Continuous Carbon Fiber Research Articles

Increasing strength and ductility of extruded polylactic acid matrix composites using short polyester and continuous carbon fibers

Increasing strength and ductility of extruded polylactic acid matrix composites using short polyester and continuous carbon fibers

Comparative Life Cycle Assessment of molding process and 3D printing of High-Performance Long-fiber Reinforced Composites

Composite materials are widely employed to produce high-performance components. However, their usage is associated with significant environmental impacts, deriving from the constituent materials (e.g., carbon fiber and epoxy resin) and the manufacturing process. Traditional methods of composite manufacturing such as bag molding or compression molding were subjected to discussion due to their high energy requirements, related to the required heat and pressure, the use of molds and the production of composite scraps. In contrast, 3D printing presents a promising alternative, that could reduce material waste and energy consumption.This study investigates an innovative 3D printing process for high-performance composites, in particular continuous carbon fiber and thermosetting epoxy matrix, with the aim of investigating its environmental impact.A comprehensive Life Cycle Assessment (LCA) was conducted to compare the environmental footprints of traditional molding and 3D printing processes of continuous fiber composites. A wide range of factors such as energy consumption, resource utilization, greenhouse gas emissions, and waste generation was considered.The outcomes of this comparative LCA reveal a significant reduction in environmental impacts associated with the innovative 3D printing system with respect to traditional methods. These findings offer crucial insights into the sustainability of 3D printing for high-performance composites, providing a valuable decision-making tool for industries seeking eco-friendly manufacturing solutions.

In-situ and adhesive repair of continuous fiber composites using 3D printing

The development of automated repair processes for continuous carbon fiber reinforced thermoplastic (CFRTP) composites is still in its early stages. However, the emergence of 3D printing technology presents a significant opportunity for the automated repair process to evolve alongside CFRTP composites. This study aims to evaluate the 3D printing repair of continuous fiber composites (CFCs) and characterize the mechanical performance of the repaired specimens. Two methods are proposed for repairing CFRTP utilizing additive manufacturing (AM): repair by a separately 3D-printed and subsequently adhesively bonded patch and repair with 3D printing in-situ at a recess damage. To compare the performance of the proposed methods, 16 test specimens were 3D printed, consisting of 4 intact and 12 damaged samples. Among the damaged samples, 4 were used as damaged specimens, 4 were repaired with adhesively bonded patches, and the remainder were repaired by in-situ printing. Mechanical tests were conducted on all four types of specimens, and the results indicate that the 3D-printed in-situ repair of carbon-reinforced polycarbonate has both the highest strength and elastic modulus. The results show that the repair using adhesive patches and repair in-situ improves the elastic modulus of the damaged specimens by 30% and 44%, respectively. Similarly, the tensile strength of the specimens repaired by adhesive patches and in-situ printing is 20% and 28%, respectively, higher than that of the damaged samples. An analytical model was developed to predict the elastic modulus of damaged and intact specimens, and the analytically predicted stiffnesses showed good agreement with the experimental measurements. Overall, this study demonstrates the potential of 3D printing technology for repairing CFRTP composites and highlights the advantages of in-situ printing over adhesive patch repair.

Twinning the future: Implementing digital twin technology in the optimisation of fibre-reinforced polymers

Optimisation of fibre-reinforced polymers (FRPs) is critical for engineering a sustainable future. This review paper explores the potential of digital twins (DTs) in enhancing the characteristics, performance, and sustainability of synthetic and sustainable FRPs. DTs provide a virtual space for real-time monitoring and predictive analysis and have revolutionised the traditional limitations of FRP production. Recent case studies, like the FASTIGUE project and advances in fibre-reinforced thermoplastics, showcase the DT’s powerful role in addressing issues during production. The paper also discusses the unique challenges of developing sustainable “green” composites that balance performance with biodegradability to meet the Sustainable Development Goals. It highlights the benefits of utilising DTs to scrutinise the manufacturing processes of both synthetic and natural FRPs. Modern DTs have demonstrated the capacity to optimise the curing kinetics and mechanical properties of these materials. Furthermore, case studies such as the 3D-printed continuous carbon fibre composites, overmoulded fibre-reinforced thermoplastics, and recyclable Elium®-based composites authenticate the capabilities of DTs in enhancing the sustainable manufacturing of FRPs. Acknowledging future challenges, the paper recommends integrating production and sustainability metrics into modern multi-tier DT systems for holistic benefits.

