Phenolic Composites Research Articles

Combinatorial approach to predict synergistic ablation behavior of carbon fiber phenolic composites under aerodynamic loading

The study conducts a comprehensive analysis across 1-D, 2-D, and 2-D axisymmetric geometries, investigating temperature profiles, surface recession patterns, pyrolysis gas flow dynamics, and density fluctuations within the composite material. The findings highlight the effectiveness of the FEA technique in modeling complex multi-physical interactions associated with ablation phenomena. The carbon-phenolic composites, characterized by low thermal conductivity, high specific heat capacity, and substantial char yield, are shown to be particularly well-suited as ablative materials. The char layer formed during ablation acts as an additional insulating barrier, enhancing thermal protection. In a specific case study, a 2 cm thick composite laminate was subjected to an intense heat flux of 200 W/cm2 for 180 s. The results demonstrate that the Thermal Protection System (TPS) effectively maintains the back face temperature below 350 K for the initial 60 s under uniform heat flux conditions. However, beyond this period, the back face temperature gradually increases, reaching 1698 K at the end of the 180-s simulation. These insights into the material’s thermal performance under severe heat exposure conditions provide valuable guidance for applications requiring effective heat management and thermal protection.

The effect of deep-sea pressure during long-term aging on the tribological performance of fabric-reinforced phenolic composites

The influence of hydrostatic pressures up to 30 MPa on the friction and wear behavior of fiber reinforced polymer composites (FRPCs) was investigated together with seawater absorption, interfacial structure and mechanical properties. The results revealed that after aging in the deep-sea environment, the wear rate of the FRPC increased from 1.53 × 10−6 mm3/N∙m to 3.61 × 10−6 mm3/N∙m, and the mechanical strength decreased reversibly. The damage mechanism was assumed to be dominated by the combined effect of crack propagation in the polymer matrix and interfacial debonding at high seawater pressures, characterized by a decreased resin modulus and increased interfacial thickness.

Thermal reaction based mesoscale ablation model for phase degradation and pyrolysis of needle-punched composite

Needle-punched composites are highly valued for their exceptional resistance to interlaminar properties, ablation, and design flexibility, making them increasingly popular in aerospace thermal protection systems. This work investigates the mesoscale structural characteristics and thermophysical properties of needle-punched composites in ablation process. Oxyacetylene ablation experiments were carried out at different temperatures, and a mesoscopic needle-punched structure model was established based on the results of CT characterization. Further, Abaqus custom subroutine was used to reveal the ablation evolution mechanism of carbon fiber reinforced phenolic resin-based needle-punched composites. The results show that, at mesoscopic scale, the acicular fiber bundle perpendicular to the ablative surface accelerates the heat conduction to the interior of the material and promotes the thermal damage and performance degradation of the composite.

Ablation resistance and high-temperature insulation capacity of TiB2-B4C modified Al-coated carbon fibre/boron phenolic resin ceramizable composites

The inherent susceptibility to oxidation limits the application of carbon fibre/phenolic resin composites (CF/Ph) in the thermal protection of hypersonic vehicle engines. Herein, TiB2-B4C modified Al-coated carbon fibre/boron phenolic resin ceramizable composites were fabricated. The optimal ceramizable composite (T30C10) exhibited excellent ablation resistance and high-temperature insulation capacity at a linear ablation rate and bottom-surface temperature of -0.00768 mm/s and 129.8 °C, respectively. Oxygen consumption and inhibition, carbon fixation, and self-healing effects contributed to the excellent ablation resistance, and the effects of the Al coatings and carbothermal reduction reactions led to excellent high-temperature insulation capacities.

