2004 Vol. 21, No. 4
2004, 21(4): 1-7.
Abstract:
The polyaniline/manganese dioxide composites (PANI/MnO2) containing different amounts of manganese dioxide were prepared by chemical polymerisation of aniline using ammonium peroxodisulfate (APS) and MnO2 as the oxidizing agent. The inclusion of PANI in the composite was confirmed by FTIR, UV-VIS, XRD and SEM analysis. It shows that PANI in the composite is amorphous and the crystal structure of MnO2 is unchanged compared with the initial MnO2. The PANI formed in the reaction is deposited preferentially on the MnO2 particles giving a PANI/MnO2 composite, in which the MnO2 is coated with the PANI. The tree-coral-shaped PANI, which differed from the common grain-like PANI in the acid/water reaction system, was obtained by treating the PANI/MnO2 composite in the static state with hydrochloride acid solution of aniline.
The polyaniline/manganese dioxide composites (PANI/MnO2) containing different amounts of manganese dioxide were prepared by chemical polymerisation of aniline using ammonium peroxodisulfate (APS) and MnO2 as the oxidizing agent. The inclusion of PANI in the composite was confirmed by FTIR, UV-VIS, XRD and SEM analysis. It shows that PANI in the composite is amorphous and the crystal structure of MnO2 is unchanged compared with the initial MnO2. The PANI formed in the reaction is deposited preferentially on the MnO2 particles giving a PANI/MnO2 composite, in which the MnO2 is coated with the PANI. The tree-coral-shaped PANI, which differed from the common grain-like PANI in the acid/water reaction system, was obtained by treating the PANI/MnO2 composite in the static state with hydrochloride acid solution of aniline.
2004, 21(4): 8-12.
Abstract:
Poly-o-phenylenediamine/montmorillonite nanocomposite (PoPD-MMT) particles were synthesized by an emulsion intercalation method and characterized by IR, XRD and TEM respectively. The structure analysis shows that the diameter of PoPD-MMT particles is about 100 nm. The electrorheological properties of the suspensions of PoPD-MMT particles in silicone oil (Volume fraction,22%) have been investigated under DC electric fields. It was found that the mechanic performance of PoPD-MMT ER fluids displays a notable ER effect. The shear stress of PoPD-MMT ER fluid is 8.27 kPa (3 kV/mm, 74.5 s-1), which is 2.5 times that of the electrorheological fluid at zero field, and much higher than that of pure poly-o-phenylenediamine (PoPD) and pure montmorillonite (MMT). Furthermore, the sedimentation ratio of PoPD-MMT ERF was about 97% after 60 days. The dielectric constant and the dielectric loss tangent of PoPD-MMT nanocomposite were higher than those of PoPD and MMT. It is apparent that the notable ER effect of PoPD-MMT ER fluid was attributed to the prominent dielectric property of the poly-o-phenylenediamine/montmorillonite nanocomposite particles.
Poly-o-phenylenediamine/montmorillonite nanocomposite (PoPD-MMT) particles were synthesized by an emulsion intercalation method and characterized by IR, XRD and TEM respectively. The structure analysis shows that the diameter of PoPD-MMT particles is about 100 nm. The electrorheological properties of the suspensions of PoPD-MMT particles in silicone oil (Volume fraction,22%) have been investigated under DC electric fields. It was found that the mechanic performance of PoPD-MMT ER fluids displays a notable ER effect. The shear stress of PoPD-MMT ER fluid is 8.27 kPa (3 kV/mm, 74.5 s-1), which is 2.5 times that of the electrorheological fluid at zero field, and much higher than that of pure poly-o-phenylenediamine (PoPD) and pure montmorillonite (MMT). Furthermore, the sedimentation ratio of PoPD-MMT ERF was about 97% after 60 days. The dielectric constant and the dielectric loss tangent of PoPD-MMT nanocomposite were higher than those of PoPD and MMT. It is apparent that the notable ER effect of PoPD-MMT ER fluid was attributed to the prominent dielectric property of the poly-o-phenylenediamine/montmorillonite nanocomposite particles.
2004, 21(4): 13-17.
Abstract:
The effects of the loop density for rib 1∶1 fabric preform made from GF/PP commingled yarn on the tensile properties of composites were investigated. Six samples of rib 1∶1 fabric preform with different loop densities were studied. It was found that the tensile strength of composites showed an increase followed by a slightly decrease as the increase of the loop density of the rib 1∶1 fabric preform, while the fracture strain just varied contrarily. This phenomenon was explained from the inherent characteristic of loop structure, the homogeneity of fiber/matrix distribution in composites and the continuousness of the reinforced fiber. Micrographic studies using optical and scanning electron microscopy revealed that the void content in the composite decreased as the loop density of the preform increased and the fiber and matrix distributed more uniformly, meanwhile, more glass fiber was broken because of the reduction of the radius of curvature of the loop.
The effects of the loop density for rib 1∶1 fabric preform made from GF/PP commingled yarn on the tensile properties of composites were investigated. Six samples of rib 1∶1 fabric preform with different loop densities were studied. It was found that the tensile strength of composites showed an increase followed by a slightly decrease as the increase of the loop density of the rib 1∶1 fabric preform, while the fracture strain just varied contrarily. This phenomenon was explained from the inherent characteristic of loop structure, the homogeneity of fiber/matrix distribution in composites and the continuousness of the reinforced fiber. Micrographic studies using optical and scanning electron microscopy revealed that the void content in the composite decreased as the loop density of the preform increased and the fiber and matrix distributed more uniformly, meanwhile, more glass fiber was broken because of the reduction of the radius of curvature of the loop.
2004, 21(4): 18-23.
