C/C soft-hard mixed preform multi-units compression compaction viscoelastic rebound technique and optimization

To address the issue of non-uniform fiber volume fraction between layers in the compression compaction process of C/C soft-hard mixed preforms, a multi-unit variable duration cyclic compression compaction process based on the inter-laminar fiber compression viscoelastic deformation behavior is proposed. This process aims to gradually eliminate the rebound characteristics of inter-laminar fibers and reduce the error of inter-laminar fiber volume fraction. The mapping relationships between the number of units, holding duration, and compaction times with the rebound height of inter-laminar fibers are established using data fitting. The compression compaction process is determined using the Box Behnken response surface design method, and digital devices are utilized for preform compaction experiments. The micro-morphology of the preform is observed using an optical microscope, and the density of inter-laminar fibers before and after process optimization is compared. Experimental results indicate that when the number of units is 3, the holding duration is 57 s, and the compaction times is 2, the fiber volume fraction of the soft-hard mixed preform is 42.90%, which is 12.16% higher than before process optimization, and the error of inter-laminar fiber volume fraction is less than 6.5%.