Effect of curing pressure on mechanical, dielectric and microwave absorption properties of carbon black (CB)-incorporated quartz glass fiber-reinforced polyimide composites

Carbon black (CB)-incorporated quartz glass fiber-reinforced polyimide composites were designed and prepared with a CB content of 5 wt%. Composites materials with different fiber volume fractions were fabricated by changing the curing pressure. The morphology, mechanical, dielectric and microwave absorption properties of the composites were investigated. The results showed that the CB distributed uniformly even under different curing pressures. With the decrease of curing pressure from 5 to 2 MPa, the flexural strengths of the composites increased first and then decreased, reaching a maximum value of 947 ± 5 MPa at the curing pressure of 4 MPa. However, both the real and imaginary parts of complex permittivity of the composites showed an increasing trend with the decrease of curing pressure. The reflection loss (RL) of the composite was calculated according to the transmission line theory. The microwave absorption property of the composite prepared at 2 MPa was the best and the minimum RL value of the composite was − 49.55 dB with the thickness of 3 mm. At the same time, the bandwidth of RL ≤ − 5 dB was in the whole X band (8.2–12.4 GHz), and the bandwidth of RL ≤ − 10 dB was in the frequency range of 8.2–11.58 GHz. Therefore, the choice of curing pressure is very important for the balance of mechanical and microwave-absorbing properties of resin-based composites.