Mixed-mode I/III fracture toughness of polymer matrix composites toughened with waste particles

Fracture toughness of particle-filled polymer composite beams with different particle content for varying of crack inclination angles was investigated in mode I and mode III loading conditions. The beams were tested using three-point bending test with crack inclination angles of 30°, 45°, 75°, and 90°. Sewage sludge ash (SSA), fly ash (FA), and silicon carbide (SiC) microparticles were used as toughening fillers with 5, 10, 15, and 20 wt% contents of the total weight of the polymer composites. The scanning electron microscope (SEM) micrographs showed that a good indication was observed for dispersion of FA, SSA, and SiC particles within the polymer matrix. The critical crack tip stress intensity factors K_Ic (crack angle 90°) and K_IIIc, and the critical strain energy release rates G_Ic and G_IIIc were calculated and their results were compared. The mode I and mode III fracture toughness of the particulate polyester composite were improved by addition of particulate fillers. The maximum values of fracture toughness mode I (K_Ic and G_Ic) and mode III (K_IIIc and G_IIIc) were recorded at particle content of 5 wt% polymer composites.