Fiber Reinforcement Research Articles

AI control-activated carbon-ZnO/CuO conductive polymer structural super-capacitor for EV

In the automobile industry, nanocomposite technologies reduce weight and emissions, increasing vehicle energy efficiency. The multipurpose structure of the electric vehicle, known as the structural super-capacitor, is 35% lighter than steel and can produce electricity by trapping solar heat. This work developed an electric double-layer structural supercapacitor (EDLC) using aqueous sodium sulphate (Na2SO4) as the electrolyte, carbon fibre reinforcement conductive polymer (CFRP) and activated carbon zinc oxide (AC ZnO) as the n-type and copper oxide (CuO) as the p-type. Different weight percentages (wt.%) of AC ZnO/CuO capacitors have been constructed and tested at 32°C solar temperatures. Compared to other wt% AC EDLC, the CFRP-EDLC with 6 wt% of AC has the maximum performance, with a capacity of 18.56 μF/cm2. In comparison to other formulations, the 70 wt% of epoxy, 6 wt.% weight AC and 30 wt% ZnO/CuO EDLC demonstrated superior charging in a shorter amount of time and discharging in a longer amount of time. If the solar trapping heat rises beyond 32°, an AI power management system (AIPMS) has been built into the EDLC EV body panel to prevent any mishaps. Depending on the current EDLC signal, AIPMS indicates EDLC operation.

Simulating the effect of elevated temperature on the compressive strength of steel fiber reinforced concrete (SFRC) using ANSYS workbench

The behavior of concrete structures at elevated temperatures is of significant importance in predicting the safety of structures in response to certain accidents or particular service conditions. The behavior of M50 Steel Fiber Reinforced Concrete (SFRC) at 28-days strength subjected to elevated temperatures was simulated using ANSYS 2020 R2 Workbench, and results validated with experimental results from a referenced Journal. M50 concrete at 28-days was modelled along with steel fibers from 0 to 4% by weight of cement. Models were made and subjected at room temperature, 100, 200, 300, 400 and 500°C from ANSYS Workbench Static Structural module. The concrete matrix was modelled as solid body, while the steel fiber reinforcement as line bodies, the new ANSYS reinforcement workflow that allows for simulating proper bond between concrete and rebar was utilized. Compressive strength results were determined as Average Von-misses stress and results validates that obtained from the referenced literature. This work has developed results with variations compared to the experimental work largely below 5% and has given important reasons to assert that results obtained from experimental works can be obtained with FE simulations and that laboratory works can be simulated with FE programs to cut down on cost and time associated with the former. In other words ANSYS Workbench program is a good validatory tool for similar experimental research.

Experimental Study of the Bearing Capacity of Hybrid Fiber-Reinforced Concrete Pipes

This paper presents the results of an experimental study on hybrid fiber-reinforced concrete pipes (HFRCP). The mechanical behavior of HFRCP, including load capacity, failure mode, and energy dissipation capacity, was evaluated through diametral compression tests. The results were compared with those obtained for reinforced concrete pipes (RCP) using traditional steel cage reinforcement and steel fiber-reinforced concrete pipes (SFRCP). A total of 26 pipes with a 600 mm internal diameter were tested, including 4 RCP, 14 HFRCP, and 8 SFRCP pipes. For the hybrid fiber reinforcement, macro steel fibers (SF) and macro polypropylene fibers (PPF) were used, combined at two different doses: 20-0.5 kg/m3 and 20-1.0 kg/m3 of SF and PPF, respectively. The results indicated that HFRCP achieved a load capacity equivalent to RCP and greater than SFRCP for the fiber dosages utilized. Additionally, HFRCP exhibited a ductile failure mode without concrete detachment or diametral crushing.

