Abstract
Delamination associated with drilling fiber-reinforced composite materials can often be the limiting factor in the use of composite materials for structural applications. It results in reducing the structural strength, poor assembly tolerance and, hence, it has the potential for long-term performance deterioration. Two mechanisms of delamination associated with drilling FRP composites are known as peel-up at the drill entrance and push-out at the drill exit. The key for reducing the delamination in drilling polymeric composite laminates lies in reducing the thrust force associated with drilling process. The heat generated in drilling polymeric composite materials assisted by a low coefficient of thermal conduction and a low transition temperature of plastics result in thermal damage. The ways in which the temperature can be observed and the form in which the thermal damage occurs remain problems to be solved.
The present review article addressed the factors affecting the thrust force and delamination onset, delamination mechanisms, and delamination measurement and assessment. Special interest was given to report. the different techniques that assist delamination-free in drilling polymeric composites. These techniques include; the proper selections of tool geometry and drilling parameters, variable feed technique, pre-machining techniques such as step drill and pilot hole, and back support. Saw, candle stick, and core drills are special types that can be used to distribute the thrust force toward the drill periphery rather than concentrated at hole center (twist drill). These drills can be operated at larger feed rate without delamination damage compared to the twist drill.