| 1. |
- Lindhagen, Johan E., et al.
(författare)
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Application of bridging-law concepts to short-fibre composites : 1. DCB test procedures for bridging law and fracture energy
- 2000
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 60:6, s. 871-883
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Tidskriftsartikel (refereegranskat)abstract
- This is the first paper in a series of four where notch sensitivities, fracture energies and bridging laws of short-fibre polymer composites are investigated. In the context of crack-bridging, the bridging law is an important material parameter. The bridging law can be used in combination with a stress analysis to address failure problems, for instance large-scale bridging, where linear elastic fracture mechanics is not valid. The bridging law of the material is sensitive to material composition and fibre architecture. Owing to the lack of established procedures, it is of interest to develop experimental and analytical methods for determination of the bridging law and fracture energy of short-fibre polymer composites. A method based on a large DCB specimen loaded by pure bending moments is used. Commercial GMT and SMC materials are investigated in addition to chopped-strand-mat laminates based on glass fibres of two different lengths and two thermoset matrices of different ductility. Fracture energies and bridging law data are successfully determined. All materials demonstrate softening bridging laws and this is discussed on the basis of observed mechanisms of failure and existing micromechanical models.
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| 2. |
- Lindhagen, J. E., et al.
(författare)
-
Application of bridging-law concepts to short-fibre composites 4. FEM analysis of notched tensile specimens
- 2000
-
Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 60:16, s. 2895-2901
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Tidskriftsartikel (refereegranskat)abstract
- This is the fourth paper in a series of four where notch sensitivities, fracture energies and bridging laws in short-fibre polymer composites are investigated. In this paper finite-element modelling (FEM) of centre-hole-notched tensile specimens is performed, with different bridging laws governing crack growth. Crack lengths, crack profiles and stress distributions are predicted. The results are compared with experimentally determined crack shapes from an earlier investigation. Only with softening bridging laws can the experimental results be matched. The predicted crack lengths are sensitive to bridging-law parameters. When bridging laws determined by the double cantilever beam (DCB) method are applied, the predicted crack lengths and profiles show good correlation with the experimental results. The results support the validity of the DCB method to determine bridging laws in short-fibre composites.
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| 3. |
- Lindhagen, J. E., et al.
(författare)
-
Application of bridging-law concepts to short-fibre composites - Part 1 : DCB test procedures for bridging law and fracture energy
- 2000
-
Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 60:6, s. 871-883
-
Tidskriftsartikel (refereegranskat)abstract
- This is the first paper in a series of four where notch sensitivities, fracture energies and bridging laws of short-fibre polymer composites are investigated. In the context of crack-bridging, the bridging law is an important material parameter. The bridging law can be used in combination with a stress analysis to address failure problems, for instance large-scale bridging, where linear elastic fracture mechanics is not valid. The bridging law of the material is sensitive to material composition and fibre architecture. Owing to the lack of established procedures, it is of interest to develop experimental and analytical methods for determination of the bridging law and fracture energy of short-fibre polymer composites. A method based on a large DCB specimen loaded by pure bending moments is used. Commercial GMT and SMC materials are investigated in addition to chopped-strand-mat laminates based on glass fibres of two different lengths and two thermoset matrices of different ductility. Fracture energies and bridging law data are successfully determined. All materials demonstrate softening bridging laws and this is discussed on the basis of observed mechanisms of failure and existing micromechanical models.
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| 4. |
- Lindhagen, J. E., et al.
(författare)
-
Application of bridging-law concepts to short-fibre composites - Part 2. Notch sensitivity
- 2000
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 60:6, s. 885-893
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Tidskriftsartikel (refereegranskat)abstract
- This is the second paper in a series of four where notch sensitivities, fracture energies and bridging laws are studied in short-fibre polymer composites. Estimates based on an order-of-magnitude criterion indicate that previous notch sensitivity studies on short-fibre composites are limited to small notch sizes in the ductile region. For this reason, centre-hole notch sensitivity is studied experimentally as a function of relatively large notch diameters in the range 15-60 mm. The materials have different matrices, glass-fibre content and fibre lengths. The onset of notch sensitivity is observed for all materials (glass-mat thermoplastics, sheet-moulding compounds and chopped-strand-mat laminates), although large notch sizes are required. The reasons for this are discussed as well as the influence of different material parameters. On the basis of the material bridging law and laminate Young's modulus, it was possible to rank different short-fibre composites with respect to notch sensitivity.
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| 5. |
- Lindhagen, J. E., et al.
(författare)
-
Application of bridging-law concepts to short-fibre composites Part 3 : Bridging law derivation from experimental crack profiles
- 2000
-
Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 60:16, s. 2883-2894
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Tidskriftsartikel (refereegranskat)abstract
- This is the third paper in a series of four where notch sensitivity, fracture energy and bridging laws are studied in short-fibre polymer composites. Here, bridging laws are derived from experimental crack-opening profiles in centre-hole notched tensile specimens. The materials studied are three types of commercial glass-mat composites with different reinforcement structures and matrices. The materials have softening bridging laws and the calculated fracture energies from bridging laws are in good agreement with values determined directly by experiment. The calculated maximum local bridging stress is found to be higher than the uniaxial tensile strength. An outline of a failure criterion for notched specimens based on the crack-bridging approach is presented.
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| 6. |
- Lindhagen, J.E., et al.
(författare)
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Bridging law determination in short fibre composites by a DCB-test
- 2000
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Ingår i: E S I S Publication. - 1566-1369. ; 27, s. 73-82
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Tidskriftsartikel (refereegranskat)abstract
- For short fibre polymer composites such as chopped strand mat laminates (CSM), glass mat thermoplastics (GMT) and sheet moulding compounds (SMC), conventional methods to measure fracture energy are often not valid since linear elastic fracture mechanics (LEFM) criteria are not fulfilled. For the case of a long bridged crack with a small damage zone perpendicular to the crack, a crack bridging approach may instead be used. In this context, the bridging law is an important material parameter. The bridging law in combination with stress analysis can be used to address problems where LEFM is invalid. The bridging law of the material is related to material composition and fibre architecture. It is therefore of interest to develop an experimental method for determination of bridging law and fracture energy in short-fibre polymer composites. A method based on a large double cantilever beam (DCB) specimen loaded by pure bending moments is used. Commercial GMT and SMC materials are investigated as well as CSM laminates. Fracture energy and bridging law data are determined. All materials demonstrate softening bridging laws and this is discussed based on observed mechanisms of failure.
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