Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generato...Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generators may require structural reinforcement or repair due to damage.This paper proposes a portable,on-site production method for molds under challenging conditions,where material supply is limited.The method utilizes large format additive manufacturing(LFAM)with recycled composite materials,sourced from end-of-life components and waste,as feedstock.The study investigates the microstructural effects of recycling through shredding techniques,using microscopic imaging.Three potential defense-sector applications are explored,specifically in the aerospace,automotive,and energy industries.Additionally,the influence of key printing parameters,particularly nonparallel plane deposition at a 45-degree angle,on the mechanical behavior of ABS reinforced with 20%glass fiber(GF)is examined.The results demonstrate the feasibility of this manufacturing approach,highlighting reductions in waste material and production times compared to traditional methods.Shorter layer times were found to reduce thermal gradients between layers,thereby improving layer adhesion.While 45-degree deposition enhanced Young's modulus,it slightly reduced interlayer adhesion quality.Furthermore,recycling-induced fiber length reduction led to material degradation,aligning with findings from previous studies.Challenges encountered during implementation included weak part adherence to the print bed and local excess material deposition.Overall,the proposed methodology offers a cost-effective alternative to traditional CNC machining for mold production,demonstrating its potential for on-demand manufacturing in resource-constrained environments.展开更多
Over the last half-century,polyether ether ketone(PEEK)has emerged as a widely adopted thermoplastic polymer,primarily due to its lower density,exceptional mechanical properties,high-temperature and chemical resistanc...Over the last half-century,polyether ether ketone(PEEK)has emerged as a widely adopted thermoplastic polymer,primarily due to its lower density,exceptional mechanical properties,high-temperature and chemical resistance,and biocompatibility.PEEK and its composites have found extensive applications across various fields,including machinery,aerospace,military equipment,electronics,and biomedicine,positioning themselves as promising substitutes for traditional metal structures.Nevertheless,achieving optimal performance and functional molding of PEEK and its composites presents a formidable challenge,given their inherent characteristics,such as semi-crystallinity,high melting temperature,heightened viscosity,low dielectric coefficient,and hydrophobic properties.In this paper,we present a comprehensive review of the molding methods and processes of PEEK and its composites,including extrusion molding,hot compression molding,injection molding,and 3D printing.We also introduce typical innovative applications within the fields of mechanics,electricity,and biomedicine while elucidating methodologies that leverage the distinctive advantages of PEEK and its composites.Additionally,we summarize research findings related to manipulating the properties of PEEK and its composites through the optimization of machine parameters,process variables,and material structural adjustments.Finally,we contemplate the prevailing development trends and outline prospective avenues for further research in the advancement and molding of PEEK and its composites.展开更多
The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 ...The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 （ wt% ） composite powders were prepared by the spray thermal decomposition-continuous reduction and carburization technology. In order to improve the properties of rods shaped by using powder extrusion molding, the cold isostatic pressing （CIP） technology was used before or after debinding. Specimens were siutered by vacuum siutering and hot isostatic pressing （HIP）. The density, Rockwell A hardness, magnetic coercivity , and magnetic saturation induction of siutered specimen were measured. The microstructure of the green bodies and the siutered specimens was studied by scanning electron microscopy （SEM）. Results show that the rod formed by using powder extrusion molding after debinding and followed by cold isostatic pressing can be siutered to 99.5% density of composite cemented carbide rods with an average grain size of about 200- 300 nm, magnetic coercivity of 30.4 KA / m, Rockwell A hardness of 92.6 and magnetic saturation induction of 85% . Superfine WC- 10 Co cemented carbide rods with excellent properties were obtained.展开更多
Short Retraction Notice The paper does not meet the standards of "Open Journal of Composite Materials". This article has been retracted to straighten the academic record. In making this decision the Editoria...Short Retraction Notice The paper does not meet the standards of "Open Journal of Composite Materials". This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused. Editor guiding this retraction: Prof. Chengye Fan (EiC of OJCM) The full retraction notice in PDF is preceding the original paper, which is marked "Withdraw".展开更多
To improve the strength of carbon fiber(CF) reinforced Polycaprolactam(PA6) composites, controlled amounts of carbon nanotubes(CNTs) were grafted onto the surface of CF to prepare the hybrid reinforcement(HR). We used...To improve the strength of carbon fiber(CF) reinforced Polycaprolactam(PA6) composites, controlled amounts of carbon nanotubes(CNTs) were grafted onto the surface of CF to prepare the hybrid reinforcement(HR). We used HR to fabricate laminate and H-sample to test the interfacial bonding strength(IBS) of the composites by means of a novel process called three-dimensional printed molding(3 D-PM). By using the melt drop printing method, we measured the contact angles between PA6 and CF(without sizing) and between PA6 and HR. The IBS and the mechanical properties of the composites were obtained by the tensile test. The experimental result indicated that CF grafted by 0.25% weight fraction of CNT or more could develop a special microstructure similar to the micro-pits on the surface of CF, which improved the wettability of CF and PA6 due to the increased surface area and the roughness of CF. When the weight fraction of CNT reached 0.25%, the IBS increased by 41.8%, the tensile strength by 130%, and the interfacial shear strength(IFSS) by 238%. The interfacial dimple fracture was observed by Scanning Electron Microscope(SEM), which revealed that the composites were able to absorb more deforming energy before fracture. The modified surface microstructure of CF would prevent crack propagation at the interface and increase the mechanical properties of thermoplastic composites(TPCs).展开更多