The polymer melt swelling behavior in micro-extrusion process for preparation of continuous carbon fiber reinforced PP prepreg filament

The micro-extrusion process for polymer melt has been increasingly used for the production of high value-added prepreg filaments with applications in the fields of fused deposition modeling (FDM). In this study, the effect of characteristic scale, defined as the gap of die land in an annular micro-extrusion die, on the extrudate swelling behaviour of viscoelastic melt is analyzed through numerical simulations and micro-extrusion experiments. The results show that the swelling behaviour displays an obvious dependence on the characteristic scale. An increase in the characteristic scale reduces the swell ratio and retards the process to reach the equilibrium state. In contrast, a decrease in the characteristic scale results in a larger magnitude of change in velocity field and faster relaxation development of stress field. The location of the maximum velocity layer for the laminar flow gradually deviates from the geometric center of channel toward the wall of mandrel with the increase in the characteristic scale. It is imperative to consider the complicated swelling behavior and remarkable viscoelastic effect simultaneously in micro-extrusion process.

Process parameters optimization for 3d printing of continuous carbon fiber reinforced composite

Process parameters optimization for 3d printing of continuous carbon fiber reinforced composite

Novel composite phase change materials supported by oriented carbon fibers for solar thermal energy conversion and storage

Phase change materials (PCMs) have aroused significant interest as promising materials for solar thermal energy conversion and storage. However, the long-standing shortcomings of liquid leakage, low thermal conductivity, and weak solar absorptance limit their practical applications. Herein, novel composite phase change materials (CPCMs) with anisotropic heat conduction are manufactured by mixing continuous carbon fibers (CFs) and palmitic acid (PA)/olefin block copolymer (OBC) mixtures using pressure induction and vacuum treatment. Because the oriented CFs in the vertical direction can offer heat transfer channels inside the composites, the vertical and horizontal thermal conductivities of the CPCMs are 5.84 W·K−1·m−1 and 1.34 W·K−1·m−1, respectively, resulting in a relatively high anisotropic degree of 4.36. Furthermore, to improve the absorption of solar radiation for the composite, carbon black is applied to the upper surface of the CPCMs, achieving a high total solar absorptance of 0.966. Due to the combination of the high solar absorptance of the carbon black and the high vertical thermal conductivity within the composites, the CPCMs exhibit outstanding solar-to-thermal efficiencies of 87.54% ∼ 95.08% at 1– 3 kW·m−2. In addition, stability testing also confirms that the CPCMs have excellent leakage-proof properties, thermal stability, and cyclic stability for long-term utilization. This work can provide an efficient route to synthesize high-performance CPCMs for solar thermal applications.

3D printing of topologically optimized wing spar with continuous carbon fiber reinforced composites

The necessity for more efficient manufacturing approaches of high-performance complex fiber reinforced composites parts is increasing. This study develops a framework to design and produce topologically optimized continuous carbon fiber reinforced composites (CCFRCs) with both high manufacturing efficiency and manufacturability, and experimentally validates via material extrusion (MEX) 3D printing technique in a more than 1-m wing spar for the unmanned aerial vehicle (UAV). The load-carrying structure can be topologically optimized by a solid orthotropic material with penalization method and further designed into a continuous fiber trajectory under the consideration of optimal material density, optimal fiber orientation and 3D printing process limitation. Based on this method, the complex topological CCFRCs can be realized by a single-stroke printing path with intact fiber. The feasibility and effectiveness of the proposed framework have been evaluated on the Messerschmitt-Bölkow-Blohm (MBB) beam which reveals obvious higher performance in specific stiffness and peak load compared with commonly used honeycomb structure. As a case study, a topologically optimized UAV wing spar was designed and validated experimentally. Mechanical testing shows that the designed wing spar can survive in operating loads. Furthermore, a proof-of-concept internal wing structure was presented where conventional wing spar and ribs are replaced by CCFRCs 3D printed structures. It exhibits high load-carrying characteristics, is lightweight and simple to fabricate.

