Preparation And Properties Of Polyimide Fiber Reinforced Cyanate Ester Wave-Transparent Composites

High-strength and high-modulus polyimide(PI)fiber has excellent mechanical properties,high and low temperature resistance,electrical properties,weather resistance,etc.And PI fiber has unique advantages as reinforcement of structural wave-transparent composite.Cyanate resin(CE)has outstanding dielectric properties,and it also has good mechanical properties,heat resistance and the like.At present,the systematic research on high-strength and high-modulus PI fiber reinforced cyanate resin composites is still blank,so this subject has important significance.The main research contents of this subject are as follows:1.According to the molding requirements of composite,several cyanate resin systems were designed which is CE-0,CE-TN,CE-TPN and CE-TEN,the curing process of the resin system was determined,and the performance of resin castings was tested.The results show that the CE-TPN system has the most excellent comprehensive performance,its dielectric constant is about 2.9,dielectric loss factor is about 0.007,and the impact strength is 14.2 kJ/m2,which is 94%higher than the unmodified CE-0 sample.Prepare the unidirectional composite spline with the S30M PI fiber as the reinforcement and the modified cyanate resin as the matrix.The PI/CE-TPN has the highest interlaminar shear strength value of 55.82 MPa,which is 28%higher than unmodified samples.2.The influence was analyzed which the pressure point and the vacuuming time on the resin content of the composite material in the autoclave molding process.The result shows that the molding effect was the best when pressurized after constant temperature at 140℃for 60 min,and stop vacuum after 20 minutes of pressurization.The resin content of the composite is 35.6%,the dielectric constant is 3.15-3.25,the dielectric loss factor is 0.004～0.006,the interlaminar shear strength is 66.2MPa,the tensile strength and modulus are 1485.MPa and 80.9GPa,compressive strength and modulus are 322.0MPa and 68.4GPa,bending strength and modulus are 766.1 MPa and 40.8GPa.Preparation composite with PPTA fiber,aramid-Ⅲ fiber,quartz fabric as the reinforcement,the performance comparison shows that PI fiber composite has the best comprehensive performance,indicating PI fiber more suitable as a reinforcement for structural wave-transparent composites.3.The PI fibers were sizing with two sizing agents(A and B)at different concentrations,and prepare the unidirectional composite by using fibers before and after sizing.The results showed that the tensile strength of the sizing treated fibers was slightly improved.The interlaminar shear strength of the composites prepared with the fiber sizing by the 4.0 wt%A and 1.0 wt%B increased by 19.16%and 13.92%.Through the DMA test of the composite,it was found that the Tg of the composite prepared by fiber after sizing was higher than the unmodified sample,it was increased by more than 10℃ indicating that the sizing treatment under the two conditions effectively improved the interfacial properties and thermal stability of the PI fiber.