Continuous Fiber-reinforced Composites Research Articles

Vertical z-axis discontinuous carbon fibers for improved lightning strike performance of continuous fiber-reinforced polymer composites

Effective lightning strike protection for critical aerospace and wind applications requires high electrical conductivity to dissipate current efficiently. However, polymer matrix composites face a challenge due to their inherently insulating nature. While conventional carbon fiber-reinforced composites (CFRP) exhibit electrical conductivity in the planar direction, achieving through-thickness conductivity remains an ongoing challenge. In this work, we have undertaken the fabrication of CFRP interleaved with vertically oriented carbon fibers (Z-fiber) to impart higher electrical conductivity along the thickness direction. Two Z-fiber composite variations are prepared: Z-1 with a single layer of Z-fiber and Z-5 with five interleaved layers and compared with no Z-fiber layer (Z-0) composite. The composite panels were subjected to lab-scale lightning strike tests with a current magnitude of 100 kA. To emulate real-world service conditions, an aerospace-grade paint coating was applied to the composite laminates. Comparative analysis shows Z-1 reduces damage diameter to ∼22 mm compared to Z-0 (∼26 mm), while Z-5 exhibits the least damage (∼16.7 mm), confirmed by optical microscopy. Z-5 demonstrates nine times higher through-thickness electrical conductivity than Z-0, reducing electrical anisotropy substantially. Thermal-electric finite element damage modeling predicts surface damage within 6% of experimental values for both Z-0 and Z-5 composites. Flexural tests post-lightning reveal Z-5 retains 66% flexural strength and 86% modulus, significantly better than Z-0, which retains less than 40% for both properties. This study highlights the efficacy of Z-fiber composites in lightning strike protection, offering improved through-thickness conductivity and mechanical property retention.

Force model based on heterogeneous components decoupling and machining behaviors of ultrasonic grinding continuous fiber-reinforced MMCs

Continuous fiber-reinforced metal matrix composites (CFMMCs), such as SiC fiber-reinforced TC17 matrix composites (SiCf/TC17), are renowned for their exceptional mechanical properties. However, their heterogeneous compositions present significant machining challenges, including fiber pullout, matrix cracking, and accelerated tool wear. Ultrasonic vibration-assisted grinding (UVAG) has proven to be an effective technique for overcoming these challenges. The material removal mechanisms in UVAG, especially in composites with both ductile and brittle phases, remain poorly understood. To explore these issues, UVAG and conventional grinding (CG) experiments were conducted on SiCf/TC17 along two grinding directions: fiber’s transverse direction (FT) and fiber’s longitudinal direction (FL). This paper aims to provide a new dynamic mechanical model and shed light on the complex removal mechanisms in CFMMCs, which are characterized by a near one-to-one alternation of ductile and brittle phases. The findings reveal that UVAG reduces fiber damage and surface roughness compared to CG, especially when grinding along FT. UVAG lowers normal (Fn) and tangential grinding forces (Ft) by 15.3% and 12.3%, respectively. This highlights UVAG’s potential for improving the machinability of complex materials like CFMMCs. The proposed grinding force model closely matches the experimental results. This paper hopes to support the precision abrasive machining of CFMMCs, a kind of complex and highly anisotropic composite material, and promote their application in the fields such as aerospace.

Advancements in Biofiller-Reinforced PLA Composites for 3D Printing: A Review

Additive manufacturing is key in realizing highly complex and high-performance composite materials. Among all the various kinds of functionality that could be added to a composite component, continuous fiber-reinforced composites have been drawing much attention because of their attractive combination of properties. The comprehensive spectrum of knowledge that ranges from the basics concerned with structure, morphology, synthesis, physical, and chemical properties finally reaches to this analytical study of advanced composites. Most generally, such a composite is structured on a thermoplastic or thermoset polymer matrix that embeds the load-carrying reinforcing fibers; probably best known are carbon, glass, and aramid fibers. These composites, which involve fibers continuously reinforcing, have high strength relative to their weight. They are also anisotropic, meaning they have qualities that vary from one direction to another – something which might be customisable for specific load cases. They warp and shrink less during their life in an outside environment than conventionally made bioplastics due to a fact that short fibers can provide reinforcement to them. This 3-D printing object is manufactured by special additive manufacture technology during the manufacturing process after compounding and extruding the fiber-reinforced composite filament. The final properties of 3D printed parts could be tailorable through changing variables such a fiber type, fiber length, volume fraction, polymer matrix material, orientation of fibers, and printing process parameters. These continuous fiber-reinforced 3D printed composites could achieve tensile strengths up to one GPa, have stiffness values reaching even a rating of countless Gpa, and have ad thicknesses in the range from about 1.4–1.8 g/cm³. This finding could be applied in basically all major industries, from aerospace and the automotive industry to sports gear. Such conclusions from the analysis may be useful in the selection of appropriate materials and techniques while even guiding the development of new applications with respect to such advanced composite materials.

