| Due to the high specific strength and specific modulus and good designability of carbon fiber/resin matrix composites prepared by wet winding,it has been widely used in the aerospace field.In order to meet the demand for high-temperature composite materials in aerospace,epoxy resin/aromatic amine systems wit h excellent heat resistance were generally selected as the resin matrix.However,the aromatic amine needs heating to react with the epoxy resin.The heating in the winding process will reduce the pretightening force of the winding,on the other hand,the difference in the thermal expansion coefficient of the composite material and the mandre leads to the poor matching of the interface,and it is difficult to obtain the composite material with excellent comprehensive properties.Therefore,it is particularly important to develop epoxy curing agents that can be cured at room temperature and used at high temperature.According to the requirements of room temperature curing and high temperature use,the effect of molecular structure on the performance of the curi ng agent was analyzed.Based on the principle of similar dissolution,4,4?-diaminodiphenylmethane(DDM)and m-xylylenediamine(MXDA)were selected as the raw materials for physical modification curing agent HGA;The molecular structure design of the curing agent was carried out,and the chemical modified curing agent HGB was synthesized by Mannich reaction of DDM,phenol and formaldehyde.The results of IR characterization confirmed the smooth operation of the reaction.When amine: phenol: aldehyde =1.5:1:1,the brown-yellow liquid product with suitable viscosity and amine value was obtained.The mixture ratio of curing agent and epoxy resin was obtained by theoretical analysis and experiment.The rheological behavior of the resin system under this ratio was analyzed.The results showed that the viscosity and application period of HGA and HGB curing agent met the requirements of wet winding molding.The curing kinetics of the curing agent was studied by differential scanning calorimetry.The activation energy Ea of the HGA curing reaction was 52.54 k J/mol,the reaction reaction series n was 0.89,and the activation energy Ea of the HGB curing reaction was 34.79 k J/mol,the reaction reaction series n was 0.94.According to the kinetic parameters and room temperature curing requirements,determine the curing regime at room temperature 25?,where HGA was 25?/12h+150?/2h,HGB was 25?/8h+150?/2h,under the curing system,the curing degree of the two cured products were higher than 95%,which further validates the rationality of the curing system.The glass transition temperature(Tg)of the HGA cured product was 144?,compared with the raw material MXDA raised 14?,compared with the raw material DDM decreased 6?,but the room temperature curing was achieved.The Tg of the HGB cured product was 154?,which not only implements the room temperature curing,and compared with the raw material DDM raised 4?.The mechanical properties of the two cured products are excellent,which meet the requirements of matrix composites.According to the test results of the contact angle and the interfacial shear strength between the carbon fiber and the TDE-85/HGB resin system,It was confirmed that Toray T700 carbon fiber was used for wet winding to prepare composite unidirectional plate.The glass transition temperature of the composite reached 169.8?,and the tensile strength,bending strength,and interlaminar shear strength were high.The SEM image shows that the surface of the damaged carbon fiber is coated with resin residue,which proves that the resin system and fiber have good infiltration and interface bonding,and play a role in transferring stress. |
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