A vibration-based structural health monitoring system for GFRP laminate structures

Structural health monitoring is being considered to detect minor damage prior to being combined and propagated to cause failure to composite structures. Composite plates made of glass fibre pre-preg and cured out-of-autoclave used in this study. A pre-defined delamination in forms of polytetrafluoroethylene was inserted between the plies during the lamination process. The effects of the delamination length on modal characteristics of the composite plates were investigated. The effect of the composite plate size on damage detection and location was also studied. A random vibration wave was used to excite the composite structure. A piezoelectric sensor, polyvinylidene fluoride, was used to capture the response of the system. Response signals were processed using an in-house built high-level estimation algorithm. It was found that damage caused a frequency shift, the amount of shift depends on the delamination length. Mode natural frequencies showed different response to the delamination.