Lamb Wave Evaluation of the Effects of Thermal-Mechanical Aging on Composite Stiffness

Lamb wave methods offer a promising approach for evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. In this work, studies have been conducted which examine the effects of combined thermal and mechanical aging in thermoplastic composite samples using symmetric mode Lamb wave velocity measurements. From the velocity measurements, the in-plane stiffnesses, A11 and A22, are calculated. The samples examined include a baseline specimen with 0 hours, specimens which have been aged 3,500 and 5,000 hours, and one specimen with 1,000 hours of accelerated aging. The results of the Lamb wave measurements are compared to C-scans of the panels.