Damage Detection in z-Fiber Reinforced, Co-Cured Composite Pi-Joint Using Pitch-Catch Ultrasonic Analysis and Scanning Laser Vibrometry

Abstract

Damage detection in constrained geometry structures like z-pinned, co-cured composite pi-joints is established using pitch-catch ultrasound and scan- ning laser vibrometry measurements. Ultrasonic pitch-catch measurements con- sisted of a network of PZT (Lead Zirconate Titanate) sensors placed on the spec- imen and sensing Lamb waves at each sensor location, where measurements were taken at symmetric top and bottom sensor locations for healthy and damaged pi- joint specimens. Results showed the presence of fatigue-induced bend damage of the joint as a reduced peak-to-peak amplitude response across the joint. Scan- ning laser vibrometry measurements were used to study the propagation of Lamb waves within the narrow, constrained geometry pi-joint structure, where the reflec- tion and superposition of propagating Lamb waves was studied using time-resolved image analysis. The presence of delamination and hidden damage was visualized as changes in the propagating Lamb wave characteristics, where a reduction in propagating energy levels and dispersive wave characteristics were observed due to delamination and thinning of the composite plies.