Composite Manufacturing Processes Research Articles

Determination of the In-Plane Shear Behavior of and Process Influence on Uncured Unidirectional CF/Epoxy Prepreg Using Digital Image Correlation Analysis

The investigation of the in-plane shear behavior of prepreg is crucial for understanding the generation of wrinkles of preforms in advanced composite manufacturing processes, such as automated fiber placement and thermoforming. Despite this significance, there is currently no standardized test method for characterizing uncured unidirectional (UD) prepreg. This paper introduces a ±45° off-axis tensile test designed to assess the in-plane shear behavior of UD carbon fiber-reinforced epoxy prepreg (CF/epoxy). Digital image correlation (DIC) was employed to quantitatively track the strains in three dimensions and the shear angle evolution during the stretching process. The influences of the temperature and stretching rate on the in-plane shear behavior of the prepreg were further investigated. The results reveal that four shear characteristic zones and wrinkling behaviors are clearly distinguished. The actual in-plane shear angle is significantly lower than the theoretical value due to fiber constraints from both the in-plane and out-of-plane aspects. When the off-axis tensile displacement (d) is less than 15.6 mm, the ±45° specimens primarily exhibit macroscale in-plane shear behavior, induced by interlaminar interface shear between the +45° ply and −45° ply at the mesoscale. The shear angle increases linearly with the d. However, when d > 15.6 mm, fiber squeezing and wrinkling begin to occur. When d > 29 mm, the in-plane shear disappears in the completely sheared zone (A). The reduction in the resin viscosity of the CF/epoxy prepreg caused by increased temperature is identified as the primary factor in lowering the in-plane shear force resistance, followed by the effect of the increasing resin curing degree. Higher shear rates can lead to a substantial increase in shear forces, eventually causing cracking failure in the prepreg. The findings demonstrate the feasibility of the test method for predicting and extracting uncured prepreg in-plane shear behaviors and the strain-rate and temperature dependency of the material response.

Bimodal coaxial fiber sensor for simultaneous strain and temperature sensing for composite manufacturing process

Coaxial structured fibers have gained significant attention in sensor applications due to their design flexibility and ability for multifunctionality. However, the complex and thicker structure of a sensor can lead to stress concentration and signal interference when utilized for strain monitoring in composite manufacturing processes. To address this issue, we propose a bimodal coaxial fiber sensor capable of simultaneous temperature and strain measurement during composite cure and strain monitoring, while preserving the mechanical properties of the fabricated composites. To achieve bimodal sensing, we employ a multi-shell structure consisting of a multi-conductive layer with varying concentrations of multiwalled carbon nanotubes and a PEDOT:PSS layer, applied to a creep-enhanced ultra-high molecular weight polyethylene core fiber using a simple dip-coating method. The bimodal coaxial fiber sensor exhibits a high gauge factor (>4.1), stable cyclic tensile response (>1000 cycles), and linear response to stepwise temperature cycles. Moreover, the sensor demonstrates high sensing accuracy (<3% error) in cure strain monitoring and maintains the fracture toughness of the composite (<1% discrepancy) wherein it is embedded. These results confirm the significant potential of the bimodal coaxial fiber sensor for various applications in the composite industry and other fields.

PENGUJIAN KEAUSAN ALUMUNIUM MATRIX KOMPOSIT DIPERKUAT DENGAN KARBON NANOTUBE

Wear testing of engineering materials is an important aspect in evaluating their performance and durability. This study aims to investigate the wear-resistant ability of aluminum composites reinforced with carbon nanotubes (CNTs). The composite manufacturing process was carried out by infiltrating CNTs into the aluminum matrix through powder metallurgy method. Tests were conducted using two methods, namely pressing and sintering with temperature variations of 0oC (non sintering), 400oC, 500oC, 600oC and 700oC. The results showed that the specific wear value on the specimen obtained the best value at a sintering temperature of 400oC with a value of 0.003632850 mm3/kg.m and the highest value at a sintering temperature of 700oC with a value of 0.042771207 mm3/kg.m. And the wear rate on the specimen obtained the best value at a sintering temperature of 400oC with a value of 0.447887285 mm3/s and the highest value at a sintering temperature of 700oC with a value of 1.155387594 mm3/s. This shows that the addition of temperatures greater than 400oC has a major influence on the specific wear value and wear rate of sintering products. In addition, this method is also a reference for further researchers in developing aluminum carbon nanotube technology to obtain optimal results.