To tackle the challenge of producing highly filled polymer composites using the traditional injection molding technique,which is characterized by the fairly high melt viscosity that makes mold filling difficult,the au...To tackle the challenge of producing highly filled polymer composites using the traditional injection molding technique,which is characterized by the fairly high melt viscosity that makes mold filling difficult,the authors propose a solution based on dynamic covalent chemistry.As demonstrated by the proof-of-concept experiments,the 4-arm starshaped polycaprolactone(PCL)oligomers and microcrystalline cel-lulose(MCC)are crosslinked by the reversible Diels-Alder(DA)bonds.The flowability of the compounds greatly decreases due to the dissociation of the intercomponent DA bonds at the retro-reaction tempera-ture,and the networked architecture is reconstructed during cooling as a result of the forward DA reaction.Consequently,the high-loading MCC fillers are well distributed in the matrix and covalently bonded to the nearby PCL,forming a striking contrast to the control in which linear PCL acts as the matrix.The DA bonds crosslinked biodegradable PCL composites exhibit decent mechanical strength(20.7 MPa)even at the MCC fraction of 65 wt%,which is superior to those(5-12.2 MPa)of the highly filled PCL composites(with filler contents of 50-63.8 wt%)reported so far.The proposed approach has sufficient expansibility for the fabrication of the highly filled polymer composites constructed by other types of matrix and fillers.展开更多
The successful manufacture of thick composites is challenging since the highly exothermic nature of thermoset resins and limited temperature control make avoiding the onset of detrimental thermal gradients within the ...The successful manufacture of thick composites is challenging since the highly exothermic nature of thermoset resins and limited temperature control make avoiding the onset of detrimental thermal gradients within the composite relatively difficult.This phenomenon is mainly caused by exothermic heat reactions.The so-called Michaud's model has been largely used in the literature to reduce the gap between experience and simulation with regard to the effective prediction of the temperature cycle in these processes.In this work,another solution is proposed to simulate the curing process for thick composites,namely preheating the resin to activate the curing reaction before resin injection into the mold.A good agreement between the experiment and the simulation is found.Moreover,in order to minimize the thermal gradient in the final composite,the thermophysical properties of the fiber and the torque(temperature,time)of the Plate have been varied leading to interesting results.展开更多
Rheological and thermal properties of LD-PE and LD-PE + 65 vol% Ni composite were examined by viscosity, pvt and thermal conductivity measurements at a wide range of shear rate, temperature and pressure. The typical s...Rheological and thermal properties of LD-PE and LD-PE + 65 vol% Ni composite were examined by viscosity, pvt and thermal conductivity measurements at a wide range of shear rate, temperature and pressure. The typical shear-thinning viscosity of LD-PE polymer melt was enhanced up to four times by adding 65 vol% Ni braze metal particles. LD-PE show increasing specific volume versus temperature, decreasing with pressure and braze particle filler content. Variation of specific volume of LD-PE was reduced to 5% by admixing 65 vol% rigid Ni braze metal particles. Thermal conductivity of LD-PE was increased up to 15 times in the composite, reduced by decreasing pressure at temperature exceeding 80℃. Furthermore, thermal analysis was performed in modulated DSC to determine the specific heat capacity in wide temperature range. Viscosity and pvt-data were fitted using Cross-WLF equation and 2-domain Tait-pvt model, respectively. Simulation of LD-PE and LD-PE + 65 vol% Ni composite was performed based on rheological and thermal properties to define processing parameters. Simulation and injection molding of ring-shaped LD-PE + 65 vol% Ni composite braze metal preforms were performed successfully.展开更多
To study the resin flow and the permeability in fabric preforms during the liquid composite molding( LCM) process,influences of stitch and overlay placement styles on the internal flow behavior in-plane and transverse...To study the resin flow and the permeability in fabric preforms during the liquid composite molding( LCM) process,influences of stitch and overlay placement styles on the internal flow behavior in-plane and transverse were investigated. The permeability tests were carried using unidirectional and biaxial noncrimp carbon fabric( NCF) by linear capacitance sensors and ultrasound monitor system. The results indicate that the internal flow behavior and permeability in plane with different stitch and overlay placement styles are significantly different. When flow channels formed by stitches penetrate along the fiber direction,the permeability is high in one direction, which makes the in-plane principle permeabilities K_1 and K_2 significantly different. When there is an angle between the flow channel and fiber direction,the in-plane principle permeabilities on all directions are nearly the same and the flow process is close to isotropy. As to transverse permeability,the exist of flow channels on thickness influences it greatly and it is about 1-2 orders of magnitude lower in unidirectional fabric than that in biaxial NCF.展开更多
