| 1. |
- Adolfsson, Erik, et al.
(författare)
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Matrix crack initiation and progression in composite laminates subjected to bending and extension
- 1999
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 36:21, s. 3131-3169
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Tidskriftsartikel (refereegranskat)abstract
- An experimental investigation of matrix crack initiation and progression in glass/epoxy laminates of different stacking sequences is presented. The laminates have been loaded in extension and bending, and the degree of damage as function of the load has been recorded. The changes in certain elastic properties caused by the damage were also measured, and are compared to results from a previously developed approximate analytic model. An energy release rate resistance curve is adopted in an attempt to describe the initiation and progression of matrix cracks in the laminates. The amount of cracking is also viewed in relation to the strain transverse to the fibres in the ply under consideration, and the ply stresses at the onset of cracking are calculated. The different damage evolution criteria are compared to the experimental results, and their validity and reliability are discussed. By use of the ply strain transverse to the fibres as a critical parameter for damage evolution, the load-deformation curves of the tested laminates are simulated taking damage progression into account.
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| 2. |
- Adolfsson, Erik, et al.
(författare)
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Thermoelastic properties in combined bending and extension of thin composite laminates with transverse matrix cracks
- 1997
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 34:16, s. 2035-2060
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Tidskriftsartikel (refereegranskat)abstract
- Approximate analytic expressions for the thermoelastic properties in combined bending and extension of composite laminates containing transverse matrix cracks are derived. The model covers two-dimensional laminates of arbitrary lay-up sequences. The derived expressions for the compliances and thermal expansion coefficients merely contain ply property data and crack distributions. In order to check the accuracy and reliability of the presented analytic method, some sample cracked geometries were examined by use of the finite element method. A good agreement was found between the numerically and analytically obtained results for all cases under consideration.
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| 3. |
- Christensen, Peter
(författare)
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A semi-smooth newton method for elasto-plastic contact problems
- 2002
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 39:8, s. 2323-2341
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we reformulate the frictional contact problem for elasto-plastic bodies as a set of unconstrained, non-smooth equations. The equations are semi-smooth so that Pang's Newton method for B-differentiable equations can be applied. An algorithm based on this method is described in detail. An example demonstrating the efficiency of the algorithm is presented. © 2002 Elsevier Science Ltd. All rights reserved.
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| 4. |
- Ciavarella, M., et al.
(författare)
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Interaction of thermal contact resistance and frictional heating in thermoelastic instability
- 2003
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 40:21, s. 5583-5597
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Tidskriftsartikel (refereegranskat)abstract
- Thermoelastic contact problems can posess non-unique and/or unstable steady-state solutions if there is frictional heating or if there is a pressure-dependent thermal contact resistance at the interface. These two effects have been extensively studied in isolation, but their possible interaction has never been investigated. In this paper, we consider an idealized problem in which a thermoelastic rod slides against a rigid plane with both frictional heating and a contact resistance. For sufficiently low sliding speeds, the results are qualitatively similar to those with no sliding. In particular, there is always an odd number of steady-state solutions, if the steady-state is unique it is stable and if it is non-unique, stable and unstable solutions alternate, with the outlying solutions being stable. However, we identify a sliding speed V0 above which the number of steady states is always even (including zero, implying possible non-existence of a steady-state) and again stable and unstable states alternate. A parallel numerical study shows that for V > V0 there are some initial conditions from which the contact pressure grows without limit in time, whereas for V < V0 the system will always tend to one of the stable steady states. © 2003 Elsevier Ltd. All rights reserved.
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| 5. |
- Giannakopoulos, A. E., et al.
(författare)
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The Stresses Around A Partly Microcracked Hole In Certain Ceramic Materials Under Internal-Pressure.
- 1991
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 28:3, s. 329-339
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Tidskriftsartikel (refereegranskat)abstract
- In the present work we examine the stress field around a hole in certain ceramic materials. The hole is under internal pressure in plane strain conditions. The material behavior is initially isotropic linearly elastic and upon loading develops microcracks. The damage is assumed to be anisotropic and microcracking is believed to take place along preferred orientations. A damaged constitutive law, appropriate for the microcracking assumptions, is used to derive exact results for the stress fields in this particular problem. The present analysis may find applications in the experimental investigation of ceramic materials behaving as anisotropically microcracking solids.
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| 6. |
- Girhammar, Ulf Arne, et al.
(författare)
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Dynamic analysis of composite members with interlayer slip
- 1993
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Ingår i: International Journal of Solids and Structures. - : Pergamon Press. - 0020-7683 .- 1879-2146. ; 30:6, s. 797-823
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Tidskriftsartikel (refereegranskat)abstract
- The exact and approximate analysis of composite members with partial interaction and subjected to general dynamic loading are presented. General closed-form solutions for the displacement functions and the various internal actions in the composite elements are presented for both the exact and approximate cases. The solutions reduce to the well-known values for the extreme cases of interlayer connection: non-composite and full composite action, respectively. An approximate solution for the eigenfrequencies in the exact analysis procedure is proposed and evaluated by comparison with the exact solution. These solutions show the effect of interlayer connection on the eigenfrequency. The exact and approximate analysis procedures are applied to simply-supported beams subjected to impulsive and step loadings to illustrate the difference in the solutions obtained by the two procedures. Very good agreement is obtained between the results of exact and approximate analysis of these particular cases
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| 7. |
- Gudmundson, Peter, et al.
