# Monitoring of Layered Thermoplastic Composites Using Shape Memory Alloys as Integrated Sensors for Multifunctional Lightweight Structures

## TL;DR

This paper explores using shape memory alloy wires in composite materials to monitor mechanical forces and improve lightweight structural safety.

## Contribution

The study demonstrates the effectiveness of embedded SMA wires for force monitoring in GFRP composites using various testing methods.

## Key findings

- SMA wires with 250 µm diameter outperformed 100 µm wires in load capacity and production feasibility.
- Thermography and computer tomography were most effective for detecting embedded SMA wires.
- The Young’s modulus of the GFRP composites with SMA wires averaged 30.8 GPa across samples.

## Abstract

Since lightweight design and construction safety is a crucial element in different sectors of industry, the use of SMA wires in composites could improve the monitoring and adjustment of mechanical properties starting from the product development process through to field use. This work shows how embedded SMA wires can lead to a better understanding of applied forces to a composite structure made of GFRP laminates. To achieve this, different methods will be addressed. Besides mechanical testing of the GFRP-samples with embedded SMA wires, NDT-methods like active thermography, high-frequency ultrasonic testing, and computer tomography are used to detect the SMA wires, whereby thermography and computer tomography are best suited. In this study, the location and the amount of the applied force on GFRP composites with embedded SMA wires could be characterized with relative resistance changes. It is shown that SMA wires with a diameter of 250 µm are preferred to wires with a diameter of 100 µm due to production process and better performance under load (4N force plateau for 100 µm in contrast to 25N force plateau for 250 µm wires). Furthermore, Young’s modulus of the GFRP composites with embedded SMA wires was measured and is similar for various samples with 30.8 GPa on average.