1986 Vol. 3, No. 3
1986, 3(3): 1-Ⅰ.
Abstract:
The surface treatment of graphite fibers with Ar,N2,O2-plasma was studied.It was found,after the surfase of the graphite fibers was treated with O2-plasma,the intelaminar shear strength (ILSS) of Graphite Fiber Reinforcecl Plastics (GrFRP) was increased by over 250% and the tensile strength (S) and Young's modulus were increased by 40% and 10%,respectively.It was also found that the relationship between the time of the sutfase treatment of the graphite fiber and the ILSS of the GrFRP was surfase treatemnt of thr graphite fiber and the ILSS of the CrFRP was
ILSS=A+Ce-B/t.
We found that the shearing fracture of the GtFRP appeared in the surface layer of the graphite fiber.After the graphite fiber surface was treated by O2-plasma,the resistence of the surface layer to shearing stress was greatly raised by improving the layer structure,which made the ILSS of the GrFRP increased greatly.
The surface treatment of graphite fibers with Ar,N2,O2-plasma was studied.It was found,after the surfase of the graphite fibers was treated with O2-plasma,the intelaminar shear strength (ILSS) of Graphite Fiber Reinforcecl Plastics (GrFRP) was increased by over 250% and the tensile strength (S) and Young's modulus were increased by 40% and 10%,respectively.It was also found that the relationship between the time of the sutfase treatment of the graphite fiber and the ILSS of the GrFRP was surfase treatemnt of thr graphite fiber and the ILSS of the CrFRP was
ILSS=A+Ce-B/t.
We found that the shearing fracture of the GtFRP appeared in the surface layer of the graphite fiber.After the graphite fiber surface was treated by O2-plasma,the resistence of the surface layer to shearing stress was greatly raised by improving the layer structure,which made the ILSS of the GrFRP increased greatly.
1986, 3(3): 8-Ⅱ.
Abstract:
This paper discusses the rheological properties of CaCO3/UP and CaCO3-glass(UP systyms respectively in which CaCO3 has been treated by coupling agents.The results indicate that the dispersion state of CaCO3 in CaCO3/UP system will change from a single particle state to aaccumulated group structure gradually,accompanying by the increase of CaCO3 content.The rheological properties of the system that consists of accumulated group structures can be shown by the formula In ηγ=9.23φ/(1-2.0φ).As to CaCO3-glass/UP system,its rheological properties ate obviousiy affected by glass fibres,and there exists a loose structure that is mechanically formed between glass fibres.Casson equation can be used to characcterize this system so long as glass fibre content is small,and ý is less than 100 s-1.It is found that the different molecular structures on coupling agents and their different combination forms on the surface of CaCos will bring about different surface effects on the rheological properties of the systems.
This paper discusses the rheological properties of CaCO3/UP and CaCO3-glass(UP systyms respectively in which CaCO3 has been treated by coupling agents.The results indicate that the dispersion state of CaCO3 in CaCO3/UP system will change from a single particle state to aaccumulated group structure gradually,accompanying by the increase of CaCO3 content.The rheological properties of the system that consists of accumulated group structures can be shown by the formula In ηγ=9.23φ/(1-2.0φ).As to CaCO3-glass/UP system,its rheological properties ate obviousiy affected by glass fibres,and there exists a loose structure that is mechanically formed between glass fibres.Casson equation can be used to characcterize this system so long as glass fibre content is small,and ý is less than 100 s-1.It is found that the different molecular structures on coupling agents and their different combination forms on the surface of CaCos will bring about different surface effects on the rheological properties of the systems.
1986, 3(3): 16-Ⅱ.
Abstract:
In this investigation the thermal expansion measurments were made on carbon-fiber aluminium unidirectional composites by a standard contact-type dilaometer,The specimens are prepared by laying precursor carbon-Al wires and aluminium alloy foil (LD2) alternately in a sandwich form and consolidating by hot-pressing at 50℃ below the matrix solidua temperature.These romposites contained fiber volume fractions of 0,27,32,34,39 and 46 percent.The thermal expansion measrurements were made at 0 and 90 centigrade degree to the fiber axis in the temperature range from room temperature(RT) to 400℃.The results showed that the thermal expansion coefficients (CTE) of carbon fiberaluminium composites are related to fiber variety,fiber volume fraction and measuring temperature range.Experimental mean values of the axial linear CTE were compared with calculated valuese,which showed that it could he described by a modification of the rule of the rule of mixtures expansion of composite.