Micro-Macro Coupling Study on the Mechanical Properties of Continuous Fiber-Reinforced Composites.

As a key and weak point of continuous fiber-reinforced composites (CFRCs), the interface between the fiber and the matrix is vulnerable to failure under external loads, with its performance directly affecting the overall properties of CFRCs. Hence, a micro-macro coupling method that considered the microscopic properties of the interface was utilized to analyze and predict the mechanical properties of CFRCs more accurately. The microscopic mechanical parameters of the fiber-matrix interface, which were obtained using molecular dynamics, were transferred to the representative volume element (RVE). The stiffness matrix of the CFRC, required for the macroscopic finite element model, was then calculated using a unified periodic homogenization method based on the RVE and assigned to the finite element model for a macroscopic simulation. Nylon/continuous carbon fiber specimens were fabricated through additive manufacturing, with the tensile and bending strengths of the specimens obtained through tensile and three-point bending tests. The tensile strength of the experimental specimen was 200.1 MPa, while the result of the simulation containing the interface was 205.5 MPa, indicating a difference of less than 5% between the two. In contrast, the result of the simulation without an interface was 317.7 MPa, representing a high error of 58.7% compared with the experimental results. Moreover, the bending strength, Young's modulus, and flexural modulus results with and without an interface showed the same trend as that for the tensile strength. This illustrates the effectiveness of the proposed micro-macro coupling method for analyzing and predicting the mechanical properties of CFRCs.

Adjustment of Mechanical Properties of 3D Printed Continuous Carbon Fiber-Reinforced Thermoset Composites by Print Parameter Adjustments.

Reinforcing thermoset polymers with continuous carbon fiber (CF) tow has emerged as a promising avenue to overcome the thermal and mechanical performance limitations of 3D printed polymeric structures for load-bearing applications. Unlike traditional methods, manufacturing continuous fiber-reinforced composites by 3D printing has the unique capability of locally varying the mechanical properties of the composites. In this study, continuous CF thermoset composite specimens were printed with varying line spacing, resin flow rate, and nozzle sizes. The resin flow rates for different line spacings and nozzle sizes were optimized by topographic analysis. Printed composite mechanical properties were evaluated, and their trends were correlated with the trend of print parameter changes. Results showed that tensile strength and modulus could be altered and improved by ~50% by adjusting the printing process parameters. Higher composite strength and modulus were obtained by shortening the line spacing and nozzle diameter.

Autonomous intelligent additive manufacturing of continuous fiber-reinforced composites: data-enhanced knowledgebase and multi-sensor fusion

ABSTRACT Additive manufacturing (AM) are an emerging technique to generate complex structures of composite. However, the instability of the AM process leads to adverse manufacturing effects, including dimensional inaccuracies and poor mechanical performance in CFRP composites. Online monitoring and adaptive control based on autonomous cognition are suggested to ensure the accuracy of as-fabricated parts and enhance their quality upon manufacturing. In this study, a method of online monitoring and self-adaptive control based on multi-sensor fusion is proposed to predict and adjust the process parameters during AM of CFRP. The force sensor, visual camera, and thermal camera are employed to obtain the multiple signals upon manufacturing and then realize the autonomous perception, cognition, and decision features. Herein, the quantitative correlations between local defects and multi-sensing features are established to guide the decision-making of closed-loop adjustment. Besides, an empirical surrogate model between the misalignment of fiber bundles and input parameters is built to predict the proper parameters. Moreover, the temperature difference and contact force are selected as the controlled features, which are acquired using a thermal camera and a force sensor. The proposed system offers a novel framework for bolstering both the stability of the AM process and the quality of fabricated components.

Effects of nozzle geometry and fiber orientation on the tensile strength of 3D printed continuous fiber reinforced composites