Multiscale modeling of multiwalled carbon nanotube‐reinforced polymer matrix nanocomposites and experimental validation

AbstractThis study developed a numerical model of multi‐walled carbon nanotube (MWCNT)‐reinforced polymer nanocomposite to predict the tensile and flexural behavior of an earth‐stationed antenna reflector. The objectives of the study were to propose a hierarchical model of nanocomposites and introduce the variability in the dimensions of the CNTs. The CNTs were meshed with beam elements and their inner, outer diameter, and length were randomized, as per field emission scanning electron microscopy image. The distribution of the CNTs was realized with the help of a random sequential adsorption algorithm. The CNT content was varied from 0.1 to 0.4 wt% of epoxy matrix. Periodic boundary conditions were implemented. Micro‐scale results were found to lie within 10% of the Halpin‐Tsai model. A concept of dynamically allocated representative volume element was implemented at the meso‐scale, which was then upscaled to macro‐scale to simulate ASTM D3039 and D790 test conditions. With 0.4 wt% of CNT into the matrix, the tensile and flexural modulus increased by 14.42% and 23.94%. The macro‐scale simulated results were compared with literature, where the tensile and flexural modulus were found to deviate by 7.5% and 3%. This model will later be upgraded with continuous fibrous reinforcement along with MWCNT‐filled epoxy, to simulate the performance of a real composite antenna reflector.Highlights Multiscale modeling of MWCNT‐based epoxy nanocomposite was developed. MWCNT was meshed with hollow beam elements as per FESEM images. 0.4 wt% MWCNT enhanced tensile and flexural modulus by 14% and 24%. Numerical tensile and flexural modulus lied within 7.5% and 3% of the tests.

Mechanical, thermal and morphological analysis of polylactic acid‐woven glass fiber composites fabricated by additive manufacturing

AbstractPolylactic acid (PLA), a biodegradable thermoplastic, is being used significantly in a wide range of applications because of its environmentally friendly nature. 3D printing is an innovative technique that is used to fabricate polymer composites with complex contours and high precision. Conventional 3D printing technologies use fiber reinforcement in the form of filament. However, fibers in the form of sheets, when used in composite materials, improve the distribution of load and enhance the multi‐directional strength. This study investigates the improvement in the tensile strength of PLA‐based composite by integrating woven glass fibers (WGF) during 3D printing processing. The composites were fabricated using an FDM‐based 3D printer where the WGF sheet was used as reinforcement and PLA filament was used as the matrix material. The main input parameters consist of the number of WGF layers and the orientation of the WGF. Taguchi orthogonal array was used to fabricate composite samples with different combinations of input parameters and then these samples were tested to evaluate the tensile properties. The finding shows that PLA composites reinforced with four layers of glass fiber at 0/90° fiber orientation showed the highest tensile strength of 52.85 MPa and a thermal degradation temperature of 330.49 °C.Highlights 3D printing of WGF‐PLA composite and mechanical characterization. The composite specimen showed the highest tensile strength of 52.85 MPa. The thermal degradation temperature reached 330.49 °C in TGA analysis. ANN predicted the optimal combination of 4 fiber layers with 0/90° orientation. Uniform PLA deposition reduced voids and enhanced interlayer adhesion.

Mechanical performance and durability attributes of biodegradable natural fibre-reinforced composites—a review

AbstractWith the rising awareness about the impact of excessive urbanization on the environment, alternative and more eco-friendly materials such as natural fibre-reinforced composites (NFRCs), which have lower embodied energy, can be considered in modern application ranging from construction housing to urban infrastructures in order to promote the concept of sustainable development. One of the current challenges faced by material engineers is to develop NFRCs with optimized durability performance which correspond to high mechanical attributes during their service lifetime while possessing satisfactory degradability trait in the disposal phase. This proposed review study principally covered the state-of-the-art progress made in the development of sustainable composite material such as advanced and biodegradable NFRC. In the first section, the review covered key aspects of NFRC fabrication including fibres and matrix selection, property-enhancing treatment for fibres and influence of nanostructures in biodegradable composites. In the second phase of this review, the fibre-matrix interaction and their corresponding physical and mechanical performance were discussed. The typical failure modes observed in NFRCs were outlined and means to improve their facture toughness were proposed. Finally, the third section comprised the durability and degradation assessment of key components of the biodegradable NFRCs, namely the fibre reinforcement, matrix and interface sections. Additionally, the impact of disposing of similar composite materials in the environment was assessed, and present-day recycling techniques were discussed. Further research on the mechanical performance, durability traits and degradability aspects of NFRCs as enumerated in this study will unquestionably promote their use and integration into a wider range of engineering applications in our modern society.

