Impact damage detection for small- and large-mass impact on CFRP and GFRP composite laminate with different striker geometry using experimental, analytical and FE methods

Small- and large-mass impacts on a CFRP and GFRP laminate composite are investigated by experimental tests as well as FE simulation and some analytical improvement technique. In the case of small mass, three different geometries including spherical, cylindrical and conical strikers with the same mass of 12 g are used in the pneumatic shooting mechanism. For the large-mass case, impact drop testing is applied using spherical, half-spherical and cylindrical strikers with the same mass of 680 g. The new contact correlation stiffness is proposed for conical and cylindrical strikers according to Hertzian contact law. The deformation time history, as well as maximum laminate deflection obtained from three strikers in both small- and large-mass cases, is compared experimentally, numerically and analytically, and a good agreement between them is found. The FE simulation with the strain criterion and surface to surf-Tied/fail contact algorithm for element erosion is applied to show the front and rear faces of the damaged laminate as well as throughout the thickness of delamination. The predicted damaged area in the FE simulations is calculated and then compared with the experimental results obtained by the ultrasonic vibrothermography technique. The results show that the surface area obtained in the FE simulation in terms of the location, shape and dimension of damage is very close to the experimental results from the vibrothermography, while the result of both methods is in a good agreement on the front and rear sides of the laminate surface.