Pulsed laser damage threshold evaluation of a carbon fiber composite skin and its effects on internal substrates

Abstract

Carbon fiber reinforced plastics (CFRP) have machinability issues, even using high quality laser beams. Since CFRP composes the skin of many aerial equipments, its damage threshold must be assessed in order to consider the vulnerability to laser weapons. This work uses an infrared Yb:fiber laser beam with a quality (M2) of nine in three power levels 400, 700 or 1000 W. The CFRP damage threshold for a focused laser beam was 0.8 J, which is sufficient to create a 0.1 mm hole in the 1 mm plate skin. When the incident energy exceeds 4 J the entire beam pass through the hole and damage the internal substrate. The simulated internal structure is a plate of glass fiber-epoxy composite (GFRP) coated with copper (Cu-GFE). The ablation threshold for the composite was 3.3 J and the board was perforated when the energy is higher than 20 J. If the Cu-layer faced the incident beam the damage threshold was 2 J. According to the analyses, the Cu-coated substrate was more susceptible to ablation because of the explosive boiling at the interface between Cu and the composite. The current results show a relatively cheap fiber laser could be used as a directional energy weapon as long as fine focusing and residence time could be assured.