Interfacial properties in commingled yarn thermoplastic composites. Part I: Characterization of the fiber/matrix adhesion

The paper aims to assess the fiber/matrix interface and adhesion quality in commingled GF/PP composites by means of complementary experimental methods. For this purpose, different interfacial qualities were obtained by a modification of the sizing of the fiber reinforcement (polypropylene specific sizing, non-specific sizing and no sizing), and of the matrix (with or without coupling agent). Transverse tensile stress-strain curves have been recorded while monitoring acoustic emissions. An analysis of acoustic emission data associated with fracture surface examinations has helped explain the differences observed in mechanical properties and damage mechanisms, emphasizing the importance of the interphase in the performance of these new composites. Thus it has been shown that the association of three experimental investigation methods (transverse tension, acoustic emission, and fracture surface analysis) makes it possible to characterize both the glass/silane bond (so-called fiber/matrix interface) and the global fiber/matrix adhesion (addition of several different zones and interfaces). (C) 2004 Society of Plastics Engineers.