Comparative life cycle assessment of aluminium and CFRP composites: the case of aerospace manufacturing

As climate change intensifies and existing resources are depleted, the need for sustainable industries becomes more important. The aviation industry is actively addressing environmental concerns by enhancing fuel efficiency and adopting lighter materials, especially carbon fibre composites. Research has proven that the use of carbon fibre composites provides cumulative benefits in reducing fuel consumption over the entire life cycle of an aircraft. However, existing studies are lack of a comprehensive exploration of the diverse impacts associated with composite manufacturing processes and recycling methods. To address this gap, a comparative life cycle assessment analysis covering the materials’ manufacturing, operation, and end-of-life phases is conducted. This analysis includes aluminium alloy and five different carbon fibre composite materials produced with varied constituents and manufacturing methods. Composite manufacturing processes, encompassing carbon fibre production, resin selection, and composite manufacturing methods, are considered. Weight savings based on the mechanical properties of utilised composite type are also taken into account. Results highlight the potential to mitigate the environmental impact of composite materials through strategic choices in constituent types, manufacturing processes, and disposal scenarios. Moreover, break-even distances indicate that aluminium becomes more environmentally detrimental than the analysed composite structures beyond a flight distance of 300,000 km.

The effect of composite materials interfacial discontinuities on the impact safety of future composite rail vehicles

AbstractIn contrast to single‐phase materials the manufacturing process of composites creates multiscale interfaces among constituent materials and between laminar multilayers. Targeting the interfaces in these composite structures, this paper presents a perspective study on the impact safety of potential future composite rail vehicles. The aim is to conceptually explore the key role of interfacial discontinuities of composite material structures as they are a critical issue affecting the impact performance of future composite rail vehicles. Following a theoretical description, the issues are addressed in two parts. First, composite materials are characteristically analyzed from the perspective of their interfacial discontinuities within the materials and between the laminate multilayers to identify their influence. Second, the structural conditions required for crashworthiness are determined in relation to the dual requirements of global stability and local deformability for efficient energy absorption. The key findings are: (1) The interfacial discontinuities of the material phases and the designed structural assemblies need to be tailored for crashworthiness performance and (2) Global stability and locally deformability are the key dual requirements for the energy absorbing progressive deformations that are essential for application of composite for crashworthiness of rail vehicles. The research conceptually explores a key issue of the impact mechanics of composite structures from the perspective of impact safety of composite rail vehicles.

Micro‐mesoscopic analysis of 3D void formation and evolution in CFRP composite using high‐resolution x‐ray microtomography

AbstractVoid defect is prevalent during the composite manufacturing process and may reduce the mechanical properties of composite structures, while limited information about three‐dimensional void distribution and evolution can be found due to the difficulties in void observation. In this work, void defects at different positions were detected and analyzed using x‐ray microtomography (XRM), and the random forest algorithm was implemented for segmenting components of CFRP samples. Results showed a trend of gradual rising porosity in the axial direction, with an increase of ~250% of porosity at the outlet of resin injection compared to the one at the inlet during the composite manufacturing process. The voids mainly featured with microscale between carbon fibers, with less distribution between fiber bundles and resin‐rich zones. Void defects achieved aggregation at the middle position of manufactured laminate, which is probably related to pressure interception. In the axial direction, the proportion of large‐diameter voids gradually increased, and a large volume of connected voids appeared near the outlet. Due to the shear deformation of resin and fiber and the pressure gradient effect, most of the voids showed stripe shape. The spatial orientation of voids was predominantly along the direction of resin flow and fluctuated due to fiber curl.Highlights 3D void characteristics in CFRP were studied using the XRM technique. Void formation and the effects of fibers on void morphology were analyzed. Dynamic void transport mechanisms during CFRP manufacturing were studied. Location and morphology of voids are helpful for CFRP damage modeling. The effective partitioning of CFRP was achieved using a random forest algorithm.

