Optimization analysis for hole diameter consistency in BCF/PEEK and PEEK stacks based on a multi-scale thermo-mechanical coupled model and XGBoost algorithm

This study introduces a novel step-variable parameter optimization method to optimize drilling parameters for hole diameter consistency. First, a comprehensive multi-scale thermo-mechanical coupled finite element (FE) model was developed for drilling Braided Carbon Fiber-reinforced Polyether Ether Ketone (BCF/PEEK) and Polyether Ether Ketone (PEEK) stacks, incorporating a newly proposed modified micro-mechanics of failure criterion. Subsequently, extensive simulation datasets were leveraged to train an XGBoost model. GridSearchCV was employed for hyperparameter optimization to enable a detailed analysis of the relative importance of various process parameters in inducing stepped hole defects. Finally, a Taguchi orthogonal experimental design was implemented in variable parameter drilling experiments, experimentally validating the XGBoost optimization outcomes and conclusively determining the optimal parameter combination. The results demonstrate that the proposed multi-scale FE model accurately predicts drilling morphology and precisely quantifies thrust force and temperature field. A key finding is that the stacking sequence significantly impacts thermal deformation and hole quality: a BCF/PEEK→PEEK sequence reduces thermal deformation and enhances hole diameter consistency. Specifically, the identified optimal parameters are a step position of −0.5 mm, a spindle speed of 2000 r/min and a feed rate of 40 mm/min for BCF/PEEK, and a spindle speed of 5000 r/min and a feed rate of 30 mm/min for PEEK. Experimental validation confirmed that this optimized parameter set successfully controls the hole diameter difference within 0.02 mm, achieving a remarkable improvement in hole diameter consistency.