Effect of laser irradiation time on the surface characteristics of a carbon fiber composite

Owing to their unique physical and mechanical properties, carbon fiber reinforced plastics (CFRPs) are finding wide applications in a variety of industries. This broad application necessitates a consideration of the material response in nontraditional environments to evaluate their overall reliability. In the current study, we investigate the time-dependent behavior of unidirectional [0°]6 CFRPs irradiated by a short pulse Nd:YVO4 near-infrared laser for durations ranging between 100 and 500 ms. Post irradiation, the damage on the surface was characterized using optical and electron microscopy as well as optical surface profilometry. Qualitatively, the heat-affected zone (HAZ) was found to primarily consist of an out-of-plane expansion and anisotropic matrix removal with no structural damage to the fibers. The growth in HAZ size is conduction dependent and has a rapid trajectory along the fiber direction and a subdued trajectory along the transverse direction. Further evaluation of the subsurface via x-ray micro-CT showed the HAZ to be surface localized. An analytical heat conduction approach was also used to understand the evolution of surface HAZ with exposure time. This simplified approach was found to adequately capture the shape and growth of the HAZ.