Tailoring Resin–Metal Adhesion by Femtosecond Laser Surface Texturing

Epoxy resin wettability and adhesion on metal surfaces are of interest to composite manufacturing processes in two aspects: while higher adhesion is desired for composite to metal part bonding, lower adhesion is expected for metal tools used in the composite fabrication process. Among several surface modification techniques to achieve such increased/decreased adhesion strengths, femtosecond laser micromachining is a sustainable and scalable technique. Therefore, this study aims to explore epoxy resin adhesion behavior against femtosecond laser micromachined aluminum surfaces as a function of different microscale topographies. The texture types include microscale hexagonal and cylindrical hole patterns with different solid/air surface fractions and comparatively smaller‐scale laser‐induced periodic surface structures. Based on polished metal contact angle results, desired texture geometries are selected in a range to theoretically favor or inhibit resin penetration into microcavities. Theoretical predictions are derived from the capillary effect and Gibb's energy difference. The adhesion strength of resin to metal is examined by tensile tests. All the laser‐textured surfaces show considerably increased adhesion strengths compared to polished surfaces. Scanning electron microscopy and laser profilometry analysis on failed surfaces confirm resin penetration into all textures. Nevertheless, hexagonal holes, which exhibit the highest microcavity volume, show potential for air trapping.

Rapid evaluation and prediction of cure-induced residual stress of composites based on cGAN deep learning model

In this piece of present work, we propose a deep learning model driven by conditional generative adversarial network (cGAN) for rapid evaluation and prediction of cure-induced residual stress (CRS) of composites. The CRS is evaluated by solving for the material behaviors of the cure kinetics, viscoelasticity, thermal expansion, and cure shrinkage under heat transfer condition using finite element (FE) method. The geometry and CRS fields are extracted from numerous simulations and subsequently utilized in the proposed cGAN training process. With this end-to-end unsupervised learning, the cGAN model can predict the CRS with high fidelity based on the fiber random distributed microstructure and capture the variation of fiber volume fraction. In qualitative measures, peak signal to noise ratio (PSNR) and structure similarity index (SSIM) are employed for accuracy verification. Moreover, the cGAN model can also significantly reduce the computational cost and provide some insights for optimizing the manufacturing process of composites.

Preparation, Microstructure, and Mechanical Properties of Aluminum Matrix Composite by Accumulating Roll Bonding Method

The ARB (Accumulative Roll Bonding) method is greatly watched as a new severe plastic deformation process that uses only a conventional general rolling machine. The ARB method is a preparation method of ultra-fine-grained, high-strength thin metal and alloy sheets by repeated rolling. The purpose of this study was to clarify the effectiveness of the ARB method as a metal matrix composite manufacturing process. At first, alumina particles and short carbon fibers were used as dispersoids, and pure aluminum was used as the thin plate. Then, the dispersoids were deposited on a pure aluminum plate to 2 vol.% dispersoids. Six of these aluminum sheets were stacked to form a multi-layer composite sheet, which was then cold rolled at a rolling reduction of 67%. After rolling, the sheet composites were cut in half, overlapped, and rolled again. The composites were obtained by repeating this process. When the repetition exceeded 6 times, the dispersoids tended to disperse in the aluminum matrix. In addition, uniform dispersion progressed through further repeat rolling. By repeated rolling, the tensile strength of the composite sheets was greatly improved. In addition, the tensile strength of the composites was higher than that of the ARB-processed monolithic aluminum sheet. The improvement in strength was caused by the refinement of aluminum grains rather than the particle dispersion.

