Short Carbon Research Articles

Static Behavior of a 3D-Printed Short Carbon Fiber Polyamide: Influence of the Meso-Structure and Water Content.

The knowledge of the mechanical behavior of a 3D-printed material is fundamental for the 3D printing outbreaking technology to be considered for a range of applications. In this framework, the significance, reliability, and accuracy of the information obtained by testing material coupons assumes a pivotal role. The present work focuses on an evaluation of the static mechanical properties and failure modes of a 3D-printed short carbon fiber-reinforced polyamide in relation to the specimen's unique meso-structural morphology and water content. Within the manufacturing limitations of a commercially available printer, specimens of dedicated combinations of geometry and printing patterns were specifically conceived and tested. The specimens' meso-structure morphologies were investigated by micro-computed tomography. The material failure mechanisms were inferred from an analysis of the specimens' fracture surfaces and failure morphologies. The outcomes of the present analysis indicate that each test specimen retained proper mechanical properties, thereby suggesting that they should be accurately designed to deliver representative information of the underlying material beads or of their deposition layout. Suggestions on the adoption of preferred test specimens for evaluating specific material properties were proposed.

Ultra-Fast Preparation of High-Strength Polymer Concrete via Frontal Polymerization at Room Temperature.

Concrete, in particular application scenarios, such as crack repair, disaster rescue and relief, and 3D printing, needs to be cured quickly. In this work, a novel synthesis strategy, UV-initiated frontal polymerization (FP), for fast preparation of high-strength polymer concrete at room temperature is proposed, and the whole fabrication progress within several minutes, in which coarse aggregates and a small amount of short carbon fibers (CF) are used to enhance mechanical properties and heat conduction and reduce the amounts of chemical adhesives. SEM, DSC, MIP, Ultra depth of field microscope, and Rheometer are employed to characterize the properties of chemical adhesives, polymer concrete, and polymerization process. In addition, the finite element method is used to investigate the internal temperature field status of the FP process. The results indicate that the compressive and flexural strengths of the polymer concrete with 1.0wt%-1mm-CF-50vol.%-quartz sand exceeded 70 and 20MPa, respectively, in which the average self-propagation velocity reached 58mmmin-1. The investigation provides a promising approach for the rapid construction of structural facilities, emergency repair after disasters, 3D printing concrete, etc.

Box-Behnken modeling to optimize the engineering response and the energy expenditure in material extrusion additive manufacturing of short carbon fiber reinforced polyamide 6

The field of production engineering is constantly attempting to be distinguished for promoting sustainability, energy efficiency, cost-effectiveness, and prudent material consumption. In this study, three control parameters (3D printing settings), namely nozzle temperature, travel speed, and layer height (LH) are being investigated on polyamide 6/carbon fiber (15 wt%) tensile specimens. The aim is the optimum combination of energy efficiency and mechanical performance of the specimens. For the analysis of the results, the Box-Behnken design-of-experiment was applied along with the analysis of variance. The statistical analysis conducted based on the experimental results, indicated the importance of the LH control setting, as to affecting the mechanical strength. In particular, the best tensile strength value (σB = 83.52 MPa) came from the 0.1 mm LH. The same LH, whereas caused the highest energy consumption in 3D printing (EPC = 0.252 MJ) and printing time (PT = 2272 s). The lowest energy consumption (EPC = 0.036 MJ) and printing time (PT = 330 s) were found at 0.3 mm LH. Scanning electron microscopy was employed as a part of the manufactured specimens’ 3D printing quality evaluation, while Thermogravimetric analysis was also conducted. The modeling approach led to the formation of equations for the prediction of critical metrics related to energy consumption and the mechanical performance of composite parts built with the MEX 3D printing method. These equations proved their reliability through a confirmation run, which showed that they can safely be applied, within specific boundaries, in real-life applications.Graphical abstract

