Carbon Fiber Reinforced Plastic Research Articles

Numerical Simulation of Fatigue Damage in Cross-Ply CFRP Laminates: Exploring Frequency Dependence and Internal Heat Generation Effects

A numerical simulation investigating the frequency dependence of fatigue damage progression in carbon fiber-reinforced plastics (CFRPs) is conducted in this study. The initiation and propagation of transverse cracks under varying fatigue test frequencies are successfully simulated, consistent with experiments, using an enhanced degradable Hashin failure model that was originally developed by the authors in 2022. The results obtained from the numerical simulation in the present study, which employs adjusted numerical values for the purpose of damage acceleration, indicate that the number of cycles required for the formation of three transverse cracks was 174 cycles at 0.1 Hz, 209 cycles at 1 Hz, and 165 cycles at 10 Hz. Based on these results, it is demonstrated that under high-frequency cyclic loading, internal heat generation caused by dissipated energy from mechanical deformation, attributed to the viscoelastic and/or plastic behavior of the material, exceeds thermal dissipation to the environment, leading to an increase in specimen temperature. Consequently, damage progression accelerates under high-frequency fatigue. In contrast, under low-frequency fatigue, viscoelastic dissipation becomes more pronounced, reducing the number of cycles required to reach a similar damage state. The rate of damage accumulation initially increases with test frequency but subsequently decreases. This observation underscores the importance of incorporating these findings into discussions on the fatigue damage of real structural components.

Reducing the taper and heat-affected zone in nanosecond laser drilling of CFRP plate using backside sacrificial layer

Owing to the anisotropic and heterogeneous properties of carbon fiber reinforced plastics (CFRP), laser drilling processes often lead to substantial heat-affected zone (HAZ) and taper formation. The introduction of a medium to facilitate heat conduction during laser processing has emerged as an efficacious strategy to mitigate these challenges. In this study, a sacrificial layer was added to the back of the CFRP plate to reduce the taper and HAZ produced by laser drilling. The effects of laser power, scanning speed, and pulse frequency on hole surface morphology and HAZ evolution were investigated. By adding a sacrificial layer, the taper was reduced by 4.6% to 31.4%, the exit roundness im-proved by 1.11% to 2.56%, and the HAZ on the exit surface decreased by 47.6% to 61.9%. The sacrificial layer had minimal impact on the entrance diameter and HAZ. This study provides a reference for improving the quality of laser drilling in CFRP plates.

Characterisation and collapse analysis of composite egg-shaped pressure housings: experimental and numerical insights

ABSTRACT This study examined the collapse performance of composite egg-shaped pressure housings made of carbon fiber reinforced plastic (CFRP) layers and a nylon liner, fabricated using filament winding and 3D printing. Two types of housings—nylon and composite—were designed, fabricated, tested, and analyzed, with experimental results aligning with numerical predictions. The composite housings had an average ultimate strength of 5.98 MPa, 6.10 times greater than the nylon housings. Matrix compression damage was observed in the CFRP layer before reaching the ultimate strength, starting from the innermost CFRP layer. The composite housings outperformed other materials, showing a performance ratio 1.95 times higher than nylon, 2.75 times higher than resin, 1.31 times higher than Q235 mild steel, and 1.17 times higher than 304 stainless steel. These findings offer valuable insights for designing composite pressure housings and preventing collapse, highlighting their potential for deep-sea submersibles.