Tensile properties of thermoset composites based on yarn structures from recycled carbon fibre and low melting temperature Co-polyamide fibre

The tensile properties of thermoplastic composites based on hybrid yarn structures consisting of recycled carbon fibre (rCF) and thermoplastic fibres (rCF content of the hybrid yarn approx. 50–60% by weight) have been reported previously. To date, no report has been found on the tensile properties of thermoset composites based on yarns with high rCF content (&gt;90% by weight). The reasons for this are the complex mechanisms involved in processing pure rCF due to the low shear strength, smooth fibre surface, small fibre diameter and high brittleness of rCF. Yarns made of rCF (≥90% weight) for thermoset composites have been developed in a fundamental research project at the ITM. This paper reports on the tensile properties of unidirectional composites based on yarns composed of staple rCF (&gt;90%) and low melting co-polyamide fibres produced by varying spinning parameters. Furthermore, in order to increase the infiltration of the epoxy matrix during the composite manufacturing process, the yarns are thermally treated at 180°C prior to infiltration and its effect on the tensile properties of the composites is analysed. The results show that the thermal treatment of the yarn prior to infiltration with the matrix, compared to the yarn without prior thermal treatment, helps to achieve better impregnation and therefore better tensile strength of the composites compared to the yarn without prior thermal treatment. A Youngs’ modulus and tensile strength of 86 ± 11 GPa and 1181 ± 71 MPa respectively are achieved in thermoset composites based on the developed yarns.

Fast and accurate prediction of cure quality and mechanical performance in fiber‐reinforced polymer composite using dielectric variables and machine learning

AbstractFiber‐reinforced polymer (FRP) composites are widely used in the aerospace and automotive industries due to their high strength‐to‐weight ratio. However, the manufacturing process of FRP composites is intricate, requiring precise control over multiple parameters, which can be challenging. To ensure top‐notch product quality and bolster confidence in the durability of composite materials, it requires a uniform curing evaluation technique and a predictive strength model. This study presents a rapid nondestructive quality inspection technique for composites, involving three distinct studies that employ machine learning techniques in combination with the frequency‐dependent dielectric response of materials. The first study introduces a nondestructive method for swiftly inspecting the cure state (degree of cure) of composite samples. This technique combines broadband dielectric spectroscopy with supervised machine learning algorithms, particularly support vector machines. The second study employs advanced artificial neural networks like multi‐layer perceptron to predict the tensile strength, a measure of mechanical performance, of composite materials. The results demonstrate an accurate classification of the curing state with 96.7% accuracy and a prediction of tensile strength with 87.5% accuracy. The final study explores the application of machine learning in quality monitoring of prepreg (raw materials for FRP) aging at room temperature.Highlights Integration of machine learning with frequency‐dependent dielectric measurement offers efficient method for inspecting and monitoring the curing state and mechanical performance of composite materials. Machine learning and frequency‐dependent dielectric response used to accurately assess the curing state of fiber‐reinforced polymer composites with 96.7% accuracy, which saves the time and effort and also reduces the need for destructive testing. Advanced artificial neural networks, specifically multi‐layer perceptron, employed to predict mechanical performance of composite materials with 87.5% accuracy, enhancing confidence in product reliability. Novel dielectric measurement technique integrated with machine learning algorithms enables prepreg age monitoring at room temperature.

Extraction and Characterization of Natural Fiber from the Stem of Dombeya Buettneri Plant for Biodegradable Polymeric Composites Application

ABSTRACT The global drive for a circular economy emphasizing sustainability in composite manufacturing processes has been the driving force for current ongoing research studies in natural fibers as sustainable substitutes for non-biodegradable synthetic fibers. The present study was carried out to characterize Dombeya buettneri fiber (DBF) extracted manually from the bark of the plant stem. Determination of physical and mechanical properties, quantitative chemical analysis, Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis and scanning electron microscopy were used to characterize the extracted fiber. Fiber constituents and XRD results showed higher cellulose content (58.45%), crystallinity index (62.32%) and percent crystalline (72.63%). The fiber had a crystallite size of 2.16 nm as determined using the Debye-Scherrer’s equation while FTIR analysis confirmed the presence of various functional groups of lignin, hemicellulose and cellulose on the fiber structure. The results revealed that DBF fiber had a thermal resistance that is up to 229.57°C with a maximum thermal degradation temperature of 356.27°C. Based on the results of this research that are comparable with other studies on cellulosic fiber, DBF fiber has a great potential as an alternative reinforcement for the development of polymer-based bio-composites.

