Method and Apparatus to Produce Auxetic Foam

Abstract

In methods and apparatuses for producing auxetic foam from conventional foam, conventional foam is compressed into a mold before thermal, chemical or thermo-chemical treatment processes are performed. A segmented mold is accommodated in a compressing apparatus. After compressing the foam between the mold segments, the mold is fastened shut and removed from the compressing apparatus. The forces applied to any given volume of foam and the amounts by which the foam is compressed while being processed are controlled to impart desired mechanical properties to the produced foam. Poisson's ratio and density of discrete portions of finished foam shapes are reliably predicted and controlled to achieve uniform and non-uniform mechanical properties within a single continuous quantity of foam.

1 .- 13 . (canceled) 
     
     
         14 . A method of processing a quantity of foam having a first initial thickness along a first axis, a second initial thickness along a second axis, and a third initial thickness along a third axis, the method comprising:
 applying at least one of a first force in the first axis to compress the quantity of foam to a first compressed thickness in the first axis, a second force in the second axis to compress the quantity of foam to a second compressed thickness in the second axis, and a third force in the third axis to compress the quantity of foam to a third compressed thickness in the third axis;   enclosing the compressed quantity of foam in a mold to limit expansion of the foam in at least one of the axes to less than the initial thickness in the axes, wherein the step of applying further includes compressing the quantity of foam against an interior surface of the mold; and   fastening the mold, with the compressed quantity of foam inside the mold, such that the mold remains in a closed position when the at least one of the first, second, and third forces is removed.   
     
     
         15 . (canceled) 
     
     
         16 . The method of  claim 14 , further comprising:
 removing at least one of the first, second, and third forces from the fastened mold, wherein the fastened mold retains the compressed quantity of foam inside;   with the compressed quantity of foam enclosed in the mold, subjecting the enclosed quantity of foam to at least one of a chemical treatment and a thermal treatment to convert the enclosed quantity of foam to an auxetic foam having at least one of a first treated thickness less than the first initial thickness in the first axis, a second treated thickness less than the second initial thickness in the second axis, and a third treated thickness less than the third initial thickness in the third axis.   
     
     
         17 . The method of  claim 14 , further comprising:
 providing a mold including
 a pair of first opposing mold segments spaced apart in the first axis, each of the first opposing mold segments having a plurality of holes around a perimeter of the mold segment, each of the holes extending parallel to the first axis, with each hole in one of the first opposing mold segments having a corresponding hole aligned in the other of the first opposing mold segments to permit a plurality of fasteners to be inserted through the plurality of holes in a direction parallel to the first axis, and
 a pair of second opposing mold segments spaced apart in the second axis; and 
 
   the applying the at least one of the first, second, and third forces includes pushing each of the second opposing mold segments from an initial position outside a convex hull defined by the plurality of holes, to a final position inside the convex hull bounded by the plurality of holes.   
     
     
         18 . The method of  claim 14 , further comprising:
 providing a sliding guide to reduce friction on at least one surface of the quantity of foam; and   inserting the sliding guide with the quantity of foam into the mold.   
     
     
         19 . (canceled) 
     
     
         20 . A method of processing foam comprising:
 placing foam on a bottom compression surface, wherein the foam is placed between a left compression surface and a right compression surface;   compressing the foam between a top compression surface and the bottom compression surface;   compressing the foam between the left compression surface and the right compression surface;   moving the compressed foam into a mold, wherein the foam in the mold remains compressed;   transferring the mold holding the compressed foam into a pressure vessel;   treating the compressed foam in the transferred mold while in the pressure vessel, wherein the treatment causes the foam to be converted to auxetic foam.   
     
     
         21 . The method of  claim 20  wherein the step of moving the compressed foam into a mold comprises using a compression surface to slide the compressed foam into the mold. 
     
     
         22 . The method of  claim 20  wherein the step of moving the compressed foam into a mold further comprises using a sliding guide. 
     
     
         23 . The method of  claim 20  wherein there is a front and back compression surface and the moving step comprises using the front compression surface to push the compressed foam into the mold. 
     
     
         24 . The method of  claim 20  further comprising the step of closing the mold, wherein, after the compressed foam is moved into the mold, the mold is closed. 
     
     
         25 . The method of  claim 20  wherein the mold is formed of segments and the method further comprising the step of holding the mold segments in place. 
     
     
         26 . The method of  claim 20  wherein the mold has small holes which allows gases to enter the mold. 
     
     
         27 . The method of  claim 20  further comprising the step of heating the compressed foam within the mold as part of a process to convert the compressed foam to auxetic foam. 
     
     
         28 . The method of  claim 20  wherein the step of placing the foam on the bottom compression surface comprises placing a non-uniform shaped quantity of foam on the bottom compression surface. 
     
     
         29 . The method of  claim 20  wherein the mold is a non-uniform shaped mold. 
     
     
         30 . The method of  claim 20  wherein the step of compressing the foam between the left compression surface and the right compression surface comprises applying a non-uniform force. 
     
     
         31 . A method of processing a quantity of foam, the method comprising:
 providing a flexible sheet which circumscribes the foam;   providing a rigid mold adjacent to a proximal end of the foam, an inner radial dimension of the mold being greater than or equal to a compressed radial thickness;   applying a force, in a first axis, to the flexible sheet circumscribing the foam to compress the foam to a compressed radial thickness;   applying a force, in a second axis, on a distal end of the of the foam to displace the foam toward the rigid mold and to compress the foam against the rigid mold; and   closing the rigid mold with the compressed foam enclosed inside the rigid mold.   
     
     
         32 . The method of  claim 31  further comprising transferring the rigid mold with the enclosed foam to a pressure vessel for treatment to convert the foam to auxetic foam. 
     
     
         33 . The method of  claim 31  wherein the compressed foam has a non-circular cross section. 
     
     
         34 . The method of  claim 31  wherein the mold is a non-uniform shaped mold. 
     
     
         35 . The method of  claim 31  wherein the step of applying a force in a second axis comprises applying a non-uniform force.