Deep Autoencoder Framework for Classifying Damage Mechanisms in Repaired CFRP

This study investigates the classification of damage modes in adhesively bonded carbon fiber-reinforced plastic (CFRP) composites, a critical factor in advancing lightweight automotive design. Adhesive bonding, replacing traditional riveting, improves structural integrity while reducing weight and CO2 emissions. Mechanical testing on CFRP composites was performed, and acoustic emission (AE) signals were collected to evaluate damage mechanisms. A deep autoencoder (DAE) framework was developed to automate damage characterization by reducing AE signal dimensionality through singular value decomposition (SVD) and classifying features using the k-means algorithm. This approach effectively identified three primary damage modes: matrix cracking, interfacial debonding, and fiber breakage. Traditional AE features, such as entropy and amplitude were also classified and validated using spectral analysis. The DAE-based strategy demonstrated superior capability in real-time damage mode differentiation. Fractographic analysis confirmed crack growth in the adhesive layer, leading to interfacial debonding, fiber-matrix separation, and eventual fiber rupture. These findings highlight the DAE framework’s effectiveness in enhancing damage mode characterization, offering valuable insights for optimizing the structural performance of bonded CFRP composites in automotive applications.

Deep transfer learning for delamination damage in CFRP composite materials

This article presents the health monitoring of carbon fiber-reinforced plastic (CFRP) structures using a data-driven deep transfer learning approach to facilitate mapping signal features to damage categories. Simulations were conducted on composite material specimens with delamination damage, with validation performed using laboratory-derived CFRP damage experimental data. Continuous wavelet transform was employed to process Lamb wave signals recorded from a specified sensor network on the composite material panel, extracting time–frequency scale representations. A cross-workpiece deep transfer learning (CWTL) model was proposed to address the interdependence of the machine learning (ML) model on a large set of labeled damage data for different composite material structures. The CWTL, by seeking an appropriate initial range with minimal data, alters the direction of gradient descent, thereby identifying initial parameters more sensitive to the task. This process allows the ML model to fit to a limited damage dataset quickly. To assess the robustness of this method, considering environmental variability as well as damage localization and quantification, further extensions of the study were explored. The results demonstrate the efficacy of CWTL in accurately classifying both undamaged and delaminated damage categories, with high accuracy, suggesting the ML model’s potential for practical applications in such structural frameworks.

Evaluating the effect of cryogenic cooling in reducing the delamination during drilling of carbon fiber reinforced plastic (CFRP) and Al 2024 stack

Evaluating the effect of cryogenic cooling in reducing the delamination during drilling of carbon fiber reinforced plastic (CFRP) and Al 2024 stack

Effect of the Degree of Crystallinity of Base Material and Welded Material on the Mechanical Property of Ultrasonically Welded CF/PA6 Joints.

Ultrasonic welding (USW) is considered one of the most suitable methods to join semi-crystalline carbon fiber-reinforced thermoplastics (CFRTPs). The degree of crystallinity (DoC) of the semi-crystalline resin will affect the ultrasonic welding process by affecting the mechanical properties of the base material. In addition, ultrasonic welding parameters will affect the joint performance by affecting the DoC of the welded material at the welding interface. This paper investigates the effect of DoC of carbon fiber-reinforced PA6 (CF/PA6) base material and welded material on its ultrasonically welded joints' performance. Distinct pre-welding heat treatments are conducted on the base material before welding. The DoC is calculated by DSC, while the crystalline phases (α and γ phases) and crystallize size are determined using XRD. The results demonstrate that the heat treatment process of heating temperature of 180 °C and cooling with an oven (180-O) could increase the DoC of CF/PA6 from 27.2% to 33% and the ratio of α/γ from 0.38 to 0.75. The joint strength of 180-O sheets reached 17.7 MPa, which is 26.7% higher than that of the as-received sheets. The DoC of the welded material at the welding interface obtained with different combinations of welding parameters is characterized. Higher welding force and amplitude result in faster cooling rate at the welding interface and more effective strain-induced crystallization, leading to higher DoC of the welding interface.

Fracture Toughness of Winding Carbon Plastics Based on Epoxy Matrices and Reinforced by Polysulfone Film.

