Carbon-bonded Carbon Fiber Composites Research Articles

Lightweight and thermally insulating carbon-bonded carbon fiber/graphite composite with enhanced in-plane heat-leading functionality for efficient thermal protection materials

Non-ablative thermal protection materials are subjected to localized high-density heat flux, facing extreme temperatures and uneven temperature distribution. Heat dredging is expected to enhance thermal protection efficiency and alleviate its resistance to temperature pressure. In this study, the function of in-plane (IP) heat leading is innovatively incorporated to increase the thermal-protection efficiency of carbon-bonded carbon fiber (CBCF) composites. The modified composite is prepared by a one-step integrated filter press process in which continuous flexible graphite paper (FGP) is used as the heat-leading layer. The typical micromorphology, mechanical response, thermal-insulation and heat-leading performance are determined. The CBCF/FGP composites with a 0.1 mm thick heat-leading layer exhibits a density of 0.22 g/cm3. The compressive strength increased by 160 % in the IP direction while remaining consistent in the through-the-thickness direction relative to that of the pure CBCFs. The thermal conductivity in the insulation and heat-leading directions at room temperature are 0.061 W/mK and 21.14 W/mK, respectively, indicating significant anisotropy with an approximately 350-fold difference. The incorporation of FGP effectively enhances the IP heat-leading capabilities of CBCF composites, potentially improving their thermal-insulation efficiency when combined with different matrix materials.

The mechanical responses of SiC-coated carbon-bonded carbon fiber composites under quasi-static cyclic compressive loading

SiC-coated carbon-bonded carbon fiber composites (CBCFs), serving as novel thermal protection materials for hypersonic vehicles, are manufactured to investigate their mechanical properties concerning reusability. Comprehensive analyses are performed on their microstructures, including the fiber arrangement and the morphology of individual fibers and interconnecting bonds. The results demonstrate that SiC-coated CBCFs exhibit higher elastic moduli and strengths in both typical directions compared to bare CBCFs. To evaluate their durability in repeated use scenarios, a series of quasi-static uniaxial cyclic compressive experiments are conducted with emphasis on the variations of deformation recovery, load bearing and energy dissipation. The results indicate that SiC-coated CBCFs exhibit stable deformation recovery ability in the OP direction after the 25th cycle, with a decelerating decline in their load-bearing capacity observed over subsequent cycles. The energy loss coefficient initially decreases with increasing cycle number, and higher compression loads enlarge the amount of energy that is dissipated in the first cycle. These insights elucidate critical correlations between the mechanical properties of SiC-coated CBCFs and the number of compressive cycles, contributing to the optimization of their practical utilization in reusable scenarios.

Eco-Friendly Preparation of Carbon-Bonded Carbon Fiber Based on Glucose-Polyacrylamide Hydrogel Derived Carbon as Binder

Lightweight, high-temperature-resistant carbon-bonded carbon fiber (CBCF) composites with excellent thermal insulation properties are desirable materials for thermal protection systems in military and aerospace applications. Here, glucose was introduced into the polyacrylamide hydrogel to form the glucose-polyacrylamide (Glu-PAM) hydrogel. The CBCF composites were prepared using the Glu-PAM hydrogel as a brand-new binder, and the synergistic effect between glucose and acrylamide was investigated. The results showed the Glu-PAM hydrogel could limit the foaming of glucose and enhance the carbon yield of glucose. Meanwhile, the dopamine-modified chopped carbon fiber could be uniformly mixed by high-speed shearing to form a slurry with the Glu-PAM hydrogel. Finally, the slurry was successfully extruded and molded to prepare CBCF composites with a density of 0.158~0.390 g cm-3 and excellent thermal insulation performance and good mechanical properties. The compressive strength of CBCF composites with a density of 0.158 g cm-3 in the Z direction is 0.18 MPa, and the thermal conductivity in the Z direction at 25 °C and 1200 °C is 0.10 W m-1 k-1 and 0.20 W m-1 k-1, respectively. This study provided an efficient, environment-friendly, and cost-effective strategy for the preparation of CBCF composites.

