<title>Shape memory alloys for damage-resistant composite structures</title>

Abstract

Shape memory alloy (SMA) materials such as nitinol have unique properties associated with the shape recovery effect and the material's phase changes that have been used in a variety of actuator and sensing applications. By embedding SMA elements into host composite materials, control or modification of the SMA hybrid composite's structural properties can be accomplished in-service, thereby increasing the hybrid composite's structural functionality. Utilizing the SMA's substantial capacity to dissipate strain energy to increase the hybrid composite's static functionality is addressed herein. Specific applications of SMA hybrid composites for improving polymer matrix composite material's impact damage resistance is presented. Hybridizing composites with nitinol improves their impact resistance because of nitinol's tremendous capacity to dissipate impact strain energy through the stress-induced martensitic phase transformation. The amount of impact damage is reduced and the material's resistance to impact perforation at various velocities is improved. The experimental response of nitinol hybrid composites to low and high velocity impact perforation is presented. The unique toughness and resistance to permanent deformation that is a result of the stress-induced martensitic phase transformation enables the nitinol to dissipate on the order of 4 times the strain energy of high alloy steel and 16 times that of many graphite/epoxy composites.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.