Enhanced thermal and mechanical properties of boron-modified phenolic resin composites with multifiller system for aerospace applications

Enhanced thermal and mechanical properties of boron-modified phenolic resin composites with multifiller system for aerospace applications

Comprehensive mechanical properties and damage mechanisms of a new type multiphase fibers braided/phenolic resin composites

The comprehensive thermodynamic properties of polymer composites play a critical role in determining their service, and internal microscopic damage will lead to severe consequences such as product deformation and cracking. This research presents the composition parameters and preparation process of a new type 2-dimension multiphase fibers braided layered phenolic resin (2D-MFRP) composites. The mechanical property test was conducted by setting the conditions of sampling angle θ, temperature load T, and tensile rate S, which the variation patterns of different characteristics were analyzed based on the specified parameters. The experimental results show that the mechanical properties exhibit high stability within 25 °C to 300 °C, and the mechanical properties sensitivity level of the corresponding parameter is T<S<θ. Additionally, the thermo-mechanical of 2D-MFRP composites were analyzed, which used the combining thermogravimetric methods and differential scanning calorimetry (DSC). The microstructure and damage were observed by scanning electron microscope (SEM), in which the 2D-MFRP composites woven fiber/bundles layered cracks and propagation micro-damage mechanism have been revealed under the influence of angle θ and temperature T. The above research content can provide valuable insights into the thermomechanical properties of a new type 2D-MFRP composites and structural products.

Effects of crosslinker concentration on curing process and performances of needled fiber preform reinforced phenolic aerogel composite using process simulation and comprehensive experiments

A kind of needled quartz/carbon fiber preform reinforced phenolic aerogel composite (NQCF/PR) was fabricated through impregnating needled fiber preform with phenolic resin precursor solution, followed by sol–gel polymerization and solvent drying. The needled fiber preform serves as lightweight quasi-three-dimensional reinforcement, while phenolic aerogel matrix provides high porosity and low thermal conductivity. During fabrication of aerogel composite part using vacuum-assisted resin infusion process, distribution of crosslinker hexamethylenetetramine (HMTA) in precursor solution can be problematic, as precipitated crosslinker particles may be filtered by fibrous preform. In this study, the impact of HMTA filtration induced heterogeneous structure on subsequent curing process was investigated using process simulation. Temperature effects of sol–gel polymerization and solvent evaporation were considered through establishment of corresponding kinetic models. Impacts of heterogenous structure on distribution of temperature, resin curing degree and solvent conversion degree in large hemispherical aerogel composite structure were investigated. This leads to variations in gel network and pore structure of aerogel, thereby affecting final material performance. Based on experimental results, as HMTA concentration increases, compressive performance of NQCF/PR obviously increases. Among these, NQCF/PR with 4.7 wt% HMTA provides a balance of lightweight nature (0.25 g/cm3), excellent thermal insulation property (0.052 W·m−1·K−1) and compressive performance (strength of 0.35 MPa).

Effect of novel aluminium titanate on mechanical, thermal and ablation performance behavior of carbon fiber reinforced phenolic resin composites

