| 1. |
- Achi, Elif, et al.
(författare)
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Characterization of viscoelasticity and damage in high temperature polymer matrix composites
- 2006
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 66:14, s. 2506-2519
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a thermodynamics based model for viscoelastic composites with damage and illustrates its use in characterization of viscoelastic response of polymer matrix woven fabric composites subjected to loading at high temperatures. The characterization is conducted by an experimental method aided by finite element (FE) modeling. The experimental characterization is based on creep data obtained under constant loads of different magnitudes and at different temperatures, and on recovery data collected after unloading. A carbon fiber/polyamide resin woven composite with glass transition temperature (Tg) of around 380 °C was used in the experimental program. A FE model was developed to determine the non-linear viscoelastic response by implementing incremental constitutive relations into an ABAQUS® code. The laminate viscoelastic properties were obtained by finite element micromechanics analysis using the neat resin data as input. Comparing its results with creep-recovery test data at different temperature and stress levels validated the FE model. There are several factors affecting the viscoelastic behavior of polymer matrix composites such as temperature, moisture and stress level. Accordingly, a large number of tests need to be performed to characterize the viscoelastic response experimentally for each fiber-matrix combination. For this purpose an efficient and systematic experimental procedure was used to understand the effects of temperature and stress level on the viscoelastic response, to clarify the damage-viscoelasticity coupling and to determine the viscoelastic properties of the material system
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| 2. |
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| 3. |
- Akshantala, Nagendra V., et al.
(författare)
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A mechanistic model for fatigue damage evolution in composite laminates
- 1998
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Ingår i: Mechanics of materials. - 0167-6636 .- 1872-7743. ; 29:2, s. 123-140
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Tidskriftsartikel (refereegranskat)abstract
- We propose a mechanistic model which is capable of describing the evolution of transverse cracking in cross ply laminates subjected to cyclic tension in the longitudinal direction. The key feature of the model is that it incorporates delamination associated with transverse cracks in a manner that induces further formation of transverse cracks as delamination grows in fatigue. A variational approach is taken to estimate the stresses in the region between transverse cracks, and these are found to be accurate away from the crack planes when comparison is made with finite element computations. The evolution of transverse crack density and the associated overall elastic moduli changes predicted by the model are in agreement with experimental results
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| 4. |
- Akshantala, Nagendra V., et al.
(författare)
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A micromechanics based model for predicting fatigue life of composite laminates
- 2001
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Ingår i: Materials Science & Engineering. - 0921-5093 .- 1873-4936. ; 285:1-2, s. 303-313
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Tidskriftsartikel (refereegranskat)abstract
- The current practice, as well as the hitherto proposed models, for assessment of fatigue life of composite laminates rely largely on experimental fatigue life data. In this paper, we propose a methodology for fatigue life prediction that utilizes a micromechanics based evaluation of damage evolution in conjunction with a semi-empirical fatigue failure criterion. The specific case treated is that of cross ply laminates under cyclic tension. The predicted results are compared with experimental data for several glass/epoxy and carbon/epoxy laminates, and good agreement is found. Published by Elsevier Science S.A. The current practice, as well as the hitherto proposed models, for assessment of fatigue life of composite laminates rely largely on experimental fatigue life data. In this paper, we propose a methodology for fatigue life prediction that utilizes a micromechanics based evaluation of damage evolution in conjunction with a semi-empirical fatigue failure criterion. The specific case treated is that of cross ply laminates under cyclic tension. The predicted results are compared with experimental data for several glass/epoxy and carbon/epoxy laminates, and good agreement is found.
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| 5. |
- Asp, Leif, et al.
