Abstract: In order to investigate the injection process of stitched foam sandwich composites, the permeability of foam sandwich fiber layer and core layer holes were measured based on Darcy’s law, and the equivalent model of foam sandwich was established. Composite materials were prepared by vacuum-assisted resin transfer molding (VARTM) process. The effects of stitch density and injection method on the permeability and filling process of stitched foam sandwich composites were systematically investigated. The results show that compared to the unstitched fabric, when stitched at a density of 8 mm×8 mm, the permeability of the fiber layer stitched fabric along the stitch direction increase by a maximum of 104.9%. When stitched at a density of 4 mm×4 mm, the permeability along the carbon fiber axis reaches its maximum value of 9.6×10^-11m², which increases by 546.0% compared to the unstitched fabric. This indicates that the introduction of stitch can effectively improve the permeability of the fabric. The efficiency of long edge injection is the highest, with a simulated injection time and actual error of 13.4%. With the increase of stitch density, the injection time of stitched foam sandwich composites increases firstly and then decreases, which may be the reason that the injection direction is in the same direction as the carbon fiber axis.

Key words: stitched foam sandwich, stitch density, composites, permeability, molding simulation