AbstractThermal Protection Systems (TPS) protect re‐entry space vehicles from the harsh heating they encounter when hypersonically flying through a planet or the earth's atmosphere. Carbon fiber‐reinforced phenolic resin composites were widely used for the thermal barrier structure of aerospace re‐entry vehicles. A Novel Aluminium Titanate (Al2TiO5/AT) micro powder‐modified Polyacrylonitrile (PAN) based Carbon Fiber Fabric‐Resorcinol Phenol Formaldehyde Resin (C‐PR) (AT‐C‐PR) composites are well prepared to meet the requirements of TPS. The AT may act as an insulating layer and anti‐ablative material due to its excellent thermal shock resistance in TPS. To understand the effectiveness of AT content on density, barcol hardness, interfacial interactions, thermal conductivity, and thermal stability, the C‐PR composites were produced with and without loading of AT with various weight percentages, namely 0 wt% (C‐PR), 1,3, and 5 wt% (AT‐C‐PR) by hot compression molding method. The microstructural and elemental change of the composites were analyzed by microscopic and spectroscopic studies. Results suggested that the Interlaminar Shear Strength (ILSS) of the composites was increased by about 14% at 1 wt% of AT loading. Mass, Linear Ablation Rates (MAR, LAR), and back‐face temperature of C‐PR and AT‐C‐PR composites were decreased to 0.15128 g/s, 0.01233 mm/s, and 405°C, respectively by loading of AT up to 1 wt%. The thermally ablated composites were also evaluated for their crystallographic phase changes. The work provided an effective way to improve the thermo‐mechanical and ablation performance characteristics of the AT‐C‐PR composites that can be potentially used in TPS of re‐entry vehicles.Highlights This investigation utilized innovative Al2TiO5/Aluminium Titanate (AT) ceramic powder as a filler in reinforcing Phenolic Resin (PR) with PAN‐based Carbon Fiber (C). It examined the impact of various loadings of AT in C‐PR composites (AT‐C‐PR) on their physical, mechanical, thermal, and anti‐ablation properties. The AT‐C‐PR composites exhibit reduced density, lower thermal conductivity, and enhanced ILSS (31 MPa) compared to the C‐PR composites. Optimal ablation resistance and thermal stability were achieved with a loading of 1 wt% AT (Mass Ablation Rate: 0.15128 g/s and Linear Ablation Rate: 0.01233 mm/s) compared to the C‐PR composites. Microstructural and elemental analysis of the composites were conducted using microscopy and energy‐dispersive spectroscopy, revealing the presence of oxides and carbides on the ablated surface. The phase transition and alterations in microstructure, coupled with the oxidation of AT, have enhanced the ablation resistance and reduced the back face temperature of different weight percentages of AT‐C‐PR composites, such as 1 wt% AT (413°C), compared to the C‐PR composites (704°C).

Enhanced mechanical property, high-temperature oxidation and ablation resistance of carbon fiber/phenolic composites reinforced by attapulgite

To meet the thermal protection and load-bearing requirements of ultra-high-speed vehicles, it is urgent to improve the ablation resistance, high-temperature oxidation resistance and mechanical properties of carbon fiber/ boron phenolic resin (CF/BPR) composites simultaneously. Herein, polyhedral oligomeric silsesquioxane-modified attapulgite (ASP) with abundant porous structure was successfully introduced into the CF/BPR (CF/ASPBPR). The co-effect of ceramization, high infrared emissivity, and low thermal conductivity endowed the CF/ASPBPR with desirable ablation resistance, where the linear ablation rate and mass ablation rate reduced to 0.038 mm/s and 0.035 g/s, respectively. Meanwhile, due to the high thermal stability and energy dissipation of ASP, the CF/ASPBPR also presented the interlaminar shear strength of 35.40 and 9.79 MPa before and after high-temperature treatment, which were 24 % and 63 % higher than that of CF/BPR, respectively. This study provides a promising pathway for preparing advanced thermal protection materials that can adapt to severe mechanical spalling and thermochemical erosion environments.

Mechanical property, oxidation resistance, and ceramization mechanism of MoSi2-SiB6 reinforced phenolic resin matrix composites

Ceramizable phenolic resin matrix composites have a significant potential for widespread applications in the field of aerospace ablation. However, due to the sharp decrease of mechanical properties at elevated temperatures, the composite fails to meet the requirements of thermal protection as well as load-bearing of aircraft in a wide temperature range. In this study, boron phenolic composites modified by MoSi2 and SiB6 with high strength in a wide temperature range are prepared. The flexural strength of composites after ablation within the temperature range of 800 °C to 1600 °C ranges from 48.07 to 82.49 MPa. In particular, a significant increase of 224.9% is obtained at 1400 °C with 6 wt% SiB6. The mass ablation rate and line ablation rate of the composites are increased to 0.054 g/s and 0.013 mm/s, respectively. The cooperation effect of oxygen consumption, carbon fixation, oxygen barrier, and liquid phase bonding produced by ceramization reactions involving SiB6, MoSi2, O2, and pyrolytic carbon at different temperatures, resulting in an improvement of the mechanical property and the oxidation resistance of the composite. These composites have a potential in long term thermal protection and load-bearing of new ablation materials.

