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In this study, the impact of three different principles of surface activation techniques for polyamide fibers on the formation of conductive percolation during the subsequent electroless copper deposition process was investigated. The techniques used are (1) polyamide complexation using a solution mixture of calcium chloride, ethanol and water, (2) atmospheric plasma surface treatment and (3) grafting of 2‐hydroxyethylmethacrylate by radical induced polymerization. As a result, the percolation threshold was shifted to lower copper contents. The copper content required to form conductive structures was reduced ranged between 59% and 89%, depending on the activation techniques. Furthermore, the deposition time was reduced by 37%–57%, resulting in a faster build‐up of the percolation on the fabric. Changes in wetting behavior and substrate surface topography were identified to be the main reasons for these observations. While all applied surface activation techniques led to higher copper contents compared to unmodified reference, the atmospheric plasma modification led to the highest copper contents during the deposition process and a more uniform appearance of the metallised layer. Highlights: Three different fiber surface activation methods are evaluated.Fiber surface activation increases wetting and polymer‐metal adhesion.Activated polymer surface leads to faster copper deposition and percolation.Atmospheric plasma modification is the most efficient technique. [ABSTRACT FROM AUTHOR]

The influence of nanofillers (cellulose nanofibers (CNF) and halloysite nanotubes (HNTs)), and basalt fibers (BF) on the morphology, mechanical and thermal of recycled polyamide 6 (PA6) composites were investigated through scanning electron microscopy (SEM), mechanical testing, rotational rheometry, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). CNF, HNTs and BF were relatively well‐dispersed in the PA6 matrix and the incorporation of these nanofillers and BF increased the strength of the matrix, which indicates a good dispersion of the nanofillers and BF. CNF and HNTs‐filled PA6 nanocomposites increased the tnsile strength by 14% and 6% compared to the neat PA6, respectively. The composites elongation at break decreased with nanofiller, BF and combined nanofillers and BF. The shear storage modulus values of PA6/20B5C, PA6/20B5H, and PA6/25B are significantly elevated compared to neat PA6, with increases of 3.7, 2.8, and 2.5 times, respectively, at an angular frequency of 100 rad/s. PA6/20B5H composites with 20 wt.% BF and 5 wt.% HNTs exhibited the highest storage modulus (9.5 GPa) from the DMA study. Thermal stability and ash content at 800°C increased with the incorporation of HNTs and BF. The DSC findings showed that the glass transition (Tg) and melting temperature (Tm) of the composites did not exhibit any notable changes when nanofillers and BF were added to the resin. The nucleation ability of PA6 was enhanced attributable to BF and hybridization of BF and nanofillers since the crystallization temperatures of PA6 in BF filled and hybrid composites were around 5°C greater than neat PA6. The results suggest hybrid composites with potential environmental characteristics and higher mechanical properties can be utilized in semi‐structural applications in automotive and construction as a sustainable and lightweight alternative to steel and other materials. Highlights: The addition of HNTs, CNF, BF and hybridization of nanofillers with BF reduced the brittleness of PA6.Nanoreinforced and hybrid PA6 composites achieved higher storage modulus than neat PA6.Thermal stability and ash content increased with the incorporation of HNTs and BF.The hybrid composites have a higher complex viscosity compared to PA6.The sustainable hybrid composites can be utilized in automotive and construction industries. [ABSTRACT FROM AUTHOR]

Highlights For traditional materials, a polymer composite with high performance and large‐scale production is still the goal pursued by researchers. In our work, polyamide 6/calcium sulfate whiskers (PA6/SCW) composites were fabricated via melt‐compouding method. The calcium sulfate whisker based on gypsum mineral was used as reinforcement. After grafting silane coupling agent on the whisker surface, the whiskers showed a significant reinforcing effect in polyamide. The mechanics and tribology performance of the samples had been significantly inhanced. Based on the nucleation mechanism of lattice matching, calcium sulfate whiskers have obvious heterogeneous nucleation effect in PA6 matrix, while the crystallization period was slightly prolonged. This was caused by the network structure formed by the whiskers in the matrix, which impeded the free movement of polymer chain segments. In combination with the orientation degree of the molecular chains measured by the interdigital electrode, the reinforcing effect of the oriented PA6 specimens was derived from the orientation arrangement of the whiskers and the efficient load transfer. Mechanical and tribological properties of composite were significantly improved. The composite could achieved large‐scale production due to simple preparation. The whiskers had obvious heterogeneous nucleation effect in matrix. The reinforcing effect was derived from efficient load transfer from whiskers. [ABSTRACT FROM AUTHOR]

Highlights By incorporating nanomaterials into polymer matrices, nanocomposites can be produced with enhanced properties, combining the ease of processing thermoplastics with the superior physical characteristics of nanoparticles. In this study, fully bio‐based polyamide 1010 was used as the polymer matrix, with graphene oxide (GO), hexagonal‐boron nitride (h‐BN), and molybdenum disulfide (MoS2), both individually and in hybrids, serving as fillers. The tensile behavior of these nanocomposites was evaluated at room temperature and −40 °C, along with their morphology and microstructure. Results showed that the nanomaterials slightly shifted the polymer's crystallization temperature upward, indicating a small nucleating effect, but also hindered the development of crystalline domains, reducing the crystallization kinetics. Despite no change in the final crystalline form, nanocomposites with h‐BN and MoS2 showed lower microstructural order as evidenced by XRD. Regarding tensile behavior, GO provided the greatest toughening at room temperature due to its larger lateral dimensions and good chemical affinity with the matrix. However, at low temperatures, h‐BN‐based nanocomposites maintained the toughening effect better than GO‐based ones. This can be attributed to the lower order of the polymer's semi‐crystalline structure promoted by h‐BN, allowing greater energy dissipation. Surprisingly, hybrid fillers did not exhibit synergistic effects, with one nanomaterial hampering the effect of the other. However, SEM analysis indicated that the fracture mechanisms of the nanocomposites remained unchanged from the neat polymer, which makes them interesting options for applications that require desirable mechanical properties at a wide temperature range. GO showed the best toughening of polyamide 1010 at room temperature. Toughening at room temperature is mainly due to nanomaterials physical traits. Most nanofillers lowered polyamide's overall microstructural order. Toughening at −40 °C is mainly due to lower microstructural order. [ABSTRACT FROM AUTHOR]

Highlights The thermoplastic composites which in the automated tape placement (ATP) process are directly consolidated and formed in situ. The interlaminar bonding quality of the product is susceptible to the ATP process. Glass fiber‐reinforced bio‐based polyamides PA5X (GF/PA5X) tapes are used to prepare samples. The effect of process parameters on the interlaminar bonding quality is explored by peel test based on the principle of the response surface. A quadratic response surface model of hot gas temperature, placement speed, and roller force on the peel strength is established, and experiments are conducted to verify the accuracy of the model. The effect of process parameters and their coupling effect on the peel strength is obtained. The interlaminar bonding quality of the samples manufactured by ATP and compression molding are comparatively analyzed through peel and short beam shear tests. The results show that the best combination of process parameters obtained is: the hot gas temperature of 619°C, placement speed of 0.540 m/min, roller force of 684 N, and predicted peel strength of 9.89 N/10 mm. The peel and short beam shear strength of the samples manufactured by ATP is 9.96 N/10 mm and 34.2 MPa, reaching 66.0% and 60.0% of the samples manufactured by compression molding respectively. GF/PA5X thermoplastic composite tapes are used to prepare ATP samples. The effect of process parameters on the interlaminar bonding quality is explored. The micromorphology of the ATP samples is characterized. The ATP and compression molding samples are comparatively analyzed. [ABSTRACT FROM AUTHOR]

