Low velocity impact on shape memory alloy stitched composite plates

Abstract

Delamination of advanced composite materials due to various scenarios such as low velocityand ballistic impacts and high strain rate is one of the major problems for aerospace andautomotive structural applications. The low velocity impact does not immediately induceany visible damage on the surface of structures whilst the stiffness and compressivestrength of the structures decrease dramatically. Shape memory alloy (SMA) materialspossess many unique mechanical, thermal and thermal–mechanical properties comparedwith other conventional materials. Many studies have reported that the superelasticand hysteresis properties of the SMA materials can absorb energies coming fromexternal excitations or sudden impacts. Stitching is well recognized as a promisingtechnique to enhance the through-the-thickness reinforcement, in order to improve thedelamination properties of composite structures. By stitching SMA wires into thecomposite structures one is theoretically able to reduce the risk of delamination of thestructures during impact. In this paper, the damage resistance properties of SMAstitched glass/epoxy composites after low velocity impact are experimentally andtheoretically studied. The results show that the tensile strength of composite platesincreased and the number of translaminar cracks decreased after being stitchedby SMA wires. Theoretical study also proves that the delamination energy ofcomposite plates after stitching by superelastic SMA wires is smaller than that of anunstitched composite plate because of the energy absorbed by the SMA wires.