Enhancement of Green Composite Performance Through the Synergistic Influence of Cashew Nut Shell Liquid and Nanoclay on Natural Fiber Reinforcement

ABSTRACTNatural fiber‐reinforced biocomposites are emerging as viable alternatives to conventional thermoplastics; however, low mechanical and physical properties limit their broad applications. This study addresses these limitations by developing a nanoclay and cashew nut shell liquid (CNSL)‐modified novel soy resin‐based jute composites by enhancing mechanical and physical performance. CNSL, rich in phenolic compounds, chemically interacts with the soy matrix, improving interfacial bonding and imparting resistance to environmental degradation. Nanoclay dispersion within the matrix optimizes load transfer, as confirmed through density functional theory (DFT) calculations of interaction energies, resulting in a synergistic effect on composite strength. The optimized composite exhibited a remarkable storage modulus of 8697 MPa at 35°C and 1 Hz, a flexural modulus of 3288 MPa, tensile strength of 61.3 MPa, and flexural strength of 62.7 MPa. X‐ray diffraction and transmission electron microscopy analyses revealed a well‐integrated nano‐biocomposite structure, confirming successful reinforcement dispersion. Thermal stability up to 290°C, a contact angle of 61.4°, and water absorption of 49.5% indicate its suitability for diverse conditions. Additionally, cytotoxicity tests demonstrated the material's biocompatibility, while soil burial tests showed a mass loss of 74.2% over 75 days, verifying its biodegradability. These biocomposites can replace nondegradable thermoplastics in various applications.

Impact compressive properties of polyurethane foams with 3D continuous fibre reinforcement

Flexible and rigid polyurethane foams are used in applications subjected to impact loads. Integrating a three-dimensional, continuous fibre reinforcement meets high requirements for stiffness and strength. A fundamental comparison of the impact compressive properties was carried out for contributing to a reasonable choice between these variants. A rigid and flexible foam with a bulk density of 85 kg/m3 each was investigated with and without reinforcement by a warp-knitted spacer fabric. The material testing was conducted using a drop weight tester in accordance with a German standard. Three impacts are applied by a hammer with a flat surface larger than the area of the sample plate. Different impact energies were investigated and the deformation behaviour was analysed using a high-speed camera. Much higher energy absorptions at low deformations were found with rigid foam. Peak stresses and decelerations were lower with flexible foam if the load did not densify the material. Reinforcing the foams leads to an anisotropic deformation and improves the impact compressive properties, especially in the case of the flexible variant. The four materials analysed had a similar rebound and largely maintained their performance when subjected to the repeated impact load.

Comparative Effects of Carbon Fiber Reinforcement on Polypropylene and Polylactic Acid Composites in Fused Deposition Modeling.

Comparative Effects of Carbon Fiber Reinforcement on Polypropylene and Polylactic Acid Composites in Fused Deposition Modeling.