This research investigates the impact of weld lines on the mechanical properties and fracture behavior of injection‐molded unfilled and glass fiber‐reinforced polyamide 6 (PA6). The study aims to predict the weld line strength by analyzing the composite's microstructure at the weld line and investigating the influence of injection molding parameters. While weld lines had minimal effects in unfilled PA6 thanks to the matrix's high healing capability, composite samples showed reduced mechanical properties due to unfavorable fiber orientation at the weld line. Fracture surfaces revealed a bell‐shaped structure linked to the 'underflow' process caused by flow imbalances during injection molding. This phenomenon impacts fiber orientation at the weld line, affecting mechanical properties. The 'underflow' is simulated using Autodesk Moldflow®, predicting enhanced fiber alignment along the flow direction. Regarding processing parameters, both melt and mold temperatures showed negligible impacts, while enhanced mechanical properties were observed at elevated packing pressures. The analysis of fracture surfaces showed intensified "underflow" with increased packing pressure. A relationship is established between weld line strength and fiber orientation at the weld line, potentially serving as a predictive tool for estimating weld line strength. Highlights: Weld lines in unfilled PA6:Negligible impact on the mechanical properties.In the PA6 composite: significant drop due to unfavorable fiber orientation.Fracture behavior of the composite: Bell‐shaped weld line linked to "underflow."Melt and mold temperature: minor effect; packing pressure enhances properties.Correlation established between the weld line strength and fiber orientation. [ABSTRACT FROM AUTHOR]

High‐strength and high‐gas‐barrier plastic packaging liners have emerged as competitive products with promising potential application in the field of Type IV hydrogen storage cylinders. Ternary composites, which contain PA6, organically modified montmorillonite (OMMT), and maleic anhydride grafted polyolefin elastomer (POE‐g‐MAH), have been proposed as possible material for this application. To achieve the goal of developing this material, the influence of material formulation on various properties such as mechanical, microstructure, gas barrier, thermal stability, and flow properties of the composites was investigated. The results show that the composites with 3 wt% OMMT had the best gas barrier and mechanical properties. Additionally, the effect of rotational molding process parameters on the wall thickness of the plastic liner was studied. Process parameter regulation methods were proposed to improve wall thickness consistency of the products. The investigation shows that the composites containing 3 wt% OMMT had the best wall thickness consistency of the products. Highlights: The effect of filler content on the properties of PA6 composites was investigated.The composites with 3 wt% OMMT had the best wall thickness consistency.The gas barrier property of the composite is improved by 43.9% over virgin PA6.The impact strength of the composite is improved by 133.8% over virgin PA6.Insights for the development of processing methods for plastic packaging inserts. [ABSTRACT FROM AUTHOR]

Toward high‐strength bio‐based polyamide 56 (PA56) fiber, we first in situ precipitate graphene oxide (GO), adipic acid and 1,5‐pentanodiamine together by reaction crystallization in ethanal to obtain PA56 salt/GO particles with well dispersed GO, then prepare PA56/GO nanocomposite with PA56 salt/GO via solvent‐free polymerization including solid‐state prepolycondensation and melt polycondensation. Finally, PA56/GO nanocomposite fiber is prepared by extrusion drawing. With 0.2 wt% GO, the tensile strength of PA56/GO fiber reaches 1050 MPa, which is 3.3 times that of pure PA56 fiber. Furtherly, we add PA56/GO with high GO content to commercial PA56 to prepare the hybrid fiber, of which the tensile strength reaches 1248 MPa. The great improvement is mainly due to the good dispersion of GO in the whole process, which increases the heterogeneous nucleation in favor of higher and oriented PA56 crystallization. Highlights: Bio‐based PA56/GO nanocomposite fiber with 1.2 GPa strength has been prepared.PA56 salt/GO particles with well‐dispersed GO are in situ precipitated.Solvent‐free polymerization is used instead of solution melt polymerization.Well‐dispersed GO results in high and oriented crystallinity of PA56/GO fiber.Tensile strength of PA56/GO fiber is 2.3 times that of commercial PA56 fiber. [ABSTRACT FROM AUTHOR]

The focus of this study is to apply finite element method (FEM) and machine learning methods to investigate the interfacial bonding strength of continuous fiber reinforced thermoset composite (TSC)‐thermoplastic structures manufactured through co‐curing and overmolding processes, with polyamide 6 (PA 6) as the thermoplastic material. A model for interfacial healing degree in TSC‐PA 6 structures was developed. Then, FEM was employed to study the influence of various injection overmolding process parameters on the interfacial bonding strength of TSC‐PA 6 structures. The results show that there is a strong correlation between the degree of interface healing and the bonding strength. Subsequently, six machine learning methods were employed to correlate interfacial healing degree with diverse injection molding process parameters. Simulation data were utilized for training, calibration, and validation of the six machine learning models. Based on the results of simulation and machine learning predictions, a quantitative analysis of the significance of injection molding process parameters on healing degree was conducted. These parameters are ranked in descending order of importance as follows: insert temperature, melt temperature, and injection rate. Highlights: The interfacial healing degree model of PA 6 was established and validated through the integration FEM and experiment.Six machine learning models were built to predict the interfacial healing degree.Grad boosting performed best in predicting the interfacial healing degree.Insert temperature had the greatest impact on the interface healing degree. [ABSTRACT FROM AUTHOR]

This study elucidates interfacial interactions in semi‐synthetic polyamides by applying dimensional analysis to graphene derived from waste sources like coffee, tires, and chopped carbon fiber resulting in lightweight and high‐performance composites. Graphene from tires in platelet form (GNP), graphene from coffee in spherical form (CWC), and carbon fiber bundles (CF) were incorporated into Polyamide 6,10 (PA6,10) with high‐shear mixer by examining the optimum loading ratio for each reinforcement through interface characterization. At the same loading ratios, specific flexural properties are significantly enhanced when employing high aspect ratio CF reinforcement, while the platelet structure of GNP is more effective in improving specific tensile properties. Additionally, the spherical graphene of CWC exhibited the highest crystallinity, along with CF. In addition, sustainable PA6,10‐based compounds reinforced with waste‐derived materials were compared to commercial synthetic PA6‐based compounds with similar thermal and mechanical characteristics. The research revealed that the addition of 20 wt% CWC to the PA6,10 matrix outperforms commercial synthetic compounds by providing lightweight in terms of specific tensile. The findings of this study demonstrate that effectively incorporating waste‐derived reinforcing materials into semi‐synthetic composites presents a promising strategy to improve performance and serve as viable alternatives to commercial products through tailored waste‐derived reinforcement, particularly in applications that require lightweight and robust load‐bearing capabilities. Highlights: Waste‐based reinforcements are sustainable alternatives to synthetic materialsSize and aspect ratio of reinforcements give varying strengthening mechanismsTailorable mechanical performance through different waste‐based reinforcementsWaste‐based reinforcements offer lightweight for automotive compositesLightweight and sustainable composites can replace commercial products [ABSTRACT FROM AUTHOR]

In this study, we investigated the morphological and mechanical properties of hybrid composites with a polyamide 6 (PA6) matrix and reinforced with basalt fibers (BFs) and halloysite nanotubes (HNTs). The presence of reinforcing materials fundamentally changed the behavior of the molecules, which was morphologically manifested in the change in the ratio of the rigid and the mobile amorphous phase. The x‐ray diffraction and transmission electron microscopic images showed the crystal nucleating effect of the halloysite nanotubes. Based on these, we concluded that around the basalt fibers, an interphase is formed, while around the nanoparticles, a two‐layer interphase is created, the inner layer of which is semicrystalline, while the outer layer is rigid amorphous (RA). The nanoparticles are surrounded by a semicrystalline interphase, which is surrounded by an RA interphase. This overlaps with the interphase of the basalt fibers, therefore the halloysite nanotubes can effectively help the stress transfer from the matrix to the basalt fibers. The mechanical properties of the samples also reflected this: the hybrid composites had a significantly higher tensile modulus, tensile strength, and an unchanged elongation at break compared to the composite reinforced with only basalt fiber. Highlights: Environmentally friendly polyamide 6 matrix hybrid composites were prepared.Uniform distribution of halloysite nanotubes was achieved.Enhanced mechanical properties were observed for hybrid composites.Halloysite nanotubes aid stress transfer from matrix to basalt fibers.Halloysite nanotubes act as crystalline nucleating agents. [ABSTRACT FROM AUTHOR]

