1990 Vol. 7, No. 1
1990, 7(1): 1-Ⅰ.
Abstract:
A study is concerned with the effects of three types of treated interfacts (carber fibers were treated-BS-6 and toughening layer-BS-1,water prevention layer-BSM2 was polyrrierized by means of a cold plasma) on interfacial and mechanical behaviour of carbon/epoxy composites.Comparative tests of interlaminar shear and fracture ware carried out under microscope. and S F.M.The results show that the interlaminar shear strength(ILSS) and fracturs toughness(K) of the three kinds specimens with treated interfaces are 30% and 40% higher than those of untreated specimens (BS-6) respectively.The reinforcing effect of SB-1 type specimens is optimum, the ILSS tis increased from 71MPa (SM-5)to 103 MPa(SB-1),and K is increased from 985 MPa√m to 1548 MPa√m, Furthmore,four types of microscopic interfaces and dynamic failure ara characterized by using SEM.The relationship of interfacial layer and mechanical properties as well as reinforcing mechanism are discussed.
A study is concerned with the effects of three types of treated interfacts (carber fibers were treated-BS-6 and toughening layer-BS-1,water prevention layer-BSM2 was polyrrierized by means of a cold plasma) on interfacial and mechanical behaviour of carbon/epoxy composites.Comparative tests of interlaminar shear and fracture ware carried out under microscope. and S F.M.The results show that the interlaminar shear strength(ILSS) and fracturs toughness(K) of the three kinds specimens with treated interfaces are 30% and 40% higher than those of untreated specimens (BS-6) respectively.The reinforcing effect of SB-1 type specimens is optimum, the ILSS tis increased from 71MPa (SM-5)to 103 MPa(SB-1),and K is increased from 985 MPa√m to 1548 MPa√m, Furthmore,four types of microscopic interfaces and dynamic failure ara characterized by using SEM.The relationship of interfacial layer and mechanical properties as well as reinforcing mechanism are discussed.
1990, 7(1): 7-Ⅱ.
Abstract:
Gas-solid chromatography (invers gas chromatography) was used to study the surfaces of copolymsr-electrodeposited and untreated carbon fibers.By adopting a series of n-alkanes and "polar" liquids as molecular probes,the retention volnmes on the surfaes of carbon fiber samples were measured under the case of "zero coverage".From the dependence of elution retention on the temperature as well as the vapor pressure of the adsorbates the, difference of the surface charaeteristic between deposition trcated and untreated carbon fidcrs was revealdd.It is shown that the enthalpy and entropy increment rsulted by aasorpting per-CH2-segment of nalkanes on the copolymer-depesited surface is much higher than on the untreated one.Besides,the tredated carbon fiber displays strong interaction with clectron-donor prolas,on the contrary,the untreated surface has no affinity for all of the used probds.
Gas-solid chromatography (invers gas chromatography) was used to study the surfaces of copolymsr-electrodeposited and untreated carbon fibers.By adopting a series of n-alkanes and "polar" liquids as molecular probes,the retention volnmes on the surfaes of carbon fiber samples were measured under the case of "zero coverage".From the dependence of elution retention on the temperature as well as the vapor pressure of the adsorbates the, difference of the surface charaeteristic between deposition trcated and untreated carbon fidcrs was revealdd.It is shown that the enthalpy and entropy increment rsulted by aasorpting per-CH2-segment of nalkanes on the copolymer-depesited surface is much higher than on the untreated one.Besides,the tredated carbon fiber displays strong interaction with clectron-donor prolas,on the contrary,the untreated surface has no affinity for all of the used probds.
1990, 7(1): 15-Ⅱ.
Abstract:
Water absorptior of the caboidal spccimens of chopped-glassfiber reinforced polysulfone (FR-PSu) and polycarbonate (FR-PC) in distilled water has been studied.Water absorptipon equation of the materials is similar to heat conduction equation.It is cepressed by a equation which is consisted of three water absorption equarions of one dimension specimen.At initeal stagd of water absorption it is coincident with Chi-hung Shen's equation.Therefore,the diffusivity and equilibrium water content can be deduced from the data.
Water absorptior of the caboidal spccimens of chopped-glassfiber reinforced polysulfone (FR-PSu) and polycarbonate (FR-PC) in distilled water has been studied.Water absorptipon equation of the materials is similar to heat conduction equation.It is cepressed by a equation which is consisted of three water absorption equarions of one dimension specimen.At initeal stagd of water absorption it is coincident with Chi-hung Shen's equation.Therefore,the diffusivity and equilibrium water content can be deduced from the data.
1990, 7(1): 24-Ⅲ.
Abstract:
The contact angles of molten Al and saveral Al alloys on polycrystal-line-Alumina were measured by sessile drop method in vacuum.The effects of temperature and currently used alloying elements such as Mg,Cu,Si and Fe on the wettability of Alumina/Al system wars investigated.The wetting phenomena and interfacial reactions were observed and analyzed with metallographic microscope,microprobe x-ray diffraction,atom absorption spectroscop9 qualitative analysis,etc.
