Strengthening thick-section 3D needled C/SiC composites by tuning matrix deposition

When ceramic matrix composites are fabricated by chemical vapor infiltration (CVI), uneven matrix infiltration/deposition (density gradient) can be exacerbated by increased preform/composite thickness, and thus causes severe mechanical losses. Here, to mitigate the uneven matrix infiltration/deposition in one such CVI composite, a thick-section three-dimensional needled (3DN) carbon fiber/silicon carbon (C/SiC), we tune matrix deposition by introducing diffusion-assisting holes, which provides more through-thickness surfaces in the deposition. Results showed that the thick-section 3DN C/SiC fabricated with matrix tuning exhibited both more balanced matrix infiltration (reduced poor infiltration regions and a 29% drop in open porosity), and higher flexural strength with a maximum value of 372 MPa (corresponding a maximum strength increase of 30.1%), than that fabricated without tuning.