Homogeneous removal of heterogeneous CFRP composite via aluminum/polyimide laminate assisted femtosecond laser processing

Carbon fiber reinforced polymer (CFRP) composed of carbon fiber and polymer matrix has been used in extensive applications due to its light weight and superior strength. However, the distinct difference in physicochemical properties between two constituents poses a significant challenge for laser homogeneous processing of heterogeneous CFRP. Herein, an aluminum/polyimide laminate is introduced onto CFRP as an assisting layer during femtosecond laser processing, which prevents CFRP from direct energy deposition of low-energy edge of the Gaussian laser. Moreover, a synergetic mechanism of horizontal heat conduction of aluminum foil and vertical heat insulation of polyimide film is proposed and confirmed through temperature measurements and simulation calculations. The heat is dissipated through the aluminum foil and obstructed by the polyimide film, alleviating the detrimental heat transfer and accumulation on CFRP. Therefore, it significantly inhibits thermal damage and entrance size expansion. Compared with traditional femtosecond laser direct processing, the maximum reduction ratio of HAZ and taper are up to 98% and 83%, respectively. High-quality CFRP homogeneous processing with an ultra-low HAZ (0.7 μm), minimal taper (0.07°) and intact smooth sidewalls can be achieved. The method shows great potential to dramatically improve processing quality and broaden applications of heterogeneous composites.