Experimental research of the tensile strength of concrete reinforced with basalt fiber

Non-metallic composite fittings are increasingly used in modern construction due to their high mechanical characteristics, corrosion resistance, durability in concrete and aggressive external environments, and other properties. At the sametime, usually, non-metallic composite reinforcement is used in the form of rods with the main supporting element in the form of basalt, glass, aramid or roving made of other materials, which is thin fibers with a diameter of 7...20 mm.The specified roving, as an element of reinforcement of concrete structures, will be used in the form of fiber to a much lesser extent, although it is a real alternative to traditional steel fiber with all the advantages of fiber reinforcement, to which corrosion resistance is also added. The limited number of experimental explains the current situation andtheoretical studies of non-metallic fiber reinforcement, in particular, tensile strength, which is one of the main advantages of fiber reinforcement of concrete.This article presents the results of experimental studies of the tensile strength of concrete reinforced with fiber from basalt roving with a diameter of 16 μm and a length of 24 mm, which included bending tensile tests of three series of concrete samples with a strength class of compression, respectively, C20/25, C25/30, C30/35 and percentage of fiber reinforcement within 2.0...8%.As a result of the conducted research, it was established that the fiber reinforcement from the baseboard roving leads to an increase in the axial tensile strength of concrete. At the same time, the most intensive increase in tensile strength took place when the percentage of reinforcement was increased in the range of 2.0...4.0%. With a further increase in the percentage of reinforcement in the range of 6.0...8.0%, this growth stopped, which indicates that fiber reinforcement in the range of 2.0...4.0% is the most effective, regardless of the class of concrete in terms of compressive strength.Other things being equal, the increase in axial tensile strength of concrete with an increase in the percentage of fiber reinforcement within the limits of 2.0...8.0% is 15...20% compared to concrete without reinforcement.

Study on the Dynamic Fracture Properties of Defective Basalt Fiber Concrete Materials Under a Freeze-Thaw Environment.

This study examines the crack resistance of basalt-fiber-reinforced concrete (BFRC) materials subjected to freeze-thaw cycles (FTCs). We utilized a φ50 mm Split Hopkinson Pressure Bar (SHPB) apparatus alongside numerical simulations to carry out impact compression tests at a velocity of 5 m/s on BFRC specimens that experienced 0, 10, 20, and 30 FTCs. Additionally, we investigated the effects of basalt fiber (BF) orientation position and length on stress intensity factors. The results reveal that with an increasing number of FTCs, the dynamic crack propagation speed of BFRC with a prefabricated crack inclined at 0° rises from 311.84 m/s to 449.92 m/s, while its pure I fracture toughness decreases from 0.6266 MPa·m0.5 to 0.4902 MPa·m0.5. For BFRC specimens with a prefabricated crack inclination of 15°, the dynamic crack propagation speed increases from 305.81 m/s to 490.02 m/s, accompanied by a reduction in mode I fracture toughness from 0.3901 MPa·m0.5 to 0.2867 MPa·m0.5 and mode II fracture toughness from 0.6266 MPa·m0.5 to 0.4902 MPa·m0.5. In the case of a prefabricated crack inclination of 28.89°, the dynamic crack propagation speed rises from 436.10 m/s to 494.28 m/s, while its pure mode II fracture toughness decreases from 1.1427 MPa·m0.5 to 0.7797 MPa·m0.5. Numerical simulations indicate that fibers positioned ahead of the crack tip-especially those that are longer, located closer to the crack tip, and oriented more perpendicularly-significantly reduce the mode I stress intensity factor. However, these fibers have a minimal impact on reducing the mode II stress intensity factor. The study qualitatively and quantitatively analyzes the crack resistance of basalt-fiber-reinforced concrete in relation to freeze-thaw cycles and the fibers ahead of the crack tip, offering insights into the fiber reinforcement effects within the concrete matrix.

Effects of discrete fibre reinforcements on the wear resistance behaviour of polyamide-based spur gears

