1989 Vol. 6, No. 3
1989, 6(3): 1-Ⅰ.
Abstract:
The moisture diffusion characteristics of high density polyethylene (HDPE) filled with mica which had been tseated by ethylene plasma of radio frequency were studied through the boiling water immersion experiment.It has been found that the equilibrium moisture.content of filled HDPE increases linearly with the volume fraction of mica,and that the proportional constant is smaller and the data dispersivity naccowed if HDPE was filled with,the treated mica;the larger the mica content is the higher the moisture diffusion verocity,and when the mica content is the same,lower diffusion velocity is found in HDPE filled with plasma treated mica.These are explained by the structure charge of mica/HDPE interface resulted from the plasma treatureat.
The moisture diffusion characteristics of high density polyethylene (HDPE) filled with mica which had been tseated by ethylene plasma of radio frequency were studied through the boiling water immersion experiment.It has been found that the equilibrium moisture.content of filled HDPE increases linearly with the volume fraction of mica,and that the proportional constant is smaller and the data dispersivity naccowed if HDPE was filled with,the treated mica;the larger the mica content is the higher the moisture diffusion verocity,and when the mica content is the same,lower diffusion velocity is found in HDPE filled with plasma treated mica.These are explained by the structure charge of mica/HDPE interface resulted from the plasma treatureat.
1989, 6(3): 5-Ⅱ.
Abstract:
This pager studies on the effect of surface treatment on the wettability of fibers by the dynamic method of wickiag.The results show that the wettability has got a great improvement after the fiber surface is treated by cold plasma.That is because oxygen-containing groups (-COOH,=C-OH and =C=O).are introduced onto the surface.At the same time,the contact angle of fiber/water has been calculated by messuring the difference of surface free energy (Δr) during the wetting process,which is close to the results obtained by using contact angle meter with tilting plate method.After the treatment,it can be seen from the measurement of contact angles that the wettability has been improved,For instance,the eontact angle of carbon fibers/water has been decreased from 17°to 83°and polyester fibers/water from 77°to 52°after they are treated by cold plasma oxygen.Besides,the wettability of water to coal powder system and to glass powder system are studied.It is found that the ettabilty of water/glass powder is better than that of water/coal powder,The wetting contact angle of the former is 47°and the later is 90°.These values of contact angle are also correspondent to those between water and flakes,which are measured by the use of contact angle meter in sessile drop method,From those aforementioned,it's clear that the dynamic method of wicking can be used to measure the wettability of fibers and powder systems,while its operation is easy and only takes a short period.
This pager studies on the effect of surface treatment on the wettability of fibers by the dynamic method of wickiag.The results show that the wettability has got a great improvement after the fiber surface is treated by cold plasma.That is because oxygen-containing groups (-COOH,=C-OH and =C=O).are introduced onto the surface.At the same time,the contact angle of fiber/water has been calculated by messuring the difference of surface free energy (Δr) during the wetting process,which is close to the results obtained by using contact angle meter with tilting plate method.After the treatment,it can be seen from the measurement of contact angles that the wettability has been improved,For instance,the eontact angle of carbon fibers/water has been decreased from 17°to 83°and polyester fibers/water from 77°to 52°after they are treated by cold plasma oxygen.Besides,the wettability of water to coal powder system and to glass powder system are studied.It is found that the ettabilty of water/glass powder is better than that of water/coal powder,The wetting contact angle of the former is 47°and the later is 90°.These values of contact angle are also correspondent to those between water and flakes,which are measured by the use of contact angle meter in sessile drop method,From those aforementioned,it's clear that the dynamic method of wicking can be used to measure the wettability of fibers and powder systems,while its operation is easy and only takes a short period.
1989, 6(3): 11-Ⅲ.
Abstract:
In this paper,we wi11 describe PA spectrum of carbon fiber and its composite materials for example,PAN,GF-PPS,CF-PEEK,CF-epoxy resin etc,by STIR-PAS technique.We make some experiments for SAN for fiber with different oxidation degree and find that the intensity of C-H staectching band at 2920 cm-1 and C≡N stiectchiag liarid at 2250 cm-1 decreases as the degree of oxidation of preoxidized PAN fiber increases.Experimental resuIfs shown good agreement with elenentary analysis.We also study PA spectrum of CF-epoxy resins before and after oxidation and find satisfaction in the results of study.
In this paper,we wi11 describe PA spectrum of carbon fiber and its composite materials for example,PAN,GF-PPS,CF-PEEK,CF-epoxy resin etc,by STIR-PAS technique.We make some experiments for SAN for fiber with different oxidation degree and find that the intensity of C-H staectching band at 2920 cm-1 and C≡N stiectchiag liarid at 2250 cm-1 decreases as the degree of oxidation of preoxidized PAN fiber increases.Experimental resuIfs shown good agreement with elenentary analysis.We also study PA spectrum of CF-epoxy resins before and after oxidation and find satisfaction in the results of study.
