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Interfibre failure characterisation of unidirectional and triax glass fibre non-crimp fabric reinforced epoxy laminates

Interfibre failure characterisation of unidirectional and triax glass fibre non-crimp fabric reinforced epoxy laminates
Interfibre failure characterisation of unidirectional and triax glass fibre non-crimp fabric reinforced epoxy laminates
The in-plane failure envelopes of unidirectional (UD) laminae in a UD and a Triax (0°, ±45°) laminate configuration have been investigated. The two laminate configurations have been characterised by testing off-axis specimens in uniaxial tension and compression at different angles relative to the fibre direction and further by Iosipescu shear tests. Strain gauge and Digital Image Correlation (DIC) measurements were used to measure the deformation states during loading, and to record the stress-strain responses to identify the initiation of failure and investigate the heterogeneity of the material and possible parasitic effects. A novel analysis methodology to determine the so-called ‘failure initiation strength’ based on the second derivative of the stresses with respect to the strains has been adopted. The experimentally determined ‘failure initiation stresses’ were compared with predictions from the commonly applied Maximum Stress, Tsai-Wu, and Puck failure criteria. From this work, a thorough comparison of the UD and Triax failure envelopes has been facilitated. It is shown that failure prediction for the Triax laminate based on the failure envelope derived from UD lamina tests may be too conservative in comparison with fitting a failure criterion directly to the Triax laminate test data. The latter approach implies that the Triax laminate is considered as a single lamina with homogenised properties, which in principle violates the theoretical background of the considered failure criteria, since these are established to predict failure for a UD lamina. However, the simple homogenisation is shown to be a useful design oriented approach for providing a simple estimation of the onset of failure in laminate configurations composed of e.g., multiple layers of Triax. Thus, a reliable and efficient approach is offered for the structural integrity assessment, which takes the non-crimp fabric configurations directly or ‘as delivered’ into account.
failure characterisation, experimental characterisation, laminated composites, glass fibre reinforced plastic
0929-189X
51-79
Laustsen, S.
ef154f62-7a9a-42dc-88e3-850c24003191
Lund, E.
c663d217-9333-4b98-b59c-06c93cf4ba81
Kühlmeier, L.
e8c683d4-aba2-4cf0-9012-6b9fd7e26f1e
Thomsen, O.T.
f3e60b22-a09f-4d58-90da-d58e37d68047
Laustsen, S.
ef154f62-7a9a-42dc-88e3-850c24003191
Lund, E.
c663d217-9333-4b98-b59c-06c93cf4ba81
Kühlmeier, L.
e8c683d4-aba2-4cf0-9012-6b9fd7e26f1e
Thomsen, O.T.
f3e60b22-a09f-4d58-90da-d58e37d68047

Laustsen, S., Lund, E., Kühlmeier, L. and Thomsen, O.T. (2015) Interfibre failure characterisation of unidirectional and triax glass fibre non-crimp fabric reinforced epoxy laminates. Applied Composite Materials, 22 (1), 51-79. (doi:10.1007/s10443-014-9391-6).

Record type: Article

Abstract

The in-plane failure envelopes of unidirectional (UD) laminae in a UD and a Triax (0°, ±45°) laminate configuration have been investigated. The two laminate configurations have been characterised by testing off-axis specimens in uniaxial tension and compression at different angles relative to the fibre direction and further by Iosipescu shear tests. Strain gauge and Digital Image Correlation (DIC) measurements were used to measure the deformation states during loading, and to record the stress-strain responses to identify the initiation of failure and investigate the heterogeneity of the material and possible parasitic effects. A novel analysis methodology to determine the so-called ‘failure initiation strength’ based on the second derivative of the stresses with respect to the strains has been adopted. The experimentally determined ‘failure initiation stresses’ were compared with predictions from the commonly applied Maximum Stress, Tsai-Wu, and Puck failure criteria. From this work, a thorough comparison of the UD and Triax failure envelopes has been facilitated. It is shown that failure prediction for the Triax laminate based on the failure envelope derived from UD lamina tests may be too conservative in comparison with fitting a failure criterion directly to the Triax laminate test data. The latter approach implies that the Triax laminate is considered as a single lamina with homogenised properties, which in principle violates the theoretical background of the considered failure criteria, since these are established to predict failure for a UD lamina. However, the simple homogenisation is shown to be a useful design oriented approach for providing a simple estimation of the onset of failure in laminate configurations composed of e.g., multiple layers of Triax. Thus, a reliable and efficient approach is offered for the structural integrity assessment, which takes the non-crimp fabric configurations directly or ‘as delivered’ into account.

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More information

Accepted/In Press date: 13 March 2014
e-pub ahead of print date: 11 May 2014
Published date: February 2015
Keywords: failure characterisation, experimental characterisation, laminated composites, glass fibre reinforced plastic
Organisations: Civil Maritime & Env. Eng & Sci Unit

Identifiers

Local EPrints ID: 381239
URI: http://eprints.soton.ac.uk/id/eprint/381239
ISSN: 0929-189X
PURE UUID: 1822d117-0c4d-4b68-a79d-7a53391e6872

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Date deposited: 04 Sep 2015 12:24
Last modified: 15 Jul 2019 21:06

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Contributors

Author: S. Laustsen
Author: E. Lund
Author: L. Kühlmeier
Author: O.T. Thomsen

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