Investigating the impact of layer thickness and print orientation on strength and structural integrity of SLA 3D printed composites

Additive manufacturing through stereolithography (SLA) offers promising capabilities for producing flexible photopolymer composites with tailored mechanical properties for advanced engineering applications. However, the influence of printing parameters and material composition on the performance of such composites remains underexplored. This study aims to evaluate the effects of layer thickness and print orientation on the mechanical and structural behavior of SLA-printed flexible composites reinforced with Kevlar fibers. Twelve composite formulations were developed using varying proportions of elastic resin (ER), standard resin (SR), and Kevlar fibers (KF). The printed samples were analyzed for tensile strength, strain, hardness, surface roughness, fiber distribution, and topographical characteristics. Among the tested formulations, sample S9 (ER: 90%, SR: 9.80%, KF: 0.20%) exhibited the highest tensile strength (7.27 MPa) and significant strain (161.60%) when printed flat at a 0.050 mm layer thickness. In contrast, pure ER (S1) demonstrated superior strain capacity (228.48%) but lower tensile strength (1.98 MPa). Hardness improved with Kevlar reinforcement, reaching up to 34.38D. Surface roughness analysis revealed the lowest values in S7 (0.49 μm, lateral orientation) and S10 (0.30 μm, flat orientation). FESEM imaging confirmed strong interlayer bonding, while topographic and particle analyses indicated enhanced particle density in S9 (0.2329 particles/mm 2 ). Fiber distribution varied significantly, with sample S11 showing the highest coverage (56.90%). These results highlight the synergistic role of SLA parameters and composite formulations in optimizing mechanical performance and structural integrity, offering valuable insights for the design of next-generation flexible materials in additive manufacturing.