Abstract:
A new woodceramics was developed by carbonizing phenolic resin/basswood powder composite under vacuum at high temperatures.The effects of carbonization temperature and weight ratio of phenolic resin to wood powder on structural changes of woodceramics were investigated by scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR)techniques.Experimental results show that woodceramics has a topologically uniform interconnected porous network microstructure,and is typical non-graphitizable carbon containing C C bonds,C—O—C bonds and C—H structure.With increasing carbonization temperature,the(002)peak becomes stronger,the (002)interplanar spacing decreases,and the dimensions of carbonized wood powder decrease,while the space between carbonized wood powders increases.The increasing weight ratio of phenolic resin to wood powder improves the forming ability of phenolic resin impregnated wood powders,and results in a more uniform microstructure,but there is a slight effect on the XRD pattern of the resulting woodceramics.
A new woodceramics was developed by carbonizing phenolic resin/basswood powder composite under vacuum at high temperatures.The effects of carbonization temperature and weight ratio of phenolic resin to wood powder on structural changes of woodceramics were investigated by scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR)techniques.Experimental results show that woodceramics has a topologically uniform interconnected porous network microstructure,and is typical non-graphitizable carbon containing C C bonds,C—O—C bonds and C—H structure.With increasing carbonization temperature,the(002)peak becomes stronger,the (002)interplanar spacing decreases,and the dimensions of carbonized wood powder decrease,while the space between carbonized wood powders increases.The increasing weight ratio of phenolic resin to wood powder improves the forming ability of phenolic resin impregnated wood powders,and results in a more uniform microstructure,but there is a slight effect on the XRD pattern of the resulting woodceramics.
2004, 21(4): 24-28.
Abstract:
A finite-element model is established for the mold filling of co-injection, and a software package of numerical simulation was developed by means of Matlab and Visual C++6.0. The numerical simulation of the relation was implemented between the core-skin-viscosity ratio and the formations of layer interface and moving melt fronts, and then a set of principles to guide the selection of the key molding parameters was put forward. The result of case study of numerical simulation is in good agreement with the experimental result given in some literature.
A finite-element model is established for the mold filling of co-injection, and a software package of numerical simulation was developed by means of Matlab and Visual C++6.0. The numerical simulation of the relation was implemented between the core-skin-viscosity ratio and the formations of layer interface and moving melt fronts, and then a set of principles to guide the selection of the key molding parameters was put forward. The result of case study of numerical simulation is in good agreement with the experimental result given in some literature.
2004, 21(4): 29-32.
Abstract:
The inner stress in an epoxy adhesive layer deposited on the steel plate at room temperature is studied.With embedded strain gauges in arranged depth of the epoxy layer,the strain changes in the adhesive layer induced by the curing procedure and the changes of environment temperature were measured to evaluate the changes of the inner stress in places during one week.The results from experiment show that the lowest transversal strain is recorded at the layer near the surface,but the highest value is recorded after 24 h.At the point near the interface the stresses are the highest when the curing procedure is about accomplished.The inner stresses in the epoxy adhesive layer during curing to 180 h were estimated based on the strain obtained from the surface of the adhesive layer.
The inner stress in an epoxy adhesive layer deposited on the steel plate at room temperature is studied.With embedded strain gauges in arranged depth of the epoxy layer,the strain changes in the adhesive layer induced by the curing procedure and the changes of environment temperature were measured to evaluate the changes of the inner stress in places during one week.The results from experiment show that the lowest transversal strain is recorded at the layer near the surface,but the highest value is recorded after 24 h.At the point near the interface the stresses are the highest when the curing procedure is about accomplished.The inner stresses in the epoxy adhesive layer during curing to 180 h were estimated based on the strain obtained from the surface of the adhesive layer.
2004, 21(4): 33-39.
Abstract:
The PP/PET in-situ fiberized composites with reinforcing effect were prepared by extrusion-drawing-injection molding. The influences of PET mass content (Cm) on the PET fiberization, tensile strength (σt) and Young's modulus (E) of the composites, together with their functional mechanisms were studied in contrast to the normally blended materials without drawing. The results show that as Cm rises from 0 to 20%, the number of PET fibers in-situ formed increases whereas their diameter and dispersity decrease till Cm=15% and then increase.Correspondingly, the σt and E of the composites increase till Cm=15% and then decrease, with maximum gains of σt and E of about 20% and 70% relative to neat PP,respectively. The fiberization of PET droplets through coalescence-deformation during melt-drawing plays a key role in the above variation of PET phase morphology with Cm. The competition between the reinforcing effect of dispersed phase on matrix and the interfacial flaw effect of the two phases, and the rigidizing effect of fiber on matrix controlled by both fiber number and fiber fineness, are dominant factors of deciding the above σt~Cm and E~Cm relations, respectively.
The PP/PET in-situ fiberized composites with reinforcing effect were prepared by extrusion-drawing-injection molding. The influences of PET mass content (Cm) on the PET fiberization, tensile strength (σt) and Young's modulus (E) of the composites, together with their functional mechanisms were studied in contrast to the normally blended materials without drawing. The results show that as Cm rises from 0 to 20%, the number of PET fibers in-situ formed increases whereas their diameter and dispersity decrease till Cm=15% and then increase.Correspondingly, the σt and E of the composites increase till Cm=15% and then decrease, with maximum gains of σt and E of about 20% and 70% relative to neat PP,respectively. The fiberization of PET droplets through coalescence-deformation during melt-drawing plays a key role in the above variation of PET phase morphology with Cm. The competition between the reinforcing effect of dispersed phase on matrix and the interfacial flaw effect of the two phases, and the rigidizing effect of fiber on matrix controlled by both fiber number and fiber fineness, are dominant factors of deciding the above σt~Cm and E~Cm relations, respectively.
2004, 21(4): 40-44.