In this investigation the thermal expansion measurments were made on carbon-fiber aluminium unidirectional composites by a standard contact-type dilaometer,The specimens are prepared by laying precursor carbon-Al wires and aluminium alloy foil (LD2) alternately in a sandwich form and consolidating by hot-pressing at 50℃ below the matrix solidua temperature.These romposites contained fiber volume fractions of 0,27,32,34,39 and 46 percent.The thermal expansion measrurements were made at 0 and 90 centigrade degree to the fiber axis in the temperature range from room temperature(RT) to 400℃.The results showed that the thermal expansion coefficients (CTE) of carbon fiberaluminium composites are related to fiber variety,fiber volume fraction and measuring temperature range.Experimental mean values of the axial linear CTE were compared with calculated valuese,which showed that it could he described by a modification of the rule of the rule of mixtures expansion of composite.
1986, 3(3): 20-Ⅲ.
Abstract:
Moire method and Linear finite element are used in order to study the failure mechanism of pin-loaded hole in orthotropic laminates.All the stages of deformation are recorded by Moue,including linear elasticity,sudden cracking,steady crack propagation and unsteady crack propagatiom.Not-only the distributions of displacement and strain at the vicinity of the hole but also the tensile cracking progress are obtained.Before crack appears,results of Moire agree quite well with that of linear finite element;and after crack propagates,Moire method describes the nonlinear properties of the pin-loaded hole.The orthotropic laminates used is of (0°n/90°m)s,n:m=1:1.The frequency of both specimen and reference gratings is 1000 L/in.The strain concentration factor Kc at the hole boundary is a constant before crack appears,and no-longer keeps constant after cracking.Three stages exist in the extension of the crack;sudden cracking,steady extension and unsteady extension until failure.At the second stage,the crack jumps forword step by step along the horizontal fiber orientation.The strain field at the crack tip moves forword in the same direction.The dimensions and the distribution forms of the field keep unchanged.The existance of the crack has no effect on the dimension of the compressive zone.The failure of laminates is brittle and the steady extension stage is short.The maximum strair at the boundary of the hole linearly varies with the applied load before crack appearss and nonlinearly after crack extends.In the steady extension,the crack opening angle is a constant,and the crack opening displacement at the tip presents nonlinear propeties.
Moire method and Linear finite element are used in order to study the failure mechanism of pin-loaded hole in orthotropic laminates.All the stages of deformation are recorded by Moue,including linear elasticity,sudden cracking,steady crack propagation and unsteady crack propagatiom.Not-only the distributions of displacement and strain at the vicinity of the hole but also the tensile cracking progress are obtained.Before crack appears,results of Moire agree quite well with that of linear finite element;and after crack propagates,Moire method describes the nonlinear properties of the pin-loaded hole.The orthotropic laminates used is of (0°n/90°m)s,n:m=1:1.The frequency of both specimen and reference gratings is 1000 L/in.The strain concentration factor Kc at the hole boundary is a constant before crack appears,and no-longer keeps constant after cracking.Three stages exist in the extension of the crack;sudden cracking,steady extension and unsteady extension until failure.At the second stage,the crack jumps forword step by step along the horizontal fiber orientation.The strain field at the crack tip moves forword in the same direction.The dimensions and the distribution forms of the field keep unchanged.The existance of the crack has no effect on the dimension of the compressive zone.The failure of laminates is brittle and the steady extension stage is short.The maximum strair at the boundary of the hole linearly varies with the applied load before crack appearss and nonlinearly after crack extends.In the steady extension,the crack opening angle is a constant,and the crack opening displacement at the tip presents nonlinear propeties.
1986, 3(3): 28-Ⅳ.
Abstract:
The concept of energy release rate and the analysis method developed by A.S.D.Wang in the case of transverse cracks are used to predict three types of matrix cracking in crossply laminate family at the late stage of uniaxial tensile loading.Cracking events analysed include longitudinal splitting in 0°-ply,0/90° interface localized delamination emanating from the intersection of the transverse crack and the coupon free edge,and similar delamination around the cross point of the transverse and longitudinal splitting cracks.A 3-D finite element analysis is performed to simulate those clack development procedures and the corresponding energy release rate curves,as functions of crack size a,are obtained on the basis of Irwin's crack closure tech nique.After determining the effective inherent flaw sites,the values of critical loading for considered cracking are then pridicted and found to agree well with the experimental results.
