Mixed Mode Crack Growth in Functionally Graded Material Under Three-Point Bending

Abstract

Functionally graded materials, FGM, permit tailoring the material volume fractions to extract maximum benefit from their in-homogeneity. Such materials offer great potential for components, which operate under severe thermal or mechanical loadings, such as spacecraft heat shields, plasma facings for fusion reactors, crucial jet fighter structures and engine components. In the present work, polyester matrix reinforced by varying glass fiber distribution was used to obtain FGM polymeric composites. The hand lay-up technique was adopted to manufacture the FGM. The mixed mode crack path of glass fiber/polyester FGM under three point bend, 3PB, was observed. The mechanical properties, such as tensile and flexural strength were determined experimentally and numerically. Pre-cracks with different lengths and locations with seven different inclination angles were considered to study the mixed mode crack growth of FGM. For the same crack length, the present results showed that the maximum applied load increased with increasing the crack inclination angle, i.e. the mode of mixity increased to reach pure mode II. Generally, the crack path initiated from the original inclination angle and grew along a curvilinear trajectory to extend toward the upper loading point.