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
A new kind of in-situ ceramic consolidation molding process was investigated on the basis of the characteristics of starch swelling in water and gelatinizing when heated. The SiC ceramic suspension containing about 50...A new kind of in-situ ceramic consolidation molding process was investigated on the basis of the characteristics of starch swelling in water and gelatinizing when heated. The SiC ceramic suspension containing about 50vol% solids loading and about 3wt% starch can be cast and molded into various complex-shape SiC ceramic parts in a water-thermostat. The dry shrinkage of the green body was less than 1.0% when the solid volume fraction of SiC suspension was up to 52.5%. The density and pore size were homogeneously distributed inside the biscuits. Soaked with melt silicon in a vacuum arc furnace, the biscuits were turn into SiC ceramic materials with homogeneous structure and high performances.展开更多
The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based ther...The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based thermoplastic binder. Microinjection molding was fulfilled at about 423 K under 100 MPa. The heating system was applied to the die to improve the fluidity of the feedstock and subsequently the cooling system was used to enhance the strength of the green compacts after injection by decreasing the temperature of the die. The gear wheels were realized successfully with their addendum circle diameter ranging from 800 to 200 um and with the center hole as small as 60 um.展开更多
In-situ reactive compatibilization of high-density polyethylene （HDPE）/ground tire rubber （GTR） blends by dicumyl peroxide （DCP） and HY-2045 - a kind of thermoplastic phenolic resin without catalyst was inves...In-situ reactive compatibilization of high-density polyethylene （HDPE）/ground tire rubber （GTR） blends by dicumyl peroxide （DCP） and HY-2045 - a kind of thermoplastic phenolic resin without catalyst was investigated by studying the mor-phology, stress and strain behavior, dynamic mechanical properties and crystallization performance of the blends. Scanning e-lectron microscopy （SEM） results show that there are a lot of fibrous materials distributing in the interface, which connects the dispersed phase with the matrix and obtains better interfacial strength for prominent mechanical properties. The addition of compatibilizers results in the decrease of crystallinity of the blends and the disappearance of an obvious yield phenomenon, which was proved by the differential scanning calorimeter （DSC） test and X-ray diffraction （XRD） characterization Although the crystallinity of the blends decreases,the tensile strength and tensile strain of the blends significantly increases, especially for the HDPE/GTR/DCP/HY-2045 blends, which is possibly attributed to the good compatibility of the blends owing to the in-situ interface crosslinking. In addition, it is found that the compatibilizing HDPE/GTR blends shows a higher tan^ peak temperature and a broaden transition peak for GTR phase.展开更多
A three-stage molding process involving microcellular injection molding with core retraction and an ＂out-of-mold＂ expansion was developed to manufacture thermoplastic polyurethane into lightweight foams of varying l...A three-stage molding process involving microcellular injection molding with core retraction and an ＂out-of-mold＂ expansion was developed to manufacture thermoplastic polyurethane into lightweight foams of varying local densities, microstructures, and mechanical properties in the same microcellular injection molded part. Two stages of cavity expansion through sequential core retractions and a third expansion in a separate mold at an elevated temperature were carried out. The densities varied from 0.25 to 0.42 g/cm3 （77% to 62% weight reduction）. The mechanical properties varied as well Cyclic com- pressive strengths and hysteresis loss ratios, together with the microstructures, were characterized and reported.展开更多
Density variation during the injection molding process directly reflects the state of plastic melt and contains valuable information for process monitoring and optimization.Therefore,in-situ density measurement is of ...Density variation during the injection molding process directly reflects the state of plastic melt and contains valuable information for process monitoring and optimization.Therefore,in-situ density measurement is of great interest and has significant application value.The existing methods,such as pressure−volume−temperature(PVT)method,have the shortages of time-delay and high cost of sensors.This study is the first to propose an in-situ density measurement method using ultrasonic technology.The analyses of the time-domain and frequency-domain signals are combined in the proposed method.The ultrasonic velocity is obtained from the time-domain signals,and the acoustic impedance is computed through a full-spectral analysis of the frequency-domain signals.Experiments with different process conditions are conducted,including different melt temperature,injection speed,material,and mold structure.Results show that the proposed method has good agreement with the PVT method.The proposed method has the advantages of in-situ measurement,non-destructive,high accuracy,low cost,and is of great application value for the injection molding industry.展开更多
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).
