Defects in composite structures, such as voids, have a major influence on the damage behaviour and mechanical properties. Based on the conducted experiments the influence of voids on the mechanical properties of multi-axial glass fibre non crimp fabric composites under quasi-static compression load was examined. Optical in-situ inspection and acoustic emission measurement were applied to detect the failure behaviour during compression tests, while paying special attention to the early stages of damage appearance where the Young's modulus is determined. The specimens were produced by resin transfer moulding with different processing parameters to obtain various void contents and morphologies.