1989, 6(3): 16-Ⅳ.
Abstract:
A new inodified bismalcimide resin,designated LL-45-1,was obtained by hot melting two different kinds of bismaleimide,one is a commerial product,4,4 bismaleimidediphenylmethane,the other is a substituted bisma-leimide,LL-45-1 resin has a low melting point (about 55℃),which is far below the polymerization temperature,though it maintains the heat resistance of polybismaleimide(decomposition temperature>400℃).Hence it is a heat resistant resin of better property.The composite made from LL-45-1 resin exhibits high strength at 250℃ as well as good thermamoisture stability.It shows that LL-45-1 resin is a hopeful matrix resin candidate for high temperature composites.
A new inodified bismalcimide resin,designated LL-45-1,was obtained by hot melting two different kinds of bismaleimide,one is a commerial product,4,4 bismaleimidediphenylmethane,the other is a substituted bisma-leimide,LL-45-1 resin has a low melting point (about 55℃),which is far below the polymerization temperature,though it maintains the heat resistance of polybismaleimide(decomposition temperature>400℃).Hence it is a heat resistant resin of better property.The composite made from LL-45-1 resin exhibits high strength at 250℃ as well as good thermamoisture stability.It shows that LL-45-1 resin is a hopeful matrix resin candidate for high temperature composites.
1989, 6(3): 20-Ⅳ.
Abstract:
Particle reinforced Al-Al2O3 composite was made through pressure infiltrating and extruding techniques,the diameters of particles are in the range of 0.15μm to 3,0μm and the particle content is about 30-40%.The structure,fracture feature,strength,hardness and interstice fraction of the composite were examined.We find that the dependence of the logarthmic hardaess on temperature T meets the case of a relaticn of brokctt curve suggested by Goto et al.The turning point of the broken curve,would shift to high temperature if the amount of the reinforcing particles are increased.The fracture is dimple-like.The size of the dimple depends on the size and the amount of the particles,and it also depends on the tension temperature,The strength of this composite is very sensitive to the topology of the particle surface.Based on the phenomeona observed in experiments a fracture mechanism and a possible strengthening way for Al-A12O composite are suggested.
Particle reinforced Al-Al2O3 composite was made through pressure infiltrating and extruding techniques,the diameters of particles are in the range of 0.15μm to 3,0μm and the particle content is about 30-40%.The structure,fracture feature,strength,hardness and interstice fraction of the composite were examined.We find that the dependence of the logarthmic hardaess on temperature T meets the case of a relaticn of brokctt curve suggested by Goto et al.The turning point of the broken curve,would shift to high temperature if the amount of the reinforcing particles are increased.The fracture is dimple-like.The size of the dimple depends on the size and the amount of the particles,and it also depends on the tension temperature,The strength of this composite is very sensitive to the topology of the particle surface.Based on the phenomeona observed in experiments a fracture mechanism and a possible strengthening way for Al-A12O composite are suggested.
1989, 6(3): 28-Ⅴ.
Abstract:
The interface in SiCw/Al composites was examined.The Auger electron spectroscope (AES) analysis of the fracture surface after the surface being sputter etched show that the bonding between SiC whisker and aluminium matrix is quite good.It was found by using transmit electron microscopy (TEM) and X-ray diffraction analysis that there is no reaction layer at the SiC-Al interface.Analyzagg results show that no Si and C can diffuse into the matrix and no Al can diffuse into the whisker either,which was further proved by the X-ray diffraction measuring results.The experimental results also show that there may be certain orientation relationships between the SiC whisker and the nearby matrix.
The interface in SiCw/Al composites was examined.The Auger electron spectroscope (AES) analysis of the fracture surface after the surface being sputter etched show that the bonding between SiC whisker and aluminium matrix is quite good.It was found by using transmit electron microscopy (TEM) and X-ray diffraction analysis that there is no reaction layer at the SiC-Al interface.Analyzagg results show that no Si and C can diffuse into the matrix and no Al can diffuse into the whisker either,which was further proved by the X-ray diffraction measuring results.The experimental results also show that there may be certain orientation relationships between the SiC whisker and the nearby matrix.
1989, 6(3): 28-Ⅵ.
Abstract:
The present paper is concerned with the application of boundary element method to plane orthotropic elasticity.In this paper,some basic problems of BENI for plane orthotropic clasticity,such as the gencral fundamental solutions,C-matrix,Gii-matrix and the expression of stresses at any internal point,are systematically studisd,Based upon this theory,the formulae of constant boundary element and linear boundary element are established.Finally,to illustrate the correctness and the accuracy of the theory and method mentioned above,the stresses in the orthotropic plates with a hole are calculated.It is found that the results are very consistent with the analytical solutions.
