A Two-Ply Termination Strategy For Mechanically Coupled Tapered Laminates

York, C. (2015) A Two-Ply Termination Strategy For Mechanically Coupled Tapered Laminates. In: 20th International Conference on Composite Materials (ICCM20), Copenhagen, Denmark, 19-24 Jul 2015,

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Abstract

Tapered designs are currently certified only for balanced and symmetric laminate construction, despite the severe design constraint that 1 angle-ply termination requires a further 3 angle-ply terminations: two terminations to maintain balanced construction and a further two terminations to maintain symmetry. This constraint is often violated in practice, leading to localised thermal warping; the effects of which have yet to be quantified.

An obvious, but somewhat controversial strategy for ‘thin laminate’ designs, with traditional uni-directional (UD) material, is to adopt unbalanced and/or nonsymmetric stacking sequence configurations to fully exploit the available design space, particularly where tapered designs are a requirement. This extended design space has previously been shown to contain warp-free laminates with either fully uncoupled mechanical properties or with Extension-Shearing and/or BendingTwisting coupling behaviour.

Extension-Shearing coupling, which arises in unbalanced construction, can be exploited to produce bending-twisting deformation in aircraft wing-box structures when top and bottom skins have identical bias fibre alignment, but equally, this can be eliminated with opposing bias fibre alignment. Bending-Twisting coupling, which is generally present in symmetric laminate construction, results in weaker compression buckling strength compared to the equivalent fully uncoupled laminate (with matching stiffness properties), but with potentially stronger shear buckling strength.

Recent studies on Extension-Shearing and Bending-Twisting coupled laminates have provided useful insight into the available design space for tapered laminates with single angle-ply or cross-ply terminations. Similar tailoring strategies are now applied to unconventional tapered laminate designs (i.e. those free from the ubiquitous symmetric and balanced, or un-balanced, design constraint) with two-ply terminations, to investigate the extent to which angleply layers can be terminated without introducing Extension-Shearing coupling, or the extent to which angle- and cross-ply combinations can be terminated to tailor or maintain Extension-Shearing throughout the tapered laminate. Consideration is also given to the potential effectiveness of introducing tailored mechanical coupling through ply terminations, e.g. to induce bending-twisting coupling in a wing-tip or winglet, using Extension-Shearing coupling at the laminate level, whilst maintaining fully uncoupled laminate behaviour in the tapered skins elsewhere in the wing-box.

Item Type:Conference Proceedings
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:York, Dr Christopher
Authors: York, C.
Subjects:T Technology > T Technology (General)
College/School:College of Science and Engineering > School of Engineering > Aerospace Sciences
Copyright Holders:Copyright © 2015 The Author
Publisher Policy:Reproduced with the permission of the author.
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