Effective volume of short carbon fibers in a composite from chopped thin tapes

Effective volume of short carbon fibers in a composite from chopped thin tapes

4D printing and annealing of PETG composites reinforced with short carbon fibers

In this study, for the first time, post-heat treatment was applied to improve the stress recovery of short carbon fiber reinforced PETG (SCFRPETG). PETG and SCFRPETG composite were printed under optimal conditions, and constrained and free shape memory cycles were applied under compression and three-point bending loadings to assess shape and stress recovery. The results of the free shape memory test for both vertical and horizontal patterns showed that PETG composite also has a higher shape memory effect (SME) compared to PETG. The SME was significantly improved by performing heat treatment. The stress recovery values for pure PETG, reinforced PETG before and after annealing are 2.48 MPa, 3.04 MPa and 3.18 MPa, respectively. It showed that the addition of 1.5% carbon fiber increases the stress recovery by 22%. The increasing trend reaches 28% by performing post-heat treatment. Additionally, altering the printing pattern affects the programming and stress recovery values. For the SCFRPETG composite samples before and after annealing, changing the printing pattern from horizontal to vertical, resulted in a 16% and 7% increase in recovery stress, respectively. SEM results confirm that the annealing process removes the layered structure, micro-holes caused by shrinkage and 4D printing mechanism. Using the controlled heat treatment method can be a practical solution to solve the problem of adhesion and reduce the anisotropy of FDM 3D printed layers.

Effect of multi-scale fillers on the tribological behavior of UHMWPE composites in water-lubricated contacts

This study investigates the impact of graphite, hexagonal boron nitride and short carbon fibers, acting as micro- and nano-fillers, on the tribological performance of ultra-high-molecular-weight polyethylene (UHMWPE) hybrid composites. The tribological performance is evaluated under boundary-lubrication conditions with distilled water at contact pressures in the range from 5 and 15 MPa. The fillers were found to work synergistically, with the best performance recorded when the compositions incorporated fillers of all scales. The most effective composite, consisting of short carbon fibers, micro-scale graphite, micro-scale hBN and nano-scale hBN, reduced the coefficient of friction by 75 %, reaching a value of 0.06, and the specific wear rate by two orders of magnitude to 2 × 10−7 mm3/Nm, compared to pure UHMWPE. The fillers' size also played an important role. Composites with nano-boron nitride led to 40 % lower friction compared to micro-scale fillers only. However, all the fillers reduced the amount of abrasive wear, especially the boron nitride, as a consequence of the tribochemical reaction between the boron nitride and water at the interface. Additionally, the formation of a transfer film was observed on the steel discs, with only short carbon fibers and graphite contributing to its formation from among the fillers used.

Void geometry analysis and multifaceted characterisation of cementitious mortar reinforced with short carbon and glass fibres – A comparative study

This paper presents comprehensive experimental and numerical studies on void analysis, durability performance, electrical properties, and microstructural behaviour of fibre-reinforced cementitious composites (FRCC) with varying short carbon and glass fibre volume fractions. Durability and electrical properties are evaluated based on the hydrochloric acid effect, water absorption, drying shrinkage and electrical resistivity changes over time. The incorporation of CF and GF remarkably limits drying shrinkage, primarily attributed to the bridging and bonding effects of fibres within the matrix. The addition of 1.0 % carbon fibre significantly decreases the electrical resistivity and improves acid resistance performance. Furthermore, for the first time, the influence of fibre type and quantity on the formation of elongated and eccentric voids is investigated by using X-ray computed tomography (micro-CT). The results demonstrate that higher porosity leads to lower strength and durability performance, while a greater occurrence of elongated voids contributes to increased length change in shrinkage.

