Mechanism and feasibility study of low frequency vibration assisted drilling of a newly developed CFRP/Al co-cured material

Abstract

CFRP/metal co-cured structure has been increasingly applied in the aerospace industry due to its outstanding mechanical properties of high specific strength and high stiffness. Compared with the stack structure, the co-cured material of which the metal was heavily wrapped by the CFRP prepregs has better interface performance due to the absence of interface gap, being helpful to improve the bonding strength with other parts. Hole making is an inevitable manufacturing process for the assembly of co-cured material while there still exists several challenges during the drilling operation. To be specific, the hole size with low accuracy and hole morphology with severe defects are the main concerns for the manufacturers, which can be mainly attributed to the tangled chips and high cutting temperatures. To solve the aforementioned problems, the low frequency vibration assisted drilling (LFVAD) operation was performed for the newly developed CFRP/Al co-cured material in the present work. The mechanism and feasibility of controlling the machining defects via LFVAD were theoretically and experimentally explored and the influence of vibration amplitude (VA) on the cutting responses was specially studied. The results show that LFVAD can reduce the average thrust forces and drilling temperatures compared to conventional drilling while the maximum thrust force shows larger magnitude with the elevation of VA, in which the VA of ∼30 μm presents the best one. Meanwhile, LFVAD can on the one hand reduce the scratch traces on the hole wall surface owing to its superior chip breakage effect and thereby improve the drilled hole accuracy, and on the other hand shrink the lower interface damage area due to the reduction of cutting temperatures. The obtained findings of the present work indicate that the proposed LFVAD method presents great superiority for the CFRP/Al co-cured material concerning the machining responses of higher hole accuracy and lower interface damage.