Preparation And Properties Of Polyimide Fabric Reinforced Thermosetting Polyimide Resin Matrix Composite

Polyimide(PI)material has excellent high temperature resistance,aging resistance,radiation resistance,chemical corrosion resistance,low dielectric resistance,high insulation and other characteristics because the molecular chain contains a large amount of aromatic heterocyclic rigid conjugated structure.As a resin matrix,it has important applications in the aerospace field,such as high-temperature bearings,engine external ducts,housing ducts,etc.With the rapid increase of the Mach number of aircraft,higher requirements have been placed on the weight reduction or wave transmission function of the material structure and the long-term use temperature.Our research has used high-strength high-modulus PI fiber fabric reinforced thermosetting PI resin to prepare a full PI composite material,which expanded a new direction for the research of structure-function integrated high-performance composite materials.The main research contents are as follows:1.PI-PEPA and PI-NA resins were prepared by the polymerization monomeric reactants(PMR).The curing process parameters of the resin system were determined and the properties of the resin molded parts were characterized.The results show that PI-PEPA has more excellent comprehensive properties,and the minimum viscosity of the melt is only 200 Pa·s.After curing,the Tg is between 330-350?,the Td5 is more than 610? and the CTE is 16.64 ppm/K.In addition,the tensile strength is more than 80 MPa,the modulus is around 2.5 GPa,the elongation at break is more than 9%,the impact strength can reach up to 26.3 kJ/m2.Especially,the dielectric constant is 2.9,and the dielectric loss is only 0.005.2.High-strength high-modulus PI fiber fabric and quartz fiber(QF)fabric reinforced thermosetting PI resin are used to prepare PI/PI and QF/PI composite materials.Additionaly,their basic mechanical properties,thermal properties and dielectric properties were characterized and analyzed.The results show that PI fabric can be closely combined with PI resin.The interlaminar shear strength of PI/PI composite is greater than 35 MPa,the flexural strength is about 400 MPa and the modulus is higher than 22 GPA.In addition,the Tg of composites is more than 320?,the Td5 is more than 600?,and the density is about 1.4g/cm3.Meanwhile,the dielectric constant of PI/PI composite is 3.2,which is lower than that of QF/PI composite.3.The PI/PI composite was heat-treated and hygrothermal treated to simulate its performance in high temperature and hygrothermal environment.The results showed that the properties of PI/PI composite remained unchanged after high temperature of 300?/2 h,the moisture absorption rate was lower than 0.1%,the retention rate of mechanical properties was higher than 90%,the dielectric constant increased less than 5%.After high temperature drying,the mechanical properties recovered to 95%,and the dielectric properties recovered to the original value.