Wrinkle detection in carbon and glass fibre laminates using ultrasonic non-destructive evaluation

Abstract

Wrinkles (out-of-plane fiber waviness) are, unfortunately, a common phenomenon during the manufacture of composite materials. Because these internal defects affect the mechanical properties, all composite structures are inspected in order to ensure they meet the high quality standards that are demanded by the industry. During the desing process, parts are generaly oversized to mitigate the risk of undetected wrinkles and defects. Delaminations are widely characterized using traditional ultrasound techniques whereas  wrinkles have traditionally been more difficult to detect using such techniques. This is due to the fact that wrinkles don’t represent a change in material density or a strong boundary for the elastic wave. The aim of this work is to detect and characterize wrinkles in thick laminates of composite material using ultrasonic non-destructive tests. Different parts with induced wrinkles have been inspected with ultrasonic techniques. The ideal frequency to perform the inspections was determined using an analytical model in MATLAB. The amplitude of the wrinkles was measured visually on the samples and compared with compared with the ultrasonic measurements to determine the accuracy of the proposed method.

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