Abstract In many situations, the polymer gears are the perfect replacement for traditional metal gears. Compared to metal gears, the polymer gears will generate more heat at the gear tooth contact surface and more wear loss. Hence, this study aims to decrease the wear loss and increase the load-carrying capacity of the polymer gears. To achieve this, the reinforcement materials were added to the base polymer gear material. In this study, Nylon-66 was chosen as the polymer matrix material and an isolated glass fibre and steel grid were used as the reinforcement materials. Three different types of polymer spur gears such as Polyamide Gear (Nylon-66), Reinforced Polyamide Gear (Nylon-66+Glass Fibre), and Hybrid Glass Fiber Steel Grid Gear (Nylon-66+Glass Fibre+Steel Grid) named PG, RPG and HGFSGG were fabricated using injection moulding machine and each type of gears were compared for wear loss and specific wear rate under the similar testing conditions. The wear test was performed in the Forschungsstelle fur Zahnrader und Getriebebau (FZG) test rig at 1500 rpm with an applied load of 20 N for 12.5 hours continuously. From the test results, it was identified that HGFSGG polymer spur gears have exhibited a lower surface temperature and better wear properties compared to the other two types of spur gears. From the Scanning Electron Microscope (SEM) analysis, it was noticed that the PG spur gear exhibited deep and uniform wear at the gear tooth surface. In contrast, RPG spur gear exhibited glass fibre distortion and abrasive-type wear. The SEM micrograph of HGFSGG spur gear reveals the presence of very few surface flaws in the gear tooth surface.

Study on Mechanical Properties and Carbon Emission Analysis of Polypropylene Fiber-Reinforced Brick Aggregate Concrete.

Given the current construction waste accumulation problem, to utilize the resource of red brick solid waste, construction waste red brick was used as a concrete coarse aggregate combined with polypropylene fiber to prepare PPF (polypropylene fiber)-reinforced recycled brick aggregate concrete. Through a cube compression test, axial compression test, and four-point bending test of 15 groups of specimens, the influences of the aggregate replacement rate of recycled brick and the PPF volume on the mechanical properties of recycled brick aggregate concrete reinforced by PPF were studied, and a strength parameter calculation formula was constructed and modified based on the above. Finally, combined with a life cycle assessment (LCA), the carbon emissions of raw materials were analyzed and evaluated. It was found that the mechanical properties of recycled concrete enhanced by PPF are critical at an addition rate of 50% and then decrease slowly with an increase in the aggregate content. PPF effectively alleviates the problem of strength reductions caused by regenerated aggregate substitution through the fiber-bridging effect. Based on the experimental data, a mechanical transformation model considering fiber reinforcement and BA weakening was constructed, and the regression accuracy R2 was around 0.90. The environmental benefit obtained when only replacing the natural aggregate is low. Although the incorporation of fiber improves the carbon emissions of the material to a certain extent, the benefits are more noticeable compared with the increase in strength. The results show that garbage recovery and strength demand benefits are achieved when the amount of recycled brick aggregate is 50% of the total. The strength conversion model established in this paper has of high accuracy and was created with careful consideration of fiber reinforcement and the regenerated aggregate weakening correction, providing it with more robust adaptability and extensibility. The mechanical properties of the recycled brick aggregate concrete enhanced by PPF are excellent and sustainable when the replacement rate of BA is 50% and the PPF volume is 0.1%.

Effect of multi-scale hybrid fiber reinforcement on mechanical properties of ultra-high performance concrete

An experimental investigation was conducted on the effect of multi-scale hybrid fiber reinforcement incorporating steel fiber and wollastonite fiber on mechanical properties (i.e. compressive strength, splitting tensile strength, flexural toughness and direct tensile properties) of ultra-high performance concrete (UHPC). The results indicate that, compared with macro-fiber, hybrid steel fiber composed of macro-fiber and meso-fiber improves the strength and toughness of UHPC significantly. The higher the dosage of meso-fiber, the better the effect of hybrid steel fiber. Meanwhile, longer meso-fiber provides a better performance in terms of interfacial bonding strength between the fiber and the matrix of UHPC, leading to an increase in the anti-cracking effect of hybrid steel fiber, and hence the improvement in the splitting tensile strength and flexural toughness of UHPC. Moreover, adding wollastonite fiber as micro-fiber is efficient to enhance the mechanical properties of UHPC incorporating with hybrid steel fiber. It may be related to the respective anti-cracking effect of three types of fiber and their synergistic snubbing effect, as well as the filling effect of wollastonite fiber and the chemical bonding effect caused by the reaction between wollastonite fiber and Ca(OH)2 in the paste.