Tetraglycidyl diamino diphenyl methane (TGDDM) and its carbon fiber composite are widely studied and used because of their heat resistance and high performance. In order to obtain efficient reinforcing effects in a simple manner, we adopt the idea of molecular composite—uniformly dispersing the rigid‐rod macromolecules in the TGDDM matrix. Herein, we prepared fully aminated‐poly(p‐phenylene terephthalamide) by direct polycondensation and hydrogenation reduction as the reinforcing agent. The fully aminated‐PPTA is distributed uniformly in the cross‐linked epoxy resin (EP) network by chemical bonds, and achieves efficient reinforcement. With the addition of only 0.5 wt% fully aminated‐PPTA, the tensile strength and Young's modulus of EP are improved to 127.7 ± 7.4 MPa (+28%) and 3.36 ± 0.15 GPa (+44%); the flexural strength and modulus are improved to 209.6 ± 9.4 MPa (+42%) and 3.70 ± 0.14 GPa (+37%); the notch impact strength is improved by 32%. Crucially, the heat resistance of EP almost remains unchanged. Furthermore, the flexural properties and interlaminar shear strength of the carbon fiber composite are also comprehensively increased. Compared with other modified fillers, the fully aminated‐PPTA is simple to prepare and blend, and is an efficient reinforcing agent for TGDDM and its carbon fiber composite benefitting from its rigid‐rod main chain and amino side groups. Highlights: Molecular composite can achieve excellent strengthen and toughen effects.Fully aminated‐PPTA is embedded uniformly in EP network by chemical bonds.TGDDM is effectively reinforced without deteriorated heat resistance.Fully aminated‐PPTA is also a comprehensive reinforcement for EP/CF composite. [ABSTRACT FROM AUTHOR]

The present study examines the influence of polyamide 6.6 (PA 6.6) nanofiber and MWCNTs reinforcements on the mechanical behavior of nanocomposite plates formed by hybridization of carbon fabric (CF) and kevlar fabric (KF). First, PA 6.6 nanofibers were manufactured by electrospinning. The produced nanofibers were placed in the interlaminar of nanocomposite plates. PA 6.6 nanofiber and MWCNT‐reinforced nanocomposite plates consisting of 12 layers were produced by the vacuum bagging method. Tensile, Mode‐II fracture and bending tests were applied to the produced composite plates in accordance with the standards. After the mechanical tests, the nanocomposite plates' macro and micro damage analysis was performed. As a result of the reinforcement of PA 6.6, MWCNTs and PA 6.6‐MWCNTs, the tensile strength, interlaminar fracture toughness and bending strength of the nanocomposite plates significantly enhanced compared to unreinforced samples. In addition, interlaminar crack propagation in reinforced samples became more stable than in the unreinforced sample. Highlights: Investigated the impact of PA 6.6 nanofiber and MWCNT reinforcements on nanocomposite plates formed through CF and KF hybridization.Reinforcement with PA 6.6, MWCNTs, and PA 6.6‐MWCNTs significantly improved tensile strength, interlaminar fracture toughness, and bending strength.Mode‐II interlaminar fracture toughness tests demonstrated enhanced crack propagation stability with PA 6.6 nanofiber and MWCNT reinforcements. [ABSTRACT FROM AUTHOR]

Fiber hybridization is suggested to enhance the properties of fiber‐reinforced composites. Regarding the matrix, thermoplastic alternatives to conventional thermosets are needed to balance mechanical performance and sustainability. We combined woven flax and carbon fibers with a polyamide 11 matrix into a hybrid biocomposite and studied its manufacturing process as well as its impact, tensile, and damping properties. Mechanical damage was investigated using scanning electron microscopy and X‐ray computed tomography. Hybridization significantly improved the tensile properties: 233% higher modulus and 432% higher strength than pure flax composites and 19% higher failure strain than pure carbon composites. Additionally, the hybrid composites exhibited a positive hybrid effect with respect to the impact resistance, characterized by higher displacement at maximum impact force and occurrence of combined damage mechanisms. Although the damping behavior of the hybrid composites remained inferior to that of pure flax composites, their damping factor was 20% higher than that of pure carbon composites. These results provide valuable insights into the mechanical performance of carbon‐flax hybrid composites. Highlights: Enhanced mechanical performance and impact resistance in woven flax‐carbon/PA11 hybrid biocomposite compared to nonhybrid reference composites.Superior tensile modulus and strength of hybrid biocomposite than pure flax fiber composite, and greater failure strain than pure carbon fiber composite.A positive hybridization effect in impact properties with a greater displacement at maximum force and higher dissipated impact energy, indicating enhanced ductility and fracture toughness.Improved damping behavior in hybrid biocomposite compared to the pure carbon composite. [ABSTRACT FROM AUTHOR]

In an attempt to enhance the properties of biobased semi-aromatic polyamide poly (decamethylene terephthalamide) acid (PA10T), the effects of different proportions of fillers [MoS2 and polyfluoroalkoxy (PFA)] were investigated. A range of stable and wear-resistant composites, with filler contents varying from 0 to 10 wt%, were successfully prepared using a one-step extrusion blending method. To analyze the chemical structures, Fourier transform infrared spectroscopy (FT-IR) experiments were conducted. Additionally, SEM, tribological tests, differential scanning calorimetry (DSC), x-ray diffraction (XRD), thermogravimetric analyzer (TGA), tensile measurement, notched impact test, and bending test were employed to thoroughly evaluate the properties of both PA10T and composites. The findings demonstrated that the target products were effectively created, and the composites with fillers exhibited superior wear resistance. Alongside this, they showcased comparable heat resistance and mechanical properties to the pure PA10T. Of particular note, when 4 wt% PFA and 6 wt% MoS2 were added, the specific wear rate of PA10T-F4M6 (0.0016 mg.min-1) was impressively reduced by 86.2% in comparison to pure PA10T (0.0116 mg.min-1). This reduction in wear mass from 0.7 mg (PA10T) to 0.1 mg (PA10T-F4M6) further confirms the improvement in wear resistance. Ultimately, these results suggest that composites, with their exceptional wear resistance, hold great potential as heat-resistant engineering thermoplastics in future applications. Thus, they offer promising prospects for wider utilization across various fields. In essence, this study provides valuable insights into the beneficial impact of MoS2 and PFA fillers on polyamide wear resistance. Highlights • The biobased poly (decamethylene terephthalamide) acid (PA10T) was synthesized through an efficient one-pot melt polymerization method. • The composites with excellent performance were prepared by blending the biobased semi-aromatic polyamide PA10T with unique fillers (MoS2 and PFA) for modification. • When 4 wt% PFA and 6 wt% MoS2 were added, the specific wear rate of composites was impressively reduced by 86.2% in comparison to pure PA10T. • The addition of fillers (MoS2 and PFA) not only improves the wear resistance of PA10T but also enhances its crystallization properties and melting points effectively. • The bending modulus of wear-resistant composites increased to 1553.66 MPa, representing an approximately 50.47% increase compared to PA10T. [ABSTRACT FROM AUTHOR]

Tailored Fiber Placement is an innovative manufacturing technique that precisely positions continuous fibers in critical areas of fiber preforms for optimal structural performance. This study focuses on producing glass fiber‐reinforced polyamide composites using TFP technology and compression molding to address the durability concerns of thermoplastic matrix composites in automotive parts. The production process involved a constant temperature of 300°C, 16 bar pressure, and holding times of 270, 300, and 330 s. Short‐term thermal aging cycles were applied to simulate automotive part acclimatization. Tensile and 3‐point bending tests were conducted to evaluate mechanical properties. Statistical analysis using response surface methodology provided insights into the relationship between production parameters and mechanical properties. Differential Scanning Calorimetry characterized the composite material, and macroscopic damage analysis was performed. Results showed a potential 10% decrease in tensile strength due to short‐term thermal aging. Aging had the most significant impact on elastic modulus and tensile strength according to the Pareto chart. Flexural modulus increased, while flexural strength decreased with thermal aging. Holding time had no effect on flexural modulus but reduced flexural strength. Highlights: Glass/polyamide composites were produced by compression molding with TFP technology.Short‐term thermal aging cycles were applied on the GF‐PA6 composite material.Mechanical properties were analyzed statistically according to the RSM.TFP technique can assist OEM companies in lowering desired target cost per vehicle. [ABSTRACT FROM AUTHOR]