L‐Cysteine‐Encapsulated MXene Nanosheet Possessing Ultra‐Antioxidation in Aqueous Suspension for Electrophoretic Deposition Assisted Carbon‐Fiber‐Surface Modification

AbstractWith recent progress in 2D materials, Ti3C2Tx MXene featured high metallic electrical conductivity, high electromagnetic interference shielding effectiveness, and super in‐plane stiffness, exhibits unique advantages in many fields, but is rarely applied as a sizing agent in long‐time continuous processing of carbon fiber sizing because of its poor ambient stability in aqueous suspension. Herein, a new strategy to chemically encapsulate the reactive sites of MXene nanosheet with l‐cysteine for restricting the attacking of water and/or oxygen in aqueous suspension is proposed. Based on the ultra‐antioxidation, polarity, and electrical properties of l‐cysteine‐encapsulated Ti3C2Tx MXene (LC‐MX) nanosheet, the LC‐MX, even if aging for weeks in aqueous suspension, can be deposited on the surface of high‐modulus carbon fiber (HMCF) uniformly via the electrophoretic deposition assisted sizing. Benefiting from the enhanced surface energy, wettability, and roughness of LC‐MX‐sized HMCF (HMCF‐LCMX) relative to that of unsized one (U‐HMCF), the interfacial property of HMCF‐LCMX/epoxy (EP) composites is also improved, for which the interlayer shear strength (ILSS) of the composite reached 88.5 MPa, 52.8% higher than that of U‐HMCF/EP composite (57.9 MPa). This work makes an essential step toward the application of ultra‐stable MXene nanosheet suspension in large‐scale continuous carbon fiber sizing.

Notch sensitivity of C/C-SiC composite evaluated by flexural tests

The notch effects on the mechanical behavior of Liquid Silicon Infiltration (LSI) based continuous carbon fiber reinforced silicon carbide (C/C-SiC) was studied. The in-plane (IP) and out-of-plane (OP) flexural properties of notched and unnotched samples with fiber orientations (0°, 45° and 60°) were determined through 3-point-bending (3PB) and single notched beam (SENB) tests. Despite the significant difference in bending modulus, the strength depends only slightly on the fiber orientation and loading direction, which could be explained through the uneven distribution of SiC-matrix within the block-like structure of C/C-SiC. This unique micro-structure also leads to a relatively constant value of notch sensitivity in the IP direction, and the sensitivity to the notch is relatively low for all tested C/C-SiC specimen configurations. Furthermore, due to the large differences of fracture mechanism, the work of fracture (WOF) in the IP direction is significantly smaller than in the OP direction for all fiber orientations.

The Non-Linear Elasticity of Unidirectional Continuous Carbon Fibre-Reinforced Composites and of Carbon Fibres.

A database of non-linear elastic parameters in axial tension and compression is provided for continuous carbon fibre polymer composites and carbon fibres of different stiffnesses. Composite laminates manufactured by conventional or automated processes are tested in bending, and parameters are extracted for strains of less than 0.5%. While fibre composites with fibres of standard and intermediate moduli exhibit a stiffening of ∼15 GPa/% (of strain) and a softening of ∼20 GPa/%, those with high-modulus carbon fibres exhibit much higher values of ∼50 GPa/% for both. This database is useful for designing composite structures in a stiffness-based design and for correlating the processing of carbon fibres with their nanostructure and induced properties. The latter is discussed in terms of reorientation of crystallites of graphene sheets vis-à-vis the carbon fibre axis during loading.

