Optimizing the stress concentrations by tailoring laminate stacking sequencing and compliant fillers for superior composite T-joint performance

The structural efficiency of composite T-joints is critically dependent on the design features, which minimize the governing stress concentrations and delay failure. This study first analyzes the failure initiation mechanism, and the results show that the regions around the deltoid are the primary areas of stress concentration, resulting in filler debonding and fracture failure. The second part, through Pearson linear correlation coefficient analysis, shows that the L-rib laminate stacking sequence, filler geometry, and filler material are critical design features to delay failure. The final part includes the investigation of five different L-rib laminate stacking sequence designs, revealing that the transverse tensile stiffness (E 2 ) primarily determines the ultimate load-carrying proficiency in T-joints under tensile pull-out. Premature transverse cracking caused a 68% decrease in strength in a shear-optimized sequence with an insufficient 90° ply content. Conversely, by appropriately optimizing axial, transverse, and shear stiffnesses, a hybrid sequence with ±30° plies produced a superior failure load of 24.3 kN. Furthermore, compliant polyvinyl chloride (PVC) foam filler outperformed stiff carbon/epoxy fillers, reducing interlaminar shear stress by 94% and increasing ultimate strength by 5% by permitting efficient stress redistribution. This study provided new design principles for efficient joint manufacturing under tensile loading.