Abstract:
A method of fabricating a composite panel is disclosed. The method includes cutting a portion of carpet, applying vacuum to the carpet portion, transferring resin into the carpet portion under vacuum, and curing the resin impregnated carpet portion.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of U.S. Provisional Patent Application No. 61/148,764 entitled “FABRICATION METHOD OF MULTI-FUNCTIONAL COMPOSITES FROM PRE/POST-CONSUMER CARPET,” filed Jan. 30, 2009, the contents of which are hereby incorporated by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under grant number SBAHQ-06-I-0097 awarded by the U.S. Small Business Administration. The government has certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     This application relates to composite materials in general and, more specifically, to the use of carpet in composite construction. 
     BACKGROUND OF THE INVENTION 
     Of the 4.6 million tons of solid waste generated in Oklahoma every year, only 1% is recycled. Currently, only ˜2% of discarded carpet (270 million pounds out of 200 million tons) is recycled through recycling programs in the United States. This represents a significant environmental burden on our landfills, a tax burden due to certain state sponsored subsidies, and a lost economic opportunity. The last factor is driven by the lack of high-value, engineering-oriented applications that could leverage advances in manufacturing technology to utilize waste to deliver commercially viable products. These advanced engineered materials are expected to have specific applications in a variety of fields ranging from sound protection of civil infrastructure to tooling materials for aerospace structures. 
     The carpet industry is a $10 billion-plus dollar industry. Over 3 million tons of carpet is produced every year and about 2 million tons are discarded. Overall in the United States, carpet accounts for about 1% of municipal solid waste by weight and 2% by volume. This is not a small amount. 
     What is needed is a system and method for addressing the above and related concerns. 
     SUMMARY OF THE INVENTION 
     The invention of the present disclosure, in one aspect thereof, comprises a method of fabricating a composite panel. The method includes cutting a portion of carpet, applying vacuum to the carpet portion, transferring resin into the carpet portion under vacuum, and curing the resin impregnated carpet portion. 
     In some embodiments, a reinforcement may be applied to the carpet portion. Vacuum film may also be utilized, along with peel plies and transfer media. The vacuum film may be sealed to the mold. The resin impregnated carpet portion may also be hot pressed. Some embodiments will provide a carpet portion with at least two layers of carpet. These may be placed back to back, fiber to fiber, or fiber to back. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cutaway view of a carpet construction. 
         FIG. 2  is a side perspective view of a fabrication setup for creating recycled carpet composite materials. 
         FIG. 3  is a side cutaway view of another fabrication setup for creating recycled carpet composite materials. 
         FIGS. 4A and 4B  are illustrations of test results for composite panels prepared according to the present disclosure. 
         FIG. 5  is a graph illustrating strain properties of composite panels prepared according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The technologies of the present disclosure present low cost processes based on vacuum-assisted resin transfer molding (VARTM) that takes advantage of the 3-D fiber architecture of carpet. The aspect ratio of the carpet fibers may be utilized so that higher mechanical properties can be obtained than are otherwise currently possible. Materials for use where high impact resistance is required may be achieved by promoting an adhesion between a composite matrix and nylon fibers through an appropriate compatibilizer, and by adding layers of impact resistant fiber architectures such as spectra and 3-D glass fabric between the carpet layers. Compatibilizers may either be utilized to prepare the carpet fibers prior to resin application and/or be included with the resin. 
     Referring now to  FIG. 1 , a side cutaway view of a carpet construction  100  is shown. The present disclosure discusses the fabrication of composite panels with carpet panels as a substrate. It is understood that the present disclosure is not limited by whether or not the carpet is used, new manufacture, or overstock. The methods of the present disclosure work equally well regardless of the source of the carpet. Most carpet consists of about 20-50 percent by weight face fiber  102 , which may comprise nylon, cotton, or other synthetic or natural material. Layers of backing materials  104 ,  106 , and an adhesive  108 , which attaches the carpet fiber to the backing material are also part of the structure  100 . The backing materials may be polypropylene or other materials or composite. The adhesive  108  may comprise a carboxylated styrene-butadiene (XSB) latex copolymer, and an inorganic filler like calcium carbonate. Further, while cured thermosetting systems may under certain circumstance be recoverable, they are not capable of being reused as raw polymeric components in the manufacture of a second-generation carpet. 
     Referring now to  FIG. 2 , a cutaway perspective view of a fabrication setup  200  for creating carpet based composite panels  100  is shown. The first step is to clean a mold  202  and apply release film  204  on it. The release film aids in the removal of the panel  100  from the mold surface  202  after infusion and curing. In order to transfer the resin quickly and efficiently over the sample, two pieces of transfer media  206  may be cut—one for the bottom face and one for the top face of the sample  100 . The size of the transfer media  206  should be such that starting from an inlet pipe  216  it spreads along the entire length of the panel  100  and should be about 1-2 inches bigger at the remaining sides. The transfer media  206  may not be utilized in every case. In one embodiment, the transfer media  206  serves to prevent collapse under a vacuum bag  210  that might prevent adequate flow of resin. Therefore, any porous, textured, honeycombed, or sufficiently durable material with passages for resin flow under vacuum could be used. 
