Properties Of High Solid Content Foamed Composites

In this study,we mainly do researches about high solid content foamed composites.The effects of foaming process parameters such as saturation time,temperature and pressure on microcellular structure and mechanical properties of microcellular combustible components have been studied.In this paper,we took TEGDN propellant and B glue as the matrix which filled with massive content of RDX and we also took PMMA as auxiliary foaming agent.Two steps intermittent foaming process of supercritical CO₂ was used to study the influence of foaming process conditions to its solubility and cell structure.We also used constrained foaming molds to produce constrained foaming mechanical spline to study the effects of various foaming conditions on its mechanical properties.The results show that the solubility of supercritical carbon dioxide in high solid content composites increased with the rising of saturation pressure and time.But the solubility decreased with the rising of saturation pressure while constrained conditions and sample thicknesses have little effect on it.The increasing of solubility can significantly increase the desorption diffusivities of CO₂ in high solid content composites.The microcellular structure of high solid content foamed energetic composites can be affected by the foaming process.It was found that increasing the foaming temperature and time can increase the cell diameter and decrease the cell density.While limited conditions and increase the saturation pressure can reduce the cell diameter and make the cell denser.Within 6 to 12h,the extending of saturation time will make the cell bigger.The effect of saturation temperature on the cell parameters is not clear and the densification of high solid content foamed energetic composites prepared by rapid depressurization method is not as good as stepwise heating method.With the treatment of supercritical CO₂ foaming,the tensile strength of high solid content foamed composites decreased but the elongation at break of it increased.The impact strength of our composites increased with the increasing of elastomer and saturation pressure.And with the increasing of foaming temperature,foaming time and the saturation time before equilibration,the impact strength of our composites decreased.The effects of saturation temperature on impact strength of our composites is not clear.At last,we studied the filling and molding of high solid content foamed composites and problems of forming thin-walled cylindrical devices were solved.In addition,supercritical CO₂ foaming method can be used to change the burning rate of combustible devices which laid the experimental foundation for the researches of lightweight and high-energy ammunition.