Abstract:
Dynamic mechanical thermal analysis(DMTA), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to study the surface of polyacrylonitrile (PAN)-based carbon fiber(CF) treated by electrochemical oxidation. The results show that the loss tangent(tanδ) of treated carbon fibers reinforced epoxy declines to 30% compared with the untreated in DMTA chart, and the change of glass transition temperature (Tg) and the peak of tanδ can availably characterize the electrochemical treatment effect of carbon fiber surface, which corresponds to SEM analysis. Quantitative analysis results reveal that the interfacial adhesion parameter A and α can reflect the interfacial bonding effect between carbon fibers and epoxy, which is compatible with what is reflected by the ILSS value of CFRP. XPS analysis indicates that the hydroxyl group content and actived carbon atom of the treated CF are higher than those of the untreated CF, which is improved to 55% and 18% respectively. Appropriate oxidative conditions can make interlaminar shear strength (ILSS) increase over 20%.
Dynamic mechanical thermal analysis(DMTA), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to study the surface of polyacrylonitrile (PAN)-based carbon fiber(CF) treated by electrochemical oxidation. The results show that the loss tangent(tanδ) of treated carbon fibers reinforced epoxy declines to 30% compared with the untreated in DMTA chart, and the change of glass transition temperature (Tg) and the peak of tanδ can availably characterize the electrochemical treatment effect of carbon fiber surface, which corresponds to SEM analysis. Quantitative analysis results reveal that the interfacial adhesion parameter A and α can reflect the interfacial bonding effect between carbon fibers and epoxy, which is compatible with what is reflected by the ILSS value of CFRP. XPS analysis indicates that the hydroxyl group content and actived carbon atom of the treated CF are higher than those of the untreated CF, which is improved to 55% and 18% respectively. Appropriate oxidative conditions can make interlaminar shear strength (ILSS) increase over 20%.
2004, 21(4): 45-49.
Abstract:
Carbon fiber was treated with plasma technology after dipped with polyarylacetylene(PAA) monomer, which enables PAA monomer to graft on the fiber. Interface characterizations of carbon fiber reinforced polyarylacetylene composite were studied by the aid of scanning election microscope, infrared spectra, ultraviolet spectra, X-ray diffraction spectra, Raman spectroscopy, etc. The results showed that the interlaminar shear strength (ILSS) of C/PAA composite was improved by 12.4% after carbon fiber was treated with plasma technology and improved by 51.27% after the fiber grafted with PAA monomer.
Carbon fiber was treated with plasma technology after dipped with polyarylacetylene(PAA) monomer, which enables PAA monomer to graft on the fiber. Interface characterizations of carbon fiber reinforced polyarylacetylene composite were studied by the aid of scanning election microscope, infrared spectra, ultraviolet spectra, X-ray diffraction spectra, Raman spectroscopy, etc. The results showed that the interlaminar shear strength (ILSS) of C/PAA composite was improved by 12.4% after carbon fiber was treated with plasma technology and improved by 51.27% after the fiber grafted with PAA monomer.
2004, 21(4): 50-53.
Abstract:
The heat-resistant property, adhesive strength and storage life were studied for Tetramaleimide (TMI) modificated polyphenylmenthylsiloxane phenolic resin (PFSi) by IR, DSC and TG analysis methods. At the curing temperature of tetramaleimide modificated polyphenylmenthylsiloxane phenolic resin(TMI/PFSi), the C C group of TMI was condensed with —CH2OH of PFSi into crosslinking structure, since the heat-resistant property and adhesive strength of PFSi are increased, the toughness is kept, and the storage life is decreased. At room temperature, a small amount of the COOH, and NH2 groups of TMI (because of the steric effection, carboxyl and amino of TMI are not all condensed into imide) are condensed with —CH2OH of PFSi into a small amount of crosslinking structural oligomer, which makes the storage life of TMI/PFSi decrease.
The heat-resistant property, adhesive strength and storage life were studied for Tetramaleimide (TMI) modificated polyphenylmenthylsiloxane phenolic resin (PFSi) by IR, DSC and TG analysis methods. At the curing temperature of tetramaleimide modificated polyphenylmenthylsiloxane phenolic resin(TMI/PFSi), the C C group of TMI was condensed with —CH2OH of PFSi into crosslinking structure, since the heat-resistant property and adhesive strength of PFSi are increased, the toughness is kept, and the storage life is decreased. At room temperature, a small amount of the COOH, and NH2 groups of TMI (because of the steric effection, carboxyl and amino of TMI are not all condensed into imide) are condensed with —CH2OH of PFSi into a small amount of crosslinking structural oligomer, which makes the storage life of TMI/PFSi decrease.
2004, 21(4): 54-57.
Abstract:
The migration phenomena of nano-SiO2 particles in UV cured composite coatings are studied by FTIR-ATR and the factors affecting the distributing gradient of nano-SiO2 particles in coating are discussed by semi-quantitative analysis. The results show that nano-SiO2 particles migrate to the surface of composite coatings. The distributing gradient of nano-SiO2 in the coating is larger when the nano-SiO2 content or its molecular weight or graft ratio or the polarity of host resin is larger.
The migration phenomena of nano-SiO2 particles in UV cured composite coatings are studied by FTIR-ATR and the factors affecting the distributing gradient of nano-SiO2 particles in coating are discussed by semi-quantitative analysis. The results show that nano-SiO2 particles migrate to the surface of composite coatings. The distributing gradient of nano-SiO2 in the coating is larger when the nano-SiO2 content or its molecular weight or graft ratio or the polarity of host resin is larger.
2004, 21(4): 58-61.
Abstract:
A β-ray monitoring system was developed, and the investigation was carried out for continuous on-line monitoring of resin content in carbon fiber/phenolic resin prepreg cloth. The calibration relationship between the values of resin content and the output signals of the β-ray monitoring system was proposed. Moreover, the effects of the steadiness of the β-ray generator and the deviation of carbon fiber cloth on the measurement accuracy were theoretically analyzed. The results show that highly accurate on-line monitoring of resin content can be performed in the continuous manufacture process of the carbon fiber/phenolic prepreg cloth.