To meet the lightweight production requirements of automobiles and achieve high strength, reinforced thermoplastic composite materials are gradually replacing metal materials. Injection molding is the preferred manufacturing method to enable the production of complex‐shaped parts, facilitate production, and reduce costs. In this study, carbon fiber (CF) was added to the commonly used resin‐reinforcing material, polyamide (nylon) PA6, to create a CF‐reinforced thermoplastic composite (polyamide 6 [PA6]/CF) that was welded using injection molding. This study not only investigates the impact of different welding conditions on shear strength but also discusses the sequence of welding. Achieving 85% of the shear strength of the PA6 base material under ideal circumstances. The CF distribution and reinforcement mechanism were analyzed by observing the connection interface and cross section using a polarizing microscope and a scanning electron microscope. When PA6/CF was used as the secondary molded body, the welding results were better. The addition of CF had a significant strengthening effect on the strength of the PA6 injection welding. Highlights: Carbon fiber‐reinforced thermoplastic composite materials were prepared, and welding with PA6 was achieved using the injection molding method.The optimal welding parameters were determined by varying the mold, injection speed, injection temperature, and order of injection. The maximum welding shear strength reached 85% of the base material shear strength.The positive effect of specific fiber distribution on welding strength was analyzed by observing the interface using a scanning electron microscope and a polarizing microscope.This study provides valuable insights into the optimization of welding processes for carbon fiber thermoplastic composite materials, offering possibilities for connecting dissimilar materials with poor compatibility. [ABSTRACT FROM AUTHOR]

The additive manufacturing of continuous fiber reinforced thermoplastics (CFRTPs) paves way for the high‐strength, light‐weight components for variety of load‐bearing applications. In this work, the continuous carbon fiber reinforced PA6 (CCF‐PA6) composites was successfully printed from the prepreg filament. The prepreg filament was prepared in‐house by impregnating the heat‐and‐acid treated 1 K carbon fiber bundle with the molten PA6. The tensile strength of the prepreg filament, which contained with 40 vol% CF, reached 984 MPa. The unidirectional CCF‐PA6 specimens were subsequently 3D‐printed with the prepreg filament, and the mechanical strength of those 3D‐printed specimens were tunable by adjusting a set of printing parameters, such as layer thickness, hatch spacing and printing temperatures. The highest tensile strength of the specimen reached 555 MPa. Those specimens also exhibited outstanding mechanical strength at elevated temperatures, still reaching 184 MPa at 150°C. The mechanical strength of those specimens was dependent on the content of the fiber. This study can hopefully provide new insights for feedstock design and spur novel ideas in tailoring the mechanical properties of the 3D‐printed CFRTPs. [ABSTRACT FROM AUTHOR]

Today, the aim is to reduce the harm caused by vehicles to the environment in accordance with decisions made to address environmental pollution and the global climate crisis. To this end, in addition to design improvements, and technological advancements, materials that can reduce the weight of the vehicles and provide the desired mechanical properties, are being studied. Glass fiber‐polyamide composites offer a unique combination of properties that make them suitable for a wide range of applications in the automotive industry. This study focused on the production of GF‐PA6 composites using compression molding and Tailor Fiber Placement (TFP) technology. The production was carried out at a constant temperature of 300°C, and 16 bar pressure, with holding times of 270–300–330 s. Short‐term thermal aging cycles were also applied to evaluate the effects of environmental exposure on the GF‐PA6 composite material. The wear behavior of the composite was then assessed through sliding wear tests, which indicated that an increase in holding time improved the wear resistance, while the aging process had a negative impact. The experimental results were analyzed statistically using response surface methodology (RSM) and showed a statistically consistent response. It was found that aging had no significant effect on the coefficient of friction (COF), but significantly impacted the wear rate. The COF of composite samples decreased approximately 35% with increasing holding time. When the sliding distance increased from 150 to 300 m, the wear rate value decreased by 24% in non‐aged samples and by 35% in aged samples. [ABSTRACT FROM AUTHOR]

In this work, graphene oxide (GO)/polyamide 6 (PA6) nanocomposites with different graphene content (0.03–0.5 wt%) were prepared via in situ polymerization of GO and ε‐caprolactam. The linear and nonlinear rheological properties and thixotropy of GO/PA6 nanocomposites are investigated using steady state, dynamic, and transient rheological method with a Haake plate rotary rheometer. Cox/Merz rules and Cross model were used to fit the shear rate sweep and dynamic frequency sweep data, and a wider range(10−2–104 s−1) of flow curve was obtained. The results show the PA6 and GO/PA6 melts are shear thinning fluid without yield stress, and have thixotropy. Highlights: Dynamic, steady, and transient rheological tests were performed.Cox/Merz rules and Cross model were used to fit the data.A wider range(10−2–104 s−1) of flow curve was obtained. [ABSTRACT FROM AUTHOR]

This study investigated the tribological performance of hybrid composites composed of scrap carbon fiber (CF), glass fabric (GF), and polyamide 6.6 (PA6.6) through an innovative approach for reusing scrap CFs in high‐value composite structures. The experimental setup included CF/GF/PA6.6 hybrid composite laminates with varying CF contents and surface‐modified GFs, as well as PA6.6 sheets and GF/PA6.6 composite laminates. Solid particle erosion and scratch tests were conducted to assess the influence of scrap CF hybridization and GF surface modification on the tribological properties of the composites. The results demonstrated that neat PA6.6 sheets exhibited the lowest erosion rate, while the incorporation of CF and GF reinforcements had a detrimental effect on erosion resistance. The highest erosion rate was observed within the impact angle range of 15°–30° for pure PA6.6 sheets, whereas for composite laminates, it occurred within the range of 30°–45°. In contrast, CFs positively affected scratch hardness despite their negative impact on erosion resistance. Additionally, the silane treatment of GFs, which enhanced interfacial strength, improved the erosion resistance and scratch hardness of GF/PA6.6 composite laminates without CF. Profilometer‐based topographic analysis revealed a correlation between the average surface roughness of the eroded surfaces and the weight loss resulting from solid particle erosion. [ABSTRACT FROM AUTHOR]

As an important surface modifier, conventional silane coupling agents generally emit volatile organic compounds (VOCs) like methanol or ethanol during the modification of glass fiber. To avoid VOCs emission, a phenol/amine co‐deposition of tannic acid (TA) with polyethyleneimine (PEI) was used to modify glass fiber (TP‐GF) based on mussel‐inspired surface chemistry. The reinforcement effect of TP‐GF on polyamide 6 (PA6) matrix was investigated, and the corresponding results were compared with those of γ‐aminopropyltriethoxysilane (KH550) modified glass fiber (KH550‐GF)/PA6 composites. The results showed that the interfacial adhesion between TP‐GF and PA6 matrix was superior to that between KH550‐GF and PA6 matrix, and thus TP‐GF/PA6 composites manifested more excellent mechanical properties than KH550‐GF/PA6 composites. Among these composites, TP‐GF (1.05 wt% of coating amount)/PA6 composites exhibited the optimal mechanical properties (tensile strength: 151.3 MPa, notched impact strength: 13.8 kJ m−2) compared with KH550‐GF (1.33 wt% of coating amount)/PA6 composites (tensile strength: 144.8 MPa, notched impact strength: 9.5 kJ m−2). In particular, the notched impact strength was significantly increased by 45%. Notably, there was no VOCs generation during the preparation of TP‐GF, indicating that TP‐GF could be used as an environmentally friendly glass fiber for the fabrication of high‐performance PA6 composites. [ABSTRACT FROM AUTHOR]