Carbon-bonded carbon fiber composites reinforced with SiOC-based polymer derived ceramics: Microstructure and properties

Carbon-bonded carbon fiber (CBCF) composites have been used extensively for lightweight thermal insulation applications. In this work, CBCF composites reinforced with SiOC, B-modified SiOC (SiBOC) or Zr-modified SiOC (SiZrOC) ceramics were investigated. The chemical modification of SiOC precursor has significant effects on the microstructure as well as the mechanical and thermal properties of the composites. The SiBOC and SiZrOC precursor exhibit higher impregnation efficiency than the SiOC precursor. The SiBOC/CBCF composites have the highest compressive strength and best oxidation resistance, which is attributed to its preferable microstructure, where the SiBOC ceramics wrap on the fibers and provide effective protection for carbon fibers from oxygen diffusion. The strength and modulus of SiBOC/CBCF composites along z direction is 4.5 and 148 MPa, respectively. The thermal conductivity and expansion coefficient of SiBOC/CBCF composites along z direction is 0.3 W/m⋅k and 1.75 × 10−6 K−1, respectively.

Resilient carbon fiber network materials under cyclic compression

The thermal protection system (TPS) for the reusable reentry spacecraft is designed to protect the structure from extremely high temperatures for many times launch and reentry. To meet the requirements, the TPS requires excellent thermal insulation performance, mechanical properties and strong ability to recover deformation with a minimum lifetime of dozens of missions. In this paper, we fabricated carbon-bonded carbon fiber composites (CBCFs) with a 3D network structure, and the deformation mechanisms under cyclic compression were systematically analyzed. This work demonstrated the excellent resilience behavior of CBCFs with cyclic loading. Quantitative numerical modeling and experimental tests revealed that the CBCFs could completely recover the deformation with strain up to 40% and maintained structural integrity with low energy dissipation (<∼0.3). The resilient behavior in the out-of-plane direction was mainly attributed to elastic deformation of fibers and contact of neighboring fibers, and most of the energy was dissipated by the sliding between fibers. The in-plane deformation of CBCFs was mainly attributed to network collapse and buckling. This paper provided a fundamental insight into the mechanical properties and deformation mechanisms of the CBCFs under cyclic compression, which may contribute to the development for the new generation of reusable TPS.

Fabrication and ultra-high-temperature properties of lightweight carbon-bonded carbon fiber composites

Carbon bonded carbon fiber (CBCF) composites with different fiber volume fractions (FVFs) are prepared. This paper mainly investigates the effect of FVFs and the ultra-high temperature on the mechanical and thermal properties of CBCF composites. Experimental results show that the microstructure of CBCF composites is anisotropic, random distribution in xy direction and layering in z direction. With higher FVFs, the modulus and fracture strength are higher. The fracture strength in xy direction is greatly higher than that in z direction, because more fibers bear the load. Elastoplastic behavior of stress-strain curves is observed in z direction, which is attributed to the compression of porosity and gap. Especially, at ultra-high temperature, the plastic hardening effect is remarkable. In addition, the thermal conductivities of CBCF composites with different FVFs are characterized, which increase exponentially with temperature.

Studies on the influence of surface treatment type, in the effectiveness of structural adhesive bonding, for carbon fiber reinforced composites

Primary intent of the present paper is to correlate the effectiveness of surface preparation type (pre-bonding), such as solvent cleaning, sanding (mechanical abrade), chemical etching (alkaline and acid), and peeling of sacrificial surface layer (peel ply) of carbon fiber reinforced composite (CFRC) test specimens, with the corresponding effect to the final strength of adhesive bonding. The analysis was performed by means of several spectroscopic and microscopic techniques, such as XPS, SEM, AFM, and a contact angle measurement technique which provides a direct, fast and easy measurement of the surface energy of the fiber composites. The adhesively bonded carbon fiber composites based on the different surface treatments were mechanically tested by employing the ASTM D 5528-0 (reapproved 2007) standard. The double cantilever beam (DCB) specimen geometry was used to evaluate the value known as opening Mode I inter-laminar fracture toughness (GIC) in adhesive bonds of carbon fiber composite materials. The results were varying between 1 and 1.8 kJ/m2 for GIC analysis and around 50 mm for delamination lengths. The mechanics of the linear elastic fracture is considered a tool for the failure of the laminate in composite materials with cracks or cuts in the plane, due to the presence of damaged zones in the tip of the crack; which is therefore applied to the study of delamination or fracture toughness.

