Significantly improve the mode Ⅰ interlaminar and three-point-bending properties of needled composite by novel short fiber felt peeling method

Traditional laminated needled preforms contain low-density short fiber felt, limiting the mechanical performance of the needled composites, which is hard to fulfill the service demands of high-speed aircraft structural functional integration components. This study proposes a novel 3D needled preform fabrication method based on short fiber felt peeling technique, significantly improving the mechanical properties of both preforms and composites. High load-bearing needled preforms and composites were designed and fabricated by this new method. Through micro-CT structural characterization, DCB tests, three-point bending experiments, and SEM fracture morphology analysis, the effects of different needling parameters on fabric structures and composite's Mode I interlaminar fracture toughness and flexural property were investigated. Results showed that compared with traditional needled preforms and composites, the fiber volume fraction of short fiber felt peeled needled preforms increased by 53.80 %–60.60 %, with needled fiber bundles' volume content enhanced by 62.08 % and bundle length extended by 110.61 %. DCB tests demonstrated 21.89 %–63.32 % improvement in maximum failure load and up to 157.41 % increase in critical energy release rate (G_ⅠC). Three-point bending strength and modulus rose by 33.27 %–83.89 % and 52.27 %–65.91 % respectively. SEM analysis revealed failure modes dominated by matrix cracking, fiber pull-out, and fiber fracture during Mode I delamination and bending failures. This method shows promise for manufacturing high load-bearing structural/functional integrated composite preforms and composites for aerospace vehicles.