Response prediction based on meso-mechanical model of graded wrinkle defects and shearography measurement

This study proposed a detection method based on shearography for the mechanical response of wrinkle defects in carbon fiber-reinforced resin polymer (CFRP). Firstly, a meso-mechanical model characterizing graded wrinkle defects was constructed. The equivalent stiffness matrix of the representative volume element containing wrinkle defects was derived using a two-step homogenization method, and the effect of graded wrinkles defects on the equivalent stiffness coefficients of laminates was analyzed. Finite element analysis was then employed to predict the mechanical response under different tensile loading conditions for various wrinkle defect parameters (such as ply sequence, wavelength λ, and amplitude A). Secondly, experimental research on wrinkle defects displacement response was conducted using shearography. Experimental results show that under tensile loading, the interference fringes are generated in the wrinkle defects region due to the gradient change in out-of-plane displacement. By processing the interference fringe images, the displacement field caused by wrinkle defects is obtained. The out-of-plane displacement values obtained from experiments match well with the finite element prediction, confirming the reliability of shearography in measuring the response of wrinkle defects in CFRP.