In this work, the fracture mechanism of winding carbon-fiber-reinforced plastics (CFRPs) based on epoxy matrices reinforced by polysulfone film was investigated. Two types of polymer matrices were used: epoxy oligomer (EO) cured by iso-methyltetrahydrophthalic anhydride (iso-MTHPA), and EO-modified polysulfone (PSU) with active diluent furfuryl glycidyl ether (FGE) cured by iso-MTHPA. At the winding stage, the reinforcing film was placed in the middle layer of the CFRP. The fracture toughness GIR of the obtained CFRP was determined by the double-cantilever beam delamination method. Additionally, the effect of cyclic loading on the fracture toughness of CFRP reinforced with polysulfone film was investigated. It was shown that heterogeneous structures arising from the dissolution of the polysulfone film in the epoxy binder during the curing process increase the fracture toughness of CFRP from 0.5 kJ/m2 to 1.2 kJ/m2. Application of cyclic loads had little effect on the fracture toughness value. As a result of this study, it was revealed that the macrocrack propagates near the reinforcement layer along the diffusion zone, which has a phase organization of the type PSU matrix-EO dispersion.

Mechanical Properties of TWILL Carbon Fiber Fabric-Reinforced Single-Layer Thermoplastic Polyamide and Polybutylene Terephthalate-Based Composite Materials Manufactured by Hot Pressing.

This study investigates carbon fabric-reinforced thermoplastic composites produced via hot pressing, using Polyamide PA6 and Polybutylene Terephthalate (PBT) as matrix materials. These materials are increasingly utilized in the development of lightweight, high-performance, multilayer structures, such as aluminum-reinforced laminates, for automotive and aerospace applications. The mechanical properties, including tensile strength and stiffness, were systematically evaluated under varying loading conditions. The PBT-CF composite exhibited a 17% higher tensile strength and stiffness compared to the PA6-CF composite, despite the low carbon fiber content. This highlights the critical role of uniform fiber distribution in enhancing material performance. Slower loading speeds (1 mm/min) resulted in higher strength, emphasizing the influence of process parameters on mechanical behavior. Cyclic loading tests showed a gradual reduction in stiffness with increasing strain range, particularly for the CF-45° configuration. The warp and weft arrangement of the carbon fabric contributed to structural inhomogeneity but did not significantly affect the global mechanical properties. These findings demonstrate the suitability of PBT as a matrix material alongside PA6 for carbon fiber-reinforced thermoplastics, offering new possibilities for the design of advanced composite materials with tailored properties.

Correlation between interlaminar shear strength of CFRP and joint strength of aluminium-CFRP hybrid joints

ABSTRACT Fibre-reinforced polymers are increasingly used due to their high specific strength, making them suitable for local sheet metal reinforcement. This allows improved overall mechanical properties with reduced wall thickness of the sheet metal part and, thus, lower weight of the components. One of the main focuses of research into such hybrid structures is on the adhesive properties and the respective failure behaviour of the interfaces. Generally, the failure behaviour under the influence of mechanical loads can be divided into adhesive, cohesive and mixed-mode failure. The correlation between observed failure behaviour and adhesion properties of the hybrid composite materials is analysed in detail in this work. The hybrid composite consists of an aluminium sheet of the alloy EN AW‑6082 T6 and thermoset carbon fibre-reinforced plastic (CFRP) prepreg. The aluminium sheet was laser pretreated before hybrid production to improve the adhesion properties. The specimens studied were produced by the prepreg pressing process, in which the components are cured and joined simultaneously. The influences of the thickness of the CFRP part, the layup, the fibre orientation at the boundary layer, and the laser pretreatment parameters on the properties of the hybrid joints were investigated.

Modelling of High-Velocity Impact on Woven Carbon Fibre-Reinforced Plastic Laminate

This paper describes a constitutive model for progressive damage in carbon fibre-reinforced composites (CFRPs), developed in the framework of thermodynamics and coupled with a vector equation of state. This made the constitutive model capable of modelling shock wave propagation within orthotropic materials. Damage is incorporated in the model by using reduction in the principal material stiffness based on the effective stress concept and the hypothesis of strain energy equivalence. Damage evolution was defined in terms of a modified Tuler–Bucher criteria. The constitutive model was implemented into Lawrence Livermore National Laboratory (LLNL) DYNA3D nonlinear hydrocode. Simulation results were validated against post-impact experimental data of spherical projectile impact on an aerospace-grade woven CFRP composite panel. Two plate thicknesses were considered and a range of impact velocities above the ballistic limit of the plates, ranging from 194 m/s to 1219 m/s. Other than for the size of the delamination zone in the minor material direction, the discrepancy between the experiments and numerical results for damage and delamination in the CFRP target plates was within 8%.