A β-ray monitoring system was developed, and the investigation was carried out for continuous on-line monitoring of resin content in carbon fiber/phenolic resin prepreg cloth. The calibration relationship between the values of resin content and the output signals of the β-ray monitoring system was proposed. Moreover, the effects of the steadiness of the β-ray generator and the deviation of carbon fiber cloth on the measurement accuracy were theoretically analyzed. The results show that highly accurate on-line monitoring of resin content can be performed in the continuous manufacture process of the carbon fiber/phenolic prepreg cloth.
2004, 21(4): 62-66.
Abstract:
The surface of ultrahigh molecular weight polyethylene (UHMWPE) fibers was grafted by an acrylamide. Using a horseradish peroxidase (HRP) as catalyst in hydrogen peroxide, the reaction was generated by free radical, which is formed by oxidizing o-methoxyphenol. The best condition of graft polymerization was determined by the orthogonal test. The results of the fiber pull out test show that after enzymatic treatment, the interfacial shear strength of the system surface increased, and the pull out strength of treated UHMWPE fibers increased by 69.8%. Its optimum value appears when the initiator concentration, H2O2 concentration and the reaction time are 0.5%, 0.03%, and 90 min, respectively. Infrared spectroscopy (IR) and Scanning Electron Microscopy (SEM) show that roughness of UHMWPE surface increased, and a new radical appears in IR. The probable catalytic mechanism of HRP was discussed.
The surface of ultrahigh molecular weight polyethylene (UHMWPE) fibers was grafted by an acrylamide. Using a horseradish peroxidase (HRP) as catalyst in hydrogen peroxide, the reaction was generated by free radical, which is formed by oxidizing o-methoxyphenol. The best condition of graft polymerization was determined by the orthogonal test. The results of the fiber pull out test show that after enzymatic treatment, the interfacial shear strength of the system surface increased, and the pull out strength of treated UHMWPE fibers increased by 69.8%. Its optimum value appears when the initiator concentration, H2O2 concentration and the reaction time are 0.5%, 0.03%, and 90 min, respectively. Infrared spectroscopy (IR) and Scanning Electron Microscopy (SEM) show that roughness of UHMWPE surface increased, and a new radical appears in IR. The probable catalytic mechanism of HRP was discussed.
2004, 21(4): 67-70.
Abstract:
Nano-CaCO3/EPR /PP composite was prepared by the two-roll mill and extruder. The mechanical properties of the composite and the dispersion of EPR and Nano-CaCO3 were investigated by means of PCM,TEM and mechanical test. The results show that not only the impact property but also the bending modulus of the system have been evidently increased by adding nano-CaCO3. The toughening mechanism of the nano-CaCO3 is due to the fact that the addition of nano-CaCO3 particles makes the EPR well-distributed and the EPR particle size small, leading to the cooperative toughening by the reaction between the smaller EPR particles and the nano-CaCO3 particles.
Nano-CaCO3/EPR /PP composite was prepared by the two-roll mill and extruder. The mechanical properties of the composite and the dispersion of EPR and Nano-CaCO3 were investigated by means of PCM,TEM and mechanical test. The results show that not only the impact property but also the bending modulus of the system have been evidently increased by adding nano-CaCO3. The toughening mechanism of the nano-CaCO3 is due to the fact that the addition of nano-CaCO3 particles makes the EPR well-distributed and the EPR particle size small, leading to the cooperative toughening by the reaction between the smaller EPR particles and the nano-CaCO3 particles.
2004, 21(4): 71-76.
Abstract:
The experiments were carried out on tensile and compressive properties of the ordinary laminates made of uniweave T300/QY9512. The effects were investigated of stitching directions, layup sequences and environmental factors on tensile and compressive properties. Tensile and compressive strength and modulus were measured for three kinds of un-notched laminates and laminates with a hole. It is shown that stitching and stitching directions have little effect on the strength and modulus of ordinary laminates, and the effects were different on the laminates with different layup sequences. Stitching and layup sequences have influence on stitching effectiveness of laminates with a hole. The best stitching direction is varied with the laminate layup sequence. The effect of stitching on the laminate compressive properties in hygrothermal environment is greatly related to layup sequences. Stitching makes compressive strength of laminates with a hole increase obviously under normal environmental condition, but decrease under hygrothermal environmental condition.
The experiments were carried out on tensile and compressive properties of the ordinary laminates made of uniweave T300/QY9512. The effects were investigated of stitching directions, layup sequences and environmental factors on tensile and compressive properties. Tensile and compressive strength and modulus were measured for three kinds of un-notched laminates and laminates with a hole. It is shown that stitching and stitching directions have little effect on the strength and modulus of ordinary laminates, and the effects were different on the laminates with different layup sequences. Stitching and layup sequences have influence on stitching effectiveness of laminates with a hole. The best stitching direction is varied with the laminate layup sequence. The effect of stitching on the laminate compressive properties in hygrothermal environment is greatly related to layup sequences. Stitching makes compressive strength of laminates with a hole increase obviously under normal environmental condition, but decrease under hygrothermal environmental condition.
2004, 21(4): 77-81.
Abstract:
Nanometer silica particles were added to epoxy resin by the sol-gel method. The mechanical properties such as impact strength, tensile strength and elongation at the break point of the materials were studied at room and cryogenic temperatures. The fracture surfaces were examined by scanning electron microscopy (SEM). The ashes of the composites were collected after burning off the nanocomposites and the silica nano-particles were observed by transmission electron microscope (TEM). At room temperature, the tensile strength and elongation at break attain a peak at approximately 2% silica content where the impact strength reaches the maxium. However, at cryogenic temperature, the tensile strength increases with the increasing silica content. DMA analysis reveals that the glass transition temperature and storage modulus are increased.
