Tensile strength degradation of a 2.5D-C/SiC composite under thermal cycles in air

Abstract

The present work investigated the effects of the thermal cycles in air on the tensile properties of a 2.5 dimensional carbon fiber reinforced silicon carbide composite (2.5D-C/SiC) in weft and warp direction, prepared by low-pressure chemical vapor infiltration. The composite was exposed to different thermal cycles between 900 ºC and 300 ºC in air. The fracture morphologies of the failed composite were examined by a scanning electron microscope to investigate the underlying damage mechanisms. It is found that the composite can retain its tensile strength within 40 thermal cycles. Comparatively, the modulus of 2.5D-C/SiC decreases with increasing thermal cycles. Extensive pullout of fibers on the fractured surface and interface debonding suggest that the damage caused by the thermal cycles involves weakening of the bonding strength of coating/composite and fiber/matrix. The above damage supply the channel for the oxidation of PyC and carbon fibers in the composites.In addition, the degradation in warp direction is faster than that in weft direction.

Three‐dimensional measurement and cohesive element modelling of deformation and damage in a 2.5‐dimensional woven ceramic matrix composite

“…The cohesive element model applied in this work has been used to simulate the onset of failure, which occurs in the matrix because of the stress concentrations of the porosity and the geometry of the weave. The potential for debonding of weak interfaces between the matrix and fibre has not been included in the modelling, as this would require higher resolution and would also introduce further model parameters that would require fitting. At the resolution of the experimental observations and the simulation, the development of damage would be similar if debonding of the matrix/fibre interface were to be introduced, and so the obtained critical strain criteria is sufficient.…”

Modelling the Tensile Damage and Fracture Processes of Fibre-Reinforced Ceramic-Matrix Composites Under the Effect of Pre-Exposure at Elevated Temperatures

“…When a fibre failure occurs, the fibre axial stress in the interface de-bonded and bonded region can be determined using the following equation. (9) where T denotes the intact fibre stress.…”

“…EXPERIMENTAL Wang et al [8] investigated the tensile behaviour of 1D, 2D and 3D C/SiC composites at room temperature. Zhang et al [9] investigated the tensile behaviour of 2.5D C/SiC composites after exposure at an elevated temperature. The material properties of the 1D, 2D, 2.5D and 3D C/SiC composites are listed in Table 1.…”

“…The tensile stress-strain curves of C/SiC depended on the fibre volume along the loading direction and the interface properties. Zhang et al [9] investigated the strength degradation of a 2.5D C/SiC composite after exposure at elevated temperature in air conditions. The composite tensile strength and failure strain decreases after exposure at an elevated temperature.…”

Cyclic Thermal Shock Damage Behavior in CVI SiC/SiC High-Pressure Turbine Twin Guide Vanes

“…Udayakumar et al [12] investigated the effect of thermal cycling of 2D plain-woven SiC/SiC composites on the mechanical properties, e.g., the proportional limit stress, percentage elongation, fracture toughness, and interfacial bonding strength. Zhang et al [13] investigated the effect of thermal cycles between 900 and 300 • C in air atmosphere on the tensile properties of 2.5D woven C/SiC composite. The composite can retain the tensile strength within 40 thermal cycles.…”