ANELASTIC DEFORMATION OF A THERMOPLASTIC-MATRIX FIBER-COMPOSITE AT ELEVATED-TEMPERATURE .1. NEAT RESIN STRUCTURE CHARACTERIZATION

This is part of a series of articles on the properties of a thermoplastic polyamide matrix [PACM-12, DuPont, poly(bis-4-4'-dicyclohexylmethane) n-dodecane-diamide]/graphite fiber (AS4, Hercules) composite. The structural characterization of the neat resin by differential scanning calorimetry (DSC) and X-ray diffraction as a function of processing history is described here. PACM-12, considered a representative thermoplastic matrix polymer for advanced composites, as well as an engineering plastic, is partially crystalline (ca. 20%) under normal composite processing conditions, but can be quenched to a completely amorphous state. The complex DSC results are shown to result, at least in part, from the presence of a different crystal structure in slow cooled PACM-12 than in quenched, annealed or fiber samples, to a melting-recrystallization-melting process during heating and to the effect of heating rate.