Recent advanced thermal interfacial materials: A review of conducting mechanisms and parameters of carbon materials

Understanding the effect of process-induced residual stresses on the final shape of fiber-reinforced polymer composites is critical due to their widespread use in structural applications. It is crucial for more dependable composite production, as residual stresses change the internal stress level of the composite component during service life, and residual shape distortions may prevent the part from achieving the required geometrical tolerances. Residual strains are the result of many interplays among physical processes, such as heat transfer, material flow, polymerization, crystallization, or heat transfer. Numerical process models must be constructed instead of time-consuming and inefficient trial-and-error procedures to design and optimize the composite manufacturing process digitally. This study aims to review the model creation and applications for predicting residual stresses and form distortions in composite manufacturing. Uses for both thermoset and thermoplastic composites are investigated in detail. Predictions of the process-induced deformations of laminated composite structures have been made using elastic constitutive models, such as a plane strain finite element model with a cure-hardening, instantaneous linear elastic constitutive model. to learn more about the factors that lead to shape distortion and how they can be reduced, such as by adjusting cure cycles, tool surfaces, geometry, or lay-up.

Toward tailoring the mechanical and dielectric properties of short glass fiber‐reinforced epoxy composites

AbstractGlass fiber‐reinforced polymer‐matrix (GFRP) composites are used to manufacture devices such as radomes, electrical insulators, and radar‐absorbing structures, many of which are used in applications with strict mechanical and dielectric property requirements. As such, designs and properties of GFRP composite materials should be regularly improved to guarantee their safe operation and meet their constantly evolving application requirements. In this study, glass fiber (GF) particles and epoxy resin 128 (EP‐128) were used to manufacture high‐performance EP/GF‐X composites with GF particle contents ranging from 5% to 40%. An investigation into their mechanical and dielectric properties revealed that EP/GF‐20 composite specimens presented the best mechanical performance with their bending strength and modulus reaching 159.68 MPa and 6521.92 MPa, respectively, and an average dielectric constant of 4.862 within the 10–105 Hz frequency range. A theoretical analysis of the EP/GF‐X composite specimens' dielectric constants using classic dielectric models based on the Lichtenecker, Bruggeman, Jaysundere‐Smith, and Maxwell‐Garnett rule‐of‐mixture equations indicated that the dielectric model based on the Bruggeman rule‐of‐mixture equation provided the dielectric constants closest to the measured values with a maximum deviation of less than −0.321% for EP/GF‐40 composites. This study provides a feasible strategy to control the mechanical and dielectric properties of GFRP composites.Highlights Glass fiber (GF) particles and epoxy 128 (EP‐128) resin were used to manufacture high‐performance glass fiber‐reinforced epoxy (EP/GF‐X) composites. The composite manufacturing process was carefully controlled to ensure uniform distribution and orientation of GF particles in the EP‐128 resin. The mechanical and dielectric properties of the manufactured EP/GF‐X composites were effectively tailored by controlling the content and distribution of GF particles in the EP‐128 resin matrix. The dielectric constants of the EP/GF‐X composites were measured experimentally and predicted using various theoretical dielectric models. The Bruggeman model provided the dielectric constants of the EP/GF‐X composites closest to the measured values.

DEVELOPMENT AND VALIDATION OF AN AUTOMATIC MANUFACTURING PROCESS FOR FIBERGLASS COMPOSITES

Fiberglass reinforced polymeric composites are ideal for various applications due to their mechanical properties and lightweight. However, nowadays many fiberglass reinforced composite manufacturing processes are manual, which makes it complicated for them to meet industrial requirements regarding the quality and reliability of the manufactured parts, limiting their applications. The development of automatic and digital processes lead to the reduction of manual labour and, as a consequence, the cost and variability of the process. Nevertheless, the industrial implementation of these automatic processes requires them to be economically affordable, flexible and simple. Therefore, the research work carried out has focused on the development of an automatic fiberglass composite manufacturing process able to produce composites with mechanical properties comparable to those obtained in conventional manufacturing processes. For this purpose, a two-stage manufacturing line has been developed: (i) the automatic manufacture of fiberglass and ultraviolet (UV) resin prepregs, and (ii) the compaction and curing of these prepregs. The process has been validated by measuring the physical and mechanical properties of the manufactured composites and comparing them to those obtained with hand lay-up and infusion processes. Key Words: Automatic process, fiberglass, prepregs, UV curing, energy efficiency, productive efficiency.

