * | 1998-03-18 | 1998-05-13 | Noise Cancellation Tech | Cushioned earphones |
US6080798A (en) * | 1998-09-28 | 2000-06-27 | Handa; Paul | Manufacturing foams by stress-induced nucleation |
US6142928A (en) * | 1998-12-21 | 2000-11-07 | Kimberly-Clark Worldwide, Inc. | Urinary incontinence device and a method of making the same |
US6090038A (en) * | 1998-12-21 | 2000-07-18 | Kimberly-Clark Worldwide, Inc. | Expandable dome-shaped urinary incontinence device and a method of making the same |
US6090098A (en) * | 1998-12-21 | 2000-07-18 | Kimberly-Clark Worldwide, Inc. | Method for alleviating female urinary incontinence |
GB9905145D0 (en) | 1999-03-06 | 1999-04-28 | Bolton Inst Higher Education | Auxetic materials |
US6602224B1 (en) * | 1999-12-22 | 2003-08-05 | Advanced Cardiovascular Systems, Inc. | Medical device formed of ultrahigh molecular weight polyolefin |
US6428506B1 (en) | 1999-12-22 | 2002-08-06 | Advanced Cardiovascular Systems, Inc. | Medical device formed of ultrahigh molecular weight polyethylene |
US7247265B2 (en) * | 2000-03-06 | 2007-07-24 | Auxetic Technologies Ltd. | Auxetic filamentary materials |
US6649898B1 (en) * | 2000-06-30 | 2003-11-18 | Intel Corporation | Method and apparatus for optically enabling a circuit component in a large scale integrated circuit |
US6558370B2 (en) | 2001-06-05 | 2003-05-06 | Kimberly-Clark Worldwide, Inc. | Urinary incontinence device |
US6837890B1 (en) | 2001-12-26 | 2005-01-04 | Advanced Cardiovascular Systems, Inc. | Expanded UHMWPE for guiding catheter liners and other lubricious coatings |
US20060129227A1 (en) | 2002-08-02 | 2006-06-15 | Auxetica Limited | Auxetic tubular liners |
US6676594B1 (en) | 2002-09-18 | 2004-01-13 | Kimberly-Clark Worldwide, Inc. | C-shaped vaginal incontinence insert |
US6770025B2 (en) | 2002-09-18 | 2004-08-03 | Kimberly-Clark Worldwide, Inc. | Molar shaped vaginal incontinence insert |
US6808485B2 (en) | 2002-12-23 | 2004-10-26 | Kimberly-Clark Worldwide, Inc. | Compressible resilient incontinence insert |
GB0307330D0 (en) * | 2003-03-29 | 2003-05-07 | Dow Corning Ltd | Improvements in and relating to composite materials and structures |
JP2006528515A (en) * | 2003-07-24 | 2006-12-21 | テコメット・インコーポレーテッド | Spongy structure |
US7252870B2 (en) * | 2003-12-31 | 2007-08-07 | Kimberly-Clark Worldwide, Inc. | Nonwovens having reduced Poisson ratio |
US20050153634A1 (en) * | 2004-01-09 | 2005-07-14 | Cabot Microelectronics Corporation | Negative poisson's ratio material-containing CMP polishing pad |
US20060186589A1 (en) * | 2005-02-18 | 2006-08-24 | Yang-Tse Cheng | Method and apparatus for damping vehicle noise |
DE102005012906B3 (en) * | 2005-03-21 | 2006-12-14 | Corovin Gmbh | Sheet-like sheeting, method and apparatus for producing the same and its use |
CA2627625C (en) * | 2005-10-21 | 2012-01-10 | The Procter & Gamble Company | Absorbent article comprising auxetic materials |
GB0522560D0 (en) | 2005-11-04 | 2005-12-14 | Auxetic Technologies Ltd | A process for the preparation of auxetic foams |
US8158689B2 (en) | 2005-12-22 | 2012-04-17 | Kimberly-Clark Worldwide, Inc. | Hybrid absorbent foam and articles containing it |
GB0604583D0 (en) * | 2006-03-08 | 2006-04-19 | Dow Corning | Impregnated flexible sheet material |
GB0610272D0 (en) * | 2006-05-24 | 2006-07-05 | Auxetic Technologies Ltd | A composite material |
US20080011021A1 (en) * | 2006-06-27 | 2008-01-17 | Hbi Branded Apparel Enterprises, Llc. | Fabrics having knit structures exhibiting auxetic properties and garments formed thereby |
US8016549B2 (en) * | 2006-07-13 | 2011-09-13 | United Technologies Corporation | Turbine engine alloys and crystalline orientations |
