Abstract: To address the challenge of detecting weak bonding defects at interfaces in carbon fiber reinforced plastics (CFRP), a novel in-situ detection method driven by “dynamic response entropy” is proposed for laser shock testing. This approach employs a Photonic Doppler Velocimetry (PDV) system to record particle velocity responses on the rear surface of CFRP specimens subjected to laser shocks of varying energy and pulse width. Post-impact, computed tomography (CT) is employed to examine the internal state of the specimen. Findings reveal a significant correlation between the temporal disorder of the dynamic response signal during laser impact and the interfacial delamination behaviour induced by the shock wave. Building upon this, the degree of pattern disorder in the dynamic response signal’s time series is defined as “dynamic response entropy”, with entropy values characterising whether delamination occurs in the material under laser impact. Results indicate that non-delaminated specimens exhibit zero dynamic response entropy values, whereas delaminated specimens consistently display values significantly above zero. This confirms the efficacy of dynamic response entropy in characterising laser shock-induced interfacial delamination behaviour in CFRP, thereby providing a technical approach for detecting weak bonding defects at the CFRP interface under laser shock loading.

Key words: carbon fiber reinforced composites, dynamic response entropy, laser shock, back-side particle velocity, weakly bonded interface defects