8 - Toughening mechanisms for glass fiber-reinforced polyamide composites

Abstract

The incorporation of fillers and the modification of polymer–filler interfaces changed the crystalline structure of the matrix in some way, which promoted the matrix polymer to undergo shear yielding and prevented the crazes from developing into catastrophic cracks. These effects, combined with the favorable stress conditions, resulted in a dramatic increase in toughness. In the last decade, several studies have demonstrated that some polymers can be toughened with the addition of fibers and rigid inorganic fillers. It has been demonstrated that the toughening mechanisms are very complex and involve many factors, including matrix characteristics, particle geometry and content, the dispersion state of the fillers in the matrix, the interface structure, the extent of interfacial adhesion, and the processing conditions. It is notable that the matrices of the successful inorganic particle toughening systems are often crystalline polymers. This chapter focuses on the factors affecting mechanical properties for fiber-reinforced composites, primarily using polyamide as a case study in a targeted automotive application.