Pyrolysis front detection in carbon phenolic composites using x-ray computed tomography

Carbon phenolic composites are used as thermal protection systems (TPS) materials on space capsules to protect them from the hot aerothermal environment. The phenolic resin in the composite material decomposes (pyrolyzes) at low temperatures resulting in a pyrolysis front within the material. The detection of the pyrolysis front after exposure to heat has historically been achieved by physically sectioning cross-sections of the material. We combine the phase contrast retrieval method to reconstruct x-ray computed tomography scans along with image convolution to identify the pyrolysis front in carbon phenolic composites. Unlike the standard filtered back projection method that captures only the carbon phase, the phase contrast retrieval method uses both the attenuation coefficients and refractive indices to illuminate all three phases (carbon, resin, and voids) of carbon phenolic composites. Image convolution is applied on scans reconstructed using the phase contrast retrieval method to develop a density map of the composite to locate the pyrolysis front. The analysis is performed on a sample of phenolic impregnated carbon ablator that was tested in an arc-jet facility. For the sample analyzed, the depth of the pyrolysis front from the surface of the sample is calculated to be 2.150 ± 0.148 mm. Although the proposed approach is applied to detect the pyrolysis front, the tools can be used to illuminate the structure of any carbon phenolic composite, and we propose the use of the phase contrast retrieval method as a methodological standard to analyze carbon phenolic composites used on space capsules.

Ablation behavior and high temperature ceramization mechanism of TiB2-B4C-ZrC modified carbon fiber/boron phenolic resin composites

The carbon fiber (CF) reinforced boron phenolic resin (BPR) matrix composite, renowned for its exceptional ablation resistance, represents a promising material for high-temperature applications. However, hypersonic vehicles are subjected to increasingly challenging service environments, which necessitate materials capable of enduring even more extreme temperatures. Consequently, there is a growing need for composites that exhibit superior ablation resistance. To tackle these demanding requirements, this research initiative introduces the integration of ceramizable fillers, including TiB2, B4C, and ZrC, into the composite structure to create a high-temperature ceramizable system. The experimental findings indicate that the composites formulated with this innovative system demonstrate extraordinary ablation resistance, even when exposed to oxyacetylene flames with a heat flux of 4364 kW/m2. Notably, the measured linear ablation rate and mass ablation rate were recorded at −0.012 mm/s and 0.0268 g/s, respectively. These values are exceptionally low. Subsequent analysis utilizing X-ray diffraction (XRD) and additional characterization techniques has confirmed the formation of a dense ceramic layer with a B-C-O-Ti-Zr composition on the composite surface at elevated temperatures. This ceramic layer acts as a formidable barrier, significantly mitigating the ablation effects caused by high-temperature exposure. Meanwhile, it is pertinent to note that the formation of the ceramic layer is accompanied by an endothermic reaction, which consequently leads to a reduction in the thermal conduction of the composite to some extent.

In-situ formation of surface “self-protective” graphitic layer on phenolic resin-based thermal protection composites

Phenolic resin (PR) composites are widely utilized as thermal protection materials for high-speed aircraft, where their protection mechanisms have been investigated in earlier studies. However, it remained indistinct about the evolution behavior of the outermost surface and its subsequent effects on the ablation performance. Herein, this work re-investigated the morphological transformation and chemical conversion on the outermost surface of a silica fiber-reinforced PR board after ablation by means of combined experimental characterizations at micro- and nanoscale (SEM, TEM, Raman spectroscopy, XRD, XPS) and computational study (ReaxFF-based molecular dynamic simulation). For the first time, our study revealed that its outermost ablated surface demonstrated a distinct evolution behavior in terms of both the in-situ formation of “self-protective” graphitic layer and the radial redistribution of surface carbonaceous substances with different degrees of graphitization, leading to varied ablation resistance along the radial direction of the PR board. In addition, the computational study investigates the ablation-induced graphitization and its influence on the ablative resistance of PR surface. It indicated that, at equivalent energy flux density, PR with graphitized structures exhibited improved thermal protection performance, which can be attributed to decreased thermal conductivity and increased density, leading to a reduced ablation recession rate. Such revelation provides an alternative route in the design of PR-based ablative materials with enhanced ablation resistance.

