Cyclic Interlaminar Crack Growth in Unidirectional and Braided Composites

Abstract

Since there is still no standard test method for the investigation of the fatigue delamination propagation behavior of fiber reinforced composites, this paper aims at examining some of the parameters that can influence this kind of measurements. Therefore unidirectionally reinforced composites were tested under displacement control and double cantilever beam specimens were used to realize mode I tensile opening loads in the material. A comparison of the effect of different parameters on this type of measurements was carried out including machine parameters (frequency, control mode, type of machine) and specimen parameters (initial crack length, thickness, material). The comparison of the results with the results from a second laboratory yielded promising results. Furthermore the damage tolerance of braided composites with different braid architectures (i.e. braiding angle) was studied.