The Preparation Of Carbon Fiber Reinforced Epoxy Composite Modified By Polyamic Acid

In this paper, the epoxy E-51 and CYD-011 were blended as the matrix resin with the ratio of 1:1, and the polyamic acid which is the processor of polyimide was used as the modifier. The epoxy resin was modified by polyamic acid followed by the preparation of carbon fiber reinforced epoxy composites at the first time. The pre-reaction of the epoxy and polyamic acid was study by Fourier Transform Infrared Spectroscopy (FTIR), the curing behaviors including the curing temperature, curing rate and curing activation energy of epoxy resin systems were studied by Differential Scanning Caborimetry (DSC), the effects of polyamic acid on the mechanical properties including the impact strength, the tensile strength and modulus, the flexural strength and modulus were studied at the same time. The results show that, by adding polyamic acid into the epoxy and after the pre-reaction, the initial curing temperature of the epoxy/DDS systems was decreased about 55.7℃, the gel-time of the resin system shorten about 72% when compare with the resin without modifying, the activation energy of the resin was lowered about 15.6KJ/mol, and the ability of thermal resistance for the resin was increased to some extent. As for the mechanical properties for the modified resin system, the impact strength of the resin with 2wt% polyamic acid was increased about 190%, the plain strain fracture toughness was increased 56% and the flexural strength was increased about 15% comparing with the resin without polyamic acid. Then the modified resin was used to prepare the carbon fiber reinforced epoxy composite through the solution method. The mechanical properties of composite laminates were conducted by tensile test machine. The test results show that the flexural strength of the composites laminates made by the modified resin matrix was increased 47.5%, the inter-laminar shear strength was increased about 33.5%, and the initial inter-laminar delamination strength was increased about 250%. The mechanism of the modification of polyamic acid to epoxy resin matrix and composite were also analyzed and the formation of semi-IPN structure was proposed to be the main reason for the improvement.