Wear-resistant phenolic composites reinforced with attapulgite and short carbon fibers for applications subjected to both dry and oil-lubricated sliding

Attapulgite (AT) nanofibers were integrated into phenol-formaldehyde resin (PF) and PF composites reinforced with short carbon fibers (CF). Inclusion of AT significantly enhances the wear resistance of PF under both dry and oil-lubrication conditions. The hybrid nanocomposites, reinforced with both AT and CF, exhibit a high mechanical strength. Interestingly, AT and CF lower synergistically the friction coefficient of PF subjected to harsh dry sliding conditions. The hybrid nanocomposites exhibit excellent tribological performance under both dry and oil-lubrication conditions. Tribofilms’ nanostructures were comprehensively analyzed for disclosing dominant tribological mechanisms. Outcome of this work provides new ideas for developing tribo-materials of a high adaptability to various dry/oil-lubrication conditions.

Synthesis of phenolic resins with cyclotriphosphazene for enhancement of ablation and char yields

A novel phenolic resin with combined hydroxymethyl-substituted phosphazene unit as a part of cured network was prepared which exhibited excellent thermal properties and ablation resistance. The novel phenolic resin was synthesized via copolymerizing from hexa (4-hydroxymethylphenoxy) cyclotriphosphazene (CHPP), phenol and paraformaldehyde. The CHPP contains abundant –CH2OH groups, which can be a part of phenolic resin network through condensation reactions between the –CH2OH groups and active hydrogens on benzene rings of phenolic resins. The optimal curing temperature for the modified phenolic resins was determined using the non-isothermal DSC method. The ablation resistance was investigated using the oxyacetylene flame method. The char yield and linear ablation rate of the modified phenolic resins are 71.3 % and 0.0020 mm/s, respectively. The ablation resistance of the novel resin is significantly improved, compared with other phenolic resin composites. The modification method for the phenolic resin provides a novel pathway to improve the application prospects of phenolic resins in the field of thermal protective materials.

Anti-oxidative quartz/carbon-braided fiber reinforced ceramizable composites modified with B4C and AlB2: Mechanical robustness, phase evolution and anti-oxidation mechanism

Carbon fiber reinforced ceramizable phenolic resin matrix composites (Cf/CPR) have been widely used in the field of thermal protection materials. However, the industrial application of the Cf/CPR is restricted by its easy oxidation failure under high temperature condition. In this work, a novel antioxidative ceramizable composites modified with AlB2 and B4C (Cf-Qf/CPR) were prepared by using quartz fiber-coated carbon fiber (Cf-Qf) as reinforcements via co-weaving technique. The thermal stability, mechanical properties, interfacial phase evolution and anti-oxidation mechanism of the composites were investigated. The residue yield and the flexural strength of the composites after treatment at 1200°C for 15 min were 93.4 % and 62.4 MPa, increased by 5.4 % and 67.3 % compared with those of Cf/CPR. Quartz fiber and ceramic protective layer showed synergistic effect to improve the oxidation resistance of carbon fiber and PyC, confirming good high temperature mechanical properties and oxidation resistance of as-received composites.

Environmental-friendly and fast production of ultra-strong phenolic aerogel composite with superior thermal insulation and ablative-resistance

There is an urgent need for developing “low-carbon” synthesis technology to prepare aerogel composites with both high mechanical strength and efficient thermal insulation for applications of modern aerospace and energy saving. Herein, we propose a strategy for fabricating lightweight phenolic aerogel composites with thick-united connected nano-structure and good aerogel-fiber interfacial compatibility. The specific micro-nano structure and optimized material synergism endow the aerogel composites with an ultrahigh tensile strength (12.84 ± 0.64 MPa), bending strength (24.69 ± 1.96 MPa) and compressive strength (1.7 ± 0.053 MPa under 5 % strain), as well as low thermal conductivity (0.0541 ± 0.0003 W/(m·K)). The aerogel composites behave excellent ablation-resistance under the flame of 1200 °C within 30 min and maintain a cold-side temperature of 56.07 °C without any shape change. The rigid-flexible comminated aerogel composites open up a new technical track for developing lightweight thermal protective composites with high strength, toughness, and efficient thermal insulation demanded in extreme environments.

