3D In-Situ Characterizations of Damage Evolution in C/SiC Composite under Monotonic Tensile Loading by Using X-Ray Computed Tomography

The damage evolution and fracture behavior in the bulk of C/SiC material under monotonic tensile loading have been investigated with the 3D in-situ observations by using X-ray CT. Crack initiated inside the matrix within 0.02 mm below surface when the load was only 19% of the failure strength, and propagated to the surface of matrix and towards the interior of specimen by breaking fibers and matrix when the load was above the elastic limit. With the further increasing of loading, other fiber breaks, matrix breaks and delaminations were observed to initiate and propagate both on the surface and in the bulk of specimen, while the cracks nucleating in the bulk of specimen are generally located at the laminae with a high volume fraction of pores. With the further propagations of cracks, the specimen split in the laminae with a large quantity of pores, while the fiber drawings results in the final fracture in the laminae without a large quantity of pores. The novel method being proposed to characterize the distribution of pores in this paper highlights the relation between the distribution of pores in the bulk of the studied material and cracks initiations and final fracture.