Hot diaphragm-forming process is a promising technology for production of angle-shaped thermosetting composites with high efficiency and consistent quality. This technique can be used to form prepreg laminates with abrupt or complex structures before final cure in an autoclave. In this work, the mechanism of the forming process using double diaphragms for carbon fiber/epoxy resin prepreg laminate with C-shaped structure was discussed, and the effect of the forming temperature on the quality of formed laminate was investigated using a designed hot diaphragm-forming device. A testing system was set up to evaluate the frictional resistance of prepreg at different temperatures. The results indicate that a proper forming temperature is essential for quality control of the process and there is a close relationship between prepreg properties and forming qualities of parts.

This paper successfully developed a resistance heating method based on carbon fiber thin veil for molding continuous glass fiber reinforced polypropylene composite. Electrical resistance, temperature distribution, and heating response of carbon fiber veil were investigated to evaluate its resistance heating behavior. One layer of carbon fiber veil with about 0.1 mm thickness was sandwiched by prepreg stacks with about 2 mm thickness and composite plate was fabricated through resistance heating and forming process. Void content, glass fiber distribution, and thickness of composite plate were obtained to evaluate forming quality. Flexural test was employed for mechanical assessment. The results shows that carbon fiber veil coupled with copper foil is an effective heating element with uniform temperature distribution and quick heating response, and the processing quality of composite plate is comparable to that using oven heating process. The feasibility of secondary resistance heating of composite plate based on carbon fiber veil was also demonstrated and the results indicate that composite plate containing carbon fiber veil can be molded into composite product using resistance self-heating process.