Sand mold 3 D printing technology is an advanced manufacturing technology which has great flexible manufacturing ability. A multi-material composite sand mold can control the temperature field of metallic parts during...Sand mold 3 D printing technology is an advanced manufacturing technology which has great flexible manufacturing ability. A multi-material composite sand mold can control the temperature field of metallic parts during the pouring process, while the current sand mold 3 D printing technology can only fabricate a single material sand mold. The casting temperature field can not be adjusted by using single sand mold material with isotropous heat exchange ability during the pouring process. In this work, a kind of novel coating device was designed. Multi-material composite sand molds could be manufactured using the coating device according to the casting process demands of the final parts. The influences of curing agent content, coating velocity and scraper shape on compactness and surface roughness of the sand layer(silica sand and zircon sand) were studied. The shapes and sizes of transition intervals of two kinds of sand granules were also tested. The results show that, with the increase of the added volume of curing agent, the compactness of sand layer reduces and the surface roughness value rises. With the increase of the velocity of the coating device, the compactness of sand layer reduces and the surface roughness value rises similarly. In addition, the scraper with a dip angle of 72 degrees could increase the compactness value of the sand layer. The criteria of quality parmeters of the coating procedure are obtained. That is, the surface roughness(δ) of sand layer should be equal to or lesser than half of main size of the sand particles(Dm). The parameter H of the coating device which is the distance between the base of hopper and the surface of sand layer impacts the size of transition zone. The width of the transition zone is in direct proportion to the parameter H, qualitatively. Through the optimization of the coating device, high quality of multi-material sand layers can be obtained. This will provide a solution in manufacturing the multi-material composite sand mold.展开更多
Acrylonitrile-butadiene-Styrene (ABS), with and without calcium carbonate (calcite) particles,was used as the matrix for reinforcement with as-received short-glass fibres (were originallytreated by the manufacturer) a...Acrylonitrile-butadiene-Styrene (ABS), with and without calcium carbonate (calcite) particles,was used as the matrix for reinforcement with as-received short-glass fibres (were originallytreated by the manufacturer) and sized short-glass fibres with two amino-silane coupling agents.The calcite particle content is 0, 11.7 and 23.5 vol. pct for the matrices. The glass fiber contentis 0, 10 and 15 vol. pct. The matrix materials and corresponding composites were compoundedusing a twin screw extruder and dumbbell-shaped tensile bars were prepared with an injectionmolding process. The tensile and flexural properties as well as the unnotched and notchedCharpy impact energies of short glass fibre/calcite/ABS composites were studied in this paper.The effects of fibres, fibre surface treatments and particles on these mechanical properties ofthe composites were discussed in detail. An importarit information was obtained, which is thatthe tensile and flexural strengths of hybrid SGF/calcite/ABS composites are the same as thoseof corresponding fibre composites when the ratio of the interfacial adhesion strength betweenparticles and matrix to that between fibres and matrix is higher than certain value. otherwise theformer are lower than the latter.展开更多
The influence of mold pressing parameters on the positive temperature coefficien t of high-density polyethylene/carbon black composites was investigated. The co mposites with a low resistivity at room temperature and ...The influence of mold pressing parameters on the positive temperature coefficien t of high-density polyethylene/carbon black composites was investigated. The co mposites with a low resistivity at room temperature and a high positive temperat ure coefficient can be obtainee with the mold pressing parameters as follows: mo ld pressing pressure 6-14MPa, mold pressing temperature 150-170℃, mold pressi ng time about 15min, and room temperature of molded specimen after cooling for 2 0-60 minutes. The positive temperature coefficient effect of the composite is 7 .7 when it is prepared under the mold pressing parameters, and the negative temp erature coefficient effect is less than 0.8. Scanning electron microscopy (SEM) reveals some aggregations of carbon black particles with a size of 1μm inside t he composite, which was obtained at the mold pressing temperature of 180℃.展开更多
The Resin Infusion or the VARTM (Vacuum Assisted Resin Transfer Molding) process has significant potential to be used to manufacture curved composites. Another way to produce curved or complex geometry is to use 3D pr...The Resin Infusion or the VARTM (Vacuum Assisted Resin Transfer Molding) process has significant potential to be used to manufacture curved composites. Another way to produce curved or complex geometry is to use 3D printers. 3D or FDM (Fused Deposition Modelling) printers are now being used to produce relatively cheaper curved parts using thermoplastics such as PLA. However, the strength and mechanical performance of these parts is limited and can be enhanced if the polymer is reinforced with a type of fiber for instance. Research is being carried out to produce fiber rein-forced thermoplastic composites but that process is expected to be more expensive than the alternative methods such as injection or compression molding. Furthermore, to understand the manufacture of a hybrid composite using thermoplastics, fibers and epoxy resin, research and investigation need to be carried out. In this research</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, there are</span></span></span></span></span><span><span><span><span><span style="font-family:""><span style="font-family:Verdana;"> single-sided, double-sided, reusable, disposable and consumable molds. Most of the molds were created either using an FDM printer or manually. These molds were then used to manufacture flat and curved composite structures via the resin injection process, </span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;"> VARTM with epoxy resin system and glass/carbon/flax fiber reinforcement. By replacing the costly metallic molds by significantly cheaper molds, the cost of production was expected to further reduce. Furthermore, using double-sided PLA molds was not expected to be a threat to the overall cost of the composite part in question compared to double-sided matched molds used in compression molding. Shear strength, tensile strength and charpy impact strength of most of the manufactured composite parts were also investigated. The strengths were compared based on the method of mold usage. The results showed that this method is effective for a cheaper production of curved epoxy resin composites. However, the strength of the part will decrease as the curved profile gets more complicated unless the basic resin infusion process is altered.展开更多