A multiscale study of heat treatment effects on the interlayer mechanical properties of 3D printed continuous carbon fiber‐reinforced composites

AbstractThe main goal of this study was to investigate the effect of heat treatment on the microstructural and interlayer mechanical properties of 3D printed continuous carbon fiber‐reinforced composites (CCFRCs). The influence of raster orientations on the interlayer properties of composites was systematically studied by the floating roller peel test. The multiscale morphological investigation was applied to analyze the influence of heat treatment on the interlayer mechanical properties and change of pores microstructure for composites. The results showed that heat treatment improved the interlayer mechanical properties of CCFRCs. During heat treatment, the pores merged, migrated, and deformed as the softening and collapse of the matrix. The average peeling strength after heat treatment for specimens increased by 10.17%–51.30%. Besides, the increase in matrix fluidity and the change of pore shape in CCFRCs were more significant than that of matrix specimens after heat treatment, since more thermal channels in CCFRCs.Highlights The interlayer mechanical properties of 3D printed continuous carbon fiber‐reinforced composites (CCFRCs) were improved by heat treatment. The pores of composites merged, migrated, and deformed as the softening and collapse of the matrix. The addition of continuous carbon fiber (CCF) made the composites have more thermal channels than those with matrix specimens.

4D printing of shape memory polymer with continuous carbon fiber

Shape memory polymer composites (SMPCs) have gained attention for their shape memory effects and wide-ranging applications. Understanding the bending shape recovery characteristics of 3D printed SMPCs is crucial for optimizing their performance. This study focuses on investigating the influence of different fiber orientations of continuous carbon fiber (CCF) in thermally stimulated SMPC. By controlling printing parameters and fiber orientation during the 3D printing process, we fabricate tailor-made rectangular composite test specimens. These specimens are subjected to controlled bending above the glass transition temperature of the polymer, inducing temporary deformation. The subsequent shape recovery process is carefully captured through high-speed video. Precise measurements of the bending curvature over time are obtained using the row-by-row image processing technique and analyzed. The shape recovery rate, shape recovery ratio, and shape fixity ratio of the test specimens were evaluated as a function of three CCF layout arrangements as well as fiber infill density embedded in Shape Memory Polymer (SMP) test specimens. The results revealed that the addition of CCF in the polymer matrix has a significant impact on shape memory behavior. Vertically aligned CCF in the SMP matrix improves the shape recovery ratio (92.97% compared to 78.77% of the pure SMP sample), while horizontal alignment of CCF ensures maximum shape fixity ratio (91.78% compared to 66.22% of the pure SMP sample). The cross-aligned CCF sample provides good recovery as well as fixity values. Further, it was observed that the horizontal alignment of CCF yields the fastest recovery performance. The outcome confirms that optimizing the fiber orientation enhances shape memory performance. Also, 40% of fiber infill density had greater shape fixity and overall recovery performance when compared to 30% and 50%. These findings have implications for tailored and high-performance SMPCs in biomedical devices, aerospace components, and robotics. Understanding temporal curvature behavior enables optimizing the design of materials with precise control over shape recovery. This research contributes to the design and optimization of SMPCs for diverse applications.

Numerical Modelling of the Heat Source and the Thermal Response of an Additively Manufactured Composite during an Active Thermographic Inspection.

This paper deals with the numerical modelling of non-destructive testing of composite parts using active thermography. This method has emerged as a new approach for performing non-destructive testing (NDT) on continuous carbon fibre reinforced thermoplastic polymer (CCFRTP) components, particularly in view of detecting porosity or delamination. In this context, our numerical model has been developed around references containing internal defects of various shapes and sizes. The first novelty lies in the fact that the heat source used in the experimental setup is modelled exhaustively to accurately model the radiation emitted by the lamp, as well as the convection and conduction around the bulb. A second novelty concerns the modelling of the CCFRTP making up the benchmark used. Indeed, its thermal properties vary as a function of the sample temperature. Therefore, the actual thermal properties have been experimentally measured and were later used in our model. The latter then captures the material dependency on temperature. The results obtained by our model proved to be in close agreement with the experimental results on real reference points, paving the way for future use of the model to optimise experimental configurations and, in particular, the heating parameters.