文摘A new kind of in-situ ceramic consolidation molding process was investigated on the basis of the characteristics of starch swelling in water and gelatinizing when heated. The SiC ceramic suspension containing about 50vol% solids loading and about 3wt% starch can be cast and molded into various complex-shape SiC ceramic parts in a water-thermostat. The dry shrinkage of the green body was less than 1.0% when the solid volume fraction of SiC suspension was up to 52.5%. The density and pore size were homogeneously distributed inside the biscuits. Soaked with melt silicon in a vacuum arc furnace, the biscuits were turn into SiC ceramic materials with homogeneous structure and high performances.
基金This study was financially supported by the Major State Basic Research Development Program of China (No.2004CB719802)the National High-Tech Research and Development Program of China (No.2006aa03Z113)the Program of the Ministry of Educa-tion of China for Changjiang Scholars and Innovative Research Team in Universities (No.I2P407).
文摘The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based thermoplastic binder. Microinjection molding was fulfilled at about 423 K under 100 MPa. The heating system was applied to the die to improve the fluidity of the feedstock and subsequently the cooling system was used to enhance the strength of the green compacts after injection by decreasing the temperature of the die. The gear wheels were realized successfully with their addendum circle diameter ranging from 800 to 200 um and with the center hole as small as 60 um.
文摘In-situ reactive compatibilization of high-density polyethylene （HDPE）/ground tire rubber （GTR） blends by dicumyl peroxide （DCP） and HY-2045 - a kind of thermoplastic phenolic resin without catalyst was investigated by studying the mor-phology, stress and strain behavior, dynamic mechanical properties and crystallization performance of the blends. Scanning e-lectron microscopy （SEM） results show that there are a lot of fibrous materials distributing in the interface, which connects the dispersed phase with the matrix and obtains better interfacial strength for prominent mechanical properties. The addition of compatibilizers results in the decrease of crystallinity of the blends and the disappearance of an obvious yield phenomenon, which was proved by the differential scanning calorimeter （DSC） test and X-ray diffraction （XRD） characterization Although the crystallinity of the blends decreases,the tensile strength and tensile strain of the blends significantly increases, especially for the HDPE/GTR/DCP/HY-2045 blends, which is possibly attributed to the good compatibility of the blends owing to the in-situ interface crosslinking. In addition, it is found that the compatibilizing HDPE/GTR blends shows a higher tan^ peak temperature and a broaden transition peak for GTR phase.
文摘A three-stage molding process involving microcellular injection molding with core retraction and an ＂out-of-mold＂ expansion was developed to manufacture thermoplastic polyurethane into lightweight foams of varying local densities, microstructures, and mechanical properties in the same microcellular injection molded part. Two stages of cavity expansion through sequential core retractions and a third expansion in a separate mold at an elevated temperature were carried out. The densities varied from 0.25 to 0.42 g/cm3 （77% to 62% weight reduction）. The mechanical properties varied as well Cyclic com- pressive strengths and hysteresis loss ratios, together with the microstructures, were characterized and reported.
基金supported by the“Pioneer”and“Leading Goose”R&D Program of Zhejiang,China(Grant No.2022C01069)the National Natural Science Foundation of China(Grant No.51875519)+1 种基金the Key Project of Science and Technology Innovation 2025 of Ningbo City,China(Grant No.2021Z044)the Project of Innovation Enterprises Union of Ningbo City,China(Grant No.2021H002).
文摘Density variation during the injection molding process directly reflects the state of plastic melt and contains valuable information for process monitoring and optimization.Therefore,in-situ density measurement is of great interest and has significant application value.The existing methods,such as pressure−volume−temperature(PVT)method,have the shortages of time-delay and high cost of sensors.This study is the first to propose an in-situ density measurement method using ultrasonic technology.The analyses of the time-domain and frequency-domain signals are combined in the proposed method.The ultrasonic velocity is obtained from the time-domain signals,and the acoustic impedance is computed through a full-spectral analysis of the frequency-domain signals.Experiments with different process conditions are conducted,including different melt temperature,injection speed,material,and mold structure.Results show that the proposed method has good agreement with the PVT method.The proposed method has the advantages of in-situ measurement,non-destructive,high accuracy,low cost,and is of great application value for the injection molding industry.
