Research On Co-curing Properties Of Carbon Fiber Reinforced Epoxy Resin And Epdm Rubber Composite System

Carbon fiber reinforced epoxy resin(CFRP)and Ethylene-propylene-diene rubber(EPDM)are critical engineering materials in the aerospace field.CFRP represents excellent mechanical properties and EPDM rubber has remarkable thermal insulation properties.However,the polarity of EPDM rubber is relatively low,so its bonding strength with other materials is extremely poor.The CFRP/EPDM composite prepared by the independent method has poor adhesive strength and the preparation process is very sophisticated coupled with unstable performance.Thus,the preparation process and conditions of CFRP/EPDM composite system need to be optimized to enhance the performance of CFRP/EPDM composite system.In this paper,the curing mechanism of m-xylylenediamine(MXDA),Phenylenediamine(MPD),3,3'diethyl-4,4'-diaminodiphenylmethane(DEDDM or H-256),and mixture of 3,5-diethyl-2,4-diamine methyl toluene and3,5-diethyl-2,6-diaminotoluene(DETDA)is determined by non-isothermal DSC analysis.At the same time,the MDR analysis is used to study the vulcanization properties of Dicumyl peroxide(DCP),dicumyl peroxide(DCP)and sulfur(S),dicumyl peroxide(DCP)and tripropylene isocyanurate(TAIC)in EPDM rubber system.According to the data obtained from above,E-51 epoxy resin and T-800 carbon fiber are selected as the matrix and reinforcement of CFRP respectively as well as CFRP/EPDM composite systems are successfully prepared by co-curing method.Thermogravimetric analysis(TG),90° peel strength test,nuclear magnetic resonance(NMR),scanning electron microscope(SEM),and interlaminar shear strength(ILSS)are used to analyze the properties of this composite material.As a result,the adhesive strength between EPDM and CFRP is 2.088 N/mm;and compared to CFRP,the Td10% of CFRP rises to approximately 400? after EPDM cured by DCP is introduced.The consequence of good adhesive strength can be mainly attributed to the diffusion process of epoxy resin before gelation.Although the mechanical strength of the CFRP maintains at a relatively healthy level with about 80 MPa,the cross-linking network integrity of the EPDM rubber hasdecreased enormously.By changing the co-curing requirements in this composite system,the performance of this co-cured system is refurbished.NMR,SEM,ILSS,and 90° peel strength data show that the best preparation process of CFRP/EPDM composite system is 80?/2 h+ 120?/2 h+140?/1 h+160?/20 min.The average peel strength of this system is 2.342 N/mm and the mass fraction of the cross-linked chain and dangling ends of the EPDM rubber has increased to more than 90%.In comparison with traditional preparation condition of CFRP with higher reaction temperature and longer time,the ILSS of CFRP prepared by co-curing method doesn't decrease significantly and keeps at 80 MPa more or less.It has also been proven by the SEM pictures of different co-curing conditions that the formation of a mixed layer providing adhesion strength between CFRP and EPDM rubber and being not affected by the reaction temperature and reaction time.