Fiber-reinforced polymer composites(FRPCs)possess outstanding specific strength and specific modulus,making them essential in aerospace,rail transportation,and other advanced engineering applications.However,during th...Fiber-reinforced polymer composites(FRPCs)possess outstanding specific strength and specific modulus,making them essential in aerospace,rail transportation,and other advanced engineering applications.However,during the molding process,non-uniform microscopic resin flow through multi-scale fiber networks often induces microscopic defects,significantly reducing the mechanical performance and reliability of the composites.Applying an electric field during molding process has demonstrated substantial advantages in void reduction by promoting uniform resin infiltration and enhancing fiber/resin wettability.Nevertheless,the dynamic resin infiltration processes and flow mechanisms within fiber tows and at single fiber surfaces remain poorly understood.To address this challenge,this study introduces a novel in-situ sensing technique for real-time monitoring of microscopic resin infiltration dynamics under applied electric field conditions.By developing glass fiber sensors coated with Ti_(3)C_(2)T_(X)(MXene)and carbon nanotubes(CNTs),we captured the real-time dynamics of infiltration states within fiber tows and at single fiber surfaces.Analysis of sensing signals confirmed that applied electric field assistance significantly increases resin infiltration velocity and infiltration sufficiency.Multi-scale numerical simulations further elucidated how electric field forces promote resin infiltration into fiber tow pores and improve single fiber surface wettability.As a result,the flexural strength and interlaminar shear strength of the composites increased by 25.5%and 37.3%,respectively.This research provides novel insights into electrically-assisted molding processes by integrating in-situ sensing with multi-scale numerical simulations,addressing a critical need for dynamic monitoring of resin infiltration and multi-scale mechanism analysis.展开更多
The hierarchical structure and interfacial morphology of injection-molded bars of polypropylene （PP） based blends and composites have been investigated in detail from the skin to the core. For preparation of injecti...The hierarchical structure and interfacial morphology of injection-molded bars of polypropylene （PP） based blends and composites have been investigated in detail from the skin to the core. For preparation of injection-molded bars with high-level orientation and good interfacial adhesion, a dynamic packing injection molding technology was applied to exert oscillatory shear on the melts during solidification stage. Depending on incorporated component, interfacial adhesion and processing conditions, various oriented structure and morphology could be obtained. First, we will elucidate the epitaxial behavior between PP and high-density polyethylene occurring in practical molded processing. Then, the shear-induced transcrystalline structure will be the main focus for PP/fiber composites. At last, various oriented clay structures have been ascertained unambiguously in PP/organoclay nanocomposites along the thickness of molded bars.展开更多
Abstract This paper deals with three-point flexure tests on hybrid I- and II-beams, made out of multi-layer carbon fiber/epoxy resin （including twill woven fabric CF3031/5284 and unidirectional cord fabric U3160/5284...Abstract This paper deals with three-point flexure tests on hybrid I- and II-beams, made out of multi-layer carbon fiber/epoxy resin （including twill woven fabric CF3031/5284 and unidirectional cord fabric U3160/5284） reinforced composites, processed using the RTM （resin transfer molding） technique. Static bending properties were determined and failure initiation mechanism was deduced from experimental observations. Failure mode of the tested hybrid RTM-made I-beams can be reckoned to be characteristic of the delamination from the cutout edge within the web and the debonding propagation along the interface between the inverted triangular resin-rich zone and the adjacent curved web until local buckling within the curved webs around the conjunction fillet region. In contrast, as distinct from hybrid RTM I-beams subjected to three-point bending loading, hybrid RTM-made H-beams in three-point flexure tests experienced the resin debonding in the inverted triangular resin-rich zones and the debonding propagation along the interface between the inverted triangular resin-rich zone and the adjacent curved web until complete separation of the curved web from the flange. Progressive damage models （PDMs） were presented to predict fail- ure loads and process of hybrid RTM-made I- and N-beams under three-point flexure. Good cor- relation was achieved between experimental and numerical results.展开更多