Short carbon fiber-reinforced PLA composites: influence of 3D-printing parameters on the mechanical and structural properties

3D printing, particularly “fused filament fabrication” (FFF), plays a crucial role in Industry 4. FFF is widely used for creating complex structures and multi-material parts across various industries such as food industry, fashion industry, and manufacturing sectors. The properties of FFF-produced objects are remarkably affected by printing parameters. This study explores the impact of printing parameters and the addition of short carbon fibers on the strength of polylactic acid (PLA) printed samples. The lowering layer height, increasing feed rate and extrusion temperature boost impact strength, while a smaller raster angle enhances it. Meanwhile, an improved flexural strength is achieved by adjusting layer height, extrusion temperature, and raster angle. Higher extrusion temperatures enhance tensile strength, microstructure, and reduce porosity. Lower layer height improves flexural and impact strength (28.05% increase in 0.1 mm layer height), higher feed rate boosts strengths (12.56% improvement in 7 mm3/s feed rate), and elevated extrusion temperatures enhance impact strength (14.49% increase in 230 °C extrusion temperature) but reduce flexural strength (14.44% decrease). Incorporating carbon fibers in PLA negatively affects the microstructure but increases crystallinity, raising the melting temperature and lowering cold-crystallization temperature. The introduction of carbon fibers into PLA results in a complex interplay of mechanical and thermal properties.Graphical abstract

Analysis of the machining process of short carbon fiber-reinforced polyamide additive manufactured parts

In recent years, additive manufacturing technologies have revolutionized the production of parts, particularly in the aeronautical sector. This new manufacturing paradigm has created significant challenges and opportunities for researchers in materials and manufacturing processes. One important aspect is the development of optimal strategies for finishing-oriented machining of parts produced through additive manufacturing.This article focuses on the analysis of reinforced polyamide materials and the integration of large-scale additive manufacturing using Big Area Additive Manufacturing (BAAM) technology, along with robotic systems for subtractive machining. The aim is to explore the potential of integrating additive and subtractive processes to produce high-quality, large-scale components.The study examines the production and subsequent machining of reinforced polyamide parts using BAAM technology, showcasing the advantages and promising results observed. By combining additive manufacturing with subtractive machining, this research contributes to the ongoing advancements in the field of manufacturing, particularly in relation to reinforced polyamide materials. The findings presented in this article shed light on the potential of integrating additive and subtractive processes in the manufacturing industry, paving the way for more efficient and high-quality production methods.

Effects of heat treatment on tensile properties of 3D-printed short fiber-reinforced composites

3D-printed carbon fibre-reinforced composites (CFRC) using fused deposition modelling (FDM) offer the potential for building complex geometries and low waste. However, these composites have weaker interlaminar bonding and higher void content than traditional composites. This paper explores the effect of temperature on improving the mechanical properties of 3D-printed short carbon fibre- reinforced polyamide (PACF). Two types of printed structures were tested: one with a 0° build orientation (parallel to extruder movement) and the other with a 90° build orientation (perpendicular to extruder movement). Both samples were heat-treated at 150°C. Force vs. displacement data was obtained from the MTS testing machine. After that, the tested samples were viewed under an optical microscope. Images obtained from the optical microscope are then analyzed to see how the samples failed by checking the microstructure. The average ultimate strength, ultimate strain, and elastic modulus were used for the analysis. The sample follows a trend where the strength and elastic modulus increase after heat treatment. The result also showed that the 0° build orientation samples have higher mechanical performance than the 90° build orientation sample. Also, from the ultimate strain values, it was evident that samples printed in the 0° absorbed more energy, exhibiting 83% higher resistance before final failure. Lastly, an optical microscope was used to investigate the failure mechanisms of the samples.

Effects of nanofillers on the physical, mechanical, and tribological behavior of carbon/kenaf fiber–reinforced phenolic composites

Abstract This research investigates the effect of kenaf/carbon fiber reinforcement with the addition of nanofillers such as multi-walled carbon nanotubes (MWCNT) and cellulose nanocrystal (CNC) in the phenolic matrix composite. Three different types of samples were made using short carbon fiber, kenaf fiber (KF), BaSO4, Cashew dust, MWCNT, and CNC. Sample 1 contains 40 wt% of carbon fiber with binders reinforced in the phenolic matrix, whereas, in sample 2, carbon fiber has been replaced with KF in the MWCNT-modified phenolic matrix. On the other hand, in sample 3, carbon fiber has been replaced with KF in a CNC-modified phenolic matrix. The physical, mechanical, and tribological properties were investigated and compared. The results showed that sample 1 exhibited higher mechanical performance compared to other samples. On the other hand, the least wear loss and a high coefficient of friction were observed for Sample 2 compared to Samples 1 and 3. Even though KF-based composites exhibited slightly lower mechanical performance, they showed excellent tribological behavior.