The contact angles of molten Al and saveral Al alloys on polycrystal-line-Alumina were measured by sessile drop method in vacuum.The effects of temperature and currently used alloying elements such as Mg,Cu,Si and Fe on the wettability of Alumina/Al system wars investigated.The wetting phenomena and interfacial reactions were observed and analyzed with metallographic microscope,microprobe x-ray diffraction,atom absorption spectroscop9 qualitative analysis,etc.
1990, 7(1): 30-Ⅳ.
Abstract:
The unidirectional and random CF/Cu-Fe,CF/Cu-Ni composites were fabricated by hot press with duplex coated CF which were made by electroplating CF with Cu prior to with Fe or Ni.The electrical resistivities are larger than those of CF/Gu composites at approximate Vf.The linear thermal expansion coefficients of composites can be drastically reduced by increasing Vf.From the SEM photos of fracture surfaces, the matrix emerges obvious plastic deformation in CF/Cu-Ni and them are discontinuous nodes on the CF surface in CF/Cu-Fe,but CF have not been pulled out long.The interface structure of composites is covered with discontinuous Fe3C grains and the interface zone between CF and Cu in CF/Cu-Ni composites is Cu-Ni solid solution which can dissolve mninute amount of carbonori.The interface bonding in CF/Cu-Fe and CF/Cu-Ni composites are strengthencd by chemical reactions and dissolution.
The unidirectional and random CF/Cu-Fe,CF/Cu-Ni composites were fabricated by hot press with duplex coated CF which were made by electroplating CF with Cu prior to with Fe or Ni.The electrical resistivities are larger than those of CF/Gu composites at approximate Vf.The linear thermal expansion coefficients of composites can be drastically reduced by increasing Vf.From the SEM photos of fracture surfaces, the matrix emerges obvious plastic deformation in CF/Cu-Ni and them are discontinuous nodes on the CF surface in CF/Cu-Fe,but CF have not been pulled out long.The interface structure of composites is covered with discontinuous Fe3C grains and the interface zone between CF and Cu in CF/Cu-Ni composites is Cu-Ni solid solution which can dissolve mninute amount of carbonori.The interface bonding in CF/Cu-Fe and CF/Cu-Ni composites are strengthencd by chemical reactions and dissolution.
1990, 7(1): 35-Ⅳ.
Abstract:
The basic principle of maKing short metal fibers by Chatter Machining method and the characteristics of short metal fibers are described in this paper.It is shown that many properties of short.metal fibers are preferable to those of nonmetallic fibers.Hybrid composite materials and their applications in industry are also discussed.
The basic principle of maKing short metal fibers by Chatter Machining method and the characteristics of short metal fibers are described in this paper.It is shown that many properties of short.metal fibers are preferable to those of nonmetallic fibers.Hybrid composite materials and their applications in industry are also discussed.
PREDICTION OF NOTCHED STRENGTH OF 3D CARBON CARBON MATERIALS UNDER TENSION WITH SMALL OFF-AXIS ANGLE
1990, 7(1): 40-Ⅴ.
Abstract:
Under tension with small off-axis angle, the notch in the plane specimen of 3D carbon carbon material propagates self-similarly at first.Finally the specimen shears to failure along the direction of the fiber bundles in some of the layers and perpendicular to the fiber bundles in the remaining layers,as the number of broken fiber bundles reaches a criticl value rc.The failure is catastrophic.No additional load is needed in order to break more, fiber bundles in front of the notch tip all along to the final rupture.It implies that the notchedst rangth of 3D carbon/carbon material under tension with small off-axis angle is dictated with the strength of fiber bundle at notch tip,that is just the same as in the case of simple tension.The difference lias only in that the fiber bundle in this case sustains also shear besides the tensile strass and the shear stress will substantially reduce its tensile strength.This paper performs the experimental measuroment of tensile strength and shearing strength under combined stress state.The statistical notch strength of the 3D C-C specimens were caleulated based on these strength data and the stress fields near the notch tip computed with FFM.The ratio of rc/n(n is the total number of fiber bundles in the width direction) were also pradicted.The predietions match the experimontal results vary well.
Under tension with small off-axis angle, the notch in the plane specimen of 3D carbon carbon material propagates self-similarly at first.Finally the specimen shears to failure along the direction of the fiber bundles in some of the layers and perpendicular to the fiber bundles in the remaining layers,as the number of broken fiber bundles reaches a criticl value rc.The failure is catastrophic.No additional load is needed in order to break more, fiber bundles in front of the notch tip all along to the final rupture.It implies that the notchedst rangth of 3D carbon/carbon material under tension with small off-axis angle is dictated with the strength of fiber bundle at notch tip,that is just the same as in the case of simple tension.The difference lias only in that the fiber bundle in this case sustains also shear besides the tensile strass and the shear stress will substantially reduce its tensile strength.This paper performs the experimental measuroment of tensile strength and shearing strength under combined stress state.The statistical notch strength of the 3D C-C specimens were caleulated based on these strength data and the stress fields near the notch tip computed with FFM.The ratio of rc/n(n is the total number of fiber bundles in the width direction) were also pradicted.The predietions match the experimontal results vary well.
