The implementation of natural fibres in polymer composites will result in biodegradable,low cost,recyclable materials for automobile and structural applications.In the process of making natural fibre composites viable...The implementation of natural fibres in polymer composites will result in biodegradable,low cost,recyclable materials for automobile and structural applications.In the process of making natural fibre composites viable in the global market,it is essential to understand its mechanical and physical properties.In the present investigation,mechanical and physical properties of pineapple Leaf(PALF)and Sun Hemp(SH)Fibre reinforced with epoxy matrix was studied in terms of weight(wt)%of fibre loading and chemical treatment.The composites were fabricated by compression moulding technique with PALF fibre content varying from 10,15 and 20%of weight fraction.The PALF and SHF were treated with NaOH solution for 1 h at room temperature.The various mechanical properties such as tensile,compression,flexural and impact strength were measured as per ASTM standard.The density and water absorption were also measured to study the physical properties of the fabricated composites.The treated composites exhibit a rough surface because of the removal of the cellulose layer which results in better adhesion between the matrix/fibre interface than untreated composites.The NaOH treated fibres composites outperformed untreated fibre composites in terms of mechanical and physical properties except for impact strength.The morphological studies of the worn surfaces are examined using Scanning Electron Microscope(SEM).展开更多
Additives of dioctyl phthalate(DOP),ethylene bis-stearomide(EBS),and epoxy(EP)were selected to modify the surface of 7075 Al alloy powder.Functional groups in DOP and EBS form hydrogen bonds with hydroxyl groups on th...Additives of dioctyl phthalate(DOP),ethylene bis-stearomide(EBS),and epoxy(EP)were selected to modify the surface of 7075 Al alloy powder.Functional groups in DOP and EBS form hydrogen bonds with hydroxyl groups on the surface of Al powder.Additionally,the epoxy groups in the epoxy resin undergo ring-opening reactions with hydroxyl groups.The above interactions increased the compatibility between alloy powder and polyoxymethylene(POM).After sintering,samples containing DOP and EP presented high contents of C and O,while the part with EBS additive exhibited the lowest contents of 0.006 wt.%C and 0.604 wt.%O,respectively.Excessive C tends to accumulate at grain boundaries during sintering.Concurrently,excessive O causes secondary oxidation of aluminium alloy powder,inhibiting the sintering densification process.Therefore,the densities of the samples containing DOP and EP were only 85.52%and 79.01%,respectively.In contrast,using EBS as an additive,high-quality aluminium alloy parts were achieved,with a relative density of 97.64%and a tensile strength of 193 MPa.展开更多
Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic inter...Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic interference(EMI)shielding performance with low reflection.Herein,a gradient distri-bution of segregated conductive network consisting of edge-selectively carboxylated graphene(ECG)nanosheets and carboxylated multi-walled carbon nanotubes(cMWCNTs)in poly(vinylidene fluoride)(PVDF)nanocomposites was first designed to achieve outstanding low reflective electromagnetic shielding performance.The sheets of PVDF nanocomposites with different contents of hybrid ECG-cMWCNTs were stacked and further hot-pressed to fabricate the layered PVDF nanocomposites.The overall EMI shielding effectiveness(EMI SE)performance could be further improved by increasing the overall thickness and the layer number.With a fixed thickness of 2.0 mm,the PVDF@7.5wt%ECG_(1)-cMWCNTs 3 six-layered nanocom-posites exhibit excellent EMI SE reaching 79.87 dB with an absorption effectiveness(SE A)of 79.62 dB.The excellent EMI SE performance was ascribed to the multiple interface reflection of the segregated conduc-tive network.Meanwhile,the gradient distribution of ECG-cMWCNTs endows the nanocomposites with a strong absorption ability.This work provides a novel strategy for fabricating EMI shielding composites with low reflection for application in portable electronic devices.展开更多
In this study,we attempted to characterise the effects of date-palm fibre(DPF)and a date-palm fibre/sheep wool hybrid in polyester to enhance high-performance and low-cost composite materials that can be used in insul...In this study,we attempted to characterise the effects of date-palm fibre(DPF)and a date-palm fibre/sheep wool hybrid in polyester to enhance high-performance and low-cost composite materials that can be used in insulation building systems,automotive parts,and home furniture.The DPF was treated using 5%NaOH solution;and the sheep wool was cleaned with 50℃hot water and detergents.The composite specimens were prepared with different fibre contents(0%,10%,20%,30%(w))using a compression moulding technique.The effect of fibre reinforcement was analysed in terms of the mechanical properties(tensile,flexural,impact,and hardness)and composite density.Additionally,scanning electron microscopy(SEM)was performed on the fibres before and after treatment,and the fractured surfaces of all composite specimens were examined after tensile testing.The results showed that the 20%DPF/sheep wool hybrid reinforced polyester produced the best results.The ultimate tensile strength and modulus were 27 MPa and 3.69GPa,respectively.The ultimate flexural strength and flexural modulus were 35.4 and 2507 MPa,respectively.The impact strength was 39.5 kJ/m^(2)and the hardness was 64 HB.The density decreased to the lowest value of 1.02 g/cm^(3)with the 30%DPF/sheep wool hybrid.The SEM showed good adhesion and interfacial bonding between DPF/sheep wool hybrid fibres and the polyester matrix,particularly at 20%fibre content.展开更多
文摘The implementation of natural fibres in polymer composites will result in biodegradable,low cost,recyclable materials for automobile and structural applications.In the process of making natural fibre composites viable in the global market,it is essential to understand its mechanical and physical properties.In the present investigation,mechanical and physical properties of pineapple Leaf(PALF)and Sun Hemp(SH)Fibre reinforced with epoxy matrix was studied in terms of weight(wt)%of fibre loading and chemical treatment.The composites were fabricated by compression moulding technique with PALF fibre content varying from 10,15 and 20%of weight fraction.The PALF and SHF were treated with NaOH solution for 1 h at room temperature.The various mechanical properties such as tensile,compression,flexural and impact strength were measured as per ASTM standard.The density and water absorption were also measured to study the physical properties of the fabricated composites.The treated composites exhibit a rough surface because of the removal of the cellulose layer which results in better adhesion between the matrix/fibre interface than untreated composites.The NaOH treated fibres composites outperformed untreated fibre composites in terms of mechanical and physical properties except for impact strength.The morphological studies of the worn surfaces are examined using Scanning Electron Microscope(SEM).
