Statistical evaluation and regression modeling of strength recovery in scarf-repaired composite laminates

Scarf repair is one of the most effective bonded repair techniques for damaged composite laminates because it can achieve high strength recovery while minimizing stress concentration. In this study, the influence of scarf geometry on the tensile behavior and strength recovery rate (SRR) of scarf-repaired composite laminates was investigated using a statistically supported approach. Experimental tensile-test data corresponding to scarf ratios of 1/10, 1/20, and 1/30, together with defect sizes of 6 mm and 12 mm, were analyzed using two-way analysis of variance (ANOVA) to evaluate the significance of geometric parameters on SRR. The results showed that scarf ratio is the dominant factor affecting repair performance (p<0.001), whereas defect size and interaction effects are statistically insignificant within the investigated range. The SRR increased significantly from approximately 51.0–52.9% at a scarf ratio of 1/10 to approximately 79.2–82.0% at scarf ratios of 1/20 and 1/30. An exponential decay relationship between SRR and scarf angle was established using nonlinear regression analysis (R2=0.898). Additional experimental results at a scarf ratio of 1/5 exhibited a noticeable deviation from the model prediction, indicating a transition in the dominant failure mechanism at relatively large scarf angles. The findings provide a statistically supported framework for evaluating scarf repair configurations and balancing mechanical efficiency with repair manufacturability.