Spallation and Dynamic Fracture as an Effect of Laser Induced Shock Waves

Abstract : A high irradiance single beam short pulsed Nd: glass laser was used to generate shock waves in 2D carbon-carbon composites. Dynamic brittle fracture at ultra high strain rate was observed as a result of reflected shock waves as tensile waves from the back surface of samples. Successive stages of damage from incipient spallation to complete sample perforation were obtained by increasing gradually the laser energy. The thermo-mechanical damage on the front surface as a result of laser interaction with the target material, and the mechanical damage at the back surface as a result of shock wave reflection were characterized by optical and scanning electron microscopy. The failure properties of the composites were related to the processing of densification and graphitization mode. Keywords: Spallation; Fracture; Composite materials; Carbon carbon composites; Laser target interactions.