This study focuses on the insert-injection molding process. The thermoset composite inserts in this study were carbon fiber/epoxy (CF/Epoxy) prepreg sheets. The injected molded part was glass fiber contained phenolic ...This study focuses on the insert-injection molding process. The thermoset composite inserts in this study were carbon fiber/epoxy (CF/Epoxy) prepreg sheets. The injected molded part was glass fiber contained phenolic resin (GF/PF). The CF/Epoxy was placed in the mold cavity prior to injecting GF/PF onto the inserted injection molded CF/Epoxy specimens. The role of adhesion between the inserted part and injected resin on the mechanical properties was evaluated by 3 point bending and impact tests. In addition, the effect of prepreg orientation on the mechanical properties of the prepreg inserted-injection molding system was investigated. It was found that the prepreg with unidirectional orientation significantly improved flexural and impact strength of the inserted injection molding composites, providing better support and resistance to bending and impact loading. The main failure modes of the specimens were structural and adhesive failure.展开更多
基金Generalitat Valenciana(GVA)and Spanish Ministry of Science and Innovation(Grant Nos.TED2021-130879 B-C21,CIACIF/2021/286,PID2023-151110OB-I00,and CIPROM/2022/3)to provide funds for conducting experiments and software licensessupported by the National Research Foundation,Prime Minister's Office,Singapore under its Campus for Research Excellence and Technological Enterprise(CREATE)programme。
文摘Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generators may require structural reinforcement or repair due to damage.This paper proposes a portable,on-site production method for molds under challenging conditions,where material supply is limited.The method utilizes large format additive manufacturing(LFAM)with recycled composite materials,sourced from end-of-life components and waste,as feedstock.The study investigates the microstructural effects of recycling through shredding techniques,using microscopic imaging.Three potential defense-sector applications are explored,specifically in the aerospace,automotive,and energy industries.Additionally,the influence of key printing parameters,particularly nonparallel plane deposition at a 45-degree angle,on the mechanical behavior of ABS reinforced with 20%glass fiber(GF)is examined.The results demonstrate the feasibility of this manufacturing approach,highlighting reductions in waste material and production times compared to traditional methods.Shorter layer times were found to reduce thermal gradients between layers,thereby improving layer adhesion.While 45-degree deposition enhanced Young's modulus,it slightly reduced interlayer adhesion quality.Furthermore,recycling-induced fiber length reduction led to material degradation,aligning with findings from previous studies.Challenges encountered during implementation included weak part adherence to the print bed and local excess material deposition.Overall,the proposed methodology offers a cost-effective alternative to traditional CNC machining for mold production,demonstrating its potential for on-demand manufacturing in resource-constrained environments.
基金supported by the National Key R&D Program of China(No.2022YFC2401903)the“Pioneer”and the“Leading Goose”R&D Program of Zhejiang Province(No.2023C01170)+1 种基金the National Natural Science Foundation of China(No.52205424)the Key Project of Science and Technology Innovation 2025 of Ningbo(No.2023Z029),China.
文摘Over the last half-century,polyether ether ketone(PEEK)has emerged as a widely adopted thermoplastic polymer,primarily due to its lower density,exceptional mechanical properties,high-temperature and chemical resistance,and biocompatibility.PEEK and its composites have found extensive applications across various fields,including machinery,aerospace,military equipment,electronics,and biomedicine,positioning themselves as promising substitutes for traditional metal structures.Nevertheless,achieving optimal performance and functional molding of PEEK and its composites presents a formidable challenge,given their inherent characteristics,such as semi-crystallinity,high melting temperature,heightened viscosity,low dielectric coefficient,and hydrophobic properties.In this paper,we present a comprehensive review of the molding methods and processes of PEEK and its composites,including extrusion molding,hot compression molding,injection molding,and 3D printing.We also introduce typical innovative applications within the fields of mechanics,electricity,and biomedicine while elucidating methodologies that leverage the distinctive advantages of PEEK and its composites.Additionally,we summarize research findings related to manipulating the properties of PEEK and its composites through the optimization of machine parameters,process variables,and material structural adjustments.Finally,we contemplate the prevailing development trends and outline prospective avenues for further research in the advancement and molding of PEEK and its composites.
基金Funded by Open Foundation of State Key Laboratory of AdvancedTechnologyfor Materials Synthesis and Processing, Wuhan Universi-ty of Technology, the Post PhD Science Foundation of China(2003034504) andthe Foundation of Wuhan University of Technol-ogy(2003XJJ202)
文摘The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 （ wt% ） composite powders were prepared by the spray thermal decomposition-continuous reduction and carburization technology. In order to improve the properties of rods shaped by using powder extrusion molding, the cold isostatic pressing （CIP） technology was used before or after debinding. Specimens were siutered by vacuum siutering and hot isostatic pressing （HIP）. The density, Rockwell A hardness, magnetic coercivity , and magnetic saturation induction of siutered specimen were measured. The microstructure of the green bodies and the siutered specimens was studied by scanning electron microscopy （SEM）. Results show that the rod formed by using powder extrusion molding after debinding and followed by cold isostatic pressing can be siutered to 99.5% density of composite cemented carbide rods with an average grain size of about 200- 300 nm, magnetic coercivity of 30.4 KA / m, Rockwell A hardness of 92.6 and magnetic saturation induction of 85% . Superfine WC- 10 Co cemented carbide rods with excellent properties were obtained.
文摘Short Retraction Notice The paper does not meet the standards of "Open Journal of Composite Materials". This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused. Editor guiding this retraction: Prof. Chengye Fan (EiC of OJCM) The full retraction notice in PDF is preceding the original paper, which is marked "Withdraw".