Short carbon nanorod-grafted N-doped carbon nanocages derived from LDH/MOFs for efficient electromagnetic wave absorption

The systematic design of morphology and structure plays a significant role in enhancing the physicochemical properties of functional materials. In this work, short carbon nanorod-grafted magnetic N-doped carbon nanocage (FeCoNi@NC) was prepared using FeCoNi layered double hydroxide (LDH)/metal organic frameworks (MOFs) as precursor. Herein, a multi-level hollow nanocage was synthesized by hydrothermal method, in which nanorods were formed on the surface of the hierarchical structure, and after annealing, an N-doped hollow nanocage with short carbon nanorod-grafted was formed. Due to its unique hollow and hierarchical interfaces, the optimal FeCoNi@NC exhibits highly efficient electromagnetic wave absorption (EWA). At 14.32 GHz, the minimum reflection loss (RLmin) reach −54.4 dB, while the effective absorption bandwidth (EAB) is over a wide range of 5.28 GHz, corresponding to a thickness of 1.5 mm. The outstanding ability to absorb electromagnetic waves is due to the hierarchical and hollow characteristics, which increase dielectric and conductive losses, while also optimizing impedance matching. The study presents a highly effective approach to fabricate hierarchical and hollow nanostructures with short nanorods, aiming to enhance the efficiency of EWA.

Carbon sequestration potential of plantation forests in New Zealand - no single tree species is universally best

BackgroundPlantation forests are a nature-based solution to sequester atmospheric carbon and, therefore, mitigate anthropogenic climate change. The choice of tree species for afforestation is subject to debate within New Zealand. Two key issues are whether to use (1) exotic plantation species versus indigenous forest species and (2) fast growing short-rotation species versus slower growing species. In addition, there is a lack of scientific knowledge about the carbon sequestration capabilities of different plantation tree species, which hinders the choice of species for optimal carbon sequestration. We contribute to this discussion by simulating carbon sequestration of five plantation forest species, Pinus radiata, Pseudotsuga menziesii, Eucalyptus fastigata, Sequoia sempervirens and Podocarpus totara, across three sites and two silvicultural regimes by using the 3-PG an ecophysiological model.ResultsThe model simulations showed that carbon sequestration potential varies among the species, sites and silvicultural regimes. Indigenous Podocarpus totara or exotic Sequoia sempervirens can provide plausible options for long-term carbon sequestration. In contrast, short term rapid carbon sequestration can be obtained by planting exotic Pinus radiata, Pseudotsuga menziesii and Eucalyptus fastigata.ConclusionNo single species was universally better at sequestering carbon on all sites we tested. In general, the results of this study suggest a robust framework for ranking and testing candidate afforestation species with regard to carbon sequestration potential at a given site. Hence, this study could help towards more efficient decision-making for carbon forestry.

Variable orientation in material extrusion of short carbon fiber reinforced polymer composites with high thermal conductivity