Effect of Glass Fiber Reinforcement on Marginal Microleakage in Class II Composite Restorations: An In Vitro Pilot Study.

Background: Polymerization shrinkage of composite resins affects the marginal closure of direct dental restorations. It is responsible for developing secondary caries and indirectly affects the survival rate of restorations. This study aims to investigate the null hypothesis, which states that there are no significant differences in the marginal microleakage of Class II restorations when examined in vitro using different dental adhesives, whether the restoration material used is a composite with glass fiber reinforcement or not. Methods: Class II cavities were prepared on both proximal surfaces of thirty-six extracted human molars. A single-component (Universal VivaPen) and a two-component (Futurabond DC) self-etch adhesive system were used for the restorations in the control group (Charisma Classic) and the experimental group (Charisma Classic with Interlig glass fiber strip). An oblique layering technique and a 40-s soft-start light-curing polymerization were used. After selective pre-isolation, the specimens were placed in a 0.2% methylene blue solution and incubated at 37 °C for 24 h. The teeth were sectioned in the mesiodistal direction, and two examiners examined and graded the extent of dye penetration. Statistical analysis was conducted using the Mann-Whitney U and chi-square tests (p < 0.05). Results: All the composite restorations reinforced with glass fiber showed significantly reduced dye infiltration compared to the control group (p < 0.05). A significant difference (p < 0.05) was also observed between the two adhesives. Conclusions: The null hypothesis was rejected. Glass fiber strips significantly reduced composite restoration microleakage regardless of the adhesive. The marginal fit of the restoration was also influenced by the adhesive system used.

Thermal Properties of Polypropylene Fibrillated Fibre Reinforced Lightweight Foamed Concrete

Thermal Properties of Polypropylene Fibrillated Fibre Reinforced Lightweight Foamed Concrete

Modeling‐based characterization for thermal expansion and chemical shrinkage of highly viscous epoxy resin with thermoplastic additives under the curing condition

AbstractThe present investigation introduced an indirect approach to accurately characterize thermal expansion and chemical shrinkage coefficients of the BA9916 resin, which is a thermoset epoxy resin with thermoplastic additives for enhanced impact performance, throughout the curing process. To ensure modeling accuracy, experimental measurements of thermal decomposition and curing kinetics were also considered. Characterization of the BA9916 resin based on experiments completely was difficult due to its exceptionally high viscosity caused by the thermoplastic additives, imposing major obstacles in degassing during sample preparation. To tackle this problem, an indirect characterization method was utilized, beginning with characterizing the unidirectional (UD) composites with the BA9916 resin. Based on the measured composite properties, the corresponding characteristics of the BA9916 resin were then calculated using the modulus‐modified rule‐of‐mixtures with carbon fiber reinforcement properties provided by the material supplier. Subsequently, the representative volume element (RVE) models for the UD composites with various configurations, including different volume fractions of carbon fibers, degrees of curing and curing temperature profiles, were established for simulation with the theoretically calculated resin properties and supplier‐provided fiber characteristics. Homogenized results of the RVE modeling were validated against the experimental measurements with an error of less than 6%, demonstrating the effectiveness of this modeling‐based method for characterizing the coefficients of thermal expansion (CTE) and chemical shrinkage (CSC) of the highly viscous thermoset resin under the curing condition.Highlights The resin is a thermoset epoxy resin toughened using thermoplastic additives. The excessive viscosity of the resin hindered effective degassing. The thermo‐chemical properties of the resin were characterized indirectly. A non‐contact approach was used to determine the CTE and CSC.

