Initiation and growth of splitting in continuous fibre-reinforced composites under static and fatigue loading: A concurrent engineering approach for life

Unidirectional fibre–reinforced composites exhibit a high degree of anisotropy in strength. Crack initiation and growth from a pre–existing notch under static or fatigue loading almost always occur along the fibre direction; this phenomenon is known as splitting. In this paper, fracture mechanics was applied to characterize the initiation and growth of splitting in unidirectional fibre–reinforced composites under static and fatigue mixed–mode loading. Fracture toughness tests and fatigue tests of rectangular specimen with an edge– notch were carried out on a carbon–fibre epoxy system, AS413501–6. The splitting initiation from a pre–existing notch by static loading and the splitting growth by fatigue loading are successfully characterized by the tensile and shear stress intensity factors along the fibre direction. Experimental results show that resistances for the splitting initiation and fatigue splitting growth under pure shear are much higher than those under pure tension, and that both the behaviours are controlled by the tensile stress intensity factor in the wide range from mode I to mixed–mode loading. It is noted that retardation of the growth of fatigue splitting is caused by fibre–bridging due to skipping of the splitting plane. Finally, the application of the characteristics obtained for the splitting to the failure analysis and design of laminated composites is discussed.