The present paper is concerned with the application of boundary element method to plane orthotropic elasticity.In this paper,some basic problems of BENI for plane orthotropic clasticity,such as the gencral fundamental solutions,C-matrix,Gii-matrix and the expression of stresses at any internal point,are systematically studisd,Based upon this theory,the formulae of constant boundary element and linear boundary element are established.Finally,to illustrate the correctness and the accuracy of the theory and method mentioned above,the stresses in the orthotropic plates with a hole are calculated.It is found that the results are very consistent with the analytical solutions.
1989, 6(3): 32-Ⅵ.
Abstract:
In this paper,the adoptable ranges of process parameters,the coupled zone,the structure and properties of eutectic and hypereutectic Al-Si alloys (A1-12.7-16.6wt,%Si) have been investigated by a new type of continuous directional solidification (CDS) apparatus.It's shown that the long casting with shining surfaece,homogeneous composition and structure can be produced within the adoptable ranges of process,and short-fine fibrous in situ composites of Al-Si eutectic and hyper-eutectic alloys can be made in some range of freezing rate depending on the silicon content by CDS technology,The flake/fibre transition of the eutectic silicon appears with increasing freezing rates from 0.02 mm/s to 2.0 mm/s,The tensile strength and percentage clongation increase with the increase of freezing rate.Corripared with cast state Al-Si eutectic alloys,the strength of continuously directionally solidified Al-Si eutectic alloys inceases by 60%,its percentage elongation inereases by two times,from 4% to 12%.The formation mechanism of the fibre structure and the effect of eutectic silicon morphology on the cracking mechanism of Al-Si in situ composites have been analysed.
In this paper,the adoptable ranges of process parameters,the coupled zone,the structure and properties of eutectic and hypereutectic Al-Si alloys (A1-12.7-16.6wt,%Si) have been investigated by a new type of continuous directional solidification (CDS) apparatus.It's shown that the long casting with shining surfaece,homogeneous composition and structure can be produced within the adoptable ranges of process,and short-fine fibrous in situ composites of Al-Si eutectic and hyper-eutectic alloys can be made in some range of freezing rate depending on the silicon content by CDS technology,The flake/fibre transition of the eutectic silicon appears with increasing freezing rates from 0.02 mm/s to 2.0 mm/s,The tensile strength and percentage clongation increase with the increase of freezing rate.Corripared with cast state Al-Si eutectic alloys,the strength of continuously directionally solidified Al-Si eutectic alloys inceases by 60%,its percentage elongation inereases by two times,from 4% to 12%.The formation mechanism of the fibre structure and the effect of eutectic silicon morphology on the cracking mechanism of Al-Si in situ composites have been analysed.
1989, 6(3): 49-Ⅶ.
Abstract:
When a notched 3D carbon carbon specimen is subjected to tension,the failure mode will change with the change of off-axis angle.If the off-axis angle is sufficiently large,the notched specimen will break along the fiber bundle nearest to the notch tip or perpendicular to the fiber bundle depending on which layer was conesrnod,oaly one fiber bundle is sufficient to cause total rupture,catastrophic regardless of the failure modes.Finite element analysis was performed to find the real failure mechanism for the case of tension with large off-axis angle.The analysis leads.to the conclusion that the failure of that case is dominated by the shear strength of the fiber bundle.The shear strengths of fiber bundle and matrix were measured with specially designed setups.Tofind the stressas in the fiber bundle immediately in front of the notch tip,the FEM plane stress analysis was conducted with 3D carbon carbon taken as homogeneous anisotropic material to find the displacements around the notch.With these displacements as boundary condition,the three dimensional FEM analysis of tip stresses were completed with the local region taken as hetarogeneous material.Similar to the average stress criterion,a portion of fiber bundle vas taken as element and the stress at the center of 8-node isoparametric element was used to predict the notched strength of 3D C/C.Assuming the probability of at least one breakage of fiber bundles is egual to the failure probability of whole 3D C/C,Zweben's statistical strength criterion was employed to predict the strength.To compare with the experimental results,26 straight specimens were tested.The comparison justifies the modelling used in this paper.
