Carbon fiber reinforced polymer (CFRP)/titanium alloy (Ti) stacks have become a research focus in aerospace and advanced manufacturing due to their superior integrated properties. However, interfacial characteristics and interlayer gaps critically influence cutting forces and hole-making quality. So, a cutting simulation model for CFRP/Ti stacks with interlayer gaps is established, the cutting force variation with interlayer gaps during milling and the mechanistic role in interfacial defect formation are deciphered through multiscale simulations. In addition, the correctness of the simulated model is verified by helical milling experiments, and the influence of machined surface quality under different clearance conditions is also evaluated. The results reveal a four-stage nonlinear evolution pattern of interfacial cutting forces during helical milling of CFRP/Ti stacks with gaps. Further investigation indicates that this nonlinear evolution pattern results in the development of localized damage evolution regions adjacent to interlayer gaps in CFRP composites, especially. A characteristic stepped distribution pattern is observed in both hole-wall topography and burr dimensions within the affected zones.

Investigation on cutting forces and damage evolution in helical milling of CFRPTi stacks with interlayer gaps
    Abstract
    1 Introduction
    2 Simulation of orthogonal cutting for stacked structures
        2.1 CFRPTi alloy stacked materials
        2.2 Orthogonal cutting models
        2.3 Damage model
            2.3.1 Carbon fiber damage model
            2.3.2 Epoxy matrix damage model
            2.3.3 Ti alloy micromechanical model
        2.4 Cutting force simulation analysis
    3 Helical milling experiment
        3.1 Experimental design
        3.2 Cutting parameters
        3.3 Cutting force analysis
    4 Results and discussion
        4.1 Comparison and validation of cutting forces
        4.2 Damage evolution influenced by interlayer gap
        4.3 Machining defects and surface morphology
            4.3.1 CFRP cutting and morphology analysis
            4.3.2 Effect of gap width on cutting quality
    5 Conclusions
    Acknowledgements 
    References

• Haiyan Wang(School of Control Engineering, Northeastern University at Qinhuangdao, Qinhuangdao 066004, Hebei Province, China) Corresponding author
• Kun Duan(School of Control Engineering, Northeastern University at Qinhuangdao, Qinhuangdao 066004, Hebei Province, China)
• Jianglong Zhang(School of Control Engineering, Northeastern University at Qinhuangdao, Qinhuangdao 066004, Hebei Province, China)
• Siyi Pan(School of Control Engineering, Northeastern University at Qinhuangdao, Qinhuangdao 066004, Hebei Province, China)