Mechanically Tailored Anisotropic Structures Using 3D Printed Core-Shell Soft Material Polymer Composites

Additive manufacturing of soft material composites holds great potential for advancing soft robotics, offering precise control over flexibility, customization, and adaptability in dynamic environments. Among various techniques, material extrusion stands out as a cost-effective, rapid prototyping method capable of tailoring mechanical properties. However, common challenges such as buckling, stringing, and surface defects must be addressed to enhance performance. We utilize ABS+TPE core-shell composites to tackle these issues, focusing on how variations in core-shell volume fractions influence mechanical tunability. We investigate the effects of raster orientation and core-shell ratio on controlled mechanical anisotropy in 3D-printed structures. Our findings indicate that a 0° raster orientation results in stiffer parts, whereas a 90° orientation yields more flexible structures, dictated by the inter-layer interfaces and raster contact area. At a 0° orientation, stress distribution is observed across the bulk material, while a 90° orientation confines stress within individual rasters, influencing the failure behavior. By adjusting ABS content and raster orientation, we achieve a broad range of tensile modulus (2242.58 MPa to 55.68 MPa) and strength (35.91 MPa to 6.90 MPa), and flexural modulus (2609.15 MPa to 48.75 MPa) and strength (75.16 MPa to 17.67 MPa). Furthermore, both symmetric and asymmetric layup structures demonstrate how raster orientation impacts bending performance, resulting in distinctly anisotropic behaviors under load. The localized orientation of rasters drives selective bending within the same layer. Through analytical and numerical modeling, we conduct homogenization of microstructural unit cells and simulate composite laminate behavior, finding good agreement with experimental results within the linear elastic range. Finite element modeling predicts asymmetric bending behavior due to local nonlinearity in the TPE material. Our findings offer valuable insights for designing soft materials in additive manufacturing, presenting pathways to optimize mechanical performance for soft robotics through precise control of raster orientation and core-shell composition.