The Manufacturing Of Composite Grids Sandwich Structure And Thestudy Of Property

Fiber sandwich grid construction has been increasingly used in applications requiring high stiffness/high strength-to-weight ratio materials. Sandwich structures generally consist of different cores in the middle which keep the two skins(top skin and bottom skins) apart from each other to provide a sandwich construction with high flexural stiffness and strength in a relatively lightweight structure. In a sandwich structure, skins commonly carry most of the bending loads, whereas the core mainly bears the transverse shear and normal loads. At present, sandwich structures are widely used in aerospace and astronautic industries due to the designable characteristic and high stiffness/high strength-to-weight ratio. The unique open cell architecture allows for lattice core sandwich structures have the potential in multi-functional applications. In this dissertation, the 2D grid core sandwich structures consisting of carbon fiber reinforced polymer(CFRP) facesheets.(1)In this study, Tsai-Hill failure criteria and paraboloidal failure criteria, were used to characterize the damage region in the sandwich structure. Dynamic models of composite sandwich structure and the strength of the whole structure were established and analyzed according to one layer stiffness of composite structure. The equivalent stiffness model of triangular composite sandwich grid structure was established by the theory of grid structure stiffness.(2) The stiffness and strength behaviors of composite sandwich structure under three-point bending load are investigated firstly. The expression for the deflection is derived by considering bending of the face sheets and transverse shearing of the core. The failure distribution of face sheets and core was analyzed. The three bending load of square, Kagome and triangular sandwich grid structure were finished to analyze and compare with each other in FEA software. Generally speaking, the numerical results are satisfied to forecast the failure mode after three-point bending test.(3)The square, Kagome and triangular composite grid sandwich structure were manufactured by the hand-modeling and vacuum-bag molding methods. The mechanical properties of CFRP sandwich grid structures were investigated by flatwise compression and three point bending test. And the stress-stain curves of three different sandwich grid structures were showed. The compressive strength(33.89MPa), sandwich flexural stiffness(3.78e8), core shear stress(3.69MPa)and bending stress(17.66MPa)of the composite sandwich structure with triangular core is the maximum value.(4)The triangular composite grid sandwich structure was stepped to analyzed, and the epoxy resin foam filled triangular composite grid structure was fabricated. A experiment showed: the failure degree of 0° more than 60° and-60°. The impact crack also along 0°(the direction of fiber).