PREDICTION OF EXTENT OF HEAT-AFFECTED ZONE IN LASER GROOVING OF UNIDIRECTIONAL FIBER-REINFORCED PLASTICS

Laser has been widely used in various industrial applications includin g machining. However, in Shaping operation of composite material after curing, thermal damage associated with laser energy can be produced. It leads to poor assembly tolerance and long-term performance deterior ation. The current research investigates the anisotropic formation of the heat affected zone (HAZ) in unidirectional fiber-reinforced plasti cs induced by laser grooving. Preliminary analytical and experimental analysis reveal that the laser energy per unit length and fiber orient ation-dependent thermal conductivity primarily determine the induced t hermal damage. The extent of HAZ is estimated by the isotherm of the m atrix char temperature. Heat conduction is maximum along the fibers, a nd the HAZ shape is thus affected by the beam scanning direction relat ive to fiber orientation. The study investigates the grooving of lamin ated unidirectional carbon/epoxy, which demonstrates clear thermal dam age in 90 degree (i.e., perpendicular grooving), 60 degree, 30 degree, and 0 degree (i.e., parallel grooving) relative to the fiber axis. A theoretical analysis based on moving point heat source is adopted to d etermine the extent of thermal damage in correlation with process para meters and material properties. Mirror Image Method is used for specim en of finite thickness. Considerations of temperature-dependence of th ermal conductivity and the emmerged heat source further improve the pr ediction of HAZ. While HAZ in grooving along the principal material ax es can be solved analytically, conductivity ellipsoid and finite diffe rence can calculate the extent of HAZ induced by grooving in any direc tion relative to fiber axis.