Study On Manufacture And Mechanical Performance Of Stitchcd Foam Core Sandwich Structure Composite

Because of the poor structural bearing capacity and the low interface strength of foam sandwich composites,the application of foam sandwich composites is limited.Therefore,the mechanical properties of stitch-reinforced foam core sandwich structure composites are studied in this paper.Although early researchers have studied in stitch-reinforced foam core sandwich structure composites to some extent,but the method of stitch is man-made operation,which not only has the low production efficiency,but man-made operation also will make stitched yarn and panel fiber cloth produce more damage that decrease the mechanical properties of the composites.Aiming at this problem,the stitched foam core sandwich structure preforms were prepared by continuous stitched machine,and the structural parameters of the preform were designed.The vacuum infusion molding process(VIMP)was used to integrate the stitch-reinforced foam core sandwich composites,and the influence of form of panel and stitched parameters on the mechanical properties was been studied,the main work is as follows:Firstly,three-point bending test was conducted to study the influence of form of panel and stitched parameters on its bending performance.The results show that the breaking load and bending stiffness of the structure increase with the increase of the number of layers of the panel and the yarn density,and decreases with the increase of the stitched angle and the stitched step length.Compared with the unstitched structure,stitching can significantly improve the bending performance of the structure,the bending stiffness of the structure increased by 10 times and the breaking load increased by 13 times largest.Secondly,the flat compression test was conducted to study the influence of form of panel and stitched parameters on its flat compression performance.The results show that the compressive strength and compressive modulus of the structure increase greatly when the number of fiber layers increases from one layer to two layers.The compression strength and compressive modulus increase with the increase of the stitched angle and the yarn density,and the compressive strength and compressive modulus increase with the decrease of the stitched step length.Compared with the unstitched structure,the stitched can significantly improve the sandwich structure of the compression properties,the compression strength and compression modulus increased by 26 times and 15 times largest.Finally,the test was conducted to study the influence of form of panel and suture parameters on its in-plane compression properties.The results show that both the in-plane compressive strength and the in-plane compressive modulus increase with the increase of the number of fiber layers and the yarn density.The in-plane compressive strength increases and then decreases with the increase of the stitched angle,and the in-plane compressive strength decreases with the increase of the stitched step length.Compared with the unstitched structure,the fiber columns introduced by stitch can increase the in-plane compressive strength and the in-plane compression modulus of the sandwich structure to some extent,but the damage caused by stitching to the panel fiber reduces the in-plane performance of the panel,which decrease the in-plane properties of the foam core sandwich composite.So the in-plane performance of the stitched structure depends on the ratio of the reinforcing effect to the weakening effect which caused by stitching.