Effect of particles on interlaminar crack growth in cross-plied carbon-fibre/epoxy laminates

This paper discusses the effect of particulate additions on the mode-I and mode-II interlaminar fracture toughness of a cross-plied, carbon-fibre-reinforced, epoxy-resin laminate. Particles of graphite, silicon carbide and polyethylene were mixed with the epoxy resin prior to laminating with woven carbon-fibre cloth. Tests have been performed on double cantilever beam (DCB) and end-notched-flexure (ENF) specimens to obtain the critical-strain energy-release rates,G_IC andG_IIC, for the laminates with and without particulate additions. The dependences of the values ofG_IC andG_IIC on the crack length are also considered. The results indicate that the interlaminar-fracture-toughness (mode-I and mode-II) values of the CFRP laminate increase with increases in the particle content up to about 3%, and thereafter they decrease with further increases in the particle content. This was thought to be due to an increase in multiple-crack formation in the middle region of the cracked-plate samples. Furthermore, mode-I tests indicate that the propagation values ofG_IC are dependent on the crack length.