Effects of drilling area temperature on drilling of carbon fiber reinforced polymer composites due to temperature-dependent properties

The aim of this study was to investigate the influence of drilling area temperature on the material properties and quality of machined carbon fiber reinforced polymer (CFRP) composites. For this purpose, an epoxy resin matrix CFRP composite was chosen and tested under carefully designed temperature-controlled drilling experiments using a climatic chamber. The results show that the optimal range of drilling area temperatures is lower than the lower limit of the glass transition zone temperature (T₀) of the CFRP composite and higher than the upper limit for brittle deformation (T_b) of the resin. The reason for this is that when the drilling area temperature is higher than T₀, the interfacial shear strength (IFSS) and anti-deformation capacity of the CFRP composite are poor, which leads to surface roughness and a large amount of exit delamination damage. For drilling area temperatures lower than T_b, the CFRP becomes more brittle leading to a substantial increase in drilling thrust force, thereby increasing the probability of exit delamination damage. By solely maintaining the drilling area temperature between T₀ and T_b, the interlaminar fracture toughness, anti-deformation capacity, and IFSS of the composite can be increased, thereby decreasing the probability of drilling damage.