基金Sponsored by the National Natural Science Foundation of China(Grant No.51373048)the National Key Research and Development Program of China(Grant Nos.U1604253 and 2016YFB0101602)
文摘To improve the strength of carbon fiber(CF) reinforced Polycaprolactam(PA6) composites, controlled amounts of carbon nanotubes(CNTs) were grafted onto the surface of CF to prepare the hybrid reinforcement(HR). We used HR to fabricate laminate and H-sample to test the interfacial bonding strength(IBS) of the composites by means of a novel process called three-dimensional printed molding(3 D-PM). By using the melt drop printing method, we measured the contact angles between PA6 and CF(without sizing) and between PA6 and HR. The IBS and the mechanical properties of the composites were obtained by the tensile test. The experimental result indicated that CF grafted by 0.25% weight fraction of CNT or more could develop a special microstructure similar to the micro-pits on the surface of CF, which improved the wettability of CF and PA6 due to the increased surface area and the roughness of CF. When the weight fraction of CNT reached 0.25%, the IBS increased by 41.8%, the tensile strength by 130%, and the interfacial shear strength(IFSS) by 238%. The interfacial dimple fracture was observed by Scanning Electron Microscope(SEM), which revealed that the composites were able to absorb more deforming energy before fracture. The modified surface microstructure of CF would prevent crack propagation at the interface and increase the mechanical properties of thermoplastic composites(TPCs).
基金the support of the National Natural Science Foundation of China(Grants:52033011,51973237,and 52173092)Natural Science Foundation of Guangdong Province(Grants:2019B1515120038,2020A1515011276,2021A1515010417)+1 种基金Science and Technology Planning Project of Guangzhou City(Grant:202201011568)Fundamental Research Funds for the Central Universities,Sun Yatsen University(Grant:23yxqntd002).
文摘To tackle the challenge of producing highly filled polymer composites using the traditional injection molding technique,which is characterized by the fairly high melt viscosity that makes mold filling difficult,the authors propose a solution based on dynamic covalent chemistry.As demonstrated by the proof-of-concept experiments,the 4-arm starshaped polycaprolactone(PCL)oligomers and microcrystalline cel-lulose(MCC)are crosslinked by the reversible Diels-Alder(DA)bonds.The flowability of the compounds greatly decreases due to the dissociation of the intercomponent DA bonds at the retro-reaction tempera-ture,and the networked architecture is reconstructed during cooling as a result of the forward DA reaction.Consequently,the high-loading MCC fillers are well distributed in the matrix and covalently bonded to the nearby PCL,forming a striking contrast to the control in which linear PCL acts as the matrix.The DA bonds crosslinked biodegradable PCL composites exhibit decent mechanical strength(20.7 MPa)even at the MCC fraction of 65 wt%,which is superior to those(5-12.2 MPa)of the highly filled PCL composites(with filler contents of 50-63.8 wt%)reported so far.The proposed approach has sufficient expansibility for the fabrication of the highly filled polymer composites constructed by other types of matrix and fillers.
文摘The successful manufacture of thick composites is challenging since the highly exothermic nature of thermoset resins and limited temperature control make avoiding the onset of detrimental thermal gradients within the composite relatively difficult.This phenomenon is mainly caused by exothermic heat reactions.The so-called Michaud's model has been largely used in the literature to reduce the gap between experience and simulation with regard to the effective prediction of the temperature cycle in these processes.In this work,another solution is proposed to simulate the curing process for thick composites,namely preheating the resin to activate the curing reaction before resin injection into the mold.A good agreement between the experiment and the simulation is found.Moreover,in order to minimize the thermal gradient in the final composite,the thermophysical properties of the fiber and the torque(temperature,time)of the Plate have been varied leading to interesting results.
文摘Rheological and thermal properties of LD-PE and LD-PE + 65 vol% Ni composite were examined by viscosity, pvt and thermal conductivity measurements at a wide range of shear rate, temperature and pressure. The typical shear-thinning viscosity of LD-PE polymer melt was enhanced up to four times by adding 65 vol% Ni braze metal particles. LD-PE show increasing specific volume versus temperature, decreasing with pressure and braze particle filler content. Variation of specific volume of LD-PE was reduced to 5% by admixing 65 vol% rigid Ni braze metal particles. Thermal conductivity of LD-PE was increased up to 15 times in the composite, reduced by decreasing pressure at temperature exceeding 80℃. Furthermore, thermal analysis was performed in modulated DSC to determine the specific heat capacity in wide temperature range. Viscosity and pvt-data were fitted using Cross-WLF equation and 2-domain Tait-pvt model, respectively. Simulation of LD-PE and LD-PE + 65 vol% Ni composite was performed based on rheological and thermal properties to define processing parameters. Simulation and injection molding of ring-shaped LD-PE + 65 vol% Ni composite braze metal preforms were performed successfully.
基金National Natural Science Foundation of China(No.11472077)Shanghai Natural Science Foundation,China(No.13ZR1400500)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.2232015D3-01)Innovation Experiment Programs for University Students,China(Nos.201410255024,201510255118)
文摘To study the resin flow and the permeability in fabric preforms during the liquid composite molding( LCM) process,influences of stitch and overlay placement styles on the internal flow behavior in-plane and transverse were investigated. The permeability tests were carried using unidirectional and biaxial noncrimp carbon fabric( NCF) by linear capacitance sensors and ultrasound monitor system. The results indicate that the internal flow behavior and permeability in plane with different stitch and overlay placement styles are significantly different. When flow channels formed by stitches penetrate along the fiber direction,the permeability is high in one direction, which makes the in-plane principle permeabilities K_1 and K_2 significantly different. When there is an angle between the flow channel and fiber direction,the in-plane principle permeabilities on all directions are nearly the same and the flow process is close to isotropy. As to transverse permeability,the exist of flow channels on thickness influences it greatly and it is about 1-2 orders of magnitude lower in unidirectional fabric than that in biaxial NCF.
