Compression Load Carrying Capacity of 3D Integrated Pyramidal Knitted Composites: Experimental and Numerical Approaches

This study aims to investigate the compression behavior of newly designed 3D weft-knitted pyramidal composites. These structures consist of upper and lower surface layers interconnected by two truncated incomplete pyramids, formulated in three varied core geometries. The 3D integrated knitted samples were manufactured on an electronic flat knitting machine using E-glass yarns and were impregnated with epoxy resin using a resin transfer molding technique. A novel ABAQUS plugin has been developed to gain insight into the deformation and failure mechanisms, facilitating the prediction and enhancement of Hashin’s benchmark data. The compressive performance of the designed structures was compared with the integrated corrugated sandwich structures containing three triangular, trapezoidal, and rectangular cross-sections. The results extracted from the experiments suggest that the structural height exerts a considerable influence on the mechanical characteristics of the 3D composite structures. Consequently, the compressive strength of the specimens exhibits a notable decline as the thickness increases. Also, the geometric configuration of the interconnected layers within the reinforcement structure is pivotal in establishing the compressive attributes of these 3D knitted reinforced composites. The developed 3D knitted composites demonstrated compressive behavior similar to honeycomb sandwich panels and showed better performance than integrated corrugated sandwich panels. The enhancements observed include a 50% increase in the fiber volume fraction, a 28.66% augmentation in the maximum compressive force, a 57.90% rise in absorbed specific energy, and an 86.55% improvement in strength compared to integrated corrugated sandwich panels. Ultimately, the comparative analysis of numerical and experimental force-displacement curves elucidated that the plugin proficiently predicts the behavior of these composites with a considerable degree of accuracy.