Nanometer silica particles were added to epoxy resin by the sol-gel method. The mechanical properties such as impact strength, tensile strength and elongation at the break point of the materials were studied at room and cryogenic temperatures. The fracture surfaces were examined by scanning electron microscopy (SEM). The ashes of the composites were collected after burning off the nanocomposites and the silica nano-particles were observed by transmission electron microscope (TEM). At room temperature, the tensile strength and elongation at break attain a peak at approximately 2% silica content where the impact strength reaches the maxium. However, at cryogenic temperature, the tensile strength increases with the increasing silica content. DMA analysis reveals that the glass transition temperature and storage modulus are increased.
2004, 21(4): 82-86.
Abstract:
The effects of polytetrafluoroethylene (PTFE) -based composites filled with nanosized SiO2 and micronsized SiO2 on friction and wear properties were investigated. The friction coefficient, wear rate and crystallinity were measured. The friction surface was observed by scanning electron microscopy (SEM). The results show that the addition of the silica micron-particles or nano-particles and surface treatment not only increases the friction coefficient of PTFE-based composites, but also results in largely decreasing the wear rate of SiO2/PTFE composites. When the filler mass fraction is lower than 6%, the wear rate of the SiO2/PTFE composites filled with untreated nanosized SiO2 falls 98.5%, while the wear rate trends to be stable after the filler mass fraction is higher than 6%. However, adding 6% of nanosized SiO2, the friction coefficient of SiO2/PTFE composites is only elevated from 0.1 of the pure PTFE to 0.12. The friction coefficient of SiO2/PTFE composites filled with nanosized SiO2 treated by coupling agent is improved to the smallest elevation.
The effects of polytetrafluoroethylene (PTFE) -based composites filled with nanosized SiO2 and micronsized SiO2 on friction and wear properties were investigated. The friction coefficient, wear rate and crystallinity were measured. The friction surface was observed by scanning electron microscopy (SEM). The results show that the addition of the silica micron-particles or nano-particles and surface treatment not only increases the friction coefficient of PTFE-based composites, but also results in largely decreasing the wear rate of SiO2/PTFE composites. When the filler mass fraction is lower than 6%, the wear rate of the SiO2/PTFE composites filled with untreated nanosized SiO2 falls 98.5%, while the wear rate trends to be stable after the filler mass fraction is higher than 6%. However, adding 6% of nanosized SiO2, the friction coefficient of SiO2/PTFE composites is only elevated from 0.1 of the pure PTFE to 0.12. The friction coefficient of SiO2/PTFE composites filled with nanosized SiO2 treated by coupling agent is improved to the smallest elevation.
2004, 21(4): 87-91.
Abstract:
In-situ TiB2 particles reinforced ZA27 composites were produced by two steps. As beginning, the reaction of creating TiB2 was processed in melting Al. After that, the second step, as a master alloy, TiB2/Al material was used to fabricate TiB2/ZA27 composites. It is found that the TiB2 particles whose size is less than 3 μm distribute in ZA27 matrix uniformly and the shape of them is equiaxed. The test results show that the tensile strength and hardness of the composites are enhanced observably following the refinement of matrix grain with the increase of TiB2 particles. For example, the tensile strength of the 2.1%TiB2/ZA27 composite is as high as 472 MPa when the hardness is 126 HB. The thermal expansion coefficient of 2.1%TiB2/ZA27 decreases compared with that of ZA27 alloy while the elastic modulus increases. At the same time, the ductility of the composites has not deteriorated and the elongation is also raised slightly.
In-situ TiB2 particles reinforced ZA27 composites were produced by two steps. As beginning, the reaction of creating TiB2 was processed in melting Al. After that, the second step, as a master alloy, TiB2/Al material was used to fabricate TiB2/ZA27 composites. It is found that the TiB2 particles whose size is less than 3 μm distribute in ZA27 matrix uniformly and the shape of them is equiaxed. The test results show that the tensile strength and hardness of the composites are enhanced observably following the refinement of matrix grain with the increase of TiB2 particles. For example, the tensile strength of the 2.1%TiB2/ZA27 composite is as high as 472 MPa when the hardness is 126 HB. The thermal expansion coefficient of 2.1%TiB2/ZA27 decreases compared with that of ZA27 alloy while the elastic modulus increases. At the same time, the ductility of the composites has not deteriorated and the elongation is also raised slightly.
2004, 21(4): 92-98.
Abstract:
A 15%SiCp/2009Al composite was fabricated by high energy milling powder metallurgy (PM) technique. The effect of velocity and time of milling as well as PM procedure on mechanical properties of the composite was investigated. The results indicate that three procedure factors are important for properties of the composite. Long duration at high speed of milling contributes to a uniform distribution of SiC particles. Compression at high temperature and vacuum can improve bonding among powder and particle, and lead to high properties. The milled powder fabricated at velocity of 190 r/min and 6 h was compacted and extruded into the composite with uniform distribution of SiC particles, and with 650 MPa of tensile strength and exceeded 5% of elongation.
A 15%SiCp/2009Al composite was fabricated by high energy milling powder metallurgy (PM) technique. The effect of velocity and time of milling as well as PM procedure on mechanical properties of the composite was investigated. The results indicate that three procedure factors are important for properties of the composite. Long duration at high speed of milling contributes to a uniform distribution of SiC particles. Compression at high temperature and vacuum can improve bonding among powder and particle, and lead to high properties. The milled powder fabricated at velocity of 190 r/min and 6 h was compacted and extruded into the composite with uniform distribution of SiC particles, and with 650 MPa of tensile strength and exceeded 5% of elongation.
2004, 21(4): 99-103.
Abstract:
Alumina and carbon short fibers reinforced Al-12Si aluminum alloy hybrid composites were fabricated by squeeze casting.The tensile test and theoretical analysis of high temperature(300℃)tensile strength of the hybrid composites were carried out.The rule-of-mixture(ROM)of tensile strength of the composites was developed and modified based on the foundation of comprehensive factors,including the change regularities of fiber-length,dislocation-strengthening resulting from residual stress and dispersion-strengthening of fibers.A new model was established for prediction of high temperature tensile strength of alumina and carbon short fibers random-orientation reinforced Al-12Si metal matrix hybrid composites.The theoretical results based on the new modified model agree well with the experimental results.The model established in this paper was proved to possess validity and practicality to a certain degree.