US7455567B2 (en) * | 2006-08-02 | 2008-11-25 | Hanesbrands Inc. | Garments having auxetic foam layers |
US20080125771A1 (en) * | 2006-11-27 | 2008-05-29 | Michael Lau | Methods and apparatuses for contouring tissue by selective application of energy |
US20080185115A1 (en) * | 2007-02-07 | 2008-08-07 | Antony Morton | Paper machine clothing with auxetic fibers and/or yarns |
US8652602B1 (en) | 2007-02-28 | 2014-02-18 | William Jacob Spenner Dolla | Rotational expansion auxetic structures |
WO2009002479A1 (en) | 2007-06-21 | 2008-12-31 | University Of Massachusetts | Auxetic fabric structures and related fabrication methods |
ITCT20080001U1 (en) * | 2008-03-07 | 2009-09-08 | Meli Giuseppe | IMPROVED DEVICE FOR THE PRODUCTION OF COMPOSITE STRUCTURES WITH A FLOOR SECTION WITH CHIRAL OR AUXETIC ASSIMETRIC GEOMETRY BUT USABLE FOR THE PRODUCTION OF GRILLES OF ANY SHAPE. |
GB2464947A (en) * | 2008-10-29 | 2010-05-05 | Global Composites Group Ltd | Auxetic foam manufacturing system |
DE102008043623A1 (en) | 2008-11-10 | 2010-05-12 | Friedrich-Alexander-Universität Erlangen-Nürnberg | Auxetic material |
US7910193B2 (en) * | 2008-11-10 | 2011-03-22 | Mkp Structural Design Associates, Inc. | Three-dimensional auxetic structures and applications thereof |
US8544515B2 (en) * | 2008-11-10 | 2013-10-01 | Mkp Structural Design Associates, Inc. | Ultralightweight runflat tires based upon negative poisson ratio (NPR) auxetic structures |
US20110029063A1 (en) * | 2008-11-10 | 2011-02-03 | Mkp Structural Design Associates, Inc. | Auxetic stents |
US8388248B2 (en) * | 2008-12-30 | 2013-03-05 | Kimberly-Clark Worldwide, Inc. | Medical liquid applicator system |
GB0919416D0 (en) * | 2009-11-06 | 2009-12-23 | Rolls Royce Plc | A method of manufacturing a foam |
WO2011090586A2 (en) * | 2009-12-30 | 2011-07-28 | 3M Innovative Properties Company | Filtering face-piece respirator having an auxetic mesh in the mask body |
CN102686380A (en) * | 2009-12-30 | 2012-09-19 | 3M创新有限公司 | Method of making an auxetic mesh |
CN102711921B (en) * | 2009-12-30 | 2015-03-25 | 3M创新有限公司 | Molded auxetic mesh |
JP5637785B2 (en) * | 2010-09-06 | 2014-12-10 | キヤノン株式会社 | Original plate and method of manufacturing article using the same |
GB201109949D0 (en) | 2011-06-14 | 2011-07-27 | Dow Corning | Pressure material |
US9936755B2 (en) | 2012-08-31 | 2018-04-10 | Under Armour, Inc. | Articles of apparel with auxetic fabric |
US11839253B2 (en) | 2012-08-31 | 2023-12-12 | Under Armour, Inc. | Article of apparel including fabric having auxetic structure |
US10426226B2 (en) | 2012-08-31 | 2019-10-01 | Under Armour, Inc. | Footwear upper with dynamic and lock-out regions |
US9629397B2 (en) | 2012-08-31 | 2017-04-25 | Under Armour, Inc. | Articles of apparel including auxetic materials |
US9538798B2 (en) | 2012-08-31 | 2017-01-10 | Under Armour, Inc. | Articles of apparel including auxetic materials |
US20140237850A1 (en) * | 2013-02-22 | 2014-08-28 | Nike, Inc. | Footwear With Reactive Layers |
US9320316B2 (en) | 2013-03-14 | 2016-04-26 | Under Armour, Inc. | 3D zonal compression shoe |
EP2969525A4 (en) * | 2013-03-15 | 2016-11-16 | Harvard College | Low porosity auxetic sheet |
US9554620B2 (en) | 2013-09-18 | 2017-01-31 | Nike, Inc. | Auxetic soles with corresponding inner or outer liners |
US9402439B2 (en) * | 2013-09-18 | 2016-08-02 | Nike, Inc. | Auxetic structures and footwear with soles having auxetic structures |
US9549590B2 (en) * | 2013-09-18 | 2017-01-24 | Nike, Inc. | Auxetic structures and footwear with soles having auxetic structures |
US9538811B2 (en) * | 2013-09-18 | 2017-01-10 | Nike, Inc. | Sole structure with holes arranged in auxetic configuration |
US9554622B2 (en) * | 2013-09-18 | 2017-01-31 | Nike, Inc. | Multi-component sole structure having an auxetic configuration |
