Structural health monitoring of a composite skin-stringer assembly using within-the-bond strategy of guided wave propagation

摘要

The objective of this paper is to investigate the within-the-bond guided wave propagation in a composite skin-stringer joint. The structure of interest is composed of three carbon fibre reinforced polymer (CFRP) plates bonded together by adhesive film. This bonded joint is prone to disbond when submitted to extreme loads or fatigue. Therefore, two bonding conditions are investigated, namely undamaged and damaged (with disbond). The artificial disbond is introduced into the joint using a circular Teflon tape during manufacturing. Two co-localized slender rectangular piezoceramics are used to generate plane guided waves within-the-bondlines and non-contact measurement is performed using a 3-D laser Doppler vibrometer (LDV) to extract the required information for evaluation of the bonding conditions. The results include reflection, transmission and also scattering of the guided waves at the joint as a function of frequency, propagating mode and presence of artificial damage. It was found that the amplitude of the reflection, transmission coefficients and directivity patterns of scattered waves are affected by the presence of damage, such that Structural Health Monitoring (SHM) design guidelines can be derived for efficient damage detection in the composite assemblies using a within-the-bond inspection strategy.