| Foam core composite sandwich not only has the structural advantages of high specific strength and modulus, high impact resistance, and light weight, but also has other functional features such as heat insulation, sound insulation and good damping. Therefore it finds increasing applications in the aerospace, marine, energy, transportation and other areas. To meet the increasingly high requirements of working conditions, the resin reforced core has become one of the important ways to enhance the mechanical properties of composite sandwich. The sandwich molded with new core, which is cut out with finishings of different sizes and distributions on the original plate foam, gets improved mechanical properties because of the resin introduced. Currently, the core processed with finishings has wide applications. However, the influence of finishing size and distribution on the mechanical property of sandwich panels has been rarely reported.In this paper, a 2-stage method is presented for the structural analysis of composite sandwich with preprocessed core. First, the overall mechanical behaviour of the resin reinforced core is predicted and second the predicted properties are applied in the structural analysis of laminate. Their structural response under flexural loading, flatwise compression and flatwise tension are examined. The comparison between experimental and numerical results verified the 2-stage method presented here. Then, the influence of finishing depth, spacing and distribution on the mechanical response of the sandwich are investigated. Composite sandwich with cores preprocessed with finishings of different sizes and distributions were prepared by vacuum-bag process. The main research contents and conclusions obtained are as follows.(1)Using the representative cell from a one-directional cut sheet ODC, its overall tensile and shear moduli of the core reinforced with resin are calculated based on micromechanics and numerical simulation using ANSYS. The results are compared and numerical method is the verified. The mechanical response of overall sandwich panels can be determined by regarding the resin-containing core as one layer in a multilayer structure.(2)Representative cells were taken from resin reinforced cores with preprocessed finishings of typical sizes and the mechanical properties of the reinforced core are calculated by numerical method using ANSYS. The results show that the reinforced core get better mechanical properties.(3)The flexural properties, flatwise tensile strength, flatwise compressive strengths of the sandwich panels were measured according to national standards. Experimental results agree well with numerical predictions, and the two-stage simulation method presented here is verified.(4)For design optimization of composite sandwich, the influence of the finishing geometry, including the depth, width and pitch, on the mechanical properties of sandwich panels are investigated for different finishing types. The results show that the depth and center-center of finishing have a large effect on stiffness and have no influence on the flatwise compression and flatwise tension strength. Moreover, the finishing width improves appreciably the the flatwise compression and flatwise tension strength while rarely influence the stiffness. The stiffness, flatwise compression and flatwise tension strength of sandwich panels are improved by the combination finishing. |