Additive Manufacturing of Large-scale Metal Mesh with Core-shell Composite Structure for Transparent Electromagnetic Shielding/glass Heater

Transparent electromagnetic (EM) shielding glass with a metal mesh has significant potential for application in different fields of EM radiation and anti-EM interference light-transmitting observation windows. In particular, a transparent EM-shielding glass with a large-aspect-ratio metal mesh can effectively alleviate the contradictory problems of shielding effectiveness and light-transmission performance constraints. However, the fabrication of high-aspect-ratio metal meshes on glass substrates has problems such as high cost, complex processes, low efficiency, small area, and easy damage issues, which limit their application in the field of high-performance, transparent EM-shielding glass. Therefore, this paper proposes a composite additive manufacturing process based on electric-field-driven microjet 3D printing and electroplating. By fabricating metal meshes with an Ag-Cu core-shell structure on a glass substrate, EM-shielding glass with high shielding efficiency and light transmission can be manufactured without increasing the aspect ratio of the metal meshes. The prepared Ag-Cu composite metal mesh has excellent optoelectronic properties (period 250 μm, line width 10 μm, 90.1% transmission at 550 nm visible light, square resistance 0.21 Ω/sq), efficient electrothermal effect (3 V DC voltage can reach 189 °C steady-state temperature), stable EM-shielding effectiveness (average shielding effectiveness 23 dB at X-band), and acceptable mechanical and environmental stability (less than 3% change in square resistance after 150-times adhesion test and less than 6% and 0.6% change in resistance after 72 h in acid and alkali environments, respectively). This method provides a new solution for the mass production of high-performance large-area transparent electric heating/EM-shielding glass.

Manufacturing Multi-Matrix Composites: Out-of-Vacuum Bag Consolidation

Abstract The formation of porosity is a major challenge in any composite manufacturing process, particularly in the absence of vacuum assistance. Highly localized injection of polymer matrix into regions of interest in a dry preform is a route to manufacturing multi-matrix fiber-reinforced composites with high filler concentrations, which are otherwise difficult to achieve. Unlike traditional composites, such multi-matrix fiber-reinforced composite systems, which combine multiple resins in continuous form, offer improved structural performance around stress concentrators and multifunctional capabilities. As the process lacks vacuum assistance, porosity becomes a primary issue to be addressed. This paper presents a rheo-kinetic coupled rapid consolidation procedure for optimizing the quality of localized matrix patches. The procedure involves manufacturing trials and analytical consolidation models to determine the best processing program for minimal voidage in the patch. The results provide a step toward an efficient manufacturing process for the optimal design of multi-matrix composites without the need for complex vacuum bag arrangements, thus reducing cost and time while opening avenues to improve overall composite performance.

Failure Mode Effect Analysis of Composites Prepreg Manufacturing Process for Airworthiness Certification - A Case Study

Airworthiness certification of aircraft structures requires a holistic approach ranging from material manufacturing process to design evaluation of airframe components. Present day airframe structures find greater applications of composite materials owing to their extraordinary mechanical properties on pro rata weight basis. In case of polymer based composites, the prepreg form of material is preferred for several applications due to matrix efficiency (high fiber-to-volume ratio) and ease of application. As part of composite material certification, the design audit of composite prepreg manufacturing process is carried out to assess the possible failure scenarios. Manufacturing Process Design and Control plays a significant role in satisfactory realization of composite parts right from raw material stage. Process variability/ scatter can lead to large variation in performance of the final product and thus stringent control of process parameters is essential to achieve aero-grade composite structures. This study provides basic understanding of composite prepreg manufacturing process and application of FMEA as a process design tool to detect and assess potential failures with an aim to devise preventive measures for improved process control. The complete process of manufacturing prepregs is divided into three stages viz.: Fabric weaving, Resin formulation and Prepregging operation. FMEA principles are used to identify the predominantly vulnerable operations and to quantify the inherent risk associated. Risk Priority Numbers (RPN) are evaluated for various operations in these three stages. Based on process technology and engineering expertise, suitable corrective and preventive measures are offered according to the potential risk factors and failure types. Emphasis is to prioritize the efforts and attention towards major preventive measures by targeting the least number of factors causing the maximum impact for failures (Pareto principle). Present study substantiates the significance of trained personnel, proper documentation of operating procedures and work instructions along with contamination control as critical factors in eliminating failures in composite prepreg manufacturing process.

