Multistep Solution Impregnation: An Innovative Strategy to Enhance the Mechanical Properties of Carbon Fiber‐Reinforced Soluble Polyarylether Composites

ABSTRACT Polyphthalazine Ether Sulfone Ketone (PPESK), a high‐performance engineering thermoplastic, possesses a heteroaromatic biphenyl structure in the molecular chain with twisted and non‐coplanar properties. This structure enhances molecular chain entanglement and perturbs chain regularity, endowing PPESK with superior solubility and heat resistance. Accordingly, PPESK is used to produce carbon fiber reinforced thermoplastic resin matrix composites (CFRTP) by means of solution impregnation. Nevertheless, in high‐concentration solution impregnation, it is a crucial challenge to achieve equilibrium between adequate resin content and carbon fiber (CF) infiltration. To overcome this issue, a two‐stage impregnation technology has been developed. Firstly, CF is comprehensively impregnated with a low‐concentration resin solution. Then, a high‐concentration resin solution is used to increase the resin content of the prepreg. This technology ensures the full spreading and impregnation of CF, leading to a sound interface and averting stress concentration due to high porosity. The flexural strength and inter‐laminar shear strength (ILSS) of the CF/PPESK composite prepared by the two‐stage impregnation technology reach 1555 and 68 MPa, respectively, which are 35.21% and 21.4% higher than those of the composites prepared through traditional solution impregnation. In brief, the two‐stage impregnation technology effectively addresses the challenge in balancing resin content and impregnation degree, providing a feasible approach to the preparation of thermoplastic prepreg via solution impregnation.