     One piece of the transfer media  206  is placed on the mold surface  202 . Two pieces of peel ply  208  of appropriate size are then cut. Where final appearance is important, the peel plies  208  may be useful used for protecting the panel  100  surfaces from the impressions of the transfer media  206  and wrinkles caused by a vacuum bag  210 . The peel plies  208  may also aid in removal of panel  100  from under the vacuum bag  210 . Above the bottom portion of the transfer media  206  is the peel ply  208 . The panel  100  is placed on the peel ply  208 , and another layer of peel ply  208  is placed on the panel  100 . On top of this is placed the other portion of the transfer media  206 . Vacuum bag sealant  212  (such as tacky tape) is then placed around the sample  100 . 
     The resin inlet pipe  214  is placed on top of the sealant  212 , near one corner. Additional sealant may be applied to and around an opening  230  for the pipe  214  in order for the vacuum bag to stick properly and close any gaps. The inlet pipe  214  may be placed such that it is 1-2 inches inside the sealant  212 . This arrangement may be further understood by reference to the cutaway portion of  FIG. 2  showing an outlet pipe  220  is similarly arranged. 
     In some embodiments, two pieces of the spiral wrap  226  may be cut to a size at least the width of the fiber cloth  110 . Both spiral wraps  226  are connected to the inlet and outlet pipes  214 ,  220 . The spiral wrap  226  is placed in between the transfer media  206  (top and bottom) at the inlet. A sufficiently large vacuum bag  210  film is cut and stuck to the sealant  212 . Care should be taken to avoid folds in the vacuum bag. A valve  216  may be installed in the resin inlet pipe to control resin flow from a reservoir  218 . It is understood that any resin having suitable mechanical and chemical properties may be utilized. Non limiting examples include epoxies, vinylesters, polyesters, polyurethanes, polyvinyl chlorides, cynate esters, and/or other thermoplastic or thermosetting resins. The outlet pipe  220  may be connected to a vacuum pump  220  via a resin trap  224 . In some cases, due to the structure of the carpet panel  100 , the spiral wraps  226  may not be needed to obtain sufficient resin flow under pressure. 
     To check the vacuum, the inlet valve  216  may be closed and the vacuum pump  222  activated. If proper vacuum is maintained, the system  200  is ready. If not, the vacuum bag  210  may be checked at the sealant  212  for any leakage. 
     The infusion process may begin with the application of vacuum pressure under the bag  210 . In one embodiment of the method, full vacuum is applied for 15 minutes before the infusion. This minimizes air inside the carpet panel  100 . After the application of full vacuum for 15 minutes the pressure should be reduced to a desired amount of pressure that is required for the flow of the resin. Once the desired pressure is achieved, the inlet pipe should be dipped into the beaker or reservoir  218  containing the resin (or otherwise attached to a resin source). The transfer media  206  permits the flow of the resin with ease. After the resin moves across the length of the setup from inlet to outlet and wets the fibers or the fiber cloth  110  completely, the inlet valve  216  may be kept open for about the next 5 minutes at the same level of pressure. This ensures that the resin has completely wetted the fibers. Then, the inlet valve  216  is closed. The vacuum remains on and pulls gas out of the mold that may be given off by the resin. After 10 minutes the pressure may be reduced slowly to 0″ of Hg. 
     The panel  100  may be left at room temperature for 10-12 hours for curing. A post curing process begins with debagging the panel  100  and placing it in an oven as a freestanding part. In one embodiment, post curing is done for 8 hours at about 75 degrees C. The final part is allowed to cool to room temperature. In some embodiments, additional steps may be taken. For example, two resin impregnated carpet panels may be hot pressed together. In another embodiment, the panel  100  may comprise multiple layers of carpet that are resin impregnated together under vacuum. Whether the panels  100  are assembled together before or after the VARTM process, they may be arranged one atop the other, backing to backing, fiber to fiber, or in combinations of these where 3 or more plies are used. 
       FIG. 3  is a side cutaway view of another fabrication setup for creating recycled carpet composite materials according to the present disclosure. The setup  300  of  FIG. 3  is operationally similar to that of  FIG. 2 . However, here it can be seen that the mold  202  has a three dimensional shape. It will be appreciated that complex shapes may be achieved using the methods of the present disclosure. A combination of shaped molds, post mold hot pressing, and/or assembly of discrete components can yield complex and useful structures. Non limiting examples of structures that may be constructed include containers, feed bins, sound proofing panels, sound barrier walls, composite roofing, construction materials, and shipping pallets. 
