Integration of Shape Memory Alloy Wires in Fiber Reinforced Polymers for Endless Crash Absorber Structures

Abstract

Today in most cases crash absorber elements are made of metals. Those materials absorb the energy during a crash event by ductile plastification, as e.g. by buckling. Fiber reinforced polymers (FRP) offer due to their heterogenic structure several failure mechanisms for energy absorption under compressive load, such as fiber-break, matrix-break, delamination, fiber pull-out, fiber-matrix-interphase failure and friction processes. This in combination with the low density leads to significantly better specific energy absorption of FRP absorbers (50 J/g to 200 J/g FRP, 20 J/g steel, 40 J/g aluminum). But in case of tensile load fiber reinforced polymers break brittle and the energy absorption level is low. Today as a consequence of rising energy costs FRP with their good specific mechanic properties are used more and more also for crash relevant structures as in automobiles and aircrafts. For this applications a good crash behavior in both cases, compressive and tensile loading, is important. The integration of metal elements in FRP-structures offers the possibility to improve the tensile crash behavior of fiber reinforced polymers as the metal elements can prevent a catastrophic failure of the structure in case of FRP-break and distributes the load during tensile deformation on a larger FRP volume. The integration of shape memory alloys (SMA) with their pseudoplastic martensitic detwinning plateau allows for manufacturing of an “endless” crash absorber in case of tensile load. Required is a well dimensioned structure of shape memory alloys, e.g. a wire mesh, the FRP component and their interface. Doing so, it is possible to get huge number of breaks in the SMA reinforced FRP. The pseudoplastic detwinning plateau and the huge strain hardening of the SMA material ensure that after a FRP-break and the drop of the force level associated therewith the force level in the whole structure raises again so that another FRP-break is initiated. Also the reinforcement prevents a complete failure of the structure. In this contribution we present a theoretical extrapolation of the behavior of these new hybrid structures under tensile loading, give an estimation of their potential and demonstrate a first experimental validation of this new concept.

Enhancing Mechanical Behavior and Energy Dissipation in Fiber-Reinforced Polymers through Shape Memory Alloy Integration: A Numerical Study on SMA-FRP Composites under Cyclic Tensile Loading

“…In another study, Wierschem and Andrawes [ 55 ] utilized SMA wires and glass fibers in GFRP composites and showed that SMA wires could improve the ductility of composites. Nissle et al [ 56 ] used super-elastic SMA wires with conventional FRP composites to avoid damage propagation in composites. Sharifi et al [ 57 ] produced a smart FRP composite consisting of two layers.…”

“…In this investigation, asymmetric specimens showed very low tensile strength. Pappada et al [ 54 ], Nissle et al [ 56 ], Cohades et al [ 58 ], and Lidan Xu et al [ 59 ] used super-elastic SMA wires with conventional FRP composites to increase their impact resistance and avoid damage propagation in composites. Zafar and Andrawes [ 10 , 14 ] produced SMA-FRP composites using SMA and glass fibers and tested them under uniaxial tensile loading.…”

“…In this investigation, asymmetric specimens showed very low tensile strength. Pappada et al [54], Nissle et al [56], Cohades et al [58], and Lidan Xu et al [59] used super-elastic SMA wires with conventional FRP composites to increase their impact resistance and avoid damage propagation in composites. Zafar and Andrawes [10,14] produced SMA- Jang et al [49] concluded that embedding nitinol wires in CFRP composites decreases their tensile strength from 1300 MPa to 1100 MPa, and the tensile strength can be reduced up to 1050 MPa regarding the orientation of CFRP layers and nitinol wires.…”

Effect of pre‐tension on tensile strength of glass fibers‐epoxy composite reinforced with shape memory alloy wire

“…Researches on designing the SMA hybrid composites (SMAHCs) show the effects of some parameters like volume fraction of SMA, surface treatment , pre‐strain of SMA wires and matrix curing process .Several researchers have investigated the use of SMA wires in fiber‐epoxy composites. Pappada et al and Nissle et al embedded superelastic SMA wires in fiber reinforced polymer composites to avoid propagating of defect in the composite and enhanced mechanical properties such as energy absorption and impact applications.…”