The concept of energy release rate and the analysis method developed by A.S.D.Wang in the case of transverse cracks are used to predict three types of matrix cracking in crossply laminate family at the late stage of uniaxial tensile loading.Cracking events analysed include longitudinal splitting in 0°-ply,0/90° interface localized delamination emanating from the intersection of the transverse crack and the coupon free edge,and similar delamination around the cross point of the transverse and longitudinal splitting cracks.A 3-D finite element analysis is performed to simulate those clack development procedures and the corresponding energy release rate curves,as functions of crack size a,are obtained on the basis of Irwin's crack closure tech nique.After determining the effective inherent flaw sites,the values of critical loading for considered cracking are then pridicted and found to agree well with the experimental results.
1986, 3(3): 34-Ⅴ.
Abstract:
With the aid of the basic theorems of Fourier transformation and Fourier series,the general solution of a pair of edge cracks at the interfaced of four different media in a rectangular sheet under longitudinal shear stress is found in this paper.It is of interest to note that the stress intensity factor of this problem is independent of the material constants of the composite rectangular sheet.The conclusion is no doubt of great importance to designers and experimenters because there is no need to carry out unnecessary tests.
With the aid of the basic theorems of Fourier transformation and Fourier series,the general solution of a pair of edge cracks at the interfaced of four different media in a rectangular sheet under longitudinal shear stress is found in this paper.It is of interest to note that the stress intensity factor of this problem is independent of the material constants of the composite rectangular sheet.The conclusion is no doubt of great importance to designers and experimenters because there is no need to carry out unnecessary tests.
1986, 3(3): 43-Ⅴ.
Abstract:
An analysis using complex exponential series is developed for the problem of a crack on the boundary between two dissimilar materials.The eigenvalues and the relations among the complex constants are determined by the use of crack face boundary conditions and the continuity conditions at the interface.From these results the stress and displacement fields and the stress intensity factors have been determined,the stress function used by Lin[1] and by Lin and Mar[2] are modified and the solution reduces to results obtained by Williams[6] and by Sih and Rice[3,4].A singular element based on the results is used to develop a finite element analysis of finite tension sheet with a central crack on a straight interface boundary.
An analysis using complex exponential series is developed for the problem of a crack on the boundary between two dissimilar materials.The eigenvalues and the relations among the complex constants are determined by the use of crack face boundary conditions and the continuity conditions at the interface.From these results the stress and displacement fields and the stress intensity factors have been determined,the stress function used by Lin[1] and by Lin and Mar[2] are modified and the solution reduces to results obtained by Williams[6] and by Sih and Rice[3,4].A singular element based on the results is used to develop a finite element analysis of finite tension sheet with a central crack on a straight interface boundary.
1986, 3(3): 52-Ⅵ.
Abstract:
Transverse shear effects are important for the bending and vibration of laminated plates.When a laminate is in bending,it is assumed in this paper that the transverse displacement is constant through the plate thickness,and the in-plane displacements vary linearly through each layer,i.e.,they are piecewise linear through the plate thickness.The tatter means that the transverse shear strains within each layer area assumed to be different each other.There are two methods to relate the transverse shear strains within each layer;(1)Demand the continuity of two shear stress components at all interfaces,It is equivalent to that tra nsverse shear stresses are constant respectively through the plate thickness.(2)Assume that transverse shear stresses vary parabolically through the plate thickness.There two metliods correspond with two models of the displacements of the laminates called Piecewise (1)and Piecewise (2) schemes respectively in this paper.According to these two schemes,the governing equations for the bending of a specially orthotropic laminate under a lateral load are obtained on the basis of the principle of minimum potential energy.
Transverse shear effects are important for the bending and vibration of laminated plates.When a laminate is in bending,it is assumed in this paper that the transverse displacement is constant through the plate thickness,and the in-plane displacements vary linearly through each layer,i.e.,they are piecewise linear through the plate thickness.The tatter means that the transverse shear strains within each layer area assumed to be different each other.There are two methods to relate the transverse shear strains within each layer;(1)Demand the continuity of two shear stress components at all interfaces,It is equivalent to that tra nsverse shear stresses are constant respectively through the plate thickness.(2)Assume that transverse shear stresses vary parabolically through the plate thickness.There two metliods correspond with two models of the displacements of the laminates called Piecewise (1)and Piecewise (2) schemes respectively in this paper.According to these two schemes,the governing equations for the bending of a specially orthotropic laminate under a lateral load are obtained on the basis of the principle of minimum potential energy.
