Embedding of Superelastic SMA Wires into Composite Structures: Evaluation of Impact Properties

Abstract

Shape memory alloy (SMA) represents the most versatile way to realize smart materials with sensing, controlling, and actuating functions. Due to their unique mechanical and thermodynamic properties and to the possibility to obtain SMA wires with very small diameters, they are used as smart components embedded into the conventional resins or composites, obtaining active abilities, tunable properties, selfhealing properties, and damping capacity. Moreover, superelastic SMAs are used to increase the impact resistance properties of composite materials. In this study, the influence of the integration of thin superelastic wires to suppress propagating damage of composite structures has been investigated. Superelastic SMAs have very high strain to failure and recoverable elastic strain, due to a stress-induced martensitic phase transition creating a plateau region in the stress-strain curve. NiTi superelastic wires (A f = 215°C fully annealed) of 0.10 mm in diameter have been produced and characterized by SAES Getters. The straight annealed wire shows the typical flag stress-strain behavior. The measured loading plateau is about 450 MPa at ambient temperature with a recoverable elastic strain of more than 6%. For these reasons superelastic SMA fibers can absorb much more strain energy than other fibers before their failure, partly with a constant stress level. In this paper, the improvement of composite laminates impact properties by embedding SMA wires is evaluated and indications for design and manufacturing of SMA composites with high-impact properties are also given.

Characteristics of adult patients with atrial septal defects presenting with paradoxical embolism

“…Therefore, improving the impact behavior of composite structures, without increasing their weight and without decreasing other mechanical properties, can be considered relevant current topic. The use of Shape Memory Alloys (SMA) to this aim can lead to the fabrication of composite materials with innovative and “smart” properties [1–8].…”

“…In this work, the study of the properties of glass reinforced polymer‐matrix composites incorporating thin superelastic SMA wires is reported. In the last years, many authors investigated the influence of SMA on the impact properties of composites, showing that SMA can lead to a significant increase of damage tolerance of composite materials [1–5]. In fact, SMAs dissipate the strain energy about four times more than high alloy steel and 16 times more than many graphite/epoxy composites [8].…”

Nitinol Reinforced Epoxy Smart Composites with Enhanced Stiffness and Damping

“…Superelastic SMA wires are embedded in resins and fibre-reinforced composites to make them smart. Superelastic SMA wires suppress the propagation of the damage in the composite and increase impact resistance [5]. The stress temperature behaviour of SMA composites is similar to that of SMA wires [6].…”

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.…”