Critical thrust force prediction in unidirectional CFRP drilling: An analytical modeling approach

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In recent trends, unidirectional carbon fiber laminates have been extensively used in the aviation sector due to their remarkable material properties. Delamination is a major damage introduced during drilling in composite laminates. One of the prime contributing factors for delamination-induced damages is considered as the thrust force. A mathematical model is proposed using an analytical approach for accurate prediction of the thrust force for the last lamina, which experience the most damage. The linear elastic fracture mechanics (LEFM), the classical bending plate theory (CPT) and the theory of elastic behavior of composite lamina are taken into consideration for the proposed analytical model because numerical prediction greatly depends on material properties and the nature of force as well. In the current research, the mathematical equation is proposed based on assumption of combined loading of drill tip and chisel edges for the elliptical delaminated area. The Mode-I interlaminar fracture toughness of unidirectional CFRP (CTC1-FUD160/CT-E556) is experimented with as per ASTM D5528 for better experimental substantiation of the proposed model. When the outcomes of the proposed model are compared with the experiment results and available literature as well, a plausible relationship between the suggested analytical model and the experimental results is found. The result also reveals that the contribution of the drill tip is more profound than the chisel edges of drill bit in drilling operations.