US9554624B2 (en) * | 2013-09-18 | 2017-01-31 | Nike, Inc. | Footwear soles with auxetic material |
US9456656B2 (en) * | 2013-09-18 | 2016-10-04 | Nike, Inc. | Midsole component and outer sole members with auxetic structure |
GB201318129D0 (en) * | 2013-10-14 | 2013-11-27 | Rolls Royce Plc | A method of manufacturing a foam showing a gradient poisson's ratio behaviour |
DE102013224751A1 (en) | 2013-12-03 | 2015-06-03 | Robert Bosch Gmbh | Battery cell with auxetic components |
USD777452S1 (en) | 2014-01-17 | 2017-01-31 | Under Armour, Inc. | Textile substrate with overlay |
USD774783S1 (en) | 2014-01-29 | 2016-12-27 | Under Armour, Inc. | Elastic textile |
US9908369B2 (en) | 2014-03-10 | 2018-03-06 | Mkp Structural Design Associates, Inc. | Airless and runflat tire structures, components and assembly techniques |
US9861162B2 (en) | 2014-04-08 | 2018-01-09 | Nike, Inc. | Components for articles of footwear including lightweight, selectively supported textile components |
US9872537B2 (en) | 2014-04-08 | 2018-01-23 | Nike, Inc. | Components for articles of footwear including lightweight, selectively supported textile components |
US9474326B2 (en) * | 2014-07-11 | 2016-10-25 | Nike, Inc. | Footwear having auxetic structures with controlled properties |
MY195851A (en) * | 2014-07-25 | 2023-02-23 | Univ Florida State Res Found Inc | Material Systems and Methods of Manufacture for Auxetic Foams |
US10064448B2 (en) * | 2014-08-27 | 2018-09-04 | Nike, Inc. | Auxetic sole with upper cabling |
US9854869B2 (en) | 2014-10-01 | 2018-01-02 | Nike, Inc. | Article of footwear with one or more auxetic bladders |
CN104401020A (en) * | 2014-11-11 | 2015-03-11 | 山东大学 | Preparation method of geogrid with negative Poisson ratio |
DE102014225069A1 (en) * | 2014-12-05 | 2016-06-09 | Robert Bosch Gmbh | Component for power absorption and / or force distribution in a battery cell module |
US9775408B2 (en) | 2014-12-09 | 2017-10-03 | Nike, Inc. | Footwear with auxetic ground engaging members |
US9681703B2 (en) * | 2014-12-09 | 2017-06-20 | Nike, Inc. | Footwear with flexible auxetic sole structure |
US9901135B2 (en) * | 2014-12-09 | 2018-02-27 | Nike, Inc. | Footwear with flexible auxetic ground engaging members |
WO2016122816A1 (en) | 2015-01-29 | 2016-08-04 | Nike Innovate C.V. | Article of footwear having an auxetic structure |
EP3250071B1 (en) * | 2015-01-29 | 2018-12-19 | Nike Innovate C.V. | Article of footwear having an integrally formed auxetic structure |
US10010133B2 (en) | 2015-05-08 | 2018-07-03 | Under Armour, Inc. | Midsole lattice with hollow tubes for footwear |
US10010134B2 (en) | 2015-05-08 | 2018-07-03 | Under Armour, Inc. | Footwear with lattice midsole and compression insert |
US10070688B2 (en) | 2015-08-14 | 2018-09-11 | Nike, Inc. | Sole structures with regionally applied auxetic openings and siping |
US9635903B2 (en) | 2015-08-14 | 2017-05-02 | Nike, Inc. | Sole structure having auxetic structures and sipes |
US9668542B2 (en) | 2015-08-14 | 2017-06-06 | Nike, Inc. | Sole structure including sipes |
NZ743673A (en) * | 2016-02-05 | 2022-05-27 | Formway Furniture Ltd | A chair and components |
ES2673213B1 (en) * | 2016-12-20 | 2019-03-26 | Bsh Electrodomesticos Espana Sa | Sealing device for a household item |
CA3074089A1 (en) * | 2017-09-13 | 2019-03-21 | Basf Se | Auxetic polyurethane and melamine foams by triaxial compression |
WO2019108203A1 (en) | 2017-11-30 | 2019-06-06 | Siemens Aktiengesellschaft | Hybrid ceramic matrix composite components with intermediate cushion structure |
USD869890S1 (en) | 2017-12-05 | 2019-12-17 | Steelcase Inc. | Chairback |
USD869889S1 (en) | 2017-12-05 | 2019-12-17 | Steelcase Inc. | Chairback |
