A new carbon-mat-thermoplastic(CMT)prepreg material has been developed for manufacturing low-cost compression moulded parts. Long discontinuous carbon fiber is combined with an inexpensive thermoplastic matrix to form an air permeable composite prepreg. The prepreg is quickly and uniformly heated to molding temperature using convective heating, and consolidated into complex shapes involving integral ribs and small radius corners. Typical semi-structural automotive components made from this material are door-panels and radiator mounts where either the part count or the weight or both could be reduced.
A patented wetlay process, similar to paper making, is used to manufacture the CMT prepregs. Chopped reinforcing fibers and cut thermoplastic fibers are mixed in aqueous slurry, formed into a mat on an inclined-wire wetlay machine, then heated in a convection oven to dry the mat and fuse the thermoplastic to the reinforcing fibers. The resulting prepreg mat is self-supporting and easy to handle and shape. The CMT can be stored at room temperature for a long time, eliminating out-time issues.
The CMT is being tested to delineate its strength, stiffness, and fracture toughness. These will be compared with literature values for currently used materials. Two original fixtures, a heated parallel plate plastometer and a single-fiber pull-out setup, have been manufactured to study the micro- and the macro-mechanical flow properties. The former will be used to study the overall squeezing flow of the CMT and simulate the compression molding process. The latter will be employed to measure the local fiber-fiber interactions that contribute to the macro flow behavior.
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