Research On Bladder-Assisted RTM Process For Composite Components

The composite skirt for solid rocket motors is commonly fabricated by winding process. While, the properties of the component are weakened by the joint due to the difficulty of integral molding. Bladder-assisted RTM was developed for the first time to fabricate the skirt integrally.Studies were focused on the design and fabrication of the mold, the determination of the process parameters of bladder-assisted RTM, the establishment of preform thickness variable model, and the test of the properties of the composite skirt. The conclusions are listed as follows:The mold system was designed and fabricated based on the characteristic of the skirt and the requirements of bladder-assisted RTM. The most important part in the mold system is the silicon rubber bladder. COCA31-11, the silicon rubber, is chosen finally compared with other silicon rubbers. The thickness of the bladder is 5mm by calculating based on the requirements of the component molding.The process parameters of bladder-assisted RTM, such as the injection pressure, temperature, the bladder pressure, and the pressure-holding time were determined. The fiber volume friction of the component exceeds 60% when the bladder pressure is 0.6MPa. The pressure-holding time continues until the resin is totally cured. The composite skirt was fabricated by bladder-assisted RTM. The skirt has good appearance, and the dimension satisfies the needs.The skirt properties were tested, and comparisons were made with the skirts fabricated by the other techniques. The fiber volume fraction of the specimen fabricated by bladder-assisted RTM reaches 61.2%, and the bending strength reaches 280.3MPa, and bending modulus 12.79GPa respectively, which are 23% and 34% higher than those of the specimens fabricated by VARTM. The fiber distribution is more compact and the void content is lower. Compared to flexible mold assisted RTM, bladder-assisted RTM is easier to control molding pressure and...