Structure And Property Of Resin Matrix Composites Reinforced Short Carbon Fiber Network

Carbon fiber network structure was fabricated based on short carbon fibers pre-bonded and carbonized. There were many studies on short carbon fiber molding composite materials, including thermal insulation materials and adsorption materials. But these studies did not take porous and monolithic materials as reinforcements to fabric ate new composites. The work described in the thesis investigated the fabrication and performance of pre-bonded short carbon fiber network-reinforced(CFNR) resin composites.A new form of short carbon fiber/ep oxy composites was fabricated based on pre-bonded short carbon fiber network reinforcement, exhibiting high stiffness and low thermal expansion.The results from scanning electron microscopy(SEM) and thermal mechanical analysis(TMA) indicated that the CFNR/epoxy composite had lots of carbon-based nodes carbonized from phenolic resin. The bending modulus of the CFNR/epoxy composite was the largest, near ly 3 times and 6 times of regular short carbon fiber/epoxy composites and pure epoxy resin, respectively. Subjected to the same load at higher temperatures, the bending modulus of all three types of specimens dropped as the component of epoxy resin softened. However, the CFNR/epoxy composite maintained higher bending modulus, approximately 7 times and 70 time s of the regular short carbon fiber/epoxy composite and epoxy resin alone, respectively. Additionally, the CFNR/epoxy composite had the smallest coefficient of thermal expansion(CTE, at 60-200?), exhibiting excellent dimension stability against temperature changes. In comparison, the values of coefficient of thermal expansion for the epoxy resin and the regular short carbon fiber/epoxy composites were about 40 times and 15 times higher than the CFNR/epoxy composite. In all samples, the CFNR/epoxy composite possessed the highest storage modulus. The storage modulus of epoxy resin was the smallest. When the temperature increased, the storage modulus reduced, and eventually reached a steady level. The glass temperature(Tg) of the regular short carbon fiber/epoxy composites was also the largest, and epoxy resin was smallest. When the carbon fiber was siz ed, the bending modulus, storage modulus and Tg of the CFNR/epoxy composite was higher than that of composites with unsized carbon fiber.Carbon-based nodes were observed by SEM on the fracture surface of CFNR/polypropylene composite. Under the same load at the room temperature, the deformation of polypropylene was the largest, about 2.4 times of CFNR/polypropylene composites. The deformation of regular short carbon fiber/polypropylene composites was between the two samples above, approaching 1.5 times of CFNR/ polypropylene composites. The bending modulus of the CFNR/polypropylene composites was about 1.6 and 6 times of regular short carbon fiber/polypropylene composites and pure polypropylene, respectively. The CFNR/polypropylene composites possessed the smallest coefficient of thermal expansion(CTE, at 60-120?), which was approximately 1/4 and 1/5 of the values for regular short carbon fiber/polypropylene composites and the polypropylene alone, respectively. The bending modulus of all samples reduced, as temperatures increased. For temperatures higher than 100?, the bending modulus of polypropylene became smaller than 100 MPa, with regular carbon fiber/polypropylene composites retained nearly 200 MPa. The CFNR/ polypropylene composites had a much higher bending modulus, over 400 MPa.