How to design the interface is a fundamental issue for the composite materials. Although a little work was concerned with the mechanical design of the interface, the effect of the initial thermal stresses has not been taken into account in those studies. While the thermal stresses due to the manufacturing process and the difference in coefficient of thermal expansion between matrix and reinforcing phase, do play an important role in the properties of the composites. In terms of a concept of the neutral inclusions that do not disturb the prescribed uniform stress field in the surrounding elastic body, the interface parameters are studied with consideration of the effect of an initial thermal stress field in this paper, indicating that the effect of thermal stresses may be eliminated by the design of interface parameters.

The recently proposed structural interface model is a realistic model of thick interfaces, but the bars of the structure are assumed iso-stiffness. In the present work, the structural interface consisting of pairs of bars with different stiffness is developed. Based on the neutral inclusion concept and elastic mechanics, the stiffness of bars of the structural interface is studied. It is found that all the bars have the same stiffness in a special loading condition of equal-biaxial tension. The finite element simulations for glass fiber-reinforced epoxy composite reveal that the fiber does not alter the prescribed stress due to the presence of the structural interface. Compared with the iso-stiffness-bar interface, the developed structure interface is more suitable for characterizing a multi-component interface and more flexible to be designed.

There has been considerable interest in inflatable space structures in last decades due to their potential application for such advantages as lightweight and high folding efficiency. As a relatively simply element, the inflatable tube has been studied in some aspects, e.g. the rigidizable materials, the mechanical properties and deploying characteristics. To achieve ultra lightweight and lower the heating energy for the thermally cured rigidizable materials, an inflatable tube with a rigidizable web is designed; and then the critical load and overall stiffness of the rigidized tube are analyzed by using finite element method (FEM). It is found that the mechanical properties of the tube are not sensitive to the material anisotropy, but to the winding angle of rigidized cord and the ratio of length to diameter of the tube.

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