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Carbon Fiber Reinforced Plastics (CFRPs) are widely used in aerospace, automotive and other transportation industries because of their excellent material and mechanical properties. Nevertheless, up to now, drilling is still regarded as the most important process in the machining of CFRPs, and the delamination is one of the most challenging damage in drilling process. In this concern, we propose and implement a bi-directional drilling method for CFRPs hole-making. In this paper, the exit delamination formation mechanism was firstly analyzed to clarify the effect of bi-directional drilling on delamination suppression. The critical thrust force was calculated by considering both conventional and bi-directional drilling conditions. Based on the model, it can find that bi-directional drilling process itself can provide support without employing any extra facility. Finally, experimental validation indicates that the calculated critical thrust force showed a reasonable agreement with the experimental results based on conventional and bi-directional drilling. The hole exit delamination damage under the bi-directional drilling reaches the desired suppression effect with a reduction of 11.3%–27.9% compared to conventional drilling based on experiment results. Through an in-depth understanding of critical thrust force, the findings of this paper not only provide a new processing technology for drilling CFRPs, but also open a new avenue to improve the quality of drilling CFRPs by reducing delamination. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastics (CFRPs) are employed in many industrial applications because of their attractive mechanical and structural properties. However, to date, drilling is still considered as the most pivotal process in manufacturing/assembly of CFRPs components, and the delamination damage can be regarded as the most severe machining-induced issue in the drilling process. To solve this problem, a delamination prediction model for CFRPs using Ultrasonic Vibration Assisted Drilling (UVAD) with the abrasive diamond hole saw or core drill is proposed to calculate delamination factor and thickness. The approach of the modeling development starts from simplified for tool and CFRPs workpiece, calculating the total cutting force and the critical thrust force, respectively, and adopting maximum nominal stress criterion to predict delamination. Experimental validation has indicated that the calculated results showed a reasonable agreement with the experimental results on the basis of both delamination factor and thickness, proving the feasibility and the accuracy of the model. This work provides an important reference for selecting and optimizing the drilling parameters to enable delamination-free holes on CFRPs composite. [ABSTRACT FROM AUTHOR]

Introducing small-sized functional features such as anti-drag and anti-icing micro structures on Carbon Fibre Reinforced Plastics (CFRPs) is challenging but a still unmet demand. Existing contact CFRP machining solutions may bring unavoidable tool wear and surface defects. Non-contact approaches may introduce significant thermal damage (laser), inconsistent features (waterjet), and limited achievable micro structure shapes and sizes (die sinking Electrical Discharge Machining). Wire Electrical Discharge Machining (WEDM) has the potential to overcome the mentioned limitations. Both theoretical thermal calculation and experimental demonstration in our work, however, showed that conventional WEDM was not working well. Here we propose and implement a Preheating Assisted Wire EDM (PAWEDM) to cut CFRPs. Machining anisotropy in terms of kerf geometry and morphology at the cut entries, ends, and edges was studied carefully. Discussions on the anisotropy principle, the influence of carbon fibre and epoxy resin, and the minimum achievable feature were also provided. PAWEDM is an entirely new CFRP cutting method and effective to enhance CFRP performances by creating micro functional and structural features on CFRP products. [ABSTRACT FROM AUTHOR]