Study On Preparation And Mechanical Property Of Stitched Foam Sandwich Structure Composites Based On VARTM Process

Compared with other materials, stitched foam sandwich structure composites have high specific stiffness and strength, the whole performance of the composites is high-strength and lightweight. Therefore, this composite has been increasingly used in all fields, especially in the aerospace and civil engineering. As an advanced composite material, it solves the shortcoming of poor performance in the thickness direction.It largely played out the superiority of the sandwich structure. By joining the stitches in the thickness direction, the performance of a sandwich structure has been changed, which greatly improves the mechanical performance of composites under external load. This advancement has drawn more and more researchers' attention. Due to the expensive raw materials, meticulous preparation step range and high research costs. Therefore, most studies and experiments of the composites are carried out on the mechanical propertiesHow to prepare the stitched foam sandwich structure composites reasonably and effectively, how to give the optimal combination on the main parameters.We can obtain the strongest combination of mechanical properties under certain indicators of the mechanical properties, It has a very important academic significance and provide a reference for the application. This article uses glass fiber for the panel, PU foam core material and unsaturated polyester resin as raw materials,adopting kevlar stitching suture, and finally through VARTM technology prepare the stitching foam sandwich composites.The main work of this article are based on the preparation and the mechanical property of stitched foam sandwich structure composites.On the basis of self-designed fixture, to arrange a combination of parameters by orthogonal design method. The main parameters are the suture needle distance, line spacing and fiber layers. Furthermore, the principles of each test mechanical properties, test procedures, test results, load displacement curve and test analysis are discussed in detail. The low-velocity impact testing is used to measure the composites to resist the impact of dynamic load performance. In this test, the load-time-energy curve and the load- displacement-energy curve are obtained.The impact energy of 60J is used to complete the test, According to the curve, the failure causes are analyzed.The destruction process is divided into three periods:the first period is the damage on the panel, and the second period is the destruction of the foam, and the third period is the back panel damage. Through software Mini tab 16.0, the effects of the orthogonal analysis on impact property were investigated. Using the maximum impact force as evaluating criterion, we drew the following conclusion:when the suture needle distance of 10mm, spacing of 20mm,9 layers of glass fiber, the mechanical properties of the composite panels stitched optimal impact. In the three-point bending test, through the load-displacement curves, we can analyze force-loading status of the material and finding a position that the composite is fisrt destroyed. With data obtained from the bending and the spring back of the bending have been discussed. Finally,through orthogonal analysis, using the flexural strength as evaluating criterion, We obtain the best combination of the parameters:the suture needle distance of 8mm, spacing of 10mm,9 layers of glass fiber. In the flatwise compression test, the load-displacement curve are obtained. This article analyzed the load pattern and the damage model, We calculated flatwise compression strength and modulus. Finally, through the orthogonal analysis, using the flatwise compression strength as evaluating criterion, we obtain the best combination of the parameters:the suture needle distance of 8mm, spacing of 10mm,9 layers of glass fiber.In the longitudinal compression test, the load-displacement curve are obtained, This article analyzed the the curve, there are three main damage models:(1)a flexural damage of the panel; (2)the fracture of the stitching resin column; (3)foam swell and extrusion. We calculated longitudinal compressive strength and modulus. Finally,through the orthogonal analysis, using the longitudinal compressive strength as evaluating criterion, we obtain the best combination of the parameters,:sture needle distance of 10mm, spacing of 10mm,9 layers of glass fiber.In this article, we discussed the stitching parameters on the mechanical properties,via the four mechanical tests, Obtained the optimal parameter combinations. The studies have shown that this material has a high anti-impact performance, anti-bending performance, anti-flatwise compression performance and anti-longitudinal compression performance. At the same time, we draw some valuable conclusions. The current work has laid a strong foundation for the following research on the stitched foam sandwich structure composite.