Experimental Study on Mechanical Performance of Single-Side Bonded Carbon Fibre-Reinforced Plywood for Wood-Based Structures.

In addition to the traditional uses of plywood, such as furniture and construction, it is also widely used in areas that benefit from its special combination of strength and lightness, particularly as a construction material for the production of finishing elements of campervans and yachts. In light of the current need to reduce emissions of climate-damaging gases such as CO2, the use of lightweight construction materials is very important. In recent years, hybrid structures made of carbon fibre-reinforced plastics (CFRPs) and metals have attracted much attention in many industries. In contrast to hybrid metal/carbon fibre composites, research relating to laminates consisting of CFRPs and wood-based materials shows less interest. This article analyses the hybrid laminate resulting from bonding a CFRP panel to plywood in terms of strength and performance using a three-point bending test, a static tensile test and a dynamic analysis. Knowledge of the dynamic characteristics of carbon fibre-reinforced plywood allows for the adoption of such cutting parameters that will help prevent the occurrence of self-excited vibrations in the cutting process. Therefore, in this work, it was decided to determine the effect of using CFRP laminate on both the static and dynamic stiffness of the structure. Most studies in this field concern improving the strength of the structure without analysing the dynamic properties. This article proposes a simple and user-friendly methodology for determining the damping of a sandwich-type system. The results of strength tests were used to determine the modulus of elasticity, modulus of rupture, the position of the neutral axis and the frequency domain characteristics of the laminate obtained. The results show that the use of a CFRP-reinforced plywood panel not only improves the visual aspect but also improves the strength properties of such a hybrid material. In the case of a CFRP-reinforced plywood panel, the value of tensile stresses decreased by sixteen-fold (from 1.95 N/mm2 to 0.12 N/mm2), and the value of compressive stresses decreased by more than seven-fold (from 1.95 N/mm2 to 0.27 N/mm2) compared to unreinforced plywood. Based on the stress occurring at the tensile and compressive sides of the CFRP-reinforced plywood sample surface during a cantilever bending text, it was found that the value of modulus of rupture decreased by three-fold and the value of the modulus of elasticity decreased by more than five-fold compared to the unreinforced plywood sample. A dynamic analysis allowed us to determine that the frequency of natural vibrations of the CFRP-reinforced plywood panel increased by about 33% (from 30 Hz to 40 Hz) compared to the beam made only of plywood.

A novel two-step process for enhancing adhesion strength of cold-spray metallization of carbon fiber-reinforced plastics

A novel two-step process for enhancing adhesion strength of cold-spray metallization of carbon fiber-reinforced plastics

Deformation of Threaded Metal – Composite Couplings Under the Action of Gas-Dynamic Loads

The combination of metal and composite in threaded couplings increases the reliability of the structure operating under conditions of intensive internal pressure. Strength analysis of threaded metal – composite couplings based on the application of modern finite element modeling methods at the stage of design documentation development allows to create more efficient structures that better meet the operational requirements. The strength of threaded couplings of cylindrical shells made of composite material and metal under the action of gas-dynamic internal pressure is analyzed in this paper. A methodology for numerical study of the problem in Ansys / Explicit Dynamics software package is proposed. Detailed modeling of threaded couplings is used. The developed model takes into account the following: dependence of material properties on ambient temperature; nonlinear relations between the components of stress and strain tensors in metal elements, orthotropic properties of composite materials; peculiarities of contact interaction in the zones of threaded couplings of prefabricated shell elements made of different materials. The stress state of a cylindrical structure with a central shell made of carbon fiber-reinforced plastic or fiberglass and with steel shells at the edges, loaded with gas-dynamic internal pressure with a maximum value of 20 MPa at a maximum ambient temperature of 100 °С was studied. It was obtained that plastic deformations are concentrated on the edges of the threaded couplings of steel shells. At the same time, the magnitude of plastic coupling deformations with the inner metal shell is an order of magnitude higher than for couplings with the outer metal shell. The magnitude of plastic deformations in couplings with an inner metal shell is twice less when using fiberglass than when using carbon fiber reinforced plastic. Localization of critical stresses was observed only in metal shells at threaded couplings. In this case, in the thread zone they are within the elasticity limits, and the stress state of the FRP shell is not critical. No local material failure was observed in the structure.

