Design, development and testing of multi-functional non-linear ultrasonic instrumentation for the detection of defects and damage in CFRP materials and structures

A multi-functional non-linear ultrasonic testing approach is presented for in situ and ex-situ detection of a variety of defects (e.g. micro-cracking, delamination and disbonding) induced by various damage mechanisms (stress, impact, heat) in CFRP materials and structures. Such multi-functionality is provided via programmable and re-configurable instrumentation that incorporates a wide range of non-linear ultrasonic testing regimes, including harmonic and overtone generation, inter-modulation product generation, resonant frequency shift and pulse-inversion techniques. The capabilities of this multi-functional approach to defect detection are demonstrated by examining CFRP samples subjected to various forms of damage, specifically stress, impact and heat induced damage. We show that the multi-functional non-linear approach is well-suited to the detection of such forms of damage and that the pulse-inversion technique, largely ‘ignored’ in the CFRP literature, potentially provides a powerful, but as yet un-tapped, simple and effective route to the defect and damage detection.