When a notched 3D carbon carbon specimen is subjected to tension,the failure mode will change with the change of off-axis angle.If the off-axis angle is sufficiently large,the notched specimen will break along the fiber bundle nearest to the notch tip or perpendicular to the fiber bundle depending on which layer was conesrnod,oaly one fiber bundle is sufficient to cause total rupture,catastrophic regardless of the failure modes.Finite element analysis was performed to find the real failure mechanism for the case of tension with large off-axis angle.The analysis leads.to the conclusion that the failure of that case is dominated by the shear strength of the fiber bundle.The shear strengths of fiber bundle and matrix were measured with specially designed setups.Tofind the stressas in the fiber bundle immediately in front of the notch tip,the FEM plane stress analysis was conducted with 3D carbon carbon taken as homogeneous anisotropic material to find the displacements around the notch.With these displacements as boundary condition,the three dimensional FEM analysis of tip stresses were completed with the local region taken as hetarogeneous material.Similar to the average stress criterion,a portion of fiber bundle vas taken as element and the stress at the center of 8-node isoparametric element was used to predict the notched strength of 3D C/C.Assuming the probability of at least one breakage of fiber bundles is egual to the failure probability of whole 3D C/C,Zweben's statistical strength criterion was employed to predict the strength.To compare with the experimental results,26 straight specimens were tested.The comparison justifies the modelling used in this paper.
1989, 6(3): 55-Ⅶ.
Abstract:
First of all,the development of inherent damage near notch tip in 3D carbon carbon was examined with polariscopic microsocpe while loading.The notch tip was tracked with a specially designed adjustable stand and loading appratus during testing.Bascd on the obserction,a very simple analytical model was cstablished.In order to use micromcchanics to prediet the notched strength,the strength of in-situ fiber bundle was measured with a specially dcsigncd fixture.The strength of 3D carbon carbon is dominated by the longitudinal strength of the portion of fiber bundle,where the stress concentration takes place.Hedgepeth's stress concentration factor for infinite plate is corrected for finite plate.Calculation of stress concentration factors of fiber bundles near notch tip also shows that failure of a single fiber bundle will cause total rupture of the spacimen.With Zweben's statistical strength criterion,the strength of the notched 3D carbon carbon was predicted and the prediction agrees with experimental results quite well.
First of all,the development of inherent damage near notch tip in 3D carbon carbon was examined with polariscopic microsocpe while loading.The notch tip was tracked with a specially designed adjustable stand and loading appratus during testing.Bascd on the obserction,a very simple analytical model was cstablished.In order to use micromcchanics to prediet the notched strength,the strength of in-situ fiber bundle was measured with a specially dcsigncd fixture.The strength of 3D carbon carbon is dominated by the longitudinal strength of the portion of fiber bundle,where the stress concentration takes place.Hedgepeth's stress concentration factor for infinite plate is corrected for finite plate.Calculation of stress concentration factors of fiber bundles near notch tip also shows that failure of a single fiber bundle will cause total rupture of the spacimen.With Zweben's statistical strength criterion,the strength of the notched 3D carbon carbon was predicted and the prediction agrees with experimental results quite well.
1989, 6(3): 64-Ⅸ.
Abstract:
It is well known that experimental methods of stress analysis are of great use for studying composite materials and structure,and optical methods have the advantage of yielding full-field quantitative results.In this papar.the application of transmission photoelastic techniques to the study of composite specimens and the survey of historical developments of photoorthotropic elasticity for composites are mainly introduced during the last two decades,The fabrication of the model materials and photoelastic calibration for determining the three independent photoelasic constants in many countries are mentioned in detail and a summary of the early prgresses about birefringant orthotropic model materials in China are presented.Then,the basic principles governing the photoelastic response in birefringent orthotropic compos are briefly reviewed.The contents of various stress-optic law and strainoptic law are discussed and compared with each other.Seven methods of separating the principal stresses in birefringent composite models are proposed.Finally,the advantages and problems of photo-orthotrpic elastic techniques are appraised.It is reasonable to expect that further developments in photor-orthotropic elasticity will lead to establishing a method to solve problems of engineering importance.
It is well known that experimental methods of stress analysis are of great use for studying composite materials and structure,and optical methods have the advantage of yielding full-field quantitative results.In this papar.the application of transmission photoelastic techniques to the study of composite specimens and the survey of historical developments of photoorthotropic elasticity for composites are mainly introduced during the last two decades,The fabrication of the model materials and photoelastic calibration for determining the three independent photoelasic constants in many countries are mentioned in detail and a summary of the early prgresses about birefringant orthotropic model materials in China are presented.Then,the basic principles governing the photoelastic response in birefringent orthotropic compos are briefly reviewed.The contents of various stress-optic law and strainoptic law are discussed and compared with each other.Seven methods of separating the principal stresses in birefringent composite models are proposed.Finally,the advantages and problems of photo-orthotrpic elastic techniques are appraised.It is reasonable to expect that further developments in photor-orthotropic elasticity will lead to establishing a method to solve problems of engineering importance.