The addition of graphene nanosheets (GNSs) into immiscible polymer composites to induce the cocontinuous morphologies shows potential application in reinforced nanocomposites and conductive polymer nanocomposites. In this work, immiscible high density polyethylene (HDPE)/polyamide 6 (PA6)/GNS composites were prepared via melt mixing. The electrical and rheological property of HDPE/PA6 composites filled with various GNS contents according to different viscosity ratios and mixing orders were investigated to reveal the double percolation effect via percolation scaling laws, and compared with those of HDPE/GNS and PA6/GNS composites. The morphology and GNS dispersion state of HDPE/PA6/GNS composites were examined via transmission electron microscopy and scanning electron microscope. Most of the GNS were selectively located in the PA6 phase of HDPE/PA6/GNS composites. The GNS‐related network and mixing order played important roles in the cocontinuous morphology formation and performance of HDPE/PA6/GNS conductive composites. Moreover, the addition of GNS also affected the crystallization kinetics and mechanical property of HDPE/PA6/GNS composites. [ABSTRACT FROM AUTHOR]

In this study, a carbon nanotube‐glass bubble/polyamide 6 (CNT‐GB/PA6) multiscale hybrid composite was manufactured. Through a coagulation process including CNT and GB, a segregated network was formed to produce a composite structure with tunable thermal conductivity. Within the segregated network structure, a complex phenomenon of decrease and increase in thermal conductivity owing to the interaction by CNT and GB, and an equation to predict thermal conductivity through the contents of GB and CNT was formulated. A model to predict the thermal conductivity using the RSM analysis was presented, and the contents of GB and CNT were adjusted according to the required thermal conductivity. It was confirmed through the LFA thermal conductivity measurement that the thermal conductivity increased with GB and CNT contents. Moreover, when 30% of GB was added to the 5 wt% CNT composite, the thermal conductivity increased by about 17%. However, in the experiment to confirm the effect of GB alone, it was confirmed that the thermal conductivity decreased as the GB content increased. Thus, the size of the structural path, which was controlled by the GB content through which electrons pass, played an important role in this study. The results of this study can be used in astronautic fields that require insulation to save energy and in construction engineering where thermal insulation and heat emission are important. [ABSTRACT FROM AUTHOR]

This article investigates the mechanical behavior of polyamide and carbon fiber‐reinforced (CFR) polyamide structures produced by Fused Filament Fabrication. CFR improves solid polyamide's tensile strength and modulus by more than 200% and 800%, respectively. The enhancement is highest in the parallel raster due to the alignment of the fibers in the printing direction. The compression tests of gyroid, honeycomb, and Voronoi cellular structures revealed the effect of geometry and fiber reinforcement on energy absorption performance. CFR gyroid infill offers the best performance with a specific energy absorption capacity reaching 10 kJ/kg and an efficiency close to 50%. Fiber reinforcement improves energy absorption by a factor of four or higher while increasing the weight by only 10%. The energy absorption capacity of the reinforced polyamide offers enormous potential for developing new lightweight load‐bearing and impact‐absorbing structures. [ABSTRACT FROM AUTHOR]

Polymer‐based nanocomposites can be used in a wide variety of applications in the industrial, electronics, and energy segments. In order to attain the application‐specific properties that are desired, good mechanical and fracture efficiency is frequently required. Polyamide 6 (PA6)/polyethylene octene grafted with maleic anhydride (POE‐g‐MA)/titanium dioxide (TiO2) nanocomposites' fracture characteristics were investigated utilizing the essential work of fracture (EWF) approach in this work. Four levels of POE‐g‐MA (0, 10, 20, and 30 wt%) and three levels of TiO2 (0, 2, and 4 wt%) are therefore utilized. The reliability of the EWF theory is demonstrated via the self‐similarity of the force‐displacement curve and Hill's analysis. Results showed that EWF and non‐essential work of fracture (non‐EWF) were improved by 73% and 54%, respectively, by increasing POE‐g‐MA up to 30 wt%. The improvement of EWF value confirmed the role of POE‐g‐MA as an impact modifier. Nevertheless, by increasing TiO2 up to 4 wt%, EWF, and non‐EWF decrease by 20% and 25%, respectively. Adding 30 wt% POE‐g‐MA reduced tensile strength and enhanced strain at the break by 45% and 109%, respectively. Moreover, the tensile strength was enhanced up to 10% by adding 4 wt% of TiO2 content. However, the strain at break was decreased by 44% by increasing 4 wt% of TiO2 nanoparticle. In addition, the dominant fracture mechanism in polyamide‐based blends and nanocomposites is shear‐yielding and fibrillation structures. [ABSTRACT FROM AUTHOR]

This study reports the effect of graphene oxide (GO) coating on carbon fiber (CF) surface on the mechanical and thermal properties and morphology of CF‐reinforced polyamide 6 (PA6) composites containing 7.5 wt% of short CFs. GO was coated on the CF surface by a physical absorption method with concentrations ranging from 0.05 to 0.5 wt% GO. The PA6/CF composites were prepared by extrusion, and the specimens were obtained by injection molding. Their morphology (SEM, XRD tests), mechanical (tensile, flexural, impact, and fatigue tests), and thermal properties (DSC, TG and HDT tests) were analyzed. A significant change in the preferential (growth) crystal planes of PA6 was observed upon the incorporation of CFs containing GO, favoring the formation of α crystals in PA6. GO coating on CFs was effective and provided an increase in tensile strength and Young's modulus up to 12% and 24%, flexural strength and flexural modulus up to 22% and 25%, and a decrease in impact strength and fatigue life up to 30% and 23%, respectively, when compared to unmodified PA6/CF composites. Fracture micrographs indicated an increase in the PA6/CF interaction and the effectiveness of GO as a coupling agent for the composite. [ABSTRACT FROM AUTHOR]

The stamping molding with self‐resistance electric (SRE) heating is advantageous for the mass production of carbon fiber reinforced thermoplastic (CFRT) because of its short production cycle and energy efficiency. The mechanism of SRE heating is different from traditional oven heating. The impact on CFRT laminates under loading is ambiguous. In this article, the tensile testing systems with SRE heating and traditional heating were designed. The temperature distribution, mechanical response, strain, and failure mode of carbon fiber reinforced polyamide 6 (CFR‐PA6) laminates under SRE heating are studied and contrasted with traditional heating. Specifically, to measure the full‐field strain distribution, digital‐image correlation (DIC) technique and high‐speed camera were introduced. It is found that the electric resistance fluctuates in tensile test with SRE heating and shown temperature sensitivity. Temperature distribution of the specimen under SRE heating is relatively uniform. Besides, the mechanical properties (i.e., tensile strength and elastic modulus) of CFR‐PA6 seem to be insensitive to heating mode. DIC results show that deconsolidation phenomenon makes the specimen fracture randomly. Inversely, heating method has an obvious influence on failure modes. To be specific, there are more shearing damage in traditional heating during high temperature. High current under SRE heating causes corrosion on fiber surface and destroy the fiber‐resin matrix interface. [ABSTRACT FROM AUTHOR]

Carbon materials have been widely used in multifunctional composites with their high electrical and thermal conductivities. However, most current research focuses on nanocarbon materials such as graphene and carbon nanotubes, ignoring their high cost, inability to mass‐produce, and poor dispersion in polymers. To address these issues, we propose one‐step melt‐blending of commercial carbon materials to construct conductive pathways in polymer matrix. Thus, low‐cost and robust polymer composites can be fabricated in a green and scalable way to achieve efficient thermal management and avoid electromagnetic radiation pollution. Here, a continuous network of carbon materials with orientation‐aligned carbon fibers and well‐dispersed mesocarbon microbeads (MCMBs) induced by melt blending is shown to be an ideal structure for thermally conductive (1.77 W m−1 K−1) electromagnetic shielding (46.9 dB) composites. In addition, the excellent mechanical properties (tensile strength 162.7 MPa and flexural strength 250 MPa) and absorption property (39.4 dB) exhibited by the composites under the optimized filler ratio also really broaden the way for the preparation of high‐strength wave absorbing materials by melt blending. This work provides a general strategy for large‐scale production of thermally conductive electromagnetic shielding composites and opens up possibilities for the application of MCMBs in high‐power electronic devices. [ABSTRACT FROM AUTHOR]