US11291305B2 (en) | 2017-12-05 | 2022-04-05 | Steelcase Inc. | Compliant backrest |
USD870479S1 (en) | 2017-12-05 | 2019-12-24 | Steelcase Inc. | Chair |
USD869872S1 (en) | 2017-12-05 | 2019-12-17 | Steelcase Inc. | Chair |
US10813463B2 (en) | 2017-12-05 | 2020-10-27 | Steelcase Inc. | Compliant backrest |
CN108386467A (en) * | 2018-05-10 | 2018-08-10 | 中国人民解放军海军工程大学 | Multi-panel indent pyramid negative poisson's ratio space lattice structure and its pressure-bearing grillage |
CN115923218A (en) * | 2018-05-31 | 2023-04-07 | 耐克创新有限合伙公司 | Cushioning members for articles of footwear and related methods |
WO2020072515A1 (en) * | 2018-10-01 | 2020-04-09 | The Board Of Supervisors Of Louisiana State University And Agricultural And Mechanical College | Bioscaffold for in vivo use |
CN109834247A (en) * | 2019-01-14 | 2019-06-04 | 南京航空航天大学 | A kind of negative poisson's ratio open celled foam aluminum material and its Seepage Foundry preparation method |
CN109722557A (en) * | 2019-01-14 | 2019-05-07 | 南京航空航天大学 | A kind of closed-cell aluminum foam and its gas injection foaming preparation method with negative poisson's ratio characteristic |
CN109722558A (en) * | 2019-01-14 | 2019-05-07 | 南京航空航天大学 | A kind of flux foaming preparation method of the closed-cell aluminum foam with negative poisson's ratio characteristic |
CN109719296A (en) * | 2019-01-14 | 2019-05-07 | 南京航空航天大学 | A kind of method for preparing powder metallurgy of the closed-cell aluminum foam with negative poisson's ratio characteristic |
CN109807310A (en) * | 2019-01-14 | 2019-05-28 | 南京航空航天大学 | Model casting preparation method with negative poisson's ratio characteristic open celled foam aluminum material |
CN109878443B (en) * | 2019-03-12 | 2022-04-19 | 南京理工大学 | Energy absorption box based on inner core with concave polyhedron negative Poisson ratio three-dimensional structure |
CN109944891B (en) * | 2019-04-12 | 2020-12-25 | 上海理工大学 | Buffer with negative Poisson ratio structure |
USD907935S1 (en) | 2019-05-31 | 2021-01-19 | Steelcase Inc. | Chair |
USD907383S1 (en) | 2019-05-31 | 2021-01-12 | Steelcase Inc. | Chair with upholstered back |
CN110851951B (en) * | 2019-09-27 | 2023-11-24 | 五邑大学 | Three-dimensional zero poisson ratio honeycomb structure with equivalent elastic performance in three main directions |
CN110619189B (en) * | 2019-09-27 | 2023-06-20 | 五邑大学 | Three-dimensional zero poisson ratio mesoscopic structure based on star-shaped structure and macroscopic structure thereof |
CN110744873A (en) * | 2019-11-22 | 2020-02-04 | 南京工业大学 | 3D printing structure composite material sandwich board with negative Poisson ratio effect and processing method |
SI26064A (en) | 2020-09-18 | 2022-03-31 | Univerza V Mariboru | Axisymmetric chiral auxetic structure |
CN112728392A (en) * | 2020-12-17 | 2021-04-30 | 中山大学 | Two-dimensional multi-cellular structure with multiple moduli and negative Poisson ratio properties |
US20230058045A1 (en) * | 2021-08-17 | 2023-02-23 | Joon Bu Park | Composite positive and negative poisson's ratio materials for medical devices |
CN113980346B (en) * | 2021-10-29 | 2022-11-04 | 中国科学院长春应用化学研究所 | Open-cell polyurethane negative Poisson's ratio foam material and preparation method thereof |
US11771183B2 (en) * | 2021-12-16 | 2023-10-03 | Joon Bu Park | Negative Poisson's ratio materials for fasteners |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3025200A (en) * | 1957-08-09 | 1962-03-13 | Scott Paper Co | Celliform structure and method of making same |
US3194854A (en) * | 1963-09-03 | 1965-07-13 | Dow Chemical Co | Process for producing thermoplastic foams |
