Damage suppression in CFRP laminates using embedded shape memory alloy foils

Abstract

This paper presents an overview of the damage growth suppression effects in CFRP laminates using embedded SMA foils, and was conducted to technically verify the application to aircraft structures. In previous studies, the authors confirmed the damage growth suppression of CFRP laminates with embedded pre-strained shape memory alloy (SMA) foils through both coupon testing and structural element testing. Through detailed observation of the damage behavior, we determined that these effects occurred due to the suppression of the strain energy release rate based on the suppression of the crack opening displacement caused by the recovery stress of SMA foils. These results were verified in this study using a demonstrator test article, which was a 1/3-scaled model of a commercial airliner's fuselage structure (B737 class). To demonstrate the damage growth suppression, the lower panel, which was dominated by tension load, was selected as the evaluation area. The evaluation area was an integrated panel including both the 'smart area' (CFRP laminate with embedded pre-strained SMA foils), and the 'conventional area' (standard CFRP laminate), for direct comparison of the damage behavior. The demonstration was conducted at 80°C in the smart area, and room temperature (RT) in the conventional area using a quasi-static load-unload test method. The demonstrator test article identified that the damage onset strain in the smart area was improved by 30% over that in the conventional area.