Microwave Absorption, Quasi‐Static Mechanical Properties, and Impact Resistance of Aramid fiber‐Reinforced Polymer Composites Enabled by Hybrid Short‐Fiber Interlaminar Toughening

ABSTRACT Based on scalable short fiber interlaminar toughening technology, a lightweight structural aramid fiber‐reinforced polymer (AFRP) composite with both impact resistance and broadband microwave absorption has been developed. Hydroxyethyl cellulose (HEC) assisted liquid dispersion method was used to fabricate hybrid short fiber veils. By controlling the mass ratio of glass fiber and carbon fiber in the suspension, unit cells with several permittivities were prepared. With the laminated structure of AFRP, the impedance matching and loss characteristics of each unit cell are optimized layer by layer to realize lightweight structural microwave absorbing composites with gradient distribution characteristics of complex permittivity. The results show that the reflection loss ( RL ) of the optimized AFRP based microwave absorption structure (MAS) is less than‐10 dB, the absorption bandwidth is 7.38 GHz, and the minimum reflection loss RL ( RL min )is‐27.63 dB. Experimental results indicate that under the same areal density, variations in carbon fiber content of less than 1.0 wt% in hybrid fiber veils do not cause significant differences in mechanical properties of AFRP. Compared to the base sample, the laminate composites with 50 g/m 2 areal density fiber veils have the best mechanical properties with strong impact resistance, in which G IC and flexural strength increased to 145% and 102% with a tolerable sacrificing flexural modulus (82%).