MICROSTRUCTURAL ASPECTS OF FRACTURE AND FATIGUE BEHAVIOR IN SHORT FIBER-REINFORCED, INJECTION-MOLDED PPS-, PEEK-COMPOSITES AND PEN-COMPOSITES

Both the fracture and fatigue behavior of temperature-resistant thermoplastic matrix composites with discontinuous fiber reinforcement are strongly affected by the microstructure. The molding-induced microstructure of the composites can be characterized by a reinforcing effectiveness parameter (R). This parameter treats a short fiber reinforced injection-molded composite as a laminate, in the layers of which the fibers are present in different amounts, in various orientations and in addition, in various aspect ratios and aspect ratio distributions. The relative change in the fracture toughness can be predicted by the microstructural efficiency concept (M). Due to analogies between static fracture and fatigue crack propagation (FCP) results, this concept seems to work well when the dependence of FCP on microstructural details is considered.