High-quality 3D printing of ethylene vinyl acetate with direct pellet-based FDM for medical applications: Mechanical analysis, energy absorption and recovery evaluation

Abstract

Ethylene Vinyl Acetate (EVA) is a biocompatible and non-toxic copolymer known for its applications in medicine, drug delivery systems, and energy absorption. This paper presents a novel method for 3D printing EVA using the Fused Deposition Modeling (FDM) technique. By directly utilizing pellet-form EVA material and employing pneumatic pressure for extrusion, we addressed the issue of filament buckling commonly encountered in traditional filament-based printing. A custom-made pellet printer enabled direct feeding of polymer pellets. The mechanical properties, microstructure of the printed EVA parts was analyzed to evaluate the suitability of the direct pellet printing technique for producing high-quality EVA components. The results showed acceptable printing quality and favorable mechanical properties (about 1000% elongation at break and 6.59 MPa tensile strength). Additionally, a cyclic compression test was conducted, subjecting specimens to various strains (30%,80% and 120%) and assessing their compressive and energy absorption properties undergoing significant deformations. Observations reveal a noticeable decline in the mechanical properties after the first compression cycle. The mechanical properties tend to stabilize and reach a steady state from the second cycle onwards until the sixth cycle. Furthermore, a compression cyclic test with various strain rates conducted, investigated the functional performance of the printed EVA components in engineering and biomedical applications, considering the impact of strain rate. Observations indicate that lower strain rates tend to enhance the material's ability to withstand deformation before yielding. This study contributes to expanding the potential of EVA in additive manufacturing, particularly in biomedical and energy absorption systems.