Effect of stitching angle on mechanical properties of stitched sandwich panels

Uniaxial tension, inter-laminar shear and bending behaviors of stitched sandwich panels (SSPs) are simulated using the finite-element method. The effects of stitching angle on the uniaxial tensile, bending and inter-laminar shear stiffness and the inter-laminar shear strength of the SSP are numerically analyzed by ABAQUS codes. The SSP consists of three components: upper and lower skins, heat insulation core and stitches, and it modeled as a discrete stitched three-layer structure. Representative volume element (RVE) with periodic mechanical boundary conditions is constructed. SSP specimens subjected to uniaxial tensile, bending and inter-laminar shear loadings to yield the mechanical response of the SSP. Sandwich panel specimens unstitched and the SSP specimens with six different stitching angles are numerically tested. The uniaxial tensile, bending and inter-laminar shear stiffness and inter-laminar shear strength of the SSP are then computed. The results of simulations showed that: stitches in SSP significantly improved the tensile and inter-laminar shear stiffness of the SSP, while the enhancement of bending stiffness by stitching is not much; except that, the tensile and inter-laminar shear stiffness are influenced by the stitching angle significantly and the value 45° is recommended.