2D bio-inspired reinforcement mesh for toughening composite bonded joints
Effect of orientation and adhesion patterning
Zhiyuan Xu (CCCC Guangdong-Hong Kong-Macao Greater Bay Area Innovation Research Institute)
Ran Tao (TU Delft - Aerospace Engineering)
Sofia Teixeira de Freitas (TU Delft - Aerospace Engineering, Universidade de Lisbon)
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Abstract
Inspired by the sacrificial bonds and hidden lengths mechanism found on the molecular structure of spider silk, this study investigates a bio-inspired overlapping curl (OC) 2D-mesh fabricated via 3D-printing and integrated into the adhesive layer as a reinforcement architecture. Mode I double cantilever beam tests were conducted to investigate the effects of mesh orientation (0° and 45°) and adhesion patterning on crack propagation and fracture toughening. The results show that the 2D-OC mesh itself effectively activates extensive filament bridging, leading to an apparent energy release rate (ERR) enhancement up to 47 %. In contrast, adhesion patterning partially suppresses bridging. X-ray computed tomography and fracture surface analyses further reveal that reinforcement orientation governs crack front evolution and bridging activation. In particular, the 45°-oriented mesh induces a zig-zag crack front that promotes crack deflection and bifurcation, thereby activating more bridging filaments than the 0°-oriented configuration. Based on these observations, a coupled toughening framework is established, linking the apparent ERR enhancement to the combined effects of adhesion patterning width, reinforcement orientation, bridging activation, and filament material behavior. The findings provide mechanistic insight into crack–reinforcement interactions and offer design guidelines for architected bio-inspired reinforcements in adhesively bonded composite structures.
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