Thermoset and thermoplastic polymer composites reinforced with flax fiber: Properties and application—A review

AbstractFlax fibers are a viable material for creating sustainable composites since they have mechanical qualities similar to those of synthetic fibers. Because of their unique hydrophilicity and strong mechanical properties, flax fibers should be taken into specific attention while creating composite materials. Vegetable fibers like flax are highly versatile and are frequently utilized in structural composites. Additionally, flax has shown potential in a variety of other uses, including as shipping, automotive, aerospace, and construction. This study aims to provide a comprehensive overview of the state of advancement in flax fiber reinforcement composite research. The most important research on thermoset and thermoplastic composites reinforced with flax fiber is compiled and analyzed in this article. This article also summarizes the main properties of flax fibers, discusses chemically enhancing their qualities, explains the process of making and analyzing flax fiber composites, and identifies areas that require more research. The article concludes with a few critical ideas and future directions that emphasize the challenges that need to be handled in more in‐depth research and probable composites industrialization.Highlights Flax fibers: Structure, composition, and extraction techniques explored. Polymer matrices in flax fiber composites: Types and processing methods. Mechanical properties of thermoset and thermoplastic flax fiber reinforced composites. Applications of flax fiber composites in automotive, construction, and aerospace. Future potential of flax fiber and hybrid composites in advanced materials.

Evaluation of theoretical models for anisotropic effective thermal conductivity in continuous fiber-reinforced thermoplastic laminates

PurposeContinuous fiber-reinforced thermoplastic composites are a class of materials highly valuable for structural applications and modeling of heat transfer within them is critical to the design of their processing methods. However, the fiber reinforcement leads to highly anisotropic thermal conduction. Among a variety of methods to account for anisotropic thermal conductivity, continuum models with effective media approximation thermal conductivity are computationally efficient and require minimal data to begin modeling a specific composite material. The purpose of this study is to evalute the utility of these models.Design/methodology/approachIn this work, six potential effective media approximation models are evaluated against experimental heating data. Thick (>25 mm) glass fiber-reinforced polyethylene terephthalate glycol (PET-G) specimens with 40% fiber volume fraction were heated with embedded resistance heating to produce validation and testing data sets. A two-dimensional finite-difference solver was implemented using each of the six effective media approximation models. The accuracy of each model is compared.FindingsThe model developed by Cheng and Vachon was found to predict the experimental results most accurately. Fit statistics were similar in the testing and validation data sets. This model is recommended for simulation of transient heating in continuous fiber-reinforced thermoplastic composites with low-to-moderate fiber volume fractions.Originality/valueThere are a wide variety of mathematical models for effective media approximation thermal conductivity, though very few have been applied to continuous fiber-reinforced thermoplastic composites. This work shows that the simplest methods based on rules of mixtures are well outperformed by more modern and complex models, and should be incorporated for accurate prediction of heating during thermal processing of fiber-reinforced thermoplastic composites.

Carbon-Phenolic Ablators Modified by Ceramic Nanofilms Deposited via Atomic Layer Deposition (ALD) Technique

Ablative materials are widely employed to protect space vehicles from the extreme thermal conditions experienced during their flight into a planetary atmosphere. Carbon-phenolic ablators are composed of a phenolic matrix and a fibrous carbon reinforcement. In the present study, the fibrous reinforcement has been modified through the deposition of thin protective layers of zirconium oxide and aluminum oxide, with the objective of reducing fiber recession and oxidation. The depositions were carried out via atomic layer deposition (ALD), a method that allows for the controlled deposition of uniform and conformal coatings on the carbon felt fibers. The depositions were subsequently evaluated through SEM-EDS analysis. Pristine and ALD-modified felts were impregnated with a phenolic resin matrix and the ablation performance of the composite materials was evaluated through oxyacetylene flame tests. The results demonstrated that, in comparison to uncoated ablators, the ALD-modified samples exhibited enhanced performance in terms of mass loss and surface recession: compared to uncoated ablators, the former was 14% lower and the latter was diminished by 50%. Moreover, the morphological characterization of the tested specimens revealed a significantly reduced degree of oxidation of the coated fibers which were directly exposed to the flame.