The effects of long-term exposure to high temperatures on the ILSS and impact performance of carbon fibre reinforced bismaleimide

Carbon fibre composite materials with high temperature bismaleimide resin systems as the matrix component are currently being used on structures for both military and civilian aircraft. A major concern with these materials is the effect of long-term exposure to service environments on their physical and mechanical properties. A carbon fibre reinforced bismaleimide composite was evaluated to determine the effect of fibre type and exposure to a high temperature environment on its interlaminar-shear strength and impact performance. Interlaminar shear and Charpy notched impact specimens were prepared, aged for certain periods of time at three different temperatures in air-circulating ovens and tested. The results reflected the degradation of matrix and the fibre-matrix interface with ageing, accordingly the interlaminar-shear strength deteriorated progressively and the failure mode of the impact specimens changed from a brittle failure in the unaged state to a progressive delamination in the aged state. Change in the impact failure modes influenced the energy dissipation characteristics of the specimens.