High-strength and high-modulus ultra-high molecular weight polyethylene(UHMWPE), named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According...High-strength and high-modulus ultra-high molecular weight polyethylene(UHMWPE), named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope(SEM) analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope(TEM) and selective area electron diffraction(SAED) analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50_200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry(DSC) analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature(136.4 ℃) is ascribed to the melting of the reinforced phase.展开更多
This paper presents the results of an investigation on stretch forming behaviour of two consolidated woven thermoplastic composites: a self-reinforced polypropylene (SRPP) and a glass-fibre reinforced polypropylene (G...This paper presents the results of an investigation on stretch forming behaviour of two consolidated woven thermoplastic composites: a self-reinforced polypropylene (SRPP) and a glass-fibre reinforced polypropylene (GRPP) composite. A custom-built press with a hemispherical punch was employed to deform composites’ specimens possessing different aspect ratios into an open die. The induced strains on the outer surface of specimens were measured continuously through two high speed, high resolution CCD cameras by employing a Digital Image Correlation (DIC) technique. The strain paths at three different locations on the surface of specimens were compared to elucidate the effect of fibre and matrix on the formability of a woven composite. The fractured surface of specimens was investigated to reveal the effect of fibre mechanical properties on failure morphologies in woven composites. It was found out that the main mode of failure in GRPP is fibre fracture while observed failure morphologies in SRPP were a complex combination of different failure mechanisms. It was revealed that the combination of applied boundary conditions and specimen’s width determines the effective forming mechanisms.展开更多
General-purpose plastics with high strength and toughness have been in great demand for structural engineering applications.To achieve the reinforcement and broaden the application scope of high-density polyethylene(H...General-purpose plastics with high strength and toughness have been in great demand for structural engineering applications.To achieve the reinforcement and broaden the application scope of high-density polyethylene(HDPE),multi-flow vibration injection molding(MFVIM)and ultrahigh molecular weight polyethylene(UHMWPE)are synergistically employed in this work.Herein,the MFVIM has better shear layer control ability and higher fabrication advantage for complex parts than other analogous novel injection molding technologies reported.The reinforcing effect of various filling times and UHMWPE contents as well as the corresponding microstructure evolution are investigated.When 5 wt%UHMWPE is added,MFVIM process with six flow times thickens the shear layer to the whole thickness.The tensile strength and modulus increase to 2.14 and 1.39 times,respectively,compared to neat HDPE on the premise of remaining 70%impact strength.Structural characterizations indicate that the enhancement is attributed to the improvement of shish-kebab content and lamellae compactness,as well as related to the corresponding size distributions of undissolved UHMWPE particles.This novel injection molding technology with great industrial prospects provides a facile and effective strategy to broaden the engineering applications of HDPE materials.Besides,excessive UHMWPE may impair the synergistic enhancement effect,which is also reasonably explained.展开更多
The present study deals with the propagation of a polarized shear horizontal(SH)wave in a pre-stressed piezoelectric cylinder circumscribed by a self-reinforced cylinder.The interface of the two media is assumed mecha...The present study deals with the propagation of a polarized shear horizontal(SH)wave in a pre-stressed piezoelectric cylinder circumscribed by a self-reinforced cylinder.The interface of the two media is assumed mechanically imperfect.For obtaining the dispersion relation,the mathematical formulation has been developed and solved by an analytical treatment.The effects of various parameters,i.e.,the thickness ratio,the imperfect interface,the initial stress,the reinforcement,and the piezoelectric and dielectric constants,on the dispersion curve are observed prominently.The dispersion curves for different modes have been also plotted.The consequences of the study may be used for achieving optimum efficiency of acoustic wave devices.展开更多
文摘High-strength and high-modulus ultra-high molecular weight polyethylene(UHMWPE), named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope(SEM) analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope(TEM) and selective area electron diffraction(SAED) analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50_200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry(DSC) analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature(136.4 ℃) is ascribed to the melting of the reinforced phase.
文摘This paper presents the results of an investigation on stretch forming behaviour of two consolidated woven thermoplastic composites: a self-reinforced polypropylene (SRPP) and a glass-fibre reinforced polypropylene (GRPP) composite. A custom-built press with a hemispherical punch was employed to deform composites’ specimens possessing different aspect ratios into an open die. The induced strains on the outer surface of specimens were measured continuously through two high speed, high resolution CCD cameras by employing a Digital Image Correlation (DIC) technique. The strain paths at three different locations on the surface of specimens were compared to elucidate the effect of fibre and matrix on the formability of a woven composite. The fractured surface of specimens was investigated to reveal the effect of fibre mechanical properties on failure morphologies in woven composites. It was found out that the main mode of failure in GRPP is fibre fracture while observed failure morphologies in SRPP were a complex combination of different failure mechanisms. It was revealed that the combination of applied boundary conditions and specimen’s width determines the effective forming mechanisms.
基金by the National Natural Science Foundation of China(No.21627804).
文摘General-purpose plastics with high strength and toughness have been in great demand for structural engineering applications.To achieve the reinforcement and broaden the application scope of high-density polyethylene(HDPE),multi-flow vibration injection molding(MFVIM)and ultrahigh molecular weight polyethylene(UHMWPE)are synergistically employed in this work.Herein,the MFVIM has better shear layer control ability and higher fabrication advantage for complex parts than other analogous novel injection molding technologies reported.The reinforcing effect of various filling times and UHMWPE contents as well as the corresponding microstructure evolution are investigated.When 5 wt%UHMWPE is added,MFVIM process with six flow times thickens the shear layer to the whole thickness.The tensile strength and modulus increase to 2.14 and 1.39 times,respectively,compared to neat HDPE on the premise of remaining 70%impact strength.Structural characterizations indicate that the enhancement is attributed to the improvement of shish-kebab content and lamellae compactness,as well as related to the corresponding size distributions of undissolved UHMWPE particles.This novel injection molding technology with great industrial prospects provides a facile and effective strategy to broaden the engineering applications of HDPE materials.Besides,excessive UHMWPE may impair the synergistic enhancement effect,which is also reasonably explained.
文摘The present study deals with the propagation of a polarized shear horizontal(SH)wave in a pre-stressed piezoelectric cylinder circumscribed by a self-reinforced cylinder.The interface of the two media is assumed mechanically imperfect.For obtaining the dispersion relation,the mathematical formulation has been developed and solved by an analytical treatment.The effects of various parameters,i.e.,the thickness ratio,the imperfect interface,the initial stress,the reinforcement,and the piezoelectric and dielectric constants,on the dispersion curve are observed prominently.The dispersion curves for different modes have been also plotted.The consequences of the study may be used for achieving optimum efficiency of acoustic wave devices.