1986, 3(3): 62-Ⅶ.
Abstract:
A series expression of deflection is presented which exactly satisfies the foundation equation of bending of symmetric crass-ply laminates,and the corresponding expressions of displacements,deformations and internal forces are derived in explicit form.The simplicity of the series makes all the derivation and the expressions simple.In general cases,the boundary conditions of the laminate can not be satisfied exactly by the series presented,but they can be satisfied approximately by the use of the discrete least squares.Because the series is proved to be complete in mathematics,if the laminate only occupies simply connected region and the number of boundary collocations is large enough,the series may approximate the exact solution of bending problem of symmetric cross-ply laminates under various boundary conditions including the cases that the edges are clamped,simply supported,and/or free.For nonsymmetric cross-ply laminates with many layers,the coupling between extension and bending is after negligible and the method can be still used as an approximation.A widely applicable program implemented with the use of micro-computer IBM.PC/XT has been written and certain laminates with different layes have been calculated.
A series expression of deflection is presented which exactly satisfies the foundation equation of bending of symmetric crass-ply laminates,and the corresponding expressions of displacements,deformations and internal forces are derived in explicit form.The simplicity of the series makes all the derivation and the expressions simple.In general cases,the boundary conditions of the laminate can not be satisfied exactly by the series presented,but they can be satisfied approximately by the use of the discrete least squares.Because the series is proved to be complete in mathematics,if the laminate only occupies simply connected region and the number of boundary collocations is large enough,the series may approximate the exact solution of bending problem of symmetric cross-ply laminates under various boundary conditions including the cases that the edges are clamped,simply supported,and/or free.For nonsymmetric cross-ply laminates with many layers,the coupling between extension and bending is after negligible and the method can be still used as an approximation.A widely applicable program implemented with the use of micro-computer IBM.PC/XT has been written and certain laminates with different layes have been calculated.
1986, 3(3): 70-Ⅶ.
Abstract:
A new method,Deply Technique,for observing the internal da mage mechanism in composite laminates proposed by S.M.Freeman,was introduced.The operation procedure and technical keys were described in detail according to authors,practical experience.Some observation results were presented.
A new method,Deply Technique,for observing the internal da mage mechanism in composite laminates proposed by S.M.Freeman,was introduced.The operation procedure and technical keys were described in detail according to authors,practical experience.Some observation results were presented.
1986, 3(3): 75-Ⅷ.
Abstract:
The non-geodesic Filament winding process is reproducible when the friction between the resin impreguated filament and bases (the core or other filament layer) is utilized in order to prevent any slippage of the reinforcing material.Based on normal and geodesic curvatures in Differential Geometry,this paper analyzed conditions of equilibrium of a non-geodesic winding:
Kg/Kn≤μ
where Kn is the normal curvature of the point on the point on the curve,Kg the geodesic curvatnte of the point on the curve,and μ the coefficient of friction between the resin impreguated filament and the bases.The calculation formulas of a non-geodesic winding on a torus are presented in this paper,which can be solved with the aid of a method of numerical mathematics (Runge-Kutta method) and can also be utilized for a geodesic winding on a torus.A non-geodesic turn-around of the winding on a torus free of slippage is easily realized and this can be a evidence for winding curved tube.
The non-geodesic Filament winding process is reproducible when the friction between the resin impreguated filament and bases (the core or other filament layer) is utilized in order to prevent any slippage of the reinforcing material.Based on normal and geodesic curvatures in Differential Geometry,this paper analyzed conditions of equilibrium of a non-geodesic winding:
Kg/Kn≤μ
where Kn is the normal curvature of the point on the point on the curve,Kg the geodesic curvatnte of the point on the curve,and μ the coefficient of friction between the resin impreguated filament and the bases.The calculation formulas of a non-geodesic winding on a torus are presented in this paper,which can be solved with the aid of a method of numerical mathematics (Runge-Kutta method) and can also be utilized for a geodesic winding on a torus.A non-geodesic turn-around of the winding on a torus free of slippage is easily realized and this can be a evidence for winding curved tube.
1986, 3(3): 80-Ⅷ.
