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Approximate method of predicting ply crack formation in general symmetric laminates subject to biaxial loading and bending.

McCartney, L N (2008) Approximate method of predicting ply crack formation in general symmetric laminates subject to biaxial loading and bending. In: 13th European Conference on Composite Materials (ECCM-13), 2-5 June 2008, Stockholm, Sweden.

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Ply cracking is a very important damage mode for laminated composite materials that has been the subject of intensive study over many years, especially cross-ply laminates. In practical applications, laminates are usually more complex than cross-plies, and they are subject to complex loading that involves both in-plane and out-of-plane deformation, in addition to residual stresses arising from thermal expansion mismatch effects between the plies. Based on a methodology that is able to predict ply cracking for: i) a multiple-ply cross-ply laminate subject to combined biaxial in-plane loading and biaxial bending, and ii) a general symmetric laminate subject to combined in-plane biaxial loading and in-plane shear loading, where thermal residual stresses can be present, this paper will attempt to combine the models developed for these situations so that ply cracking in general symmetric laminates subject to combined in-plane biaxial and out-of-plane biaxial bending can be treated. It is first assumed that laminates have at least one 90o ply, and that ply cracking occurs only in some of all of the 90o plies. The off-axis plies in the laminate, which are uncracked, are first homogenised into an orthotropic effective medium. The next step is to apply the homogenised properties to the 0o plies of an equivalent hybrid cross-ply laminate that is then subject to progressive loading involving any combination of in-plane biaxial loading and out-of-plane bending. The homogenisation approach is tested, for the case of uniaxial in-plane loading, by comparing predictions of the homogenised model with those of an existing model that allows for the presence of all the off-axis plies. For more complex loading states, an example will be given of a prediction of the progressive growth of ply cracking, and of laminate stress-strain behaviour.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Keywords: Composites, laminates, ply cracking, biaxial loading, bending deformation
Subjects: Advanced Materials
Advanced Materials > Metals and Alloys
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4492

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