Deformation mechanism in compression molding of discontinuous thermoplastic composites

Processing plays a key role in determining the final properties of the product during compression molding of thermoplastic composites. In order to manufacture defect free composite products, the essential material behavior needs to be identified, modeled and characterized. This work focuses on the experimental determination of those mechanisms, that play an important role during the manufacturing of compression molded products. Chopped tapes of unidirectional carbon fiber reinforced thermoplastic composite are used for the compression molding experiments with different processing conditions. A transparent matrix is used with un-impregnated tows to visualize the deformation of flakes and movement of fluid. Experiments reveal that intra flake shear, in plane deformation of flakes (flake spreading, fiber bending) and fiber matrix separation are the dominant mechanisms. These mechanisms also show dependence on physical parameters like fiber volume fraction and fiber orientation.