1990, 7(1): 45-Ⅴ.
Abstract:
To determine the relationship between the macroscopic behavior of mufti-phase materials and their microscopic structure is nowadays an important subject of computational mechanics.In this paper,the efficient quadratic isoparametric boundary element and the mufti-region technique were adopted to solve the macroscopic elastic modulus of a biphase medium with random order,The numerical results were compared with several common analytical formuli so as to provide a basis for appreciating the reliability of those, expressions.It can be seen that the BIM method possesses a great potenial in computational mechanics of conlposite materials.
To determine the relationship between the macroscopic behavior of mufti-phase materials and their microscopic structure is nowadays an important subject of computational mechanics.In this paper,the efficient quadratic isoparametric boundary element and the mufti-region technique were adopted to solve the macroscopic elastic modulus of a biphase medium with random order,The numerical results were compared with several common analytical formuli so as to provide a basis for appreciating the reliability of those, expressions.It can be seen that the BIM method possesses a great potenial in computational mechanics of conlposite materials.
1990, 7(1): 51-Ⅵ.
Abstract:
Epoxy is the main matrix material for fiber-reinforced plastics(FRP) and is always in complicated stress state in FRP.The content of this paper may be summarized as follows:a) The relacionship betwcen streas and strain for epoxy cast has been established when it is in plane stress state and during linear elastic siage.b) Triaxial material tests have been made ott epoxy cast thitt-walled cylinderical samples when they arc in plane stress state where there arc six principal stress ratios(1:0,1:0.5,1:0.96,1:-1,1:0.38,1:-0.155).c) Analyzing theccommon reasons of the failure in the six types of tests,it may come to the conclusion that the maximum tensile stress theory can be applied to epoxy cast when its two principal stresses are both positive or when one is positive while the other is negative whose absolute value is less than that of the positive one.
Epoxy is the main matrix material for fiber-reinforced plastics(FRP) and is always in complicated stress state in FRP.The content of this paper may be summarized as follows:a) The relacionship betwcen streas and strain for epoxy cast has been established when it is in plane stress state and during linear elastic siage.b) Triaxial material tests have been made ott epoxy cast thitt-walled cylinderical samples when they arc in plane stress state where there arc six principal stress ratios(1:0,1:0.5,1:0.96,1:-1,1:0.38,1:-0.155).c) Analyzing theccommon reasons of the failure in the six types of tests,it may come to the conclusion that the maximum tensile stress theory can be applied to epoxy cast when its two principal stresses are both positive or when one is positive while the other is negative whose absolute value is less than that of the positive one.
1990, 7(1): 59-Ⅶ.
Abstract:
When the boundary clement method (BEM) is used to calculate the stresses in the neighborhood of the boundary、there are always some errors.The reason is that the boundary integrals in BEM contain singular factors.To solve this problem, a so-called boundary finite element (BFE) based on the complementary energy theorem is praposed,including four nodes BFE and eight nodes BFE, It is found that based on the solutions of BEM and using BFEM presented in this paper accurate results are obtained.
When the boundary clement method (BEM) is used to calculate the stresses in the neighborhood of the boundary、there are always some errors.The reason is that the boundary integrals in BEM contain singular factors.To solve this problem, a so-called boundary finite element (BFE) based on the complementary energy theorem is praposed,including four nodes BFE and eight nodes BFE, It is found that based on the solutions of BEM and using BFEM presented in this paper accurate results are obtained.
1990, 7(1): 66-Ⅶ.
Abstract:
This paper debatad the damage of the "baring fatigue" in CFRP laminates arouud a loaded hole.according to the theory of the "residual stif fness".It described the damage initiation and propagation by the permanent deformation of a circular hole. This paper gave the definition and measuring method for "damge parameter" and the new notion of the "fatigue damage point".The testing program also was performed to study the effect of temperature and the fatigue life.The damaged specimens were detected and analysed by using "deply technique",X-ray radiographs" and "scanning electron microscopy" to study the damage mechanisms.
This paper debatad the damage of the "baring fatigue" in CFRP laminates arouud a loaded hole.according to the theory of the "residual stif fness".It described the damage initiation and propagation by the permanent deformation of a circular hole. This paper gave the definition and measuring method for "damge parameter" and the new notion of the "fatigue damage point".The testing program also was performed to study the effect of temperature and the fatigue life.The damaged specimens were detected and analysed by using "deply technique",X-ray radiographs" and "scanning electron microscopy" to study the damage mechanisms.