Ablation behavior of functional gradient ceramic coating for porous carbon-bonded carbon fiber composites

To improve the ablation resistance of low density carbon bonded carbon fiber (CBCF) composites at high temperature, a novel functional gradient ceramic coating was prepared. The coating exhibits a two layer structure with a compact HfB2-MoSi2 outer layer and an inner Si-CBCF layer with gradient transition structure. The high temperature ablation resistance of the coated CBCF composites was investigated with an arc-jet testing at temperature 1500–2200 °C. The results showed that the prepared functional ceramic coating exhibited good ablation resistance and good thermal shock resistance after four ablation cycles. After ablation, the surface coating exhibit three different ablation regions due to the different ablation temperature. The formation of a dense silica glass layer embedded with HfO2 particles or a molten HfO2 layer was responsible for the good ablation resistant to the functional gradient ceramic coating.

Preparation of a high spectral emissivity TaSi2-based hybrid coating on SiOC-modified carbon-bonded carbon fiber composite by a flash sintering method

The most recent and innovative metal disilicide-based hybrid coatings are used for protecting carbon fiber-based composites in aerospace application. Here, we investigate a high emissivity coating on SiOC-modified carbon-bonded carbon fiber composites (SiOC/CBCF) for thermal protection material. Both tantalum silicide (TaSi2) and molybdenum silicide (MoSi2)-based coatings are prepared on SiOC/CBCF composites using flash sintering method, and the emissivity value of MoSi2-based coating is higher than that of TaSi2-based coating. Significantly, improvement the density of the coating has a positive role on emissivity resulting in MoSi2-based coating increases about 7.2% at 400 °C and 11.5% at 1000 °C, respectively; TaSi2-based coating increases about 15.4% at 400 °C and 2.6% at 1000 °C. After exposure to 1500 °C for 60 min in air, the emissivity values of the coated-samples are also investigated.

Thermal conductivity enhancement of phase change materials with form-stable carbon bonded carbon fiber network

Carbon bonded carbon fiber (CBCF) monoliths were prepared from graphite fibers with high thermal conductivity, to promote heat transfer and to stabilize the shape of phase change material (PCM). The CBCF monoliths with density from 0.09 to 0.39g/cm3 were filled with paraffin wax to form PCM composites. Due to the anisotropy of the CBCF material, the PCM composites had varied thermal conductivities with their directions. Results showed that the in-plane thermal conductivity of the PCM composites was markedly improved by 18 to 57 times over the pure wax, depending on the density of CBCF composites, while the out-of-plane thermal conductivity was also increased by 3.7 to 5.5 times. In addition, the improvements in thermal conductivity showed almost linear relationship with the volume fraction of carbon fibers in the PCM composites. The charging time of the composites with the high CBCF density was reduced to one quarter of pure paraffin, while the discharging time was about one sixth. The apparent enthalpy of PCM composites was found to vary with the loadings of paraffin wax, by differential scanning calorimetry (DSC). After 40cycles, the wax loadings in the PCM composites were retained at 56–70%.

Preparation and mechanical behaviors of SiOC-modified carbon-bonded carbon fiber composite with in-situ growth of three-dimensional SiC nanowires

Carbon-bonded carbon fiber (CBCF) composites are novel and important high-temperature insulation materials owing to their light weight, low thermal conductivity and high fracture tolerance. To further improve the mechanical property of CBCF composite, we propose a three-dimensional (3D) SiC nanowires structure, which is in situ grown on a CBCF matrix via directly annealing silicon oxycarbide (SiOC) ceramic precursor. The synthesized multiscale reinforcements including microscale SiOC ceramics and nanoscale SiC nanowires are mainly attributed to the initial phase separation of SiOC phase and subsequent solid-phase reaction of SiO and C phases. Compared to SiOC/CBCF composite, the resulting 3D SiC nanowires/SiOC/CBCF hybrid structure exhibited high flexural/tensile strength and fractured strain due to the pull-out and bridging behavior of SiC nanowires. This one-step process supplied a feasible way to synthesize 3D SiC nanowires to reinforce and toughen SiOC-modified CBCF composite.

Fabrication of low-density carbon-bonded carbon fiber composites with an Hf-based coating for high temperature applications.

