A study of short-beam-shear and double-lap-shear specimens of glass fabric/epoxy composites

Two experimental methods for determining the inter-laminar shear strength (ILSS), are compared: the short-beam-shear (SBS) and the double-lap-shear (DLS) test method. Specimens with a constant ply angle for all layers are considered. The experimental results show a significant difference (up to 50%) in the obtained ILSS. A finite element analysis shows that both test methods underestimate the real ILSS and demonstrate that the standardized ILSS evaluation procedures are more or less valid for the SBS test, but require modifications in the case of the DLS test. Acoustic emission measurements and numerical investigations were performed to determine the real ILSS from the DLS results. The real ILSS cannot be obtained from the SBS test without an extended analysis. It is, however, possible to determine bounds for the real ILSS from the SBS results.