Fracture Properties of Polyphenylene Oxide Composites

Abstract

The mechanical properties of glass bead, randomly oriented short glass fiber and randomly oriented short graphite fiber polyphenylene oxide composites were investigated. Fracture toughness measurements were made using double edge-notched tensile specimens and tensile strength, tensile strain and initial elastic modulus were measured in standard ASTM tensile tests. It was found that the fracture toughness was relatively independent of filler types and geometry (and nearly equal to that of the unfilled polymer) when no polymer-filler adhesion was present. When adhesion was promoted by surface treatment of the reinforcement, the fracture toughness of the treated fiber composites was greater than that of the untreated composites, while that of the treated particulate composites was below that of the untreated materials. The fracture toughness was also relatively independent of fiber concentration, but decreased sharply with increased glass bead concentration. The elastic moduli of the composites varied in a predictable fashion with temperature and reinforcement concentration. The ultimate tensile strength and the elongation at break were a sensitive function of interfacial adhesion and reinforcement geometry. The overall performance of the various systems was evaluated by considering the combined mechanical response of each system and rating them relative to one another.