GB1240649A (en) * | 1969-01-30 | 1971-07-28 | Olin Corp | Polyurethane foams having increased density and process therefor |
GB1419962A (en) * | 1972-04-05 | 1975-12-31 | Beecham Group Ltd | Free-radical reagent for oxidation |
FR2428519A1 (en) * | 1978-06-13 | 1980-01-11 | Ameublement Ind Et Tech | PLUG FOR CAST HOLE OF EXPANDED MATERIAL IN A MOLD |
FR2447802A1 (en) * | 1979-01-30 | 1980-08-29 | Roth Sa Freres | PROCESS FOR MANUFACTURING A SOUND ABSORBING MATERIAL AND MATERIAL THUS OBTAINED |
US4264673A (en) * | 1980-05-12 | 1981-04-28 | The Upjohn Company | Oriented cell polyisocyanurate foam laminate |
DE3246538A1 (en) * | 1982-12-16 | 1984-06-20 | Basf Ag, 6700 Ludwigshafen | METHOD FOR MODIFYING ELASTIC AMINOPLAST FOAMS |
-
1986
- 1986-07-18 US US06/886,833 patent/US4668557A/en not_active Expired - Lifetime
-
1987
- 1987-05-12 CA CA 536960 patent/CA1316310C/en not_active Expired - Lifetime
- 1987-05-21 AU AU75129/87A patent/AU610505B2/en not_active Ceased
- 1987-05-21 KR KR1019880700308A patent/KR910006378B1/en not_active IP Right Cessation
- 1987-05-21 JP JP62503971A patent/JPH02500894A/en active Pending
- 1987-05-21 EP EP19870903634 patent/EP0328518B1/en not_active Expired - Lifetime
- 1987-05-21 WO PCT/US1987/001148 patent/WO1988000523A1/en active IP Right Grant
Also Published As
Publication number | Publication date |
---|---|
AU610505B2 (en) | 1991-05-23 |
EP0328518A1 (en) | 1989-08-23 |
JPH02500894A (en) | 1990-03-29 |
KR910006378B1 (en) | 1991-08-21 |
US4668557A (en) | 1987-05-26 |
AU7512987A (en) | 1988-02-10 |
KR880701632A (en) | 1988-11-04 |
WO1988000523A1 (en) | 1988-01-28 |
EP0328518B1 (en) | 1991-05-29 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA1316310C (en) | Polyhedron cell structure and method of making same | |
US3483069A (en) | Polyurethane foam reinforced fibrous article and method of forming the same | |
Friis et al. | Negative Poisson's ratio polymeric and metallic foams | |
US3906137A (en) | Laminate having a compressed foam core | |
US7101607B2 (en) | Process for enhancing material properties and materials so enhanced | |
US7624462B2 (en) | Load bearing or cushioning elements and method of manufacture | |
US3401128A (en) | Polyurethane foam product and method of making same | |
US3389964A (en) | Process for preparing low density graphite structrues | |
WO1995012632A3 (en) | Low density materials having good compression strength and articles formed therefrom | |
US3025200A (en) | Celliform structure and method of making same | |
DE1704531B2 (en) | METHOD FOR MANUFACTURING SPECIFIC LIGHT PLASTIC BODIES | |
Lakes | Re-entrant transformation methods in closed cell foams | |
US4269889A (en) | Polyurethane cushion material and preparing the same | |
WO1999025530A1 (en) | Scale-up of negative poisson's ratio foams | |
US3425890A (en) | Stretched-set reticulated polyurethane foam and method of making same | |
US4338271A (en) | Method for manufacturing a low density synthetic resin body | |
IE60288B1 (en) | "Porous ptfe" | |
US4387066A (en) | Method of making a foamed resin sheet | |
Lakes | Polyhedron cell structure and method of making same | |
EP0032557B1 (en) | An expanded cross-linked polyethylene particle and methods to produce molded products thereof | |
ES2087444T3 (en) | PROCEDURE TO MANUFACTURE CELLULAR MATERIAL. | |
CA1055621A (en) | Foam bed pillow and method of making same | |
JPS6071243A (en) | Heat insulator and manufacture thereof | |
FR2385658A1 (en) | Storage stable, flame retardant, moulding compsn. - contains inorganic hollow beads and poly:isocyanate | |
JPH05329852A (en) | Manufacture of foamed polyurethane molded matter |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
MKLA | Lapsed | ||
MKEC | Expiry (correction) |
Effective date: 20121205 |