     In  FIG. 3 , the carpet panel  100  has been placed in the mold  202  and conformed to its basic shape. Peel plies and transfer media may be used in this embodiment as well but are not shown for simplicity. In the present embodiment, to ensure that the panel  100  maintains the correct shape, a reinforcement  302  may be placed over the panel  100 . The panel may be metallic or a polymer. In some embodiments, this may be removed from the panel  100  or it may remain as an integral component. As before, the vacuum bag  210  is placed over the sample  100  and the bag  210  may be sealed to the mold  202  with tape  212 . A vacuum may be created by the vacuum pump  218  allowing which is used to draw in resin from the resin container  218 . A curing process may proceed as described above, with the end result being a carpet based composite panel having a complex shape according to the mold  202  and/or the reinforcement  302 . 
     For establishing feasibility of the processes described herein, post consumer carpet and a commercially available VAR™&#39;able resin system, SC-79 from Applied Poleramic Inc., (Benicia, Calif., USA) were acquired. Other facilities included a VARTM setup as described above and a Hot press. 
     2″×12″ samples were fabricated using the vacuum assisted resin transfer molding approach. Three different samples were fabricated. Sample 1 was fabricated with a single layer carpet by infiltrating it with VARTM&#39;able epoxy (SC-79) and left under vacuum for 6 hours. Sample 2 was fabricated with two layers of carpet and SC-79 epoxy. Sample 1 and 2 were subsequently post-cured at 350° F. for 1 hour. Sample 3 was VARTM&#39;ed with two layers of carpet, and subsequently hot pressed at 350° F. for 1 hour. 
     In sample 1, it was observed that the infiltration of the sample was not yet optimized, while sample 2 showed an improvement in the infiltration of the epoxy resin into the fiber bundles. It should be noted that no compatibilization was used in either of these cases. However, improved interfacial bonding and mechanical properties would be achieved through compatibilization of the nylon fibers with the matrix resin. Similar results were obtained from sample 3 but with a smoother top surface. Additionally, the samples showed very little porosity between the layers indicating that subsequent hot pressing to remove any porosity that was observed in the previous samples. 
     Composite samples of approximate size 228 mm×25.4 mm×12.54 mm were cut from the larger pieces and tested in 3-point bending mode under ASTM D-790 test procedure. The load span was 200 mm.  FIG. 4A  shows the results for modulus of rupture, while  FIG. 4B  shows the modulus of elasticity of all the composite samples. For comparison sake, the results for the carpet/HDPE and the results reported by Mancosh are also shown here. It is evident that the VARTM process as well as VARTM and subsequent hot pressing produced significant improvement in both modulus of elasticity and modulus of rupture, demonstrating the promise of the proposed approach. 
     The single layer carpet epoxy samples after VARTM showed an average modulus of elasticity 0.817 GPa (118.50 ksi), flexural strength 27.91 MPa (4.048 ksi) and density 0.849 g/cc. The two layer carpet epoxy samples after VARTM showed an average modulus of elasticity 1.567 GPa (227.27 ksi), average flexural strength 25.34 MPa (3.68 ksi) and average density of 1.072 g/cc. The two layer carpet epoxy samples after hot pressing showed an average modulus of elasticity 2.041 GPa (296.022 ksi), average flexural strength 26.64 MPa (3.86 ksi) and average density of 1.151 g/cc. In comparison, the carpet/HDPE samples initially fabricated by KT Plastics showed an average modulus of elasticity 1.23 GPa (178.40 ksi), average flexural strength 10.590 MPa (1.54 ksi) and density 1.177 g/cc. The data presented by Mancosh et al. was modulus of elasticity 0.37921-0.6894 GPa (55-100 ksi), flexural strength 4.13-17.23 MPa (1-2.5 ksi) and density 0.6407-1.2815 g/cc. 
     Without limitation, the functionality of the samples can be varied by using different thermoset or thermoplastics. Specific acoustic properties can be attained by incorporating cenospheres/crumb rubber. Incorporation of spectra based fibers may lead to knife proof vests. Both used and unused carpets can be used to fabricate the composite. 
     In another test, preliminary samples were fabricated from recycled carpet pieces that were cut into rectangular pieces of approximately 12″×1″×2″ thick pieces and stacked inside an aluminum mold. The mold was heated while recycled high density polyethylene (HDPE) was added and heated to temperature of approximately 350° F. to compression mold the carpet/polyethylene mix into a solid composite piece. However, the process suffered from the fact that the cut carpet pieces did not fit perfectly into the mold and the polyethylene was not uniformly spread around the carpet pieces. Due to this fact, the homogeneity of the final composite piece was non-optimal. 
     Nevertheless, composite samples of approximate size 190 mm×15 mm×12 mm were cut from the larger piece and tested in an Instron 5567 mechanical testing equipment using a 30 kN load cell. A 165 mm loading span was used with a 16:1 span to depth ratio and tested in 4-point bending mode under ASTM D6272-02 test protocol. The samples showed an average flexural strength of 10.6±2 MPa (1536±294 psi) and an average flexural modulus of 1.23±0.16 GPa (179±23 Ksi). Typical stress-strain curves obtained for the samples are shown in  FIG. 5 . The samples exhibited excellent load transfer and failed in a tensile mode, the preferred fracture mechanism for a polymer composite material. 
     Thus, the present invention is well adapted to carry out the objectives and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those of ordinary skill in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the claims.