A novel Hf-based anti-oxidation coating has been prepared on the surface of low-density carbon-bonded carbon fiber composites (CBCFs). The coating exhibits a gradient transition structure, with mainly HfB2, Hf2Si and SiC ceramics. Oxyacetylene torch testing has been utilized to evaluate the ablation resistance under the condition ranging from 1.6 MW m−2 to 2.2 MW m−2 for 300 s. The experimental results show that the as-prepared Hf-based coating can effectively protect CBCFs under high-temperature oxidation conditions. The surface maximum temperature can reach 1616–2037 °C, and the mass ablation rates vary from −3.5 × 10−5 g s−1 cm−2 to 1.5 × 10−5 g s−1 cm−2. The formation of a dense SiO2 glass layer embedded with HfO2 grains or particle accumulation in the HfO2 layer is responsible for the good ablation resistance.

Porous carbon-bonded carbon fiber composites impregnated with SiO2-Al2O3 aerogel with enhanced thermal insulation and mechanical properties

To improve the thermal insulation and mechanical properties of lightweight carbon- bonded carbon fiber composites (CBCF), a porous CBCF decorated with nano SiO2-Al2O3 aerogel was prepared by sol-gel impregnation. Results showed that the nano aerogel were uniformly assembled within the pores in the CBCF framework. The aerogel played a significant role on reducing the thermal conductivity of CBCF, which could be mainly ascribed to reduced radiation and gas thermal conductivity of CBCF. Moreover, the aerogel in the CBCF pores hindered the bending fracture or elastic bending/rotation of the fibers and enhanced the mechanical properties of the composites.

Oxidative protection of a carbon-bonded carbon fiber composite with double-layer coating of MoSi 2 -SiC whisker and TaSi 2 -MoSi 2 -SiC whisker by slurry method

Abstract This paper presents a double-layered coating system consisting of MoSi2 ceramic reinforced with SiC whiskers and a MoSi2-TaSi2 ceramic coating reinforced with SiC whiskers. This system improves oxidation resistance of carbon-bonded carbon fiber (CBCF) composites. Double-layer coating was about 160 µm in thickness and no interfaces or cracks between the layer and matrix were observed. Isothermal oxidation tests revealed that as-prepared coating presented excellent oxidation resistance, which could protect CBCF composites at 1500 °C for 160 min with 0.02% weight loss, whereas weight loss of single MoSi2 ceramic coating reinforced with SiC whiskers reached 0.08%. High-temperature resistance barrier of the glassy phase and Ta2O5 had a positive effect on improving the oxidation resistance of double-layer coating.

Fabrication and characterization of carbon-bonded carbon fiber composites with in-situ grown SiC nanowires

In order to improve the mechanical properties of CBCFCs, the CBCFCs with in-situ grown SiC nanowires (SiCNW) were fabricated based on the chemical vapor reaction process and precursor impregnation and pyrolysis (PIP) process. The effect of multi-scaled reinforcements (micro-scaled carbon fibers and nano-scaled SiCNW) on the mechanical properties was investigated. The phase, microstructure and fracture surface of the composites were characterized by XRD, SEM and TEM. Microstructure characterization found that the in-situ grown SiCNW randomly distributed in the matrix and formed a network structure in the CBCFCs. The carbon fibers and the SiCNW formed the multi-scaled reinforcements can significantly improve the mechanical properties of CBCFCs. More importantly, the orientation anisotropy on mechanical properties of the composites is also obviously deceased due to the in-situ grown SiCNW. The improved mechanical properties and decreased orientation anisotropy could be attributed to the pull-out and bridging of carbon fibers and SiCNW, which formed multi-scaled reinforcements.

Compression behaviors of carbon-bonded carbon fiber composites: Experimental and numerical investigations

Carbon-bonded carbon fiber composites (CBCFs) were widely used as thermal insulation materials due to their light weight and ultra-low thermal conductivity. The CBCFs with density of about 0.256 g/cm3 were tested in compression with the modulus and strength evaluated. The in-plane and out-of-plane tests revealed obvious anisotropic behavior of the material, which could be attributed to the fibers distribution. The unloading-reloading tests showed more evidence for the difference of the mechanical behaviors between in-plane and out-of-plane. In addition, we presented a finite element model to predict the mechanical properties of the CBCFs, and the deformation mechanisms as well. The numerical results showed the compressive modulus and strength increased with density following exponential functions. Moreover, the effects of fiber length and the fiber orientation on the mechanical properties were also discussed numerically. The results of this paper are helpful for the design and optimization of these materials for potential applications.