Alumina and carbon short fibers reinforced Al-12Si aluminum alloy hybrid composites were fabricated by squeeze casting.The tensile test and theoretical analysis of high temperature(300℃)tensile strength of the hybrid composites were carried out.The rule-of-mixture(ROM)of tensile strength of the composites was developed and modified based on the foundation of comprehensive factors,including the change regularities of fiber-length,dislocation-strengthening resulting from residual stress and dispersion-strengthening of fibers.A new model was established for prediction of high temperature tensile strength of alumina and carbon short fibers random-orientation reinforced Al-12Si metal matrix hybrid composites.The theoretical results based on the new modified model agree well with the experimental results.The model established in this paper was proved to possess validity and practicality to a certain degree.
2004, 21(4): 104-109.
Abstract:
The thermal shock resistance of ZrO2(3Y) and ZrO2(3Y)/Fe3Al composite was studied using indentation-quench technique. The results show that the pattern of crack growth is similar for the two materials. Low crack growth in a stable manner happened when ΔT<ΔTU, and cracks grew unstably when ΔT>ΔTU. The ΔTU of ZrO2(3Y)/Fe3Al composite is higher than that of ZrO2(3Y), indicating the improved thermal shock resistance. The higher fracture toughness and thermal conductivity and lower elastic modulus and Poisson's ratio of ZrO2(3Y)/Fe3Al composite compared with monolith ZrO2 are the main reasons for the elevated ΔTU value of ZrO2(3Y)/Fe3Al composites.
The thermal shock resistance of ZrO2(3Y) and ZrO2(3Y)/Fe3Al composite was studied using indentation-quench technique. The results show that the pattern of crack growth is similar for the two materials. Low crack growth in a stable manner happened when ΔT<ΔTU, and cracks grew unstably when ΔT>ΔTU. The ΔTU of ZrO2(3Y)/Fe3Al composite is higher than that of ZrO2(3Y), indicating the improved thermal shock resistance. The higher fracture toughness and thermal conductivity and lower elastic modulus and Poisson's ratio of ZrO2(3Y)/Fe3Al composite compared with monolith ZrO2 are the main reasons for the elevated ΔTU value of ZrO2(3Y)/Fe3Al composites.
2004, 21(4): 110-113.
Abstract:
The expert system based on artificial neural network was used, and the constitutive equation of PRMMCs was built. After training the network with experimental data which was investigated by the application of a thermecmasor simulator for hot working, it can correctly predict the relationship between process parameters and flow stress. The deviation of the analytical results from the experimental data is less than 10%.
The expert system based on artificial neural network was used, and the constitutive equation of PRMMCs was built. After training the network with experimental data which was investigated by the application of a thermecmasor simulator for hot working, it can correctly predict the relationship between process parameters and flow stress. The deviation of the analytical results from the experimental data is less than 10%.
2004, 21(4): 114-117.
Abstract:
Al2O3/W and Al2O3/Ni nano-composite powders, with mean particle sizes less than 50 nm, were prepared by the heterogeneous precipitation process using Al(NO3)3·9H2O and (NH4)2CO3 solutions as raw materials and tungsten and nickel nanometer powders as additive in different volume fractions (5%,10%). The α-Al2O3/W(Ni) nano-composite was obtained by calcining Al(OH)3/W(Ni) dried gel at 1000(1150)℃ for an hour in vacuum. Adding tungsten or nickel nanometer powder can both reduce the phase transformation temperature to alpha alumina, which is lower by adding tungsten than that by adding nickel. The more secondary nanometer phase is, the lower the phase transformation temperature to alpha alumina will be. The composite powder is simply mechanically mixed together, because no new phases were observed, which is different from alumina and tungsten or nickel.
Al2O3/W and Al2O3/Ni nano-composite powders, with mean particle sizes less than 50 nm, were prepared by the heterogeneous precipitation process using Al(NO3)3·9H2O and (NH4)2CO3 solutions as raw materials and tungsten and nickel nanometer powders as additive in different volume fractions (5%,10%). The α-Al2O3/W(Ni) nano-composite was obtained by calcining Al(OH)3/W(Ni) dried gel at 1000(1150)℃ for an hour in vacuum. Adding tungsten or nickel nanometer powder can both reduce the phase transformation temperature to alpha alumina, which is lower by adding tungsten than that by adding nickel. The more secondary nanometer phase is, the lower the phase transformation temperature to alpha alumina will be. The composite powder is simply mechanically mixed together, because no new phases were observed, which is different from alumina and tungsten or nickel.
2004, 21(4): 118-123.
Abstract:
Aluminum-based composites reinforced with in-situ Al2O3, TiB2 and Al3Ti particles were prepared through reactive hot pressing from Al, B2O3 and TiO2 powders and Al, B and TiO2 powders. There is fine Al3Ti precipitation in composite fabricated by Al, B, TiO2 powders. The low cycle fatigue behavior of in-situ composites was investigated under total strain-controlled conditions at the room temperature. The composite free of precipitation Al3Ti phase exhibits a stable cyclic response at lower total strain amplitudes. The cyclic hardening in the first cycle followed by cyclic softening occurs in the composite free of precipitation at higher total strain amplitudes.The composite containing Al3Ti phase exhibits a stable cyclic response at all amplitudes adopted in the study. The sets of crack initiation are broken Al3Ti phase, the debonded interface between Al3Ti phase and matrix, and microcracks in the matrix. The cracks propagate through the matrix, passing by Al2O3 and TiB2 particles. The fatigue life of two composites can be described by the Coffin-Manson relationship.