In this study, polyamide fibers, which stand out with their excellent plastic deformation and energy absorption capacity, were used as reinforcement materials, and in‐house manufactured composite specimens were subjected to low‐velocity impact (LVI), compression after impact (CAI) and tensile tests. Within this scope, one and two repeated drop tests were performed under 3 m/s velocity to determine LVI responses and how impact number affects the dynamic properties. CAI tests were also performed at a 1 mm/min crosshead speed, and mechanical properties for non‐impacted, one‐impacted, and two‐impacted specimens were determined. As a result of the outstanding plastic deformation capacity of thermoplastic fabrics, it is concluded that polyamide composites exhibited quite large strains. Furthermore, it was understood from the tensile responses that tensile stresses were carried by the thermoplastic fibers in two different regimes and significantly high toughness was obtained. Moreover, reductions in the maximum compression loads, critical buckling loads and axial stiffness were observed due to degradation in structural integrity after impact loads. Additionally, the utilization of recyclable thermoplastic polyamide fibers as reinforcement material instead of conventional reinforcement materials such as carbon and glass fibers provide more environmentally friendly products. [ABSTRACT FROM AUTHOR]

This study utilizes the Taguchi optimization technique to investigate the effects of FDM processing parameters on the Charpy impact strength of 3D printed CF/PA composites experimentally and statistically. The four 3D printing parameters employed in the experiment are the infill density, raster angle, extruder temperature, and printing speed, which were used to create the experimental plan with the L18 orthogonal array. Signal to noise (S/N) ratios and analysis of variance (ANOVA) were utilized to identify the optimum values and the interactions between the process parameters. SEM and thermography techniques were employed to assess the microstructural and damage status of the CF/PA composite specimens. ANOVA results determined that only three factors–infill density, raster angle, and extruder temperature–had a statistical significance, while printing speed did not. The outcomes demonstrated that the optimal 3D printing parameters are infill density (100%), raster angle (60°), extruder temperature (260°C), infill density (100%), and printing speed (30 mm/s), with the maximum contribution of 54.19% belonging to infill density, and the minimum contribution of 2.84% belonging to printing speed. The optimal combination of these 3D printing parameters yielded a Charpy impact strength of 10.54 kJ/m2, resulting in an increase of almost 150% compared to the worst‐case situation. The Taguchi approach proves to be a proficient technique to boost the Charpy impact strength of 3D‐printed CF/PA composites. [ABSTRACT FROM AUTHOR]

Vehicle mass reduction can be achieved through the utilization of carbon fiber reinforced composites within the vehicle body structure. In this study, planar isotropic compression molded carbon fiber reinforced composites are studied for their potential utilization as automotive primary energy absorbing structures. The energy absorption behavior of a discontinuous randomly oriented 2‐D planar isotropic carbon fiber reinforced nylon 6 thermoplastic composite and a continuous 2 × 2 twill quasi‐isotropic carbon fiber reinforced epoxy thermoset composite are studied by dynamic flat plaque crush testing. Post‐mortem failure modes of both materials are related back to their load‐displacement and energy‐displacement curves under different test conditions. It is shown that crush fixture support length dictates the failure mode and specific energy absorption (SEA) of all fiber reinforced composites tested. In addition, elevated temperature testing of the nylon 6 carbon fiber reinforced composites reduces the SEA in all test configurations. Finally, an automotive carbon fiber composite front end energy absorbing structure is considered as the replacement over a legacy metallic energy absorbing structure. Mass reduction benefits beyond the improved SEA of the composite as compared to the metallic structure it replaces are discussed by considering the increased crush length efficiency of the composite structure which can reduce the vehicle front end length, and therefore the mass of the vehicle. These results are expected to direct the future development of fiber reinforced composites structures in energy absorbing automotive structures. [ABSTRACT FROM AUTHOR]

In this study, a novel functionalized graphene oxide (F‐GO) modified polyamide 6 (PA6) sizing agent is developed to improve the interfacial and mechanical properties of carbon fiber (CF) reinforced PA6 composites. To enhance compatibility between GO and sizing agent, PA6 molecular chains are covalently grafted onto the GO sheets in advance. The results show that the F‐GO modified sizing layer improves interfacial compatibility and wettability of the CF surface. Moreover, F‐GO nanoparticles retard crack propagation along the interface based on the reinforcement effect. Accordingly, the interfacial shear strength increases by 54.5% from 45.1 MPa for desized CF/PA6 composites to 69.7 MPa for F‐GO modified sizing agent treated CF/PA6 composites. Meanwhile, the average interlaminar shear strength, tensile strength, and flexural strength increase by 45.2%, 15.6%, and 19.3% from 45.7, 1307.4, and 792.2 MPa for desized CF/PA6 composites to 66.3, 1511.2, and 945.2 MPa for those reinforced with the CFs treated by the F‐GO modified sizing agent due to the effective stress transfer across the interface. The improvement in the mechanical properties is verified based on the cross‐section morphology and fracture surfaces. [ABSTRACT FROM AUTHOR]

Additive manufacturing has been widely used in the field of bonded magnets manufacturing. However, there are some key issues to be faced in order to obtain bonded magnets (BMs) with high performance. In this study, four different particle sizes of flake NdFeB powder (volume‐weighted mean diameter [VMD] of 5.60 μm, 19.21 μm, 33.25 μm, and 66.69 μm) were obtained by vibratory sieving. Flexible filaments for 3D printing BMs were produced using polyamide‐6 (PA6) as the substrate, and the production process is reported in this paper. Characterization of the performance of the 3D‐printed BMs revealed that the BMs with VMD less than 10 μm have excellent mechanical strength, but the ductility of the magnets decreases with decreasing VMD of NdFeB powder. As the NdFeB VMD decreases, the coercivity of the sample decreases and the remanence increases. This study provides a reference for the selection of filler particle size for 3D printing BMs, which can be used to develop 3D‐printed BMs with excellent performance. [ABSTRACT FROM AUTHOR]

Sustainable manufacture caused shift in automotive manufacturing practices. Polymer‐based composites make up almost 15% mass of the entire vehicle, most importantly the fuel system of the vehicle. Poor electrical conductivity of the polymer composites leads to electrostatic deposition, which can lead to issues. Carbon based synthetic fillers like carbon fiber and carbon nanotubes are attractive options to develop electrically conductive composites, owing to their excellent electrical and mechanical properties. However, the production process of these reinforcements is highly time and energy intensive making it quite expensive and not quite sustainable. Lignocellulosic feedstock can be carbonized at a high treatment temperature of ≥1000°C to produce electrically conductive biocarbon filler. In this study biocarbon fibers developed using Douglas fir pulp, were incorporated into polyamide 12 matrix to develop composites. The composites were fabricated using hot compression mounting. At a filler loading of 7.5 wt% the composites reported log electrical conductivity value of −6.67 S/cm and at 35 wt% filler loading rate the composite conductivity was −0.31 S/cm. An electrical conductivity of −8.70 S/cm for polyamide 6 composites filled with 20 wt% carbon fiber and −1.03 S/cm were reported for 40 wt% carbon fiber concentration in reviewed literature. The electrical conductivity values for the samples with 20 and 40 wt% carbon fibers are significantly lower compared to the biochar fiber filled composites at 25 and 35 wt% biochar filler loading rates, indicating the effectiveness of the biochar filler as a conductive filler in developing electrically conductive, sustainable composites. [ABSTRACT FROM AUTHOR]

In the present study, polyamide 12 (PA12) and 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (PBO) were used to modify polyamide 11 (PA11), and then microcrystalline cellulose (MCC) reinforced PA11 composites was prepared via hot pressing. The results showed that the thermoplastic elastomer PA12 was in favor of the toughness of the composites, 12% PA12 increased the impact strength by 53%. The molecular chains of PA11/PA12 blends were extended by PBO, and then had positive effects on the mechanical properties, as evidenced by the fact that the flexural strength and the impact strength of the composites with 0.3% PBO were increased by 13% and 14%, respectively. In addition, morphology analysis indicated PBO was in favor of the interfacial bonding of the composites. MCC significantly increased the flexural strength and modulus by 68% and 283%, respectively. [ABSTRACT FROM AUTHOR]