Investigation on thermal conductivities of plain-woven carbon/phenolic and silica/phenolic composites at high temperature: Theoretical prediction and experiment

Phenolic resin-based ablation materials have found widespread applications in the aerospace industry. The prediction of their thermal conductivity is of paramount importance for the optimization and evaluation for thermal protection systems. However, there is rarely reported thermal conductivity performance of phenolic composites during ablation processes. Therefore, this investigation theoretically predicts the dynamic response of thermal conductivity at high temperatures for plain-woven carbon/phenolic and high silica/phenolic composites. By combining the progressive cubic ablation model with existing composite material property formulas, a multiscale prediction model for effective thermal conductivity is developed. The thermal performance of the resin matrix, reinforcing fibers, yarns, and overall fabric composites is calculated. Additionally, mesoscale representative volume elements are implemented to investigate the overall heat transfer characteristics of carbon/phenolic and high-silica/phenolic composites, including temperature and heat flux distributions. Moreover, both composites thermal conductivities are measured in the range from 298 K to 473 K. The proposed prediction model demonstrates good reliability, with average deviations of 3.76 % and 7.36 % compared to finite element analysis results and experimental data, respectively.

Volatile oil constituents, antioxidant and antibacterial activities of Lonicera caprifolium L. in different areas of Iran

The genus of Lonicera is the largest genus of Caprifoliaceae family. This study revealed the composition, antioxidant, and antibacterial actions of essential oils of Lonicera caprifolium L. in different areas of Iran; Qom, Mashhad, Shiraz. Gas chromatography-mass spectrometry examination was applied to recognise the oil conformation. The essential oils of Qom included a high number of monoterpenes, with linalool as the significant constituent. In the essential oil of Mashhad, the main elements were methyl linoleate. The essential oil of Shiraz displayed a similar profile, including a large quantity of fatty acid, with methyl palmitate as the main component. The antioxidant activity was assessed via the DPPH exam, and the antimicrobial action was verified using the broth microdilution procedure. The essential oils of Qom revealed the maximum antimicrobial and antioxidant actions between the three regions, ascribed to its high concentration of monoterpenes and phenolic composites. Moreover, principal component analysis (PCA) and heat map successfully revealed the variation and correlation between metabolites of the three oils. These conclusions highlight the potential of L. caprifolium as natural foundations of antimicrobial and antioxidant representatives, with investigation required to reveal their therapeutic requests.

Temperature-dependent creep damage mechanism and prediction model of fiber-reinforced phenolic resin composites

Carbon fiber-reinforced phenolic resin (CF/PF) and glass fiber-reinforced phenolic resin (GF/PF) composites are crucial for thermal insulation and load-bearing capabilities in the aerospace industry. Understanding their creep behavior at various temperatures is essential. This study investigates the impact of temperature on the bending creep properties of CF/PF and GF/PF composites, focusing on deformation response, damage mechanisms, and prediction models. Results reveal that the decrease in creep properties at elevated temperatures is mainly attributed to the increased viscoplastic strain. At room temperature, CF/PF composite demonstrates exceptional creep properties. CF/PF composite exhibits heightened sensitivity to elevated temperatures, undergoing creep rupture at 210 °C and 240 °C with failure strains of 0.48 % and 0.49 %, respectively. High-temperature damage mechanisms have been analyzed in depth using a combination of thermal stress finite element simulation and microscopic characterization. Thermal stress is directly related to the difference in thermal expansion between the fibers and the resin. The influence of fiber distribution and geometry results in the interface being subjected to both normal and shear stresses. The accumulation of interfacial damage increases the plastic deformation and degrades creep performance. Additionally, an advanced temperature-dependent Burgers model has been developed and effectively predicted the creep curves under different temperatures and loads. This model demonstrated great potential as a general predictive model.