Fabrication and characterization of spicule-inspired composites using stereolithography technique

The hierarchical architectures found in biological systems provide a powerful blueprint for designing fracture-resistant brittle materials. This study aimed to fabricate and characterize spicule-inspired composites composed of rigid resin cylinders combined with various adhesive interlayers. The tereolithography technique was used to produce the cylinders, followed by vacuum-assisted infiltration of an adhesive between the layers. Nested cylindrical structures (NCSs) with varying rigid resin layer thicknesses (0.5, 1.0, 1.3 mm) and inter-cylinder spacings (0.05, 0.1, 0.15 mm) were fabricated and infiltrated with different organic adhesives. The results demonstrated that a geometry of 0.5 mm layer thickness and 0.15 mm spacing, combined with Titebond adhesive (sample S0.5t-3-T), yielded a significant improvement in mechanical properties. S0.5t-3-T achieved maximum flexural strength and modulus of 55.49 ± 4.46 MPa, and 2.2 ± 0.12 GPa, respectively, compared with 27.05 ± 3.45 MPa, and 0.8 ± 0.1 GPa for the unfilled S0.5t-3. Increasing cylinder thickness from 0.5 mm to 1.3 mm further enhanced performance, with the S1.3t-3-T sample achieving a maximum flexural strength of 118.13 ± 11.34 MPa and modulus of 3.48 ± 0.21 GPa. Microscopic analysis and fractography identified asperity interlocking, surface waviness, and organic layer stretching as the primary toughening mechanisms. These findings provide specific geometric and interfacial design windows for bioinspired brittle composites, promoting translation of natural spicule structures into high-performance engineering materials.