基金financially supported by the National Excellent Young Scientists Fund(NO.51525503)
文摘Sand mold 3 D printing technology is an advanced manufacturing technology which has great flexible manufacturing ability. A multi-material composite sand mold can control the temperature field of metallic parts during the pouring process, while the current sand mold 3 D printing technology can only fabricate a single material sand mold. The casting temperature field can not be adjusted by using single sand mold material with isotropous heat exchange ability during the pouring process. In this work, a kind of novel coating device was designed. Multi-material composite sand molds could be manufactured using the coating device according to the casting process demands of the final parts. The influences of curing agent content, coating velocity and scraper shape on compactness and surface roughness of the sand layer(silica sand and zircon sand) were studied. The shapes and sizes of transition intervals of two kinds of sand granules were also tested. The results show that, with the increase of the added volume of curing agent, the compactness of sand layer reduces and the surface roughness value rises. With the increase of the velocity of the coating device, the compactness of sand layer reduces and the surface roughness value rises similarly. In addition, the scraper with a dip angle of 72 degrees could increase the compactness value of the sand layer. The criteria of quality parmeters of the coating procedure are obtained. That is, the surface roughness(δ) of sand layer should be equal to or lesser than half of main size of the sand particles(Dm). The parameter H of the coating device which is the distance between the base of hopper and the surface of sand layer impacts the size of transition zone. The width of the transition zone is in direct proportion to the parameter H, qualitatively. Through the optimization of the coating device, high quality of multi-material sand layers can be obtained. This will provide a solution in manufacturing the multi-material composite sand mold.
文摘Acrylonitrile-butadiene-Styrene (ABS), with and without calcium carbonate (calcite) particles,was used as the matrix for reinforcement with as-received short-glass fibres (were originallytreated by the manufacturer) and sized short-glass fibres with two amino-silane coupling agents.The calcite particle content is 0, 11.7 and 23.5 vol. pct for the matrices. The glass fiber contentis 0, 10 and 15 vol. pct. The matrix materials and corresponding composites were compoundedusing a twin screw extruder and dumbbell-shaped tensile bars were prepared with an injectionmolding process. The tensile and flexural properties as well as the unnotched and notchedCharpy impact energies of short glass fibre/calcite/ABS composites were studied in this paper.The effects of fibres, fibre surface treatments and particles on these mechanical properties ofthe composites were discussed in detail. An importarit information was obtained, which is thatthe tensile and flexural strengths of hybrid SGF/calcite/ABS composites are the same as thoseof corresponding fibre composites when the ratio of the interfacial adhesion strength betweenparticles and matrix to that between fibres and matrix is higher than certain value. otherwise theformer are lower than the latter.
基金Funded by the Key Program of Education Department of Hubei Province(2002A00007)
文摘The influence of mold pressing parameters on the positive temperature coefficien t of high-density polyethylene/carbon black composites was investigated. The co mposites with a low resistivity at room temperature and a high positive temperat ure coefficient can be obtainee with the mold pressing parameters as follows: mo ld pressing pressure 6-14MPa, mold pressing temperature 150-170℃, mold pressi ng time about 15min, and room temperature of molded specimen after cooling for 2 0-60 minutes. The positive temperature coefficient effect of the composite is 7 .7 when it is prepared under the mold pressing parameters, and the negative temp erature coefficient effect is less than 0.8. Scanning electron microscopy (SEM) reveals some aggregations of carbon black particles with a size of 1μm inside t he composite, which was obtained at the mold pressing temperature of 180℃.
文摘The Resin Infusion or the VARTM (Vacuum Assisted Resin Transfer Molding) process has significant potential to be used to manufacture curved composites. Another way to produce curved or complex geometry is to use 3D printers. 3D or FDM (Fused Deposition Modelling) printers are now being used to produce relatively cheaper curved parts using thermoplastics such as PLA. However, the strength and mechanical performance of these parts is limited and can be enhanced if the polymer is reinforced with a type of fiber for instance. Research is being carried out to produce fiber rein-forced thermoplastic composites but that process is expected to be more expensive than the alternative methods such as injection or compression molding. Furthermore, to understand the manufacture of a hybrid composite using thermoplastics, fibers and epoxy resin, research and investigation need to be carried out. In this research</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, there are</span></span></span></span></span><span><span><span><span><span style="font-family:""><span style="font-family:Verdana;"> single-sided, double-sided, reusable, disposable and consumable molds. Most of the molds were created either using an FDM printer or manually. These molds were then used to manufacture flat and curved composite structures via the resin injection process, </span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;"> VARTM with epoxy resin system and glass/carbon/flax fiber reinforcement. By replacing the costly metallic molds by significantly cheaper molds, the cost of production was expected to further reduce. Furthermore, using double-sided PLA molds was not expected to be a threat to the overall cost of the composite part in question compared to double-sided matched molds used in compression molding. Shear strength, tensile strength and charpy impact strength of most of the manufactured composite parts were also investigated. The strengths were compared based on the method of mold usage. The results showed that this method is effective for a cheaper production of curved epoxy resin composites. However, the strength of the part will decrease as the curved profile gets more complicated unless the basic resin infusion process is altered.
