Investigation On Mechanical Property Of Hollow Integrated Sandwich Composites

Hollow integrated sandwich composite is a new kind of 3D-woven sandwich composite which has a good integrated capability. It is and will be more and more widely used in aviation, aerospace, marine, automobile, architecture, chemical industry and other fields. Therefore, it is important to carry out theoretical and experimental investigations for this material. In this thesis, the micro-geometry structure and manufacturing process of this material are studied and then a mechanical model is build to predict its mechanical properties. Experiments are performed to verify the predicted results. The main research contents consist of the following three parts.The first part of this thesis focuses on investigations of the micro-geometry structure and elastic mechanical behaviors of the hollow integrated sandwich composites. Tracks of the yarn are analyzed from the hollow textile weaving techniques. A minimal structure element is build according to the micro-geometry structure. The shape of the fiber cross-section is assumed as an ellipse. Use a sine wave to simulate the 8 shape fibers in the core section. Together with a method of average cubage, a mechanical model is established to predict the in-plane engineering constants for the hollow integrated core sandwich composites. Then the influence of weave parameter to the elastic constants is discussed.In the second part of this thesis the mechanical behavior of hollow integrated sandwich composites is carried out by the finite element (FE) method. An FE model is constructed to predict the bending stiffness of the composite structure. Using FEM and Tsai-Wu tensor theory predicts the strength of flat-wise compression, flat-wise tensile and shear. It is found that the calculate method is reasonable by comparing the predicted results to the experimental data.The last part of this thesis performs the experimental research on the manufacturing process and mechanical properties. The manufacturing process,3-step roller molding,is obtained. Samples met the requirement are made. Tensile, compression, bending, shear, low velocity impact tests are performed on both the new and traditional honeycomb sandwich composites. Some useful conclusions are drawn based on the test data.