A Basic Study of CFRP Laminates with Embedded Prestrained SMA Foils for Aircraft Structures

Abstract

This paper presents some basic research results for the application of the smart materials and structural systems to aircraft structure. The authors conducted quasi-static load-unload tests and fatigue tests on several kinds of quasi-isotropic carbon fiber-reinforced plastic (CFRP) laminates with embedded prestrained shape memory alloy (SMA) foils. The damage behavior and the fatigue behavior were evaluated based on the effects of the recovery stress of SMA, and the relationship between the applied strain and the transverse crack density is discussed. It was found that the developed smart materials achieved a maximum improvement of 34% in the onset strain of the transverse cracks and a maximum improvement of 60% in the onset strain of delamination as compared with the standard CFRP laminates in the static condition. However, the fatigue properties of the smart material were not improved due to the material degradation of the 90°-ply at 80°C. The fatigue test by the multistep strain method using a structural element specimen was used to verify the results of coupon tests. The results indicate the possibility of using coupon data as a design database.