(författare)
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Criterion for crack initiation in glassy polymers subjected to a composite-like stress state
- 1996
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 11, s. 1291-1301
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Tidskriftsartikel (refereegranskat)abstract
- Three epoxy systems of interest as composite matrix materials are examined for their yielding and failure behavior under uniaxial, biaxial and triaxial stress states. Yield criteria applicable to glassy polymers, i.e. accounting for the hydrostatic stress effect on the deviatoric stress to yielding, are assessed. It is found that under stress states resembling those in matrix constrained between fibers, e.g. equibiaxial and equitriaxial tension, yielding is suppressed while brittle failure, presumably caused by crack growth from cavitation, occurs. A criterion for this mode of failure is proposed as the critical dilatational strain energy density. Experimental data are found to support this criterion.
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| 6. |
- Asp, Leif, et al.
(författare)
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Effects of fiber and interphase on matrix-initiated transverse failure in polymer composites
- 1996
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 45:6, s. 657-665
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Tidskriftsartikel (refereegranskat)abstract
- Failure initiation in polymer-matrix composites loaded transverse to the fibers is investigated by a numerical parametric study where the effects of constituent properties, interphase properties and thickness are examined. Failure initiation in the matrix only is studied, interfacial debonding not being considered. Two modes of failure - yielding and cavitation-induced brittle failure - are examined. A criterion for the cavitation-induced brittle failure has been proposed previously and failure prediction based on this criterion was found to agree with experimental data for a glass-fiber-reinforced epoxy. The present study shows that the elastic modulus of fibers has a large effect on the stress and strain to failure initiation. A rubbery interphase material is found in most cases to have a beneficial effect. The site at which failure initiates and the governing mode of failure initiation are also affected by the fiber modulus and the interphase properties
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| 7. |
- Asp, Leif, et al.
(författare)
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Prediction of matrix-initiated transverse failure in polymer composites
- 1996
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 56:9, s. 1089-1097
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Tidskriftsartikel (refereegranskat)abstract
- A study has been conducted of failure in unidirectionally-reinforced fiber composites loaded in tension normal to the fibers. The case considered is when this failure is governed by failure of the matrix rather than fiber/matrix debonding. Both yielding and cavitation-induced brittle failure of the matrix are considered. The latter mode of failure was suggested previously as the likely mode to occur in epoxies under stress states that are purely or nearly hydrostatic tension. Three fiber packing arrangements (square, hexagonal and square-diagonal) with different fiber volume fractions were studied numerically by a finite element method to determine the local stress states. It is found that cavitation-induced brittle failure occurs much before yielding in all cases. Experimental data taken from the literature support this finding.
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| 8. |
- Benzerga, Ahmed Amine, et al.
(författare)
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A computational framework for analyzing the dynamic behavior and failure of amorphous polymers
- 2008
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Ingår i: Earth & space 2008. - Reaston, Va : American Society of Civil Engineers (ASCE). - 9780784409886
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Konferensbidrag (refereegranskat)abstract
- A framework is presented for analyzing the low-temperature inelastic behavior of a class of amorphous polymers with full account taken of finite deformations and inertial effects. Viscoplastic constitutive equations are used and supplemented with a new model for craze initiation, growth and breakdown. The capabilities of the framework are illustrated by finite element solutions of initial/boundary-value problems under plane strain conditions. Three illustrative benchmark problems are used to evaluate the proposed implementation: shear band formation and propagation under compression, dynamic response under impact and quasi-static response of a polymer composite unit-cell subject to uniaxial tension transverse to fibers.
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| 9. |
- Benzerga, A. A., et al.
(författare)
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Computational methodology for modeling fracture in fiber-reinforced polymer composites
- 2009
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Ingår i: Journal of Aerospace Engineering. - 0893-1321 .- 1943-5525. ; 22:3, s. 296-303
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Tidskriftsartikel (refereegranskat)abstract
- A framework is presented for analyzing the inelastic behavior and fracture of polymer matrix composites. Physics-based viscoplastic constitutive equations are used and supplemented with a matrix cracking model and an energy-based debonding model. The capabilities of the framework are illustrated by finite-element solutions of boundary-value problems under plane strain conditions using the unit-cell concept. In the application, focus is centered on the effect of manufacturing induced voids on local modes of fracture under both tension and compression
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| 10. |
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