Incremental drilling method for measuring and analyzing residual stress in multi‐layered L ‐shaped carbon fiber laminates

Abstract Carbon fiber reinforced polymer (CFRP) components are widely used in aerospace, nuclear, and automotive industries due to their excellent mechanical properties. Residual stresses in CFRP affect manufacturing optimization and product lifespan, but precise measurement is challenging. This study applies the incremental hole drilling (IHD) method to L‐shaped CFRP laminates with different stacking sequences. Eight‐step drilling experiments were conducted in critical regions, comparing experimental results with predictions from Classical Laminate Theory (CLT). The results demonstrate that experimental values exhibit better agreement with CLT predictions during the initial drilling stages, indicating that the IHD method provides accurate data for shallow‐depth measurements. The stacking sequence [±45, (0/90), ±45, (0/90)]3s in L‐shaped laminates effectively minimizes interlaminar stresses. Notably, stress concentrations were significantly higher in the fillet region due to curvature effects, particularly in deeper layers. Proper design of stacking sequences and geometric configurations can substantially mitigate these stresses, thereby enhancing the overall performance and lifespan of composite components. Highlights The IHD method provides sufficiently accurate data for low‐layer drilling. Quantitative analysis of the mechanical mechanism in L‐shaped laminates. The L‐shaped laminate with [±45, (0/90), ±45, (0/90)]3s shows minimal interlaminar stress. Fillet region residual stress in L‐shaped laminates exceeds planar areas, notably at depth.