High resolution ply-by-ply ultrasound imaging of impact damage in thick CFRP laminates by high-frequency acoustic microscopy

Impact behavior of the carbon fiber reinforced polymers (CFRP) is still actual issue despite long history of laminate application and investigation of impact resistance. Expansion of knowledge on fracture mechanisms in reinforced composites could be related to development of methods for composite material investigations. In this work the high-frequency (50 MHz) impulse acoustic microscopy has been proposed for visualization and investigation of microstructure damages in the volume of CFRP laminates under low-velocity impact. Short probing pulses of high-frequency focused ultrasound provide both high lateral and axial resolution in layered structures. It has been shown possibilities of the acoustic microscopy to high-resolution imaging of delamination, matrix cracking and fiber fractures through the thickness of thick laminates. Mechanisms of high-resolution acoustical image formation have been described. The results of ply-by-ply ultrasound imaging of carbon fiber reinforced laminates with [+45°/0°/−45°/90°]NS lay-up have been supplemented by impact force histories and calculated values of the energies.