Influence of Patch Size Design on Flexural Properties of Curved Composite Laminates With Different Stringer Heights

ABSTRACT Curved composites are widely used in aerospace applications, and the stepped‐lap repair method is a commonly employed technique for their restoration. However, research on how patch size designs affect the mechanical properties of curved structures with varying stringer heights remains scarce. In this paper, curved laminates with three stringer heights (10 mm, 15 mm, and 20 mm) and three patch size combinations ( m1 : 25.4 mm–38.1 mm–50.8 mm, m2 : 25.4 mm–44.45 mm–63.5 mm, and m3 : 25.4 mm–50.8 mm–69.85 mm) were tested under three‐point bending, complemented by numerical simulations. Results showed that the damage propagated asymmetrically in the repaired laminates with hybrid failure modes, and the parametric sensitivity was found to vary with stringer heights. Specimens with stringer heights of 10 mm and 15 mm ( h10‐CFRP and h15‐CFRP ) showed low sensitivity and high sensitivity to patch designs, respectively. h20‐CFRP was sensitive only to the non‐uniform patch size design ( m3 ), showing noticeable changes in flexural strength. The optimal repair efficiency was demonstrated by the uniform small‐step‐size patch design ( m1 ). Compared to the original undamaged specimen, the repaired specimens with the m1 patch design achieved recovery rates of 56.86%, 64.35%, and 65.44% for stringer heights of 10 mm, 15 mm, and 20 mm, respectively.