Tensile behavior of multilayer 3D smart woven composites embedded with shape memory alloy (SMA) wires

Shape memory alloys (SMA) are reputable for their capability of regaining shape at certain temperatures even after large deformations. In the martensite phase, when a load is applied on SMA wire, it accommodates strain rather than breakage by unfolding its lattice that results in improving damping and stiffness. Also, SMA generates stresses due to phase transformation from martensite to austenite at higher temperatures. This coupling effect of SMA in response to load and temperature makes its use for improving properties of composites by embedding in composite structures. The major factor considered during embedding SMA wires into composite structures is the compatibility between SMA and matrix. SMA wires should have excellent adhesion with matrix otherwise, cracking and delamination in the composite will occur. Therefore, different techniques are carried out for surface modification of SMA wire to improve the bonding between matrix and SMA wire. These techniques are expensive, time-consuming and sometimes give undesirable results. An alternative approach used in this research is to weave SMA wires in 3D structures for providing better grip to these wires before composite fabrication. 3D structures have higher through-the-thickness properties and delamination resistance, but their in-plane properties are lower than 2D laminated composites. Due to the weaving of SMA wires into 3D structures, binder yarns provide a better grip to SMA wire that ultimately increases the interfacial strength of composite while SMA wire improves the tensile properties of 3D structures. Results show that a single SMA wire embedded in three different 3D configurations contributes in improving the tensile properties of each 3D structure depending on the interlocking behavior of fibers with SMA wire. The layer-to-layer 3D configuration loosely grips SMA wire, hence SMA wire faces less resistance upon activation and improves Young’s Modulus to 34.9%. The modified 3D structure provides a strong grip to the SMA wire, hence limitise the increment of Young's Modulus to 16.06%. Tensile behavior along with structural failures of SMA embedded 3D woven composites are discussed in detail.