基金supported by the National Key Research and Development Program of China(No.2021YFB3701900)。
文摘Additives of dioctyl phthalate(DOP),ethylene bis-stearomide(EBS),and epoxy(EP)were selected to modify the surface of 7075 Al alloy powder.Functional groups in DOP and EBS form hydrogen bonds with hydroxyl groups on the surface of Al powder.Additionally,the epoxy groups in the epoxy resin undergo ring-opening reactions with hydroxyl groups.The above interactions increased the compatibility between alloy powder and polyoxymethylene(POM).After sintering,samples containing DOP and EP presented high contents of C and O,while the part with EBS additive exhibited the lowest contents of 0.006 wt.%C and 0.604 wt.%O,respectively.Excessive C tends to accumulate at grain boundaries during sintering.Concurrently,excessive O causes secondary oxidation of aluminium alloy powder,inhibiting the sintering densification process.Therefore,the densities of the samples containing DOP and EP were only 85.52%and 79.01%,respectively.In contrast,using EBS as an additive,high-quality aluminium alloy parts were achieved,with a relative density of 97.64%and a tensile strength of 193 MPa.
基金support from the Sichuan Science and Technology Program(2022YFH0090)and the Fundamental Research Funds for the Central Universities.
文摘Highly efficient electromagnetic shielding materials have become an increasing requirement for high-power electronic equipment.Nevertheless,there still remains a challenge in achieving excellent elec-tromagnetic interference(EMI)shielding performance with low reflection.Herein,a gradient distri-bution of segregated conductive network consisting of edge-selectively carboxylated graphene(ECG)nanosheets and carboxylated multi-walled carbon nanotubes(cMWCNTs)in poly(vinylidene fluoride)(PVDF)nanocomposites was first designed to achieve outstanding low reflective electromagnetic shielding performance.The sheets of PVDF nanocomposites with different contents of hybrid ECG-cMWCNTs were stacked and further hot-pressed to fabricate the layered PVDF nanocomposites.The overall EMI shielding effectiveness(EMI SE)performance could be further improved by increasing the overall thickness and the layer number.With a fixed thickness of 2.0 mm,the PVDF@7.5wt%ECG_(1)-cMWCNTs 3 six-layered nanocom-posites exhibit excellent EMI SE reaching 79.87 dB with an absorption effectiveness(SE A)of 79.62 dB.The excellent EMI SE performance was ascribed to the multiple interface reflection of the segregated conduc-tive network.Meanwhile,the gradient distribution of ECG-cMWCNTs endows the nanocomposites with a strong absorption ability.This work provides a novel strategy for fabricating EMI shielding composites with low reflection for application in portable electronic devices.
文摘In this study,we attempted to characterise the effects of date-palm fibre(DPF)and a date-palm fibre/sheep wool hybrid in polyester to enhance high-performance and low-cost composite materials that can be used in insulation building systems,automotive parts,and home furniture.The DPF was treated using 5%NaOH solution;and the sheep wool was cleaned with 50℃hot water and detergents.The composite specimens were prepared with different fibre contents(0%,10%,20%,30%(w))using a compression moulding technique.The effect of fibre reinforcement was analysed in terms of the mechanical properties(tensile,flexural,impact,and hardness)and composite density.Additionally,scanning electron microscopy(SEM)was performed on the fibres before and after treatment,and the fractured surfaces of all composite specimens were examined after tensile testing.The results showed that the 20%DPF/sheep wool hybrid reinforced polyester produced the best results.The ultimate tensile strength and modulus were 27 MPa and 3.69GPa,respectively.The ultimate flexural strength and flexural modulus were 35.4 and 2507 MPa,respectively.The impact strength was 39.5 kJ/m^(2)and the hardness was 64 HB.The density decreased to the lowest value of 1.02 g/cm^(3)with the 30%DPF/sheep wool hybrid.The SEM showed good adhesion and interfacial bonding between DPF/sheep wool hybrid fibres and the polyester matrix,particularly at 20%fibre content.