Finite element modeling of viscoelastic creep behavior and transverse cracking in fiber-reinforced composite materials

Fiber-reinforced composites are essential in the aerospace industry, highlighting the need for an in-depth understanding of their durability. This study introduces a novel approach that integrates viscoelasticity and damage evolution based on continuum damage mechanics, employing finite element analysis. The method utilizes an anisotropic viscoelastic constitutive law to examine creep behavior under constant stress, decomposing stresses into equilibrium and non-equilibrium components. Moreover, it integrates a transverse crack damage variable associated with crack density. After solving stiffness equations, a detailed analysis of transverse crack propagation is conducted. This technique was applied to creep tests on carbon fiber-reinforced plastics and 3D woven ceramic matrix composites, resulting in strain and crack density profiles. The numerical simulations successfully reproduced experimental outcomes. The developed method offers a comprehensive tool for analyzing transverse crack propagation under viscoelastic creep conditions through finite element analysis, significantly enhancing design considerations by incorporating aspects of long-term durability.

Enhancing Machine Tool Housing Design through Ultra High-Performance Concrete

Machine tool housing design is pivotal in optimizing manufacturing processes, focusing on functionality, ease of assembly, and alignment precision. Current materials face challenges in static, dynamic, and thermal behaviors, impacting machining quality. The properties of ultra high-performance concrete (UHPC) such as high strength, low porosity, and corrosion resistance make it ideal for machine tool applications, promising increased precision and efficiency while reducing material costs and labor. Its recyclability adds environmental benefits. Incorporating UHPC in machine tool structures, including hybrid materials like Carbon Fiber Reinforced Plastic (CFRP), achieves superior static, dynamic, and thermal stability. Experimental results demonstrate UHPC’s compressive strengths (17,000-22,000 psi), surpassing conventional materials, and its ability to enhance machine tool performance and sustainability. This research highlights UHPC as a transformative material for resilient, precise, and eco-friendly manufacturing solutions.

Enhancing in‐plane elasticity of carbon fiber reinforced thermoplastic multilayer films with polyrotaxane and nanocellulose composites

AbstractSandwich films were prepared by inserting resin sheets between carbon fiber‐reinforced thermoplastic (CFRTP) sheets, and their tensile and bending strengths were evaluated. The CFRTP sheets used nylon 66, polyurethane, and polyphenylene sulfide as impregnating resins. The resin sheet used was polypropylene, a general‐purpose resin, combined with a composite material incorporating polyrotaxane and cellulose nanofibers as organic fillers. The sample containing both components showed a 134% improvement in Young's modulus compared to neat polypropylene. This study controlled the number of layers in the sandwich film and assessed the dependence of mechanical properties on layer count. The sandwich films demonstrated particularly good strength in the in‐plane direction, exhibiting excellent bending properties. Furthermore, using composite materials for the resins sandwiched between CFRTP sheets further enhanced mechanical properties. The film material, which can be prepared through simple press molding, is a lightweight material composed of light elements, and exhibits a Young's modulus in the gigapascal scale. CFRTP sheets using nylon 66 as the impregnating resin, the flexural modulus improved by approximately 5.8 times. Furthermore, by increasing the number of laminations, an additional improvement of 3.1 times was observed. This study also identified conditions for improving elongation properties.Highlights A new material was created using carbon fiber reinforced thermoplastics (CFRTP). Multilayered alternating films made of CFRTP and polymer composite were created. Corresponding multilayer films showed anisotropy in mechanical properties. Corresponding multilayer films exhibited excellent in‐plane elasticity. In‐plane elasticity showed a clear dependency on the number of layers.

