Fiber-reinforced polymer (FRP) composites are widely being used for structural applications due to their attractive properties. Particularly, to fabricate complicated structures by FRP composites, joining composite structure elements through fasteners require drilled holes. More than 60% of the structural FRP components are rejected owing to poor quality of holes. The FRP composites are heterogeneous due to multi-layer architecture, multi-phase material combinations, and hybridization. Hence, while drilling the behavior of FRP composites depends on various machining and tool parameters in addition to workpiece properties. As a result of drilling, the quality of drilled holes deteriorates due to delamination, matrix crack, matrix burning, fiber pull-out, buckling, spalling, and fuzzing in the drilled hole zone. To minimize all these defects researchers tried to design material, tool and machining parameters and reported. In this paper, the authors have made an attempt to summarize up-to-date progress in structure properties and drilling study of unidirectional and bidirectional multi-layered composites, three-dimensional fabric-reinforced composite and hybrid composite and similarly, emphasize the advanced characterization techniques to investigate the drilled hole quality. In addition, cryogenic assisted drilling, lubricated drilling, and micro-drilling literatures have been discussed. Based on the literature, conclusions and future scope have been reported.

Polymer-based composite materials possess superior properties such as high strength-to-weight ratio, stiffness-to-weight ratio, and good corrosive resistance and therefore, are preferred for high-performance applications such as in the aerospace, defense, and sport goods industries. Drilling is one of the indispensable methods for building products with composite panels. Drilling tests have been conducted on glass fiber-reinforced plastic composite GFRP laminates using an instrumented CNC milling center. Machining parameters such as drill size, feed rate, and cutting speed have been observed for damage-free drilling of GFRP materials. A series of drilling experiments have been conducted on glass fiber-reinforced polyester laminates and the responses experienced such as thrust force and torque as functions of feed rate and drill size have been characterized to develop a semiempirical relationship which correlated well with an established model in terms of cutting parameters. Results indicated that experimental values correlated better with the model of thrust for 6 mm drill size than for 10 mm and torque correlated better for lower feed ranges than for the higher feed ranges.

The present study aims to improve the tensile and hardness properties of carbon fabric–reinforced epoxy composite (CFEC) by using hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS₂) fillers. Magnetic stirring and ultrasonication were used to disperse fillers in epoxy resin. CFEC, h-BN filled CFEC and MoS₂ filled CFEC fabricated as per hand layup and vacuum bag technique. The tensile strength of CFEC was remarkably improved up to 6 wt.% h-BN and MoS₂ addition separately in the resin matrix. The maximum tensile strength of 486 MPa and Young’s modulus of 44 GPa were noticed in 6 wt.% h-BN incorporated CFEC displaying 59% and 47% improvements, respectively. The maximum toughness is shown by 6 wt.% MoS₂ incorporated CFEC indicating 102% improvement. The uniformly dispersed high-performance filler in the epoxy effectively transferred stress, improving tensile properties. However, filler agglomerates, stress-raising spots, and poor filler–matrix interaction beyond 6 wt.% filler reduced the tensile property improvement. The introduction of h-BN and MoS₂ in the composite increased hardness, with 6 wt.% h-BN added CFEC recording the highest hardness denoting 23% greater than the neat CFEC.