Three‐dimensional printing has proven to be a convenient and effective method for manufacturing structured electromagnetic wave (EMW) absorbers with adjustable EMW absorption characteristics. In this study, composites of multi‐walled carbon nanotube (MWCNT) and polyamide 12 (PA12) were prepared via wet dispersion and mechanical ball milling followed by melt extrusion. The effects of different levels of MWCNT content on the EMW absorption and mechanical properties of the MWCNT/PA12 composite were examined. Within the MWCNT content from 7 to 12 wt%, the flexural strength of the composite increases with the addition of MWCNT, and the impact strength, tensile strength, and volume resistivity of the composite decrease with the addition MWCNT. With regard to the best impedance matching, when sodium dodecylbenzene sulfonate was used as the dispersant, the lowest reflection loss observed herein for the MWCNT/PA12 composite was −20 dB, which was achieved with an MWCNT content of 10 wt%. Furthermore, the composite exhibited superior mechanical properties. The tensile and flexural moduli of the composite were 18.85% and 33.97% higher than those of pure PA12, respectively. Moreover, the MWCNT/PA12 composite was proven to be a high performance modeling material suitable for fused deposition modeling. And the tensile strength, flexural modulus, and impact strength of the printed samples can reach 94.45%, 92.94%, and 85.51% of those of the injection‐molded samples, respectively. [ABSTRACT FROM AUTHOR]

The excellent lubricating properties of microcapsules have been well recognized in modified polymers though very few reports have mentioned the practical application for engineering parts. In this study, different short fibers and nickel shell microcapsules (NMS) synergistically modify PA6 and injection molded to prepare bearings. With 10 wt% NMS, the COF could be reduced from 0.45 to 0.1. Fibers can effectively overcome bearing failure resulting from crushing the matrix under high loads or rapid peeling wear at high swing frequencies, which can warrant the effective lubrication of NMS and the formation of high‐quality transfer film. The bearing long‐life test shows very stable and low COF and wear with the feasibility to utilize microcapsules modified polymers in journal bearings. [ABSTRACT FROM AUTHOR]

Polyamide 6/Acrylonitrile butadiene rubber/Perlite nanocomposites with different percentages of NBR phase and perlite nanoparticle were prepared using the melt mixing process. The fracture behavior of PA6/NBR/Perlite nanocomposites was studied by the essential work of fracture method (EWF). Furthermore, response surface methodology (RSM) was employed to evaluate the effect of input variables, namely NBR and perlite content, on fracture behavior and Young's modulus of these nanocomposites. Scanning electron microscopy was used as a method for studying the morphology of the thermoplastic elastomer matrix containing different percentages of NBR elastomer and perlite nanoparticles. The results confirmed that, with controlling input variables, the optimum conditions of the system could be obtained, which leads to an improvement in fracture behavior and modulus strength of PA6/NBR/Perlite nanocomposites. RSM results illustrated that Young's modulus is increased from 2539 to 2862 MPa with an increase in perlite content from 3 to 7 wt%, when NBR content is 20 wt%. Moreover, Elongation at break is increased from 59.8% for 20 wt% NBR elastomer up to 102.8% for 40 wt%. The results of the EWF test illustrated that the samples with 30 and 10 wt%. NBR and 5 wt% perlite, have the maximum values of essential work of fracture (283.8 N/mm) and nonessential work of fracture (22.2 N/mm2), respectively. [ABSTRACT FROM AUTHOR]

Recently, Carbon fiber reinforced thermoplastic polymer (CFRTP) has been widely used in automotive, aviation, and aerospace. However, the traditional epoxy Carbon fiber (CF) sizing for thermosetting composites was unsuitable for high‐performance CFRTP due to the high‐molding temperatures and incompatibility between them. Herein, a novel semi‐aromatic polyamide‐imide (PAI) backbone structure with multi‐ethoxy pendant groups was designed and synthesized via click‐reaction and solvent‐free polymerization. Waterborne PAI sizing was prepared via self‐emulsifying without surfactants. CF/PEEK (polyether‐ether‐ketone) and CF/PEI (polyether‐imide) composites were manufactured. Results showed that novel PAI had excellent thermal stability and solubility, PAI sizing was stable after 6‐month‐storage. Mechanical performances and hydrothermal aging resistance of composites were improved. Compared with commercial‐sized CF (eCF)/PEI, the flexural strength of sCF/PEI increased by 35.2% to 753.47 MPa, and retention rates of them with aging also increased. Noted, mechanisms of interface enhancement were revealed by quantum chemical calculations, ππ stacking and hydrogen bonding between PAI and PEI, PEEK was found. [ABSTRACT FROM AUTHOR]

Owing to its good tribological and mechanical properties, polyamide material was widely applied to prepare sliding mechanical parts. A lot of studies confirmed that adding different functional materials or surface modifications to polyamide could reduce the friction coefficient, improve wear resistance and reduce water absorption, so as to prolong the service life of polyamide parts. This paper summarized the common reinforcement methods of polyamide materials: blending, surface modification and filler. The reinforcing mechanism of different fillers and polymers, the effects of different methods on the tribological properties, mechanical properties and water absorption of polyamide composites, and the preparation methods of polyamide composites have been systematically discussed. [ABSTRACT FROM AUTHOR]

This article fabricated toughening and self‐healing carbon/epoxy composites based on electrospinning thermoplastic polyamide nanofiber (PAnf). When the incorporation of PAnf was merely 1.2 wt%, the interlaminar shear and bending strength of composites increased by 17.6% and 14.7%. The two main toughening mechanisms were the entangled porous nanofiber structure with a large specific surface area and the strong interface resulting from the interaction between PAnf and epoxy. Multiple short beam shear cycles generating interlaminar fracture were conducted to evaluate the healing efficiency. The obtained results for three damage‐healing cycles achieved 110.4%, 88.4%, and 70.1%, respectively. The melting thermoplastic PAnf would thermally expand, flow across microcrack, and fill delamination at healing temperature. This process was the inherent characteristic of thermoplastic PAnf, and thus, the composites can heal the damaged region rapidly and repeatedly. Moreover, PAnf with low incorporation showed no adverse effect on the storage modulus and Tg of composites, which maintained their original properties. [ABSTRACT FROM AUTHOR]

Using star‐branched polyamide 6 (SPA6) with hexafunctional cyclotriphosphazene core as a matrix resin and glass fiber (GF) as a reinforcing material, star‐branched polyamide 6/glass fiber (SPA6/GF) composites with different GF content were prepared by melt‐compounding method. The star‐branched structure of SPA6 and GF content have great effects on the properties of SPA6/GF composites. Compared with linear polyamide 6 (LPA6), SPA6 with star‐branched structure has low viscosity, high melt flowability and good impregnation and adhesion to GF, which endow SPA6/GF composites outstanding processability, good surface qualities and excellent mechanical properties even when the content of GF reaches 60 wt%. The use of SPA6 resin with star‐branched structure fundamentally solves the industry problem of traditional LPA6 resin in high‐filled modification. Such high‐performance SPA6/GF composites will provide great promise for large‐scale applications. [ABSTRACT FROM AUTHOR]

Hybrid thermoset‐thermoplastic composites were fabricated by injection overmolding technique in this paper. To improve the interfacial bonding between short fiber reinforced polyamide 6 and continuous fiber reinforced epoxy composites, three different surface pretreatment methods (i.e., surface silanization, plasma treatment and CO2 laser ablation) were employed. The results show that surface silanization leads to a weak increase in polar functional groups of thermoset composites surface, resulting in a weak increase in interfacial bonding strength of overmolded composites. Compared with plasma pretreatment, CO2 laser ablation can achieve a highest shear bonding strength due to the formation of interface between injected melt polymer and carbon fibers. This kind of structure is favorable for the bonding strength due to mechanical interlocking. CO2 laser ablation is a promising technology to improve the bonding strength between short fiber reinforced polyamide 6 and continuous fiber reinforced epoxy composites. [ABSTRACT FROM AUTHOR]

