Abstract The present study explored the effect of medium texture (MT) content on flexural properties and thermal expansion coefficients (CTES) of carbon/carbon (C/C) composites with multilayered pyrolytic carbon. The specimen with 39% MT exhibited maximum flexural strength of 221.55 MPa, increasing by 52% compared with pure high texture. While the flexural strength decreased when the MT content exceeded 39%. The excellent strength can be attributed to crack deflection between multilayered texture and the strong interface bonding between fibers and matrix. Moreover, the four specimens expressed a similar trend of CTES in the direction of XY and Z. In the direction of XY, the specimen with 39% MT had the lowest CTES from 800 °C to 2100 °C. Therefore, the C/C composites with 39% MT have the best mechanical and thermal expansion properties, which means that the properties of C/C composites can be optimized by controlling the texture.
Last. Shouyang Zhang(NPU: Northwestern Polytechnical University)H-Index: 19
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Abstract In order to explore the dependence of mechanical properties on the microstructure of high-textured (HT) pyrolytic carbon (PyC), the microstructure and properties of HT PyC specimens prepared by isothermal isobaric chemical vapor infiltration (ICVI) and thermal gradient chemical vapor infiltration (TCVI) processes were investigated. The HT PyC of ICVI was uniform and exhibited a more distinct long-range order compared to that of TCVI. Besides, a spatial gradient in texture existed within...
Last. Hejun Li(NPU: Northwestern Polytechnical University)H-Index: 68
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Abstract This paper investigates the feasibility of using porous pyrolytic carbon (PyC) to produce low thermal expansion (CTE) carbon/carbon composites by using a multi-scale representative volume element (RVE) based on a finite element (FE) homogenisation strategy. The distribution of pores is characterized by mercury intrusion test and multi-peak Gaussian function. The RVEs of porous structures at micro- and macro-scale are generated using a modified random sequential adsorption (RSA) algorith...
Last. Wei Li(NPU: Northwestern Polytechnical University)H-Index: 206
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Abstract In order to investigate the effect of microstructural evolution on the micromechanical behavior of pyrolytic carbon (PyC), the microstructural parameters and evolution of high texture (HT) and medium texture (MT) PyC after heat treatment from 1600 °C to 2450 °C were studied comparatively. The micro-indentation test was also performed to reveal the micromechanics. In terms of microstructure, after heat treatment, the HT matrix was directly delaminated into many nano-layers accompanied by...
Last. Wei Li(NPU: Northwestern Polytechnical University)H-Index: 99
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Abstract Fatigue strengthening of composites refers to the increase of residual strength after a specific number of loading cycles. This eccentric behavior widely exists in carbon/carbon composites and some ceramic matrix composites while few reasonable mechanisms have been proposed. In the present work, a comparative study of two different types of C/C composites (CNT-C/C with enhanced fiber-matrix interface and SiCNW-C/C composites with strengthened matrix) is performed to probe into the inher...
Last. Shengyue Gu(NPU: Northwestern Polytechnical University)H-Index: 1
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Abstract Chemical vapor infiltration (CVI) is the most extensive industrial preparation of carbon/carbon (C/C) composites. Precursor affects the CVI process considerably. In the present study, using carbon fiber bundles as preforms, methane and ethanol as precursors, the C/C composites were densified by decomposition of various gases in CVI. The thickness and texture of deposited pyrolytic carbon (PyC) were characterized by polarized light microscopy (PLM). The microstructure of PyC was analyzed...
Last. Hejun Li(NPU: Northwestern Polytechnical University)H-Index: 68
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Numerical simulation with progressive damage criterion is implemented to investigate the effect of porosity on the bending properties of 2D cross-ply carbon/carbon (C/C) composites. The mechanical properties of Pyrocarbon matrix regarding the change of porosity are calculated by using Mori-Tanaka approach. Combining with the stiffness degradation scheme, the ultimate bending strengths are calculated in Abaqus though a user-defined subroutine (USDFLD). Delamination is modelled by inserting cohesi...
Abstract Effects of impact defects on thermal expansion behavior of 2.5D C/C composites were studied in this work. A 6 mm steel ball driven by solid explosive was used as a projectile to simulate hypervelocity impact of debris or flying stones. The coefficients of thermal expansion (CTEs) of post-impacted samples located in different areas were investigated from 850 to 2500 °C. The results show that impact defects are primarily focused on crater regions. These defects can significantly decrease ...
A novel core-shell-structured carboxylated-styrene butadiene rubber (XSBR)-functionalized nanodiamond (ND-XSBR) was synthesized and characterized. Epoxy (EP) nanocomposites toughened by pristine ND and ND-XSBR were investigated and compared. The ND-XSBR-reinforced nanocomposite exhibited mechanical properties superior to those of the one filled by pristine ND. At a low-filler loading, the ND-XSBR exhibited an impressive toughening effect. The maximum flexural strength was shown when the filler l...
Last. Tao Feng(NPU: Northwestern Polytechnical University)H-Index: 8
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Abstract To optimize the bonding strength and ablation resistance of HfC based coating on hemisphere shaped C/C composites, a HfC-SiC diffusion interface was introduced by in-situ reaction and chemical vapor deposition. The microstructure, bonding strength and ablation resistance were characterized. After introducing HfC-SiC diffusion, the bonding strength significantly increased by 179 %. For hemisphere shaped samples, the linear and mass ablation rates decreased by 65.0 % and 53.0 %, respectiv...
Carbon-carbon composites (C/C) are those that have carbonaceous matrix reinforced with carbon fiber. They are widely used in the aerospace field, due mainly to the properties such as low density, high stiffness, and excellent thermal resistance, in comparison to the ones with polymer or metallic matrix. They are obtained through composites of polymer matrix (thermoset or thermoplastic), from the heat treatment of carbonization. The objective of this work is to produce the C/C composite material ...