Comprehensive parametric analyses on the mechanical performance of 3D printed continuous carbon fibre reinforced plastic

This study presents a novel in-house modelling method called “Fibre Path Generator” and comprehensive parametric analyses on the mechanical performance of carbon fibre reinforced plastic (CFRP) with the fibre path along the principal stress direction, using both finite element (FE) simulations and experiments. The reliability of the developed CFRP model is validated through the fabrication of open-hole tensile test specimens using a co-extrusion composite 3D-printer, which demonstrated a highly compatible maximum tensile load with an error less than 3%. A comparative analysis is conducted to assess the mechanical performance of the CFRP specimen with principal stress fibre placement, which result shows that the maximum tensile load achieved is 172.84% higher than a CFRP model with uniaxial fibre placement. Furthermore, comprehensive parametric studies are carried out, varying the carbon fibre location and width-to-depth (w/D) ratio of the open-hole specimen, in order to evaluate the mechanical performance under the tensile loading. This study results provide useful insights to engineers when enhancing the mechanical performance of CFRP composite structures with effective continuous fibre placement.

Interfacial performance and build orientation of 3D‐printed poly(ether‐ketone‐ketone) reinforced by continuous carbon fiber

AbstractContinuous fiber reinforced thermoplastic composites (CFRTPCs) prepared by fused deposition modeling (FDM) have gained great attention for the benefit of preparing products without molds. However, unexpected debonding and defects are derived from insufficient impregnation between fiber and matrix in 3D‐printed samples, resulting in weak interfacial performance. In this work, a polyetherimide (PEI) sizing agent was used to improve the fiber‐matrix interfaces, and the interlaminar shear strength (ILSS) of the continuous carbon fiber reinforced poly(ether‐ketone‐ketone) composites was increased to 27.1 MPa, 12.4% higher than that of unmodified composite. Meanwhile, the performance of CFRTPCs is affected by process parameters in FDM. Build orientation of FDM was discussed and PEI weakened the anisotropy of samples' mechanical properties because the performance variation caused by build orientation decreased from 86.8% to 65.2%, which may be beneficial for the forming freedom of in situ impregnated FDM. The addition of PEI makes sense to apply in situ impregnated FDM in high‐tech fields.Highlights CCF/PEKK composites were prepared by in situ impregnated FDM. ILSS of flat‐oriented CCF/PEKK was 86.8% higher than that of on‐edge. 5 wt% PEI sizing agent promoted adhesion of CCF and PEKK to obtain the best mechanical properties. PEI weakened the anisotropy of samples' mechanical properties, which was conducive to forming freedom.

Robot-assisted laser additive manufacturing for high-strength/low-porosity continuous fiber-reinforced thermoplastic composites

Additive manufacturing (AM) of continuous fiber-reinforced thermoplastic composites (CFRTPCs) has become a hot area for both academia and industry. In this paper, a robot-assisted laser additive manufacturing (RLAM) technique is proposed, which involves utilizing a laser beam to heat the filament to a semi-molten state, followed by compacting it with a roller and bonding it layer by layer to create densely structured components. Firstly, an integrated framework of hardware, software, and control systems is presented. Then, the relationship between the processing parameters and the properties of the final specimens was examined. Finally, a process strategy was proposed to improve the forming accuracy. Due to the effective impregnation of continuous carbon fibers, the printed CFRTPCs using the LRAM process exhibit comparatively low porosity and superior mechanical performance. Specifically, the flexural strength, flexural modulus, and interlayer shear strength reached 584 MPa, 43.7 GPa, and 28.0 MPa, respectively. The prepared specimens boast a porosity of 0.19%, approaching levels achieved through autoclave processes. In addition, it was found that the dynamic offset of the yaw axis could be utilized to correct the deviation of the actual forming path due to the pultrusion force, thus making the position of the towpreg under the rollers controllable and improving the accuracy of the parts. This new method combines the advantages of industrial robotics and laser&roller-based continuous fiber additive manufacturing processes to enable high-performance additively manufactured large and complex CFRTPCs, which shows great potential for printing lightweight structures in the rail transit and aerospace industries.

