Heat partition in edge trimming of glass fiber reinforced polymer (GFRP) composites

Thermal loading of fiber reinforced composites during traditional machining is inevitable. This is due to the fact that most of the mechanical energy utilized in material removal is converted into heat, which is subsequently dissipated into the workpiece, the cutter and is carried away by the chips. Heat conduction into the workpiece might cause thermal damage if the generated temperatures exceeded the glass transition temperature of the epoxy matrix. In this work, the amount of heat flux applied to the machined edge and the temperature distribution in a multidirectional GFRP composite laminate was determined using an inverse heat conduction method. The spindle electric power, cutting forces and boundary temperatures on the workpiece were measured during edge trimming of the GFRP laminate with a PCD cutter at different spindle and feed speeds. The transient heat conduction problem in the laminate was simulated using the finite element method and the amount of heat flux conducted through the machined surface was determined. It was found that the heat flux conducted to the workpiece represented only a small fraction of the total heat and is more influenced by the feed speed than the spindle speed. The temperature of the machined surface was found to be lower than the glass transition temperature of epoxy for all cutting conditions tried in this study.