In material extrusion (MEX) based 3D printing, inter-filament voids are intrinsic to printing process. The void orientation, volume and shape are affected by multiple factors including the nozzle shape, stacking sequence and printing direction. In this study, the adverse effects of the inter-filament voids on tensile properties and damage modes were investigated numerically on 3D printed acrylonitrile butadiene styrene-carbon fiber (ABS/CF) continuous fiber-reinforced composites (CFRCs). Uniaxial tensile simulations were performed considering various nozzle geometries (circular, square), fiber orientations (θ=0o,30o,45o,60o,90o) relative to loading direction, and a regular stacking sequence of extrudates. The extrudate cross-section was modeled either using elliptical or superelliptical extrudates deposited from a circular or square nozzle, respectively. Excellent agreement was seen when the simulated results were benchmarked against several published experimental and numerical work. Simulated results showed that changing the nozzle shape from circular to square improved the mechanical properties across all fiber angles by lowering the void content by 7−8% and increasing the ultimate tensile strength (σT) by 11−18%, tensile stiffness (ET) by 6−8%, and the tensile failure strains (ϵT,fail) by 1−11%. For superelliptical extrudates the number of observed damage modes also reduced, and this is due to a 37.2% and 58.2% improvement in the inter-filament and inter-layer bond lengths, respectively. Also, when fiber angle became increasingly off-axis to tensile load direction, the strengths, moduli, and failure strains reduced for both circular and square nozzles. The significance of using microstructure geometries and explicitly modeling inter-filament voids for simulating MEX printed CFRCs was highlighted by comparing these results with both analytical calculations and simulated results of homogeneous solid CFRC blocks without voids.

Additive manufacturing of continuous fiber-reinforced polymer composites: current trend and future directions

Additive manufacturing of continuous fiber-reinforced polymer composites: current trend and future directions

Coupled heat transfer–crystallization analysis in continuous carbon fiber-reinforced thermoplastic composites 3D printing: simulation and experimental validation

AbstractThis study proposes an advanced progressive numerical modeling approach to investigate heat transfer phenomena occurring in the 3D printing of continuous carbon fiber-reinforced co-polyamide (Copa) composites. The material extrusion process is simulated using element activation techniques and active cooling methods, while thermal boundary conditions are updated during the printing process. Differential Scanning Calorimetry (DSC) tests are conducted on composite and neat polymer samples to include the crystallization behavior, where the Hoffman–Lauritzen model is employed for crystallization modeling based on the input data from DSC tests. It is demonstrated that the proposed modeling approach, coupled with the Hoffman–Lauritzen crystallization model, accurately predicts the thermal history of the composite extrudate post-deposition. In the case of a neat polymer, the results of the developed FEM model align well with existing literature. Experimental in-situ temperature measurements utilizing thermal vision agree very well with the predictions of the heat transfer model developed for 3D printing of continuous fiber-reinforced Copa composites, demonstrating the model's capability to predict temperature profiles during printing.

Multiscale Computational Modeling of 3D Printed Continuous Fiber-Reinforced Composites

The printing parameters used during the printing procedure have a significant effect on the mechanical characteristics of 3D printed continuous fiber reinforced composites (3DP-CFRPCs). However, conducting experimental assessments of the material characteristics of 3DP-CFRPCs may require more effort and incur more costs. Computational material modeling may be used as a viable alternative to investigate the behavior of 3DP-CFRPCs under various printing conditions. The current work used material modeling approaches to examine the impact of different printing settings on the elastic characteristics of 3DP-CFRPCs. The inherent flexibility of beads is primarily established by homogenizing the pores within the matrix via the use of the Mori-Tanaka process. Subsequently, the elastic modulus is calculated by using finite element modeling on Representative Volume Element (RVE), which takes into account the microstructure and other printing attributes. An inconsistency was seen in the variation of projected elastic properties across models distinguished by various microstructures, with a more pronounced differentiation observed between intricate and simpler microstructures. Computational modeling has enhanced our understanding of the elastic properties of 3DP-CFRPCs under various printing conditions. Moreover, it has been shown that alterations in printing parameters have diverse impacts on the pliable characteristics of 3DP-CFRPCs. The impact of layer thickness on the mechanical characteristics of 3DP-CFRPCs was determined to be more substantial compared to the effect of printing temperature. The application of offset layup printing techniques enhanced the elastic properties of 3DP-CFRPCs, with the degree of improvement varying based on the orientation. As the level of porosity increased, the influence of pores situated between beads on the overall stiffness of 3DP-CFRPCs gradually diminished, while the impact of matrix pores on the overall stiffness of 3DP-CFRPCs gradually intensified.

An overview of 4D printing of smart multifunction continuous fiber-reinforced composites: recent advances and novel applications

An overview of 4D printing of smart multifunction continuous fiber-reinforced composites: recent advances and novel applications

A design method for continuous fiber-reinforced composite patches

The urgent need for lightweight and high-strength patches in the field of aircraft structural repair has propelled continuous fiber-reinforced thermoset composites into a research hotspot. However, constrained by manufacturing processes, the designs of composite repair structures primarily focus on external shape and ply layup. These approaches presently lack design methods for the internal fiber adaptability of patches driven by in-service loads. In this paper, we proposed a method for fiber distribution and orientation design based on maximum normal stress. The composite simulation model was established based on fracture toughness. The influence of tensile-shear coupling effects on the mechanical response of composites and the fiber orientation design were examined in the study. The orientation-density coupling effects on the enhancement of patch strength were also analyzed. Furthermore, additive manufacturing technology was employed to fabricate thermoset composite patches. The results show that the composite patches designed in this paper exhibit a 10.50 % improvement in strength compared to traditional unidirectional patches.