Aluminum-based composites reinforced with in-situ Al2O3, TiB2 and Al3Ti particles were prepared through reactive hot pressing from Al, B2O3 and TiO2 powders and Al, B and TiO2 powders. There is fine Al3Ti precipitation in composite fabricated by Al, B, TiO2 powders. The low cycle fatigue behavior of in-situ composites was investigated under total strain-controlled conditions at the room temperature. The composite free of precipitation Al3Ti phase exhibits a stable cyclic response at lower total strain amplitudes. The cyclic hardening in the first cycle followed by cyclic softening occurs in the composite free of precipitation at higher total strain amplitudes.The composite containing Al3Ti phase exhibits a stable cyclic response at all amplitudes adopted in the study. The sets of crack initiation are broken Al3Ti phase, the debonded interface between Al3Ti phase and matrix, and microcracks in the matrix. The cracks propagate through the matrix, passing by Al2O3 and TiB2 particles. The fatigue life of two composites can be described by the Coffin-Manson relationship.
2004, 21(4): 124-128.
Abstract:
3D C/SiC composites with PyC interlayer were fabricated by low pressure chemical vapor infiltration(LPCVI). The different expansion behavior of the composites was qualitatively analyzed before and after different heat treatments. The results show that the expansion behavior of 3D C/SiC composites, which was affected by interfacial thermal stress, can be regarded as the result of interaction of fibers and matrix. The thermal expansion behavior of the composites is changed after heat treatment due to the increase of thermal stability and the change of thermal stress and microstructure of the materials. The coefficient of thermal expansion (CTE) of the composites is decreased by the increase of matrix cracks at low temperatures and changed by the redistribution of thermal stress at high temperatures. However, the matrix cracks sealing temperature was not changed by heat treatment.
3D C/SiC composites with PyC interlayer were fabricated by low pressure chemical vapor infiltration(LPCVI). The different expansion behavior of the composites was qualitatively analyzed before and after different heat treatments. The results show that the expansion behavior of 3D C/SiC composites, which was affected by interfacial thermal stress, can be regarded as the result of interaction of fibers and matrix. The thermal expansion behavior of the composites is changed after heat treatment due to the increase of thermal stability and the change of thermal stress and microstructure of the materials. The coefficient of thermal expansion (CTE) of the composites is decreased by the increase of matrix cracks at low temperatures and changed by the redistribution of thermal stress at high temperatures. However, the matrix cracks sealing temperature was not changed by heat treatment.
2004, 21(4): 129-133.
Abstract:
The sintering mechanism was investigated for (SiC, TiB2)/B4C matrix composites fabricated under hot pressing conditions. It is believed that the sintering mechanism is liquid phase sintering caused by the addition of the sintering additive in this research system. The micro particles in the powders in the system worked out a significant contribution to the sintering compaction of the composites. And the phase composition, microstructure, and mechanical properties of the composites were measured and analyzed. The results show that SiC, TiB2 and a bit of BN are produced by sintering reaction at sintering temperature 1800~1880℃, pressure 30 MPa with original powders B4C, Si3N4, a little of SiC and TiC and the sintering additive of (Al2O3 +Y2O3). The microstructure of the crystal formed in the system is sandwich. The hardness, bending strength and fracture toughness of the fabricated samples are HRA88.6, 540 MPa and 5.6 MPa·m1/2, respectively.
The sintering mechanism was investigated for (SiC, TiB2)/B4C matrix composites fabricated under hot pressing conditions. It is believed that the sintering mechanism is liquid phase sintering caused by the addition of the sintering additive in this research system. The micro particles in the powders in the system worked out a significant contribution to the sintering compaction of the composites. And the phase composition, microstructure, and mechanical properties of the composites were measured and analyzed. The results show that SiC, TiB2 and a bit of BN are produced by sintering reaction at sintering temperature 1800~1880℃, pressure 30 MPa with original powders B4C, Si3N4, a little of SiC and TiC and the sintering additive of (Al2O3 +Y2O3). The microstructure of the crystal formed in the system is sandwich. The hardness, bending strength and fracture toughness of the fabricated samples are HRA88.6, 540 MPa and 5.6 MPa·m1/2, respectively.
2004, 21(4): 134-139.
Abstract:
The mechanical modeling is established for the 3-D braided composite structures with embedded optical fiber sensors, the braiding process technique and trend of the fibers are introduced first of all, the interior cell model containing optical fiber section of the braided composite structure and the geometry relationship between the optical fiber and the fiber bundles or interior cells subsequently are setup,also a construction of the stress-strain relationship and state formula with the multi finite element variation method are presented. The consistency between the rational simulation and the test results systematically verifies the feasibility of optical fiber braided in the 3-D braided composites so as to improve detecting method effectiveness on dealing with the internal parameters.
The mechanical modeling is established for the 3-D braided composite structures with embedded optical fiber sensors, the braiding process technique and trend of the fibers are introduced first of all, the interior cell model containing optical fiber section of the braided composite structure and the geometry relationship between the optical fiber and the fiber bundles or interior cells subsequently are setup,also a construction of the stress-strain relationship and state formula with the multi finite element variation method are presented. The consistency between the rational simulation and the test results systematically verifies the feasibility of optical fiber braided in the 3-D braided composites so as to improve detecting method effectiveness on dealing with the internal parameters.
2004, 21(4): 140-145.
Abstract:
The interfacial damage of fiber-reinforced composite under two-stage tension fatigue loading is studied. Based on the shear-lag model, the governing equations of the problem are established and the related solution is obtained. By the aid of the Paris law and the energy release theory, the relationship between debond rate and debond force is established. As an example, the interfacial debonding is simulated under the two-stage tension fatigue loading. The rules of the crack growth are analyzed for several kinds of two-stage loadings. The effect of Poisson's contraction on interfacial debonding is studied also. The present study is helpful for analyzing the damage of engineering materials and structures under fatigue loading.
