Thick-section AS4-graphite/E-glass/PPS hybrid composites: Part II. Flexural response

Abstract

The flexural behavior of 16- and 40-ply hybrid composites consisting of E-glass and AS4 graphite fibers in PPS has been studied as a function of fiber hybridization and fiber orientation. Two different stacking sequences (unidirectional and [ 0 90 ] s ) were selected for study. A symmetric sandwich configuration consisting of exterior E-glass fibers and AS4 graphite in the core was used to attain improved impact damage response and to enhance the mechanical properties by delaying the failure of the AS4/PPS. Composites of five different AS4 fiber contents (100, 75, 50, 25 and 0% by volume) have been studied, and theoretical predictions based on the classical laminate theory have been used to analyse the experimental data. The hybrid effect in the composites was quantified by measuring the increases in the failure strains of the 0 ° graphite fiber layers furthest from the midplane compared to the theoretical expectations. The flexural strengths were influenced by the compressive properties of the composites. As in the case of the tensile properties, a failure strain enhancement was observed in the hybrid composites by comparison with the plain AS4/PPS composites. The hybrid effect is attributed to the better transverse support and crack arresting characteristics of the E-glass fibers. The development of these hybrid composites has demonstrated that optimum tailoring of composite structures can result in compressive and flexure property enhancement as a result of appropriate fiber selection, geometry and placement.