Multi-Cellular 3D Flat-Knitted Composite Panels Strengthened by PU-Foam: Manufacturing, Testing and Simulating

Composite panels made-up of multi-cellular 3D flat-knitted (M3DFK) fabrics were manufactured in this research and mechanically evaluated in order to analyze their bending functionality after being filled with polyurethane (PU) foam. Using an electronic flat knitting machine, two different groups of M3DFK fabrics varied in their cross-sectional shapes were initially prepared from glass/polyester yarns and then, being molded through vacuum injection method with epoxy resin. A three-point bending test was used to experimentally evaluate the mechanical performance of PU-foam filled composite panels. Also, the composites mechanical behaviors were theoretically investigated using the multi-scale modeling method. The results indicated that the reinforcement structural geometries and foam presence in the composite specimens have a significant impact on their bending properties. The empirical findings revealed that foam injection resulted in a 113.8% and 92.3% increase in energy absorption for double- and single-decker composite structures during the bending process, respectively. According to the results, foam-filled composite structures experience a significant increase in core shear and facing stresses. This increase amounts to 18.4% for the single-decker and 84.7% for the double-decker 3D structure. The results of the simulation method were used to understand the effect of composite structure as well as foam injection on the stress distribution and maximum stress applied during the bending process. Also, no delamination between foam and facing layers was observed.