Towards in-situ acoustic emission-based health monitoring in bio-based composites structures: Does embedment of sensors affect the mechanical behaviour of flax/epoxy laminates?

Abstract

Monitoring integrity of operating structures has become a crucial need in industrial applications while motivation for more sustainable materials pushes forward the development of natural fibre composites (NFC). The complexity and variability of their failure behaviour and mechanical properties still limit the exploitation of their full potential. Acoustic Emission (AE) has shown promising results to predict remaining service life of structures, allowing identification, localisation and assessment of damages in composite materials. Thus, embedment of AE sensors could be a reliable solution for real-time Structural Health Monitoring (SHM). This paper aims to quantify the effect of embedded millimetre-sized metallic inserts mimicking sensor integration on material integrity under tensile and bending loads by means of Digital Image Correlation , AE, and infrared thermography . Results show a limited effect on monotonic tensile properties , driven by the size of the sensor, while highlighting an increase of strain and stress at failure under three-point bending. Tensile-tensile fatigue resistance is only slightly affected by the embedment of sensors, with a small increase in the S–N curve slope. Overall results suggest that the embedment of miniature sensors in NFC is possible and could be a suitable solution for damage assessment and health monitoring in such sustainable structures.