In‐plane and in‐depth frontal polymerization behaviors of continuous fiber‐reinforced epoxy composites

AbstractFrontal polymerization (FP) is a self‐sustaining reaction that relies on polymerization exothermicity and heat transfer. This study explores the in‐plane and in‐depth FP mechanisms of continuous fiber‐reinforced epoxy composites. First, the effects of initiator and diluent concentrations on the FP behaviors of neat epoxy resins were examined. It was found that the frontal velocity and frontal temperature of the neat resins increase with an increase of either the initiator concentration or the diluent content, depending on the polymerization enthalpy and curing kinetics. Then, the FP behaviors of continuous carbon fiber and glass fiber‐reinforced epoxy woven composites were investigated. The results showed that the in‐plane FP behavior of the composites was primarily controlled by the thermal conductivity and specific heat capacity of the continuous fibers, whereas the in‐depth FP behavior mainly depended on the pores of the woven fabrics.Highlights Frontal velocity and temperature of neat resins are controlled by the polymerization enthalpy and curing kinetics. The in‐plane FP behavior of continuous fiber reinforced composites is dependent on the thermal conductivity and specific heat capacity of the fibers. The in‐depth FP behavior of composite is determined by both the thermal conductivity of fibers and the pores of fabrics.

Evaluating the Electromagnetic Shielding of Continuous Carbon Fiber Parts Produced by Additive Manufacturing.

Electronic devices are sensitive to electromagnetic (EM) emissions, and require electromagnetic shielding protection to ensure good operation, and prevent noise, malfunctioning, or even burning. To ensure protection, it is important to develop suitable material and design solutions for electronic enclosures. Most common enclosures are made with metal alloys using traditional manufacturing methods. However, using thermoplastic composites combined with additive manufacturing (AM) technologies emerges as an alternative that enables the fabrication of complex parts that are lightweight, consolidated, and oxidation- and corrosion-resistant. In this research, an AM technique based on material extrusion was used to print 2 mm-thick specimens with a multi-material made of micro-carbon fiber (CF)-filled polyamide that was reinforced at specific layers using continuous carbon fibers stacked with a 90° rotation to each other. The specimens' electromagnetic shielding effectiveness (EMSE) was evaluated in the frequency band of 0.03-3 GHz using the coaxial transmission line method. Depending on the number of CF layers, the EM shielding obtained can be up to 70 dB, with a specific shielding up to 60 dB.cm3/g, predominantly by the absorption mechanism, being 22 times higher than without the CF layers. These findings promote this innovative approach to lightweight customizable solutions for EM shielding applications.

The influences of international standards on structural performance and fracture behaviour of 3D printed long fiber composite structures

The material properties of the additive manufactured composite structures are usually done following international standards, that show some difference dimensionally. This study focuses on the impact-induced on the tensile properties of the 3D printed continuous carbon fiber reinforced composite part due to the standards applied for sample preparation. The specimens were fabricated by Markforged® Mark two 3D printing machine using carbon fiber as reinforcement and Onyx® as matrix material based on ASTM D638 and ASTM D3039-D3039M standards. The experimental results revealed that the specimens fabricated based on ASTM D638 showed a premature failure at the location where the straight gauge section of the specimen ends, and the curved transition regions begin due to stress concentration. The tests based on ASTM D3039-3039M standard showed better tensile strength and less stress concentration compared to ASTM D638. Fracture test with SEM reveals fiber breakage, debonding, and fiber pullout, which created cavities and voids between layers as the reasons for the tensile failure.