Mechanical behavior and recoverable properties of CFRP shape memory alloy composite under different prestrains

Abstract

This paper explored a prestressed CFRP/SMA composite system, which can be applied to add prestress to the civil structural members. The composite system was composed of carbon fiber reinforced polymer (CFRP) sheets and the embedded shape memory alloy (SMA) wires. The prestress in CFRP sheets was formed by the recovery of SMA wires. Four groups of fully composite (Type I) specimens were fabricated to bear a unidirectional static load to investigate their tensile mechanical properties. Three groups of partial composite (Type II) specimens and five groups of SMA wire specimens were used to study their recoverability. The static test results showed that two main failure modes of the Type I specimens were observed, and the strength of the material was affected by the structural form of the composite. The recovery test results showed that the SMA wire could generate different levels of recovery stress under various amounts of prestrain, and the maximum recovery stress can reach 394.2 MPa for the SMA wire with 6% prestrain by heating it to 131℃. More importantly, the recovery stress can be introduced into the CFRP sheets. In addition, an analytical model for predicting the stress–strain relationship and material strength of the fully composite was proposed, and an improved segmented recovery stress–temperature model of the SMA wire under constraint conditions was also put forward. The results indicated that the calculated values are in good agreement with the experimental values, and the proposed model can effectively predict the mechanical and recoverable properties of the composites.