Mechanism of damage to polymers by pulse-periodic CO2 laser radiation

An investigation was made of the laws governing the formation of a crater having a high "keyhole- penetration" parameter in a specimen of poly methylmethacry late under the action of pulseperiodic CO₂ laser radiation. It was found that an important part is played in this process by the absorption of the incident radiation in the gaseous phase and also by the excitation of forced acoustic standing vibrations within the crater cavity. The acoustic flow patterns increase the heat flux to the walls of the cavity and produce locally broadened regions. These processes limit the feasibility of attaining high values of the depth-to-diameter ratio of the crater.