Design, Manufacture And Mechanical Performance Of 3D Integrated Composite Sandwich Structures

Composite sandwich structures have been widely used to manufacture the accessorial components of locomotives due to their excellent mechanical properties, such as high strength and low weight, excellent thermal insulation and acoustic damping. However, the primary shortcomings of traditional foam core sandwich structures are low load bearing capacity, the weaker interface berween facesheets and core, low core strength, which limit their applications on the structural components suffering the main loads. To overcome these shortcomings, in the present paper, a new sandwich structure, namely three dimention (3D) integrated composite sandwich structure, is advanced. And studies on the new sandwich structure are conducted.Firstly, different configurations of 3D integrated composite sandwich structure are designed. The preform is manufactured by stitching process using continous fibers. And the 3D integrated composite sandwich structure samples are manufactured by Vacuum Infusion Molding Process (VIMP). While infusing resins, the facesheets and composite columns, which are obtained in the foam core, are wetted and cured together. And the surface mass of samples is good.Secondly, flatwise compressive tests were carried out in order to investigate raw materials and structural parameters on compressive properties effect of samples. The results indicate that: first, compressive properties of 3D integrated composite sandwich structures are obviously better than traditional sandwich structures. Second, while the matrix material is epoxy resin (EP), compressive properties and specific properties, which is defined as the ratio of mechanical property to density of sample, are better than those, in which matrix material is unsaturated polyester resin (UP). And while the reinforcement is carbon fiber (CF), compressive properties and specific properties are better than those, in which reinforcement is glass fiber (GF). Third, while the core is polymethacrylimide (PMI) foam, compressive properties and specific properties of sample are the best. Forth, compressive modulus is increased with the increase of thickness of facesheets (t) or the decrease of thickness of foam cores (h). Fifth, compressive strength and modulus are increased with the increase of diameter of columns (D) or the decrease of distance between two adjacent columns (d).Thirdly, three point bending tests were carried out. The results indicate that: first, flexural properties of 3D integrated composite sandwich structures are higher than those of traditional sandwich structures. Second, while the matrix material is EP, flexural properties are higher than those, in which the matrix material is UP. But specific properties are lower. While the reinforcement is CF, flexural properties and specific properties are better than those, in which the reinforcement is GF. Third, while the core is polyvinyl chloride (PVC) foam which shear properties is the best, flexural properties of sample are the best. And while the core is PMI foam, specific flexural stiffness of the sample is the highest. Forth, flexural stiffness is increased with the increase of t or h. Fifth, flexural properties are increased continuously with the increase of D or the decrease of d.Finally, tension shear tests were carried out. The results show that: first, shear properties of 3D integrated composite sandwich structures are higher than those of traditional sandwich structures. Second, while the matrix material is EP, shear properties are better than those, in which the matrix material is UP. But specific shear modulus is lower. While the reinforcement is CF, shear properties are better than those, in which the reinforcement is GF. But specific shear strength is lower. Third, while the core is PVC foam, shear properties of sample are the best, PMI foam and polyester (PET) foam are the better ones, and polyurethane (PUR) foam is the worst. Furthermore, specific properties of the sample in which the core is PVC foam are the highest. Forth, shear properties are increased with the increase of D or the decrease of d, especially is shear modulus.