Microstructural characteristics and mechanical properties of 3D printed Kevlar fibre reinforced Onyx composite

Abstract The main objective of this study is to develop the Kevlar fibre reinforced Onyx composite (KFRO) material by employing the 3D printing technology and examine the effect of Kevlar fibre reinforcement percentage on microstructural characteristics and mechanical properties of developed composite material. The methodology of continuous fibre reinforced composites (CFRC) was followed and the Kevlar fibre reinforcement % was varied as 10 %, 20 % and 30 % in the composite material fabrication. Results disclosed that the KFRO composite 3D printed using 30 % Kevlar fibre reinforcement in Onyx matrix yielded greater tensile strength of 124 MPa, flexural strength of 105 MPa, impact toughness of 2.4 J and shore hardness of 76 D. The mechanical properties of KFRO composite were significantly improved at 20 % of Kevlar fibre reinforcement compared to 10 % of Kevlar fibre reinforcement. Further increase in Kevlar fibre reinforcement up to 30 % showed slight enhancement in mechanical properties of KFRO composite when compared to 20 % of Kevlar fibre reinforcement. The overall strength improvement is a result of the increased reinforcement, precise alignment of fibres in the loading direction, and the uniform distribution of fibres within the onyx.

Topology optimization of 3D continuous fiber-reinforced composites using Cartesian parametrization of fiber orientations

Topology optimization of 3D continuous fiber-reinforced composites using Cartesian parametrization of fiber orientations

Probability Prediction of Curing Process-Induced Deformation for V-Shape Composite Structures Based on FEM Method and Data Mining.

Continuous fiber-reinforced composites are increasingly used in industry for their superior specific modulus and strength. The curing process-induced deformation (PID) has been a critical problem during manufacturing, which always exhibits dispersed values even if the curing process curve and structural parameters remain consistent. This work conducted probability prediction of PID for V-shape composite structures based on the FEM method and data mining. A sequential coupling thermal-chemical-mechanical coupling FE model is established in ABAQUS. The prediction accuracy of the included angle between two sides is verified by the experimental results. Material parameter uncertainties are considered for V-shape structures with different radii and thicknesses. Based on the dataset from the FE model, a decision tree is established and trained to analyze the sensitivity and to predict the probability distribution of PID. The results show that PID increases with the coefficients of thermal expansion in the in-plane perpendicular fiber direction and out-of-plane normal direction. The data-mining method is accurate enough for the PID prediction, and its efficiency provides an additional calculation option in engineering applications.

Performance and failure modes of continuous fibre-reinforced energy absorption tubes by cylindrical layered 3D printing

ABSTRACT Precisely controlling the distribution of continuous fibres on a cylindrical surface is crucial for manufacturing high-performance continuous fibre-reinforced composite (CFRC) tubular structures. Existing manufacturing processes are complex, hindering the regulation of fibre orientation and content. Therefore, this study achieved unrestricted control of 3D-printed continuous fibres in terms of content and arbitrary orientation on a cylindrical surface using a cylindrical layered path planning strategy. The study investigated the impact of different fibre orientations and printing parameters on the compressive performance and energy absorption of 3D-printed CFRC tubes under quasi-static axial compression by analysing fibre distribution and failure modes. Compared to the flat layered printing strategy, the cylindrical layered printing strategy showed significant increases in compressive strength and energy absorption, by 44.3% and 85.2%, respectively. A cusp height analysis model demonstrated that the cylindrical layered printing strategy significantly enhances forming accuracy compared to the conventional flat layered method. The CFRC lightweight energy absorption tubes fabricated with this strategy demonstrated the viability of the manufacturing process. This new manufacturing technology has significant potential for producing high-performance and high-precision CFRC energy absorption tubes, applicable in aeronautics and astronautics.

Additive Manufacturing of Continuous Fiber-Reinforced Polymer Composites via Fused Deposition Modelling: A Comprehensive Review.