Ablation behavior and mechanism of double-layer ZrB2-based ceramic coating for lightweight carbon-bonded carbon fiber composites under oxyacetylene flame at elevate temperature

Ablation behavior of double-layer ZrB2-based ceramic coating for lightweight ZrB2 modified carbon-bonded carbon fiber (CBCFs/ZrB2) composites was tested under an oxyacetylene flame at elevate temperature (1500, 1600 and 1700 °C) for 600s. The results indicate that the ablation temperature has significant effect on the microstructure and ablation behavior of the coated CBCFs/ZrB2 composites. The as-prepared coating could efficiently protect CBCFs/ZrB2 composites against oxidation from 1500 to 1700 °C for 600s. The ZrB2-based ceramic coating had a good self-healing ability at 1500 °C and 1600 °C. With the increasing ablation temperature to 1700 °C, the coating exhibited severe ablation. However, the molten SiO2 from the coating seeped into the CBCFs/ZrB2 composites forming a coating layer on the carbon fibers surface which acted as an efficacious oxidation protective barrier.

Microstructure and ablation behavior of double anti-oxidation protection for carbon-bonded carbon fiber composites

To improve the oxidation protective ability of carbon–bonded carbon fiber (CBCF) composites, double anti-oxidation protection for CBCF composites were prepared, i.e., ceramic coating-coated CBCF composites combined with ceramic-modified carbon fiber in CBCF matrix. The ablation behavior of modified CBCF composites was tested under an oxyacetylene flame at 1600°C for 300s and 800s, respectively. The results indicate that the ZrB2 in matrix and ZrB2-based ceramic coating can play double protection for CBCF composites during ablation process. The linear ablation rate of the sample after ablation for 300s and 800s were −1.1×10−4 and 8.38×10−4cms−1, respectively. The modified CBCF composites presented excellent oxidation resistance for 300s. With the increase of the oxidation time for 800s, the ZrB2-based ceramic coating experienced catastrophic damage. However, the carbon fiber surface only exhibited some circular pits instead of complete oxidation, implying that the ZrB2 on the carbon fiber surface improved the anti-oxidation and ablation resistance of CBCF composites.

Microstructure, surface emissivity and ablation resistance of multilayer coating for lightweight and porous carbon–bonded carbon fiber composites

To improve the oxidation protective ability of carbon–bonded carbon fiber (CBCF) composites. A multilayer coating containing ZrB2, MoSi2, SiCw and borosilicate glass was prepared on ZrB2-modified carbon–bonded carbon fiber composites (CBCFs/ZrB2) by a trace oxygen sintering method and a pre-oxidation process. The microstructure, surface emissivity and ablation resistance of the multilayer coating were studied. The coating containing dense surface layer and porous inner layer was obtained. The total emissivity of the coating in the wavelength range of 6–16 μm at 300, 500 and 800 °C was 0.72, 0.73 and 0.78, respectively. The prepared multilayer coating exhibited excellent ablation resistance for 1000 s under simulated atmospheric re-entry conditions by high frequency plasma wind tunnel test with a heat flux of 131.8 W/cm2 and stagnation pressure of 2.7 KPa.

Multi-composition coating for oxidation protection of modified carbon-bonded carbon fiber composites

Multi-composition coating consisting of multilayer MoSi2-SiCw-SiB6-borosilicate glass/TaSi2-MoSi2-SiCw-SiB6-borosilicate glass has been prepared on the surface of SiOC ceramics-modified carbon bonded carbon fiber composites by a rapid sintering method. Arc jet test has been utilized to evaluate the oxidation-resistance ability from room temperature to 1800K during the total exposure time between 1000s and 1500s. The experimental results show that the multilayer coating can form a robust oxidation protection layer to protect M-CBCF substrates effectively. The surface temperatures of tested samples reach 1573–1973K and mass ablation rates of the samples vary from 1.23×10−6g/scm2 to 9.39×10−6g/scm2.