(författare)
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An analytic model for thermoelastic properties of composite laminates containing transverse matrix cracks
- 1993
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 30:23, s. 3211-3231
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Tidskriftsartikel (refereegranskat)abstract
- An analytical model for the prediction of the thermoelastic properties of composite laminates containing matrix cracks is presented. In particular, transverse matrix cracks with their crack surfaces parallel to the fibre direction and perpendicular to the laminate plane are treated. Two- and three-dimensional laminates of arbitrary layup configurations are covered by the model. The presented expressions for stiffnesses, thermal expansion coefficients, strain contributions from release of residual stresses and local average ply stresses and strains do solely contain known ply property data and matrix crack densities. The key to the model is the judicious use of a known analytical solution for a row of cracks in an infinite isotropic medium. The model has been verified against numerically determined stiffnesses, thermal expansion coefficients and local average ply stresses for matrix cracked angle-ply and cross-ply laminates. Comparisons to experimental data for cross-ply laminates are also presented. It is shown that the present model to a very good accuracy can predict thermoelastic properties of matrix cracked composite laminates at varying matrix crack densities and layup configurations.
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| 8. |
- Ireman, Peter, et al.
(författare)
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A model of damage coupled to wear
- 2003
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Ingår i: International Journal of Solids and Structures. - : Elsevier. - 0020-7683 .- 1879-2146. ; 40:12, s. 2957-2974
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Tidskriftsartikel (refereegranskat)abstract
- The present paper presents a model of damage coupled to wear. The damage model is based on a continuum model including the gradient of the damage variable. Such a model is non-local in the sense that the evolution of damage is governed by a boundary-value problem instead of a local evolution law. Thereby, the well-known mesh-dependency observed for local damage models is removed. Another feature is that the boundary conditions can be used to introduce couplings between bulk damage and processes at the boundary. In this work such a coupling is suggested between bulk damage and wear at the contact interface. The model is regarded as a first attempt to formulate a continuum damage model for studying crack initiation in fretting fatigue. The model is given within a thermodynamic framework, where it is assured that the principles of thermodynamics are satisfied. Furthermore, two variational formulations of the full initial boundary value problem, serving as starting points for finite element discretization, are presented. Finally, preliminary numerical results for a simple one-dimensional example are presented and discussed. It is qualitatively shown how the evolution of damage may influence the wear behaviour and how damage may be initiated by the wear process. © 2003 Elsevier Science Ltd. All rights reserved.
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| 9. |
- Isaksson, Per, et al.
(författare)
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Directional crack path criterion for crack growth in ductile materials subjected to shear and compressive loading under plane strain conditions
- 2003
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 40:13-14, s. 3523-3536
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Tidskriftsartikel (refereegranskat)abstract
- A directional crack growth criterion in a compressed elastic perfectly plastic material is considered. The conditions at the crack-tip are evaluated for a straight stationary crack with a small incipient kink. Remote load is a combined hydrostatic pressure and pure shear applied via a boundary layer. Crack surfaces in contact are assumed to develop homogenous Coulomb friction. The crack opening displacement of an extended kink is examined in a finite element analysis to judge the risk of opening mode failure. It has been found that the direction that maximizes the crack opening displacement of an extended kink tip coincides very well with a prediction of the crack growth direction obtained by using a criterion for continued crack growth direction discussed by the authors elsewhere [Int. J. Fract. 108 (2001) 351]. Moreover, the by the model predicted incipient crack growth directions are qualitatively comparable with reported crack paths obtained in ductile materials in a limited number of experiments performed under a combined load of inplane shear and compression.
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| 10. |
- Isaksson, Per, et al.
(författare)
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Mode II crack paths under compression in brittle solids : A theory and experimental comparison
- 2002
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Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 39:8, s. 2281-2297
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Tidskriftsartikel (refereegranskat)abstract
- A study of crack propagation paths in the situation where the crack is suppressed to open during growth due to high compressive forces has been performed. This problem was analyzed theoretically very recently by the authors and is here extended to involve a limited number of illustrative experimental results reported elsewhere in the literature. By analyzing the experimental crack growth patterns, the conclusion is that the model cannot describe the more realistic microscopic failure in detail. Since shear crack growth on the microscale strongly depend on inhomogenities in the material, like cavities, grains or inclusions; the closed crack growth patterns observed are not smooth or free of kinks. Nevertheless, the model show good agreement with the reported experimental observations of the paths of closed macroscopic mode II cracks on samples in brittle materials, induced under overall compression. Failure patterns experimentally observed supports the theory that the growth of mode II cracks under compression in brittle materials follow a propagation path described by a function y ¼ kxb, where b ¼ 3=2. This is strongly supported by the measured values obtained from various experiments. In all the studied experiments, the exponent b was found in the interval [1.43–1.58]. Further, an investigation of the curvature parameter k has been performed and the conclusion is that k does also agree with the simplified model, even though not as good as the exponent b. However, k differs in general <15% from the theoretical value predicted by the model. The process of crack growth is in the simplified model assumed to be controlled by the mode II stress intensity factor KII of the main crack and the difference between the compressive remote normal stress parallel with the crack plane (r111) and the compressive remote normal stress perpendicular to the crack plane (r122).
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