Impact damage assessment in biocomposites by micro-CT and innovative air-coupled detection of laser-generated ultrasound

The increasing use of natural fibre composites in at least semi-structural applications along with a demand for a fast and accurate damage detection for quality purpose and in-service reliability promote a need for non-contact non-destructive testing techniques. To this purpose, ultrasound is probably one of the most widely used testing techniques but the need of a coupling fluid like water limits its use with natural fibre composites. In this work, a novel non-contact set-up based on laser excitation of ultrasound and detection with a broadband, air-coupled optical microphone is presented and tested on flax/PLA laminates. This material system has been characterized in terms of quasi-static mechanical properties and low velocity impact response. The outcomes of this study demonstrate the potential of this non-contact and nondestructive system for quality and damage inspection purposes of natural fibre composites.