DcAFF (Discontinuous Aligned Fibre Filament) – Mechanical properties investigation on multilayer 3D printed parts

DcAFF (Discontinuous Aligned Fibre Filament) is a novel thermoplastic filament developed for 3D printing. This filament is reinforced with highly aligned discontinuous fibres and is based on the High Performance Discontinuous Fibre (HiPerDiF) method which produces thin tapes suitable for a range of different composite manufacturing processes. The HiPerDiF, using fibres longer than the critical length, provides mechanical performance comparable to continuous fibre composites with the high formability typical of short fibre composites. Thanks to the development of the third-generation HiPerDiF machine and the DcAFF filament forming method, circular DcAFF filaments can be produced consistently and at high rates. In this paper, both the physical properties and the internal architecture of the produced filament were investigated. In particular, μCT scanning and image post-processing were used to quantify fibre alignment. The designed filament-forming process ensures that the large fraction of the fibres in the final product are well aligned with the longitudinal axis of the filament. The mechanical properties of the multilayer DcAFF 3D printing part are presented for the first time in this paper with tensile, short beam shear (SBS), and open-hole tensile testing. The comparison with the previous studies and data in the literature shows comparable or indeed superior stiffness of DcAFF over existing methods for 3D printing composite parts; however, to be able to consider this material as a viable candidate for high-performance 3D printing further improvements are required in term of strength, e.g. increasing fibre-matrix adhesion or substituting the proof-of-concept PLA matrix with a high performance one.

The Effects of Polyaniline Nanofibers and Graphene Flakes on the Electrical Properties and Mechanical Properties of ABS-like Resin Composites Obtained by DLP 3D Printing.

Three-dimensional printing is regarded as a future-oriented additive manufacturing technology that is making significant contributions to the field of polymer processing. Among the 3D printing methods, the DLP (digital light processing) technique has attracted great interest because it requires a short printing time and enables high-quality printing through selective light curing of polymeric materials. In this study, we report a fabrication method for ABS-like resin composites containing polyaniline (PANI) nanofibers and graphene flakes suitable for DLP 3D printing. As-prepared ABS-like resin composite inks employing PANI nanofibers and graphene flakes as co-fillers were successfully printed, obtaining highly conductive and mechanically robust products with the desired shapes and different sizes through DLP 3D printing. The sheet resistance of the 3D-printed composites was reduced from 2.50 × 1015 ohm/sq (sheet resistance of pristine ABS-like resin) to 1.61 × 106 ohm/sq by adding 3.0 wt.% of PANI nanofibers and 1.5 wt.% of graphene flakes. Furthermore, the AP3.0G1.5 sample (the 3D-printed composite containing 3.0 wt.% of PANI nanofibers and 1.5 wt.% of graphene flakes) exhibited 2.63 times (22.23 MPa) higher tensile strength, 1.47 times (553.8 MPa) higher Young's modulus, and 5.07 times (25.83%) higher elongation at break values compared to the pristine ABS-like resin with a tensile strength of 8.46 MPa, a Young's modulus of 376.6 MPa, and an elongation at break of 5.09%. Our work suggests the potential use of highly conductive and mechanically robust ABS-like resin composites in the 3D printing industry. This article not only provides optimized DLP 3D printing conditions for the ABS-like resin, which has both the advantages of the ABS resin and the advantages of a thermoplastic elastomer (TPE), but also presents the effective manufacturing process of ABS-like resin composites with significantly improved conductivity and mechanical properties.