Additive manufacturing (AM) has arisen as a transformative technology for manufacturing complex geometries with enhanced mechanical properties, particularly in the realm of continuous fiber-reinforced polymer composites (CFRPCs). Among various AM techniques, fused deposition modeling (FDM) stands out as a promising method for the fabrication of CFRPCs due to its versatility, ease of use, flexibility, and cost-effectiveness. Several research papers on the AM of CFRPs via FDM were summarized and therefore this review paper provides a critical examination of the process-printing parameters influencing the AM process, with a focus on their impact on mechanical properties. This review covers details of factors such as fiber orientation, layer thickness, nozzle diameter, fiber volume fraction, printing temperature, and infill design, extracted from the existing literature. Through a visual representation of the process parameters (printing and material) and properties (mechanical, physical, and thermal), this paper aims to separate out the optimal processing parameters that have been inferred from various research studies. Furthermore, this analysis critically evaluates the current state-of-the-art research, highlighting advancements, applications, filament production methods, challenges, and opportunities for further development in this field. In comparison to short fibers, continuous fiber filaments can render better strength; however, delamination issues persist. Various parameters affect the printing process differently, resulting in several limitations that need to be addressed. Signifying the relationship between printing parameters and mechanical properties is vital for optimizing CFRPC fabrication via FDM, enabling the realization of lightweight, high-strength components for various industrial applications.

Additive manufacture of programmable multi-matrix continuous carbon fiber reinforced gradient composites

Bio-inspired gradient materials and structures, including cartilage scaffolds, soft actuators, and sensors, demonstrate significant potential applications in the fields of biomedicine, robotics, and flexible electronics. This paper introduces a novel method for fabricating continuous fiber-reinforced gradient composites using additive manufacturing techniques. In-situ impregnation 3D printing of two distinct matrix materials and continuous fibers was realized utilizing a specially designed multi-channel nozzle. This allowed for the personalized distribution of matrix materials within the composite by controlling the extrusion rates. Employing polylactic acid (PLA) and thermoplastic polyurethane (TPU), which possess differing mechanical properties, as matrix materials, the study examined the tensile and three-point bending mechanical properties of continuous carbon fiber-reinforced PLA/TPU (CCFR-PLA/TPU) composites with varying ratios of the two matrix materials. Moreover, the ability to control the distribution of matrix materials enabled the tailoring of gradient composites. Additionally, this research investigated the fabrication and compression behavior of gradient thin-walled structures and lattice structures composed of CCFR-PLA/TPU composites. The findings suggest that this programmable, multi-material, continuous carbon fiber-reinforced composites additive manufacturing approach can fabricate composites with a broad spectrum of tunable mechanical properties.

Effects of internal configurations and its processing quality on compressive performance for 3D printed continuous fiber reinforced composites honeycomb sandwich

Continuous fiber reinforced composites (CFRCs) 3D printing technology has the advantage of integrated fabricating for honeycomb sandwich structures, the load-bearing capacity of the fabricated honeycomb sandwich structures still needs to be investigated and improved. This study aims to reveal compression failure modes of 3D printed CFRCs honeycomb sandwich structures with various internal configurations by conducting flatwise compression tests. The deviations of single-layer CFRCs honeycomb cores with different core sizes and core heights and their impacts on the compression failure process were analyzed. A 3D printing method with multilayer cores and core/panel variable printing thickness was proposed, and the effects of multilayer core structure and different core printing parameters on the compressive properties of honeycomb sandwich structures were investigated. The results showed that interlayer cracking caused by core buckling deformation was the leading cause of failure of 3D printed CFRCs honeycomb sandwich structures when subjected to compression. The core buckling deformation could be suppressed by printing multilayer cores and using low core printing thickness, and the compression strength and specific energy absorption of the sandwich structures reached 38.1 MPa and 25.4 kJ/kg, respectively. This study provides guidance for the customization of the 3D printing process of CFRCs honeycomb sandwich structures.

Prediction and analysis of flexural stiffness for 3D-printed continuous fiber–reinforced composites with different matrix fill ratios and layer orders

Bending load is often encountered in engineering applications, but it is less studied for 3D-printed continuous fibre–reinforced composites (CFRC). We present the flexural properties of 3D-printed composites as a function of layer order and matrix fill ratio. We applied Classic Laminate Theory to estimate the flexural modulus and showed that the Kerner-Hashin model is suitable for taking voids into account when calculating the elastic properties of the matrix layer. Using optical microscopic analysis, we identified the main defect sources of 3D-printed CFRC structures, such as voids, fibre waviness, fragmentation and poor bonding between laminas. By performing failure analysis based on the Fibre Bundle Cell method, we found that the use of top/bottom-type reinforcement instead of alternating layering will increase the reliability of the 3D-printed composites under bending load. Furthermore, the failure process will be more gradual and cover higher load levels, which increases safety.