Controllable orientation architecture possesses tunable thermal behavior for effective heat dissipation in unidirectional product fields, meanwhile without interference with adjacent components. Herein, we proposed a variable orientation strategy in material extrusion of short carbon fiber (SCF) reinforced polymer composites framework with spatially tunable thermal properties. It was achieved due to the following reasons: (Ⅰ) Inherent shear flow in the nozzle; (Ⅱ) Increasing tensile flow by changing the ratio between the printing speed of monofilament and the feeding speed of filament (Vp/f); (Ⅲ) Further surface tension due to thinning monofilament by varying Vp/f. The SCF with different orientations and content reinforced polyether-ether-ketone (PEEK) composites were successfully fabricated. The microcosmic orientation of SCF could be programmed from a three-layer hierarchical framework to a single-layer oriented framework at different Vp/f. Benefit from variable orientation, the through-plane thermal conductivity of SCF/PEEK composites achieved a thermal conductivity enhancement of 173.9 %. In addition, the simulated application of SCF/PEEK composites in the CPU of the computer showed excellent heat transfer during heating. Further, the thermal conductivity mechanism of the synergistic influence between Vp/f and SCF content was analyzed by cross-sectional microstructure. The proposed strategy in this work for fabricating variable orientation of SCF reinforced polymer composites showcases great application prospects in electronic devices and unidirectional product fields.

Elucidation of role of carbon fibers on joining of metal to composite

Weight reduction in the various application fields has propelled to the forefront in investigations of combining metal with polymer. Different from other studies, this work focused on exploring the effect of carbon fibers on the thermal joining of metal to composite. Three plastics with different fiber contents including pure polyether-ether-ketone (PEEK), short carbon fibers reinforced PEEK (SCF/PEEK), and continuous reinforced PEEK (CF/PEEK) were chosen to join to the 6061aluminum alloy using a fiber laser. Results showed the thermal transfer was fostered along the carbon fiber orientation due to a higher thermal conductivity, decreasing the heat accumulation at the interface. However, the existence of carbon fibers also hindered the spreading of plastics on the aluminum alloy surface. This led to a smaller adhesion width and lower tensile-shear force of joints. In addition, the tensile-shear strength of joints prepared with carbon fibers was enhanced owing to lower thermal expansion coefficient, which improved the thermal shrinkage and reduced the stress concentration at the interface. Ultimately, the role of carbon fibers during laser joining of aluminum alloy to plastics was explained, clarifying the bonding mechanism of two materials.

Enhanced mechanical and tribological properties of 3D printed short carbon fiber reinforced polyether ether ketone composites

AbstractMaterial extrusion additive manufacturing provides an effective solution for fabrication of highly customized polyether ether ketone (PEEK) composite parts with any complex shape. Nevertheless, compared with conventional methods, the mechanical strength of 3D printed carbon fiber reinforced PEEK (CF/PEEK) composites is unsatisfactory due to the weak interface bonding strength and high voids content induced by the temperature difference. To overcome this challenge, a temperature‐control 3D printer was used to investigate the effects of ambient temperature and annealing temperature on the microstructure, crystallization behavior and mechanical properties of 3D printed parts. Moreover, the tribological properties of parts printed at different ambient temperature were also studied under various contact pressure. Experimental results showed that the ambient temperature and annealing treatment directly affected the interfacial bonding (fiber/matrix, filament/filament, layer/layer), crystallinity of printed samples, thus affecting their mechanical and tribological properties. The CF/PEEK parts printed at high ambient temperature of 200°C exhibited outstanding mechanical and tribological properties. This study has positive significance for promoting the application of 3D printed PEEK composites in the field of structural load‐bearing and friction materials.Highlights Structure–property relationships for 3D printed CF/PEEK composites. The ambient temperature strongly affects the thermal and microstructural properties Interaction between crystallization and molecular interface diffusion. Interfacial bonding and crystallinity determine the mechanical properties. Tribological properties are highly dependent on applied pressures.

Characterisation and mathematical modelling of nonlinear mechanical behaviour of 3D printed short carbon fibre reinforced composites

Short carbon fibre reinforced plastic composites (SCFRP) that can be used in 3D printing exhibit excellent properties such as high specific strength and modulus, fatigue resistance, and efficient production at a lower cost. However, in the process of 3D printing, short carbon fibres tend to be distributed along the axial direction of the printed filament when they flow in the nozzle, leading to anisotropy and dispersity at the macro level. This brings difficulties to the design and application of materials. This paper developed a novel fix point iteration method based on classical laminate theory and Euler's integral method to accurate predict the nonlinear mechanical behaviour of SCFRP and verified via experiments. Results showed that the predicted curve and experimental data were in excellent agreement with only a 5 % error for 0°/90° laminate under uniaxial tensile loading. The accuracy of strength prediction for the -45°/45° laminate was improved and stabilised with the introduction of the fix point iteration method. These findings provide a useful framework for predicting the mechanical properties of the short fibre reinforced composited prepared by 3D printing.

