Impact damage assessment in patch‐repaired carbon fiber‐reinforced polymer laminates using the nonlinear Lamb wave‐mixing technique

Abstract

AbstractThis study investigates assessment of the barely visible impact damage (BVID) caused by low‐velocity impact (LVI) in single‐sided patch‐repaired orthotropic carbon fiber‐reinforced polymer (CFRP) laminates using experimental and numerical nonlinear Lamb wave‐mixing techniques. An accurate finite element method (FEM) approach consisting of three analysis steps of LVI, vibration damping, and nonlinear ultrasonic mixing detection is proposed to predict the relationship between LVI damage and nonlinear Lamb wave‐mixing propagation. The LVI step in the FEM simulation is verified by drop‐weight impact tests, and the nonlinear Lamb wave‐mixing detection step in FEM is verified by comparing with the RITEC RAM‐5000 SNAP nonlinear mixing detection system. The BVID of patch‐repaired specimens is assessed with mixing relative acoustic nonlinearity parameters (MRANPs). CFRP laminates repaired with various external patch parameters of different sizes, numbers of layers and stacking sequences are evaluated by the FEM approach. Finally, an optimized patch design in which the MRANPs are the smallest is determined. Therefore, the CFRP laminate containing a hole is recommended to be repaired with a circular three‐layer patch with a radius of 2.5 r and a stacking sequence of [90/90/90].