The halogen‐free flame‐retardant continuous glass fiber/polyamide 6 (GF/PA6) composites containing hexaphenoxycyclotriphosphazene (HPCTP) were prepared by the resin transfer molding (RTM) process. The influence of HPCTP content on mechanical properties of GF/PA6 composites was studied. The addition of HPCTP has no obvious effect on the tensile properties of composites, and the tensile strength of GF/PA6 composites with the addition of 30% HPCTP reaches 425.2 MPa. However, with the addition of HPCTP, the flexural strength and interlaminar shear strength of GF/PA6/30%HPCTP composites decrease to 246.4 and 20.9 MPa, respectively. The flame retardancy, thermal stability, and burning behavior of the composites were evaluated by means of limited oxygen index (LOI), UL‐94, thermogravimetric analysis and cone calorimeter. The results show that the LOI value of GF/PA6 composites can reach up to 30.9% corresponding to the grade of UL‐94V‐0 with the addition of 30% HPCTP. The flame retardancy mechanism of GF/PA6/30%HPCTP composites is attributed to the combined effects of releasing incombustible gases in gas phase at the early stage and forming char layers in the condensed phase, which can dilute the concentration of combustible gas and retard the mass and heat transfer. [ABSTRACT FROM AUTHOR]

In this study, flax fiber char (CH), a kind of biomass carbon material obtained by thermochemical conversion of flax fibers in a nitrogen environment in a fixed bed reactor, was used as a reinforcing constituent together with carbon fiber (CF) to produce polyamide 66 (PA66) hybrid composites. The potential use of biochar as a promising substitutional filler candidate for CF in composite applications was deemed in principle. Biochar and carbon fiber surfaces were treated with nitric acid followed by modification with a 3‐aminopropyltriethoxysilane coupling agent to improve their interfacial compatibility with PA66. The overall characterization of the composite materials was conducted by performing the thermal gravimetric analysis and differential scanning calorimetry measurements and tensile and water absorption tests. Scanning electron microscopy was further employed to examine the fracture surface of the specimens. The findings obtained revealed that silane ‐modified CF and CH altered composite material crystallization behavior, thus enhancing the ultimate composite tensile strength and Young's modulus. Moreover, the tailored interfacial interactions associated with enhanced thermal stability were determined to reduce water absorption capacity for composites with CH. In brief, CH may be substituted with CF, cost‐effectively, at a 50:50 w/w ratio of total reinforcement (10 wt%) in PA66 without compromising ultimate composite performance. [ABSTRACT FROM AUTHOR]

Polyamide nanocomposites (PANC) were prepared from an aliphatic–aromatic polyamide (PA) containing hydrazide–hydrazone groups in the side chain, reinforced with functionalized polyethyleneimine (FPEI)/modified Mg(OH)2 nanoparticles (FPMN). For this purpose, a new structure, aromatic diamine (DAHH), containing the hydrazide–hydrazone group, was synthesized, and used to synthesize PA by direct polycondensation. Also, polyethyleneimine (PEI) was structurally modified with salicylaldehyde for the modification of the surface of Mg(OH)2 nanoparticles (MDH). The Field‐Emission Scanning Electron Microscopy and X‐ray diffraction results revealed that MDH were uniformly dispersed in nano‐size in the PA matrix. The thermogravimetric analysis results in both N2 and air environments showed that PANC possesses higher thermal resistance than that of the neat PA. The 5% degradation temperature (T5) of PANC containing 8 wt% of FPMN was obtained 40°C more than that of the pure PA in the N2 environment. The microscale combustion calorimetry (MCC) results exhibited that the loading of FPMN into the PA matrix can efficiently increase the combustion resistance by decreasing the MCC parameters such as the heat release rate values. In addition, the lead ions adsorption efficiency of the prepared nanostructure materials was investigated, and the results exhibited that the adsorption data were obtained following the Langmuir isotherm model. The maximum adsorption efficiency was calculated to be 99.96% for PANC 8. [ABSTRACT FROM AUTHOR]

Carbon fiber and glass fiber are two dominating reinforcements for polymer composites. Fiber‐reinforced thermoplastics are widely used in many applications. It has a higher growth rate than thermoset composites due to ease in processing and recyclability. Glass fiber has been on the market for 80 years and carbon fiber over 50 years. There are hundreds, if not thousands, of research paper to compare the performance of the two fibers and hybrid. All the studies are from commercially available products. In all those cases, these two fibers are non‐comparable. They have different fiber diameter, size and sizing content, chop length and chopping process. Taiwan Glass Industries, Corp. has cordially provided two experimental chopped strands that match the characteristics of chopped carbon fibers. The first one is for nylon reinforcement and the second one is for polypropylene. Now the glass fiber and carbon fiber have the same fiber diameter (7 microns), same size and sizing content (1%), and same chop length (6 mm). Most importantly, they are produced in identical way (off‐line chop). The only difference between two fibers is silane on glass surface. This is the first of this kind of study. It gives a true comparison of two fibers with identical characteristics. As expected, fiber diameter has the biggest influence in mechanical properties among all fiber characteristics. For nylon, the difference between 7 micron and 10 micron glass fiber is small in tensile and flexural strength. It has bigger difference in impact strength. For polypropylene reinforcement, the fiber diameter of standard polypropylene dispersion (PP) glass fiber is 13 microns; almost double that of carbon fiber. Seven‐micron PP glass actually outperforms PP carbon fiber in composite strengths. [ABSTRACT FROM AUTHOR]

Fused filament fabrication (FFF) has seen broad industrial adoption as it is capable of manufaturing large complex parts from robust thermoplastics in a cost‐effective manner. However, the mechanical performance of the printed parts is limited due to poor interlayer bonding and the presence of voids. In order to overcome these drawbacks, the addition of short or continuous fibers into the polymer matrix has been investigated, as the fibers can act as a mechanical reinforcement while also mitigating residual stress resulting from the material's rapid solidification following extrusion. Therefore, understanding the implications of process parameters and fiber reinforcements on printed part properties through detailed crystallization analysis and rheological characterizations is of paramount importance. The goal of this study is to understand the process–structure–property relationships of short carbon fiber‐reinforced polyamide 6 (CF‐PA6) by comparing the melt rheology and crystallinity of CF‐PA6 versus a neat PA6 polymer. Differences in the melting and crystallization behavior resulting from the reinforcing fibers revealed an increased time window for crystallization in the fiber‐reinforced matrix. Rheological characterizations at the recommended printing temperatures demonstrate the shear‐thinning behavior of the samples at shear rates relevant to FFF. From a statistical design of experiments analysis, the layer thickness was found to be the most significant parameter affecting the tensile properties of a printed part at a constant printing temperature and printing speed. The tensile fracture surfaces of the printed specimens using scanning electron microscopy were analyzed to provide insights into the failure mechanisms as a function of AM processing variables. [ABSTRACT FROM AUTHOR]

In the conventional process of thermoplastic composites, a heating stage from the external heat source usually consumes a large amount of energy. To solve this problem, self‐resistance electric (SRE) heating of carbon fiber‐reinforcement was introduced to form a continuous carbon fiber reinforced polyamide 6 (CF/PA 6) composite based on film stacking technique in this paper. The temperature distribution was first measured to verify the temperature uniformity for SRE heating process. X‐ray photoelectron spectroscopy (XPS) was used to assess effects on the chemical properties of carbon fibers from SRE heating and conventional convective heating. To evaluate forming quality by SRE heating, the physical properties, crystallinity, and mechanical properties of CF/PA 6 composites were measured. The results show that the forming time and energy consumption of SRE heating process are significantly reduced compared with that of the traditional heating process because of fast heating/cooling rate. While fast heating/cooling rate of SRE heating process leads to a higher void content, which finally results in a slightly lower flexural strength and impact properties of composite laminates. It is clear that SRE heating technique is one of the energy‐ and cost‐effective ways to fabricate continuous carbon fiber reinforced thermoplastic composites although the forming quality is still improved in future investigation. [ABSTRACT FROM AUTHOR]