Carbon Footprint of Electricity Produced in the Russian Federation

Energy generation makes a significant contribution to greenhouse gas emission. The carbon footprint of electricity significantly affects the total carbon footprint of a wide variety of products, which is especially relevant for energy-intensive industries (aluminum, platinum, carbon fiber-reinforced plastics, etc.) and hydrogen energy. The carbon footprint of aluminum, produced in Russia is 8.0–15.0 kg CO2-eq./kg. It is lower than the actual carbon footprint of aluminum produced in other countries due to the lower carbon intensity of Russian grid electricity in comparison with the world average. The carbon footprint of hydrogen, produced by photovoltaic modules with electricity consumption from the Russian national electricity grid is 16.6 kg CO2-eq./kg, while the world average carbon footprint of photovoltaic hydrogen is 18.1 kg CO2-eq./kg. The average carbon footprint of electricity generated and consumed in Russia ranges from 310 to 634 g CO2-eq./kWh. This paper analyzes methodological approaches to determining grid emission factors for Russian electricity. It has been established that different principles of spatial division of the Russian energy system can be used to determine grid emission factors (national average grid emission factor, grid emission factors for the integrated energy system, grid emission factors for price and non-price zones of the wholesale electricity market).

Experimental investigation of the corrosion effect and repair effectiveness for an RC beam with the corroded stirrups

To investigate the effectiveness of selected repair materials and reinforcement methods on the shear strength of reinforced concrete (RC) beams with corroded stirrups, 14 RC beam specimens were designed with corroded stirrups exhibiting weight loss rates of 10% and 17%. Additionally, control specimens without repairs were included to assess the impact of pre-corroded stirrups on strength development. A three-point bending test was conducted to evaluate the shear strength of the specimens under various repair and reinforcement scenarios. Epoxy mortar, cement mortar, and non-shrinkage cement mortar were selected as repair materials, while spot-welded steel wire mesh (WWM) and carbon fiber-reinforced plastics (CFRP) were used to enhance repair effectiveness. The results indicate that, for the specimens with corroded stirrups showing weight loss rates of 10% and 17%, their shear strengths decreased by up to 17% and 21%, respectively, compared to specimens without any corrosion. Additionally, the shear strengths of the specimens repaired using epoxy mortar were slightly increased by reinforcing with WWM and CFRP. However, the shear strengths of most specimens with repair and reinforcement were lower than their original shear strengths. For practical design applications, this work introduces a novel approach to quantifying the effectiveness of repair materials in conjunction with reinforcement methods, based on the softened strut-and-tie model (SST), which was verified using experimental data.

Vibration characteristics of CFRP sandwich panels with acoustic black hole structures

An acoustic black hole, as a structure with a continuous gradient of thickness, has a good aggregation effect for bending waves. This paper introduces a novel carbon fiber reinforced plastic (CFRP) acoustic black hole sandwich structure. This structure comprises a CFRP panel and an acoustic black hole core layer, leveraging the aggregation effect of acoustic black holes to achieve vibration damping in low-frequency bands. Initially, the vibration transfer characteristics of acoustic black hole beams are examined based on the acoustic black hole effect. Subsequently, the influence of material, structure, and the number of acoustic black holes within the sandwich structures on their vibration transfer characteristics is investigated. Finally, the vibration characteristics of the CFRP sandwich structures are experimentally tested. The results indicate that the vibration transmission curve of the acoustic black hole beam exhibits multiple attenuation intervals within the 0-1200 Hz frequency range. Moreover, by adjusting the material and structural parameters of the core layer, the vibration bandgap of the sandwich structure can be shifted to the low-frequency region.