Abstract:
Three groups of the equations of restrictions on elastic constants of orthotropic materials are derived by positive definition of complementary elastic energy density and compliance matrix.Some relative conclusions are derived,too.
Three groups of the equations of restrictions on elastic constants of orthotropic materials are derived by positive definition of complementary elastic energy density and compliance matrix.Some relative conclusions are derived,too.
1986, 3(3): 84-Ⅸ.
Abstract:
The stress concentration factors for the unidirectional solid and hollow fiber reinforced composites subjected to transverse,shear,longitudinal loads are computed with taking the basic properties of the fiber and matrix into account in micro-state by finite element method,The paper gives numerical results in graphical form varying with the fiber volume content and value of Ef/Em,and emphatically discusses the stress concentration factor in longitudinal tension.The results show as following.1) The stress concentration factor of unidirectional solid fiber composites is,in general,greater than that of the a nidirectional hollow fiber composites under transverse or shear load.2) The maximum stress concentration factor resulted from shear load occurs at bond face,that is,the bond face is weak area.3) The unidirectional hollow fiber composite is inferior to the unidirectional solid fiber composite in longitudinal tension,but its longitudinal stress gradient at bond face is smaller than that of the unidirectional solid fiber composite.
The stress concentration factors for the unidirectional solid and hollow fiber reinforced composites subjected to transverse,shear,longitudinal loads are computed with taking the basic properties of the fiber and matrix into account in micro-state by finite element method,The paper gives numerical results in graphical form varying with the fiber volume content and value of Ef/Em,and emphatically discusses the stress concentration factor in longitudinal tension.The results show as following.1) The stress concentration factor of unidirectional solid fiber composites is,in general,greater than that of the a nidirectional hollow fiber composites under transverse or shear load.2) The maximum stress concentration factor resulted from shear load occurs at bond face,that is,the bond face is weak area.3) The unidirectional hollow fiber composite is inferior to the unidirectional solid fiber composite in longitudinal tension,but its longitudinal stress gradient at bond face is smaller than that of the unidirectional solid fiber composite.
1986, 3(3): 88-Ⅹ.
Abstract:
The development of advanced composites has opened up a vast vistas in aeronautical and astronautical industry.Recently composite lifting surfaces have been broadly researched in abroad.Aeroelastic tailoring is defined as the technology to design a lifting surface which exhibits a desired aeroelastic response.This paper is to illustrate an application of the aeroelastic tailoring concept for swept wings.Specifically,the application involves the design of composite material wing.T.A.Weisshaar presented a simple theory to predict the divergence behavior of moderate to swept laminated composite wings with high aspect ratio,The equations developed from the strip theory and the classical Euler-Bernoulli beam theory to predict the effect of laminat construction upon wing divergence.Wing taper ratio is of importance for the determination of the divergence speed where such a speed actually exists.However,decreasing the taper ratio tends to decrease critical swept angle,although these decreases are very small.There are some figures to show the behavior of flutter and divergence speed as function of fiber orientation for three sectional centre of gravity positions.The effect of wing aspect ratio has also illustrated.From aeroelastic viewpoint,the primary effect of the elastic coupling between bending and torsion of composites,introduced by the laminated material through the parameter k,can successfully negatect the undesirable influnce of forward swept on aileron operation efficency and divergence.
The development of advanced composites has opened up a vast vistas in aeronautical and astronautical industry.Recently composite lifting surfaces have been broadly researched in abroad.Aeroelastic tailoring is defined as the technology to design a lifting surface which exhibits a desired aeroelastic response.This paper is to illustrate an application of the aeroelastic tailoring concept for swept wings.Specifically,the application involves the design of composite material wing.T.A.Weisshaar presented a simple theory to predict the divergence behavior of moderate to swept laminated composite wings with high aspect ratio,The equations developed from the strip theory and the classical Euler-Bernoulli beam theory to predict the effect of laminat construction upon wing divergence.Wing taper ratio is of importance for the determination of the divergence speed where such a speed actually exists.However,decreasing the taper ratio tends to decrease critical swept angle,although these decreases are very small.There are some figures to show the behavior of flutter and divergence speed as function of fiber orientation for three sectional centre of gravity positions.The effect of wing aspect ratio has also illustrated.From aeroelastic viewpoint,the primary effect of the elastic coupling between bending and torsion of composites,introduced by the laminated material through the parameter k,can successfully negatect the undesirable influnce of forward swept on aileron operation efficency and divergence.