基金supported by the National Natural Science Foundation of China(Grant Nos.52175544,52172098)the Key R&D Program of Gansu province(Grant No.25YFGA076)+1 种基金the National Key R&D Program of Shaanxi province(Grant No.2023QCY-LL-26)the Key R&D Program of Guangdong province(Grant No.2023A0505010019)。
文摘Fiber-reinforced polymer composites(FRPCs)possess outstanding specific strength and specific modulus,making them essential in aerospace,rail transportation,and other advanced engineering applications.However,during the molding process,non-uniform microscopic resin flow through multi-scale fiber networks often induces microscopic defects,significantly reducing the mechanical performance and reliability of the composites.Applying an electric field during molding process has demonstrated substantial advantages in void reduction by promoting uniform resin infiltration and enhancing fiber/resin wettability.Nevertheless,the dynamic resin infiltration processes and flow mechanisms within fiber tows and at single fiber surfaces remain poorly understood.To address this challenge,this study introduces a novel in-situ sensing technique for real-time monitoring of microscopic resin infiltration dynamics under applied electric field conditions.By developing glass fiber sensors coated with Ti_(3)C_(2)T_(X)(MXene)and carbon nanotubes(CNTs),we captured the real-time dynamics of infiltration states within fiber tows and at single fiber surfaces.Analysis of sensing signals confirmed that applied electric field assistance significantly increases resin infiltration velocity and infiltration sufficiency.Multi-scale numerical simulations further elucidated how electric field forces promote resin infiltration into fiber tow pores and improve single fiber surface wettability.As a result,the flexural strength and interlaminar shear strength of the composites increased by 25.5%and 37.3%,respectively.This research provides novel insights into electrically-assisted molding processes by integrating in-situ sensing with multi-scale numerical simulations,addressing a critical need for dynamic monitoring of resin infiltration and multi-scale mechanism analysis.
基金This work was supported by the National Natural Science Foundation of China (Nos. 20404008, 50533050, 50373030 and 20490220). This work is subsidized by the Special Funds for Major State Basic Research Projects of China (No. 2003CB615600) by Ministry of Education of China as a key project (No. 104154).
文摘The hierarchical structure and interfacial morphology of injection-molded bars of polypropylene （PP） based blends and composites have been investigated in detail from the skin to the core. For preparation of injection-molded bars with high-level orientation and good interfacial adhesion, a dynamic packing injection molding technology was applied to exert oscillatory shear on the melts during solidification stage. Depending on incorporated component, interfacial adhesion and processing conditions, various oriented structure and morphology could be obtained. First, we will elucidate the epitaxial behavior between PP and high-density polyethylene occurring in practical molded processing. Then, the shear-induced transcrystalline structure will be the main focus for PP/fiber composites. At last, various oriented clay structures have been ascertained unambiguously in PP/organoclay nanocomposites along the thickness of molded bars.
基金supported by the National Natural Science Foundation of China(No.51375033)
文摘Abstract This paper deals with three-point flexure tests on hybrid I- and II-beams, made out of multi-layer carbon fiber/epoxy resin （including twill woven fabric CF3031/5284 and unidirectional cord fabric U3160/5284） reinforced composites, processed using the RTM （resin transfer molding） technique. Static bending properties were determined and failure initiation mechanism was deduced from experimental observations. Failure mode of the tested hybrid RTM-made I-beams can be reckoned to be characteristic of the delamination from the cutout edge within the web and the debonding propagation along the interface between the inverted triangular resin-rich zone and the adjacent curved web until local buckling within the curved webs around the conjunction fillet region. In contrast, as distinct from hybrid RTM I-beams subjected to three-point bending loading, hybrid RTM-made H-beams in three-point flexure tests experienced the resin debonding in the inverted triangular resin-rich zones and the debonding propagation along the interface between the inverted triangular resin-rich zone and the adjacent curved web until complete separation of the curved web from the flange. Progressive damage models （PDMs） were presented to predict fail- ure loads and process of hybrid RTM-made I- and N-beams under three-point flexure. Good cor- relation was achieved between experimental and numerical results.
文摘This study focuses on the insert-injection molding process. The thermoset composite inserts in this study were carbon fiber/epoxy (CF/Epoxy) prepreg sheets. The injected molded part was glass fiber contained phenolic resin (GF/PF). The CF/Epoxy was placed in the mold cavity prior to injecting GF/PF onto the inserted injection molded CF/Epoxy specimens. The role of adhesion between the inserted part and injected resin on the mechanical properties was evaluated by 3 point bending and impact tests. In addition, the effect of prepreg orientation on the mechanical properties of the prepreg inserted-injection molding system was investigated. It was found that the prepreg with unidirectional orientation significantly improved flexural and impact strength of the inserted injection molding composites, providing better support and resistance to bending and impact loading. The main failure modes of the specimens were structural and adhesive failure.