The interfacial damage of fiber-reinforced composite under two-stage tension fatigue loading is studied. Based on the shear-lag model, the governing equations of the problem are established and the related solution is obtained. By the aid of the Paris law and the energy release theory, the relationship between debond rate and debond force is established. As an example, the interfacial debonding is simulated under the two-stage tension fatigue loading. The rules of the crack growth are analyzed for several kinds of two-stage loadings. The effect of Poisson's contraction on interfacial debonding is studied also. The present study is helpful for analyzing the damage of engineering materials and structures under fatigue loading.
2004, 21(4): 146-151.
Abstract:
The cure kinetic of HD03 epoxy resin system was analyzed using isothermal DSC. A series of isothermal DSC curves provided information about the kinetics of cure in the limited temperatures. From the experimental data, it was found that the autocatalytic cure kinetic modeling correctly represented the cure kinetics of this system. All kinetic parameters of this epoxy resin system were calculated. In the latter cure stage, the cure reaction shifted from chemical reaction controlled to diffusion controlled. A defined numerical chemoviscosity model of epoxy resin, which was based on the absolute reaction rate theory, was given. Isothermal chemoviscosity of HD03 epoxy resin at some high temperatures and dynamic chemoviscosity at variant heating rate were measured by MCR 300 rheometer. The experimental data were analyzed and calculated. The model predicted results were compared with the experimental measurements, and it was found that the model predictions agreed well with the experimental observations.
The cure kinetic of HD03 epoxy resin system was analyzed using isothermal DSC. A series of isothermal DSC curves provided information about the kinetics of cure in the limited temperatures. From the experimental data, it was found that the autocatalytic cure kinetic modeling correctly represented the cure kinetics of this system. All kinetic parameters of this epoxy resin system were calculated. In the latter cure stage, the cure reaction shifted from chemical reaction controlled to diffusion controlled. A defined numerical chemoviscosity model of epoxy resin, which was based on the absolute reaction rate theory, was given. Isothermal chemoviscosity of HD03 epoxy resin at some high temperatures and dynamic chemoviscosity at variant heating rate were measured by MCR 300 rheometer. The experimental data were analyzed and calculated. The model predicted results were compared with the experimental measurements, and it was found that the model predictions agreed well with the experimental observations.
2004, 21(4): 152-156.
Abstract:
An analysis model based on the microstructure and the stiffness averaging method is established to predict the elastic constants of 2-D braided composites. The computer software based on the model of the 2-D biaxial braided composite was compiled. The elastic performances of braided composites were studied, and many useful results that can be used in structures designing were obtained. The effects of braiding structure parameters on the elastic properties of composites were also analyzed. Comparing the relevant predictions with the experimental results validates the model presented. The comparison shows that there is good agreement for the elastic properties and it can be used in the engineering design.
An analysis model based on the microstructure and the stiffness averaging method is established to predict the elastic constants of 2-D braided composites. The computer software based on the model of the 2-D biaxial braided composite was compiled. The elastic performances of braided composites were studied, and many useful results that can be used in structures designing were obtained. The effects of braiding structure parameters on the elastic properties of composites were also analyzed. Comparing the relevant predictions with the experimental results validates the model presented. The comparison shows that there is good agreement for the elastic properties and it can be used in the engineering design.
2004, 21(4): 157-161.
Abstract:
Based on the hypothesis of plane stress, a method is proposed for calculating the centrifugal stress and initial ultimate rotating speed of the multi-ring intermixing composite flywheel. 2D axisymmetric FEM is used to verify the effectiveness of this method. It can provide the reference for the elementary design of the multi-ring intermixing composite flywheel. The results also show that the initial ultimate rotating speed and energy-storage density of a hollow structural flywheel are both higher than of the solid structural flywheel of whether a single material or an intermixing material. As to hollow structures, it can realize an equal-strength design through the selection of a suitable material sequence.
Based on the hypothesis of plane stress, a method is proposed for calculating the centrifugal stress and initial ultimate rotating speed of the multi-ring intermixing composite flywheel. 2D axisymmetric FEM is used to verify the effectiveness of this method. It can provide the reference for the elementary design of the multi-ring intermixing composite flywheel. The results also show that the initial ultimate rotating speed and energy-storage density of a hollow structural flywheel are both higher than of the solid structural flywheel of whether a single material or an intermixing material. As to hollow structures, it can realize an equal-strength design through the selection of a suitable material sequence.
2004, 21(4): 162-166.
Abstract:
Fiber-bridging effect has significant influnce on the crack growth of fiber reinforced matrix composites.A first crossing diffusive process stochastic model of fiber-bridging fatigue crack growth was established on account of statistical characteristics of related data of the fiber-bridging fatigue crack.First,based on Paris law,the material inhomogeneity and loads randomicity were considered,the fiber-bridging fatigue crack growth process was assumed to be a diffusive Markov process and the stochastic averaging method was employed to establish the FPK equation with the transition probability function satisfied.Second,the differential equation,of which the kth order conditional moment of the first crossing fatigue crack growth time is satisfied, was established and the kth order conditional moment was solved.From the numerical results,the established stochastic model is comparatively effective for simulating the fiber-bridging effect.
Fiber-bridging effect has significant influnce on the crack growth of fiber reinforced matrix composites.A first crossing diffusive process stochastic model of fiber-bridging fatigue crack growth was established on account of statistical characteristics of related data of the fiber-bridging fatigue crack.First,based on Paris law,the material inhomogeneity and loads randomicity were considered,the fiber-bridging fatigue crack growth process was assumed to be a diffusive Markov process and the stochastic averaging method was employed to establish the FPK equation with the transition probability function satisfied.Second,the differential equation,of which the kth order conditional moment of the first crossing fatigue crack growth time is satisfied, was established and the kth order conditional moment was solved.From the numerical results,the established stochastic model is comparatively effective for simulating the fiber-bridging effect.