Surface Quality Related to Face Milling Parameters in 3D Printed Carbon Fiber-Reinforced PETG

Three-dimensional printing technology holds significant potential for enhancing the flexibility and cost-efficiency of producing carbon fiber-reinforced polymer composites (CFRPs). However, it faces limitations such as challenges in achieving high surface qualityand precise dimensional accuracy and managing the distinctive anisotropic mechanical properties that it demonstrates. This study aims to explore the machinability of 3D printed PETG infused with 20% short carbon fiber and to assess the resulting surface roughness and burr formation. Employing a Design of Experiments (DoE) approach, three factors were considered: rotational speed, feed rate, and depth of cut. These factors were tested at varying levels—rotational speeds of 3000, 5500, and 8000 rpm; feed rates of 400, 600, and 800 mm/min; and depth of cut values of 0.2, 0.4, 0.6, and 0.8 mm. The evaluation of machinability relied on two key response parameters: surface roughness (Sa) determined from the milled surface and burr height measured on both sides using a roughness meter. The findings revealed a significant influence of milling parameters on both roughness and burr formation. However, the ideal conditions for minimizing roughness and reducing burr formation did not align. Furthermore, a comparative analysis was conducted between these results and the machinability of PETG under similar conditions.

An ingenious synergistic solid lubricant of copper and graphite for exceptional wear resistance of the SCF/PTFE/PEEK composite

In this work, the conventional short carbon fiber (SCF)/polytetrafluoroethylene (PTFE)/polyetheretherketone(PEEK) (SCF/PTFE/PEEK) composite was elected as the matrix, copper and graphite micron flakes were further blended to prepare PEEK self-lubricating composites. At a pressure of 12 MPa and a speed of 0.5 m/s, with a graphite content of 7.5 wt% and copper of 2.5 wt% (Gr7.5Cu2.5), the composite exhibited a COF of 0.23 and the lowest wear rate of 4.1 × 10−7 mm3/Nm. Physicochemical analysis of the worn surface of the steel ring revealed that the introduction of appropriate amounts of copper facilitated the tribo-physicochemical reaction during the rubbing process, which favored the formation of a thin and tough transfer film of Gr7.5Cu2.5 on the worn surface of the steel ring.

Anisotropic elastoplasticity and fracture of SCFR-PEEK composites in complex biaxial loading: Experiments and modelling

This research aims to gain insight into the anisotropic deformation and fracture behaviours of short carbon fibre reinforced polyether-ether ketone composites (SCFR-PEEK) under complex loading using experimental and modelling approaches. Novel biaxial tensile experiments using optimised cruciform specimens are designed and performed to study the anisotropic elastoplasticity and fracture behaviours of SCFR-PEEK in various stress states. An advanced anisotropic constitutive model was developed, experimentally calibrated, numerically implemented, and successfully verified by mechanical responses of biaxial tension with various stress ratios. Furthermore, using a hybrid experimental-numerical approach, the biaxial failure stress at crack initiation sites captured by a high-speed camera in biaxial tension was obtained. Employing experimental failure stresses at various uniaxial and biaxial stress states, a maximum stress based failure criterion was developed, which is coupled with the anisotropic elastoplastic model, thus enabling the description the anisotropic elastoplastic and failure behaviours under complex loading. The prediction of the failure of SCFR-PEEK in complex biaxial stress states using the coupled model is in good agreement with biaxial tensile experimental results using circular-notched specimens. Therefore, the developed model is verified to be capable of describing both elastoplastic deformation and fracture failure behaviours of SCFR-PEEK composites in complex loading.