Loading direction dependence of the tensile stiffness, strength and fatigue life of biaxial carbon/epoxy NCF composites

In this work, the effect of the loading direction on the tensile properties of a cross-ply carbon/epoxy NCF composite was studied. Both static and fatigue properties were investigated for several sample orientations. For small off-axis angles, a moderate influence on the stiffness was found. For larger angles, the stiffness could be predicted by means of the CLT. An important influence of the sample aspect ratio was found on the strength and fatigue life of the 5° off-axis samples. Normalisation of the fatigue life curves for the different off-axis angles with respect to the static strength removes the loading direction dependence and produces a master curve.