eprintid: 754
rev_number: 6
eprint_status: archive
userid: 17
dir: disk0/00/00/07/54
datestamp: 2019-05-11 14:01:46
lastmod: 2019-05-11 14:01:46
status_changed: 2019-05-11 14:01:46
type: report
metadata_visibility: show
creators_name: Barton, David
creators_name: Ockendon, H.
creators_name: Piette, Bernard
creators_name: Whittaker, Robert
creators_name: Campillo-Funollet, Eduard
creators_name: Jeffrey, Mike
creators_name: Ockendon, John
creators_name: Walsh, E.
corp_creators: Geoff Williams
title: New Techniques for Composite Wing Manufacture
ispublished: pub
subjects: aerodef
studygroups: ESGI138
companyname: Airbus
full_text_status: public
abstract: This report addresses the construction of carbon fibre wing boxes and the problems as- sociated with using carbon fibre sheets rather than individual carbon fibre tapes. In the case that the wing boxes are developable surfaces the lay up of carbon fibre sheets is straightforward, since the fibres can follow the contours of the surface without any need for shearing or extension of the fibres. To further expand the potential design space for the wing boxes, this report investigates the lay up of sheets over non-developable surfaces where some shearing of the sheet is required to achieve the desired results. In this report, three analytical approaches are considered, driven by the results from numerical studies on different surface geometries. Each of the approaches offers insights as to the type of geometric perturbations achievable when constrained by a maximum shear angle.
problem_statement: Within the aerospace industry there is an ongoing trend to manufacture large parts of new aircraft using carbon fibre rather than aluminium/titanium as is more conventional. This trend presents challenges; there is considerable expertise available within the manufac- turing community to produce a wide variety of complex geometries by machining aluminium — such expertise is not yet readily available for carbon-fibre parts which are constructed from flexible, but inelastic, fabric sheets.
Current wing box designs do not take into account the difficulties associated with carbon- fibre manufacturing methods. In particular, they do not consider that they should be easily constructed from flexible sheets that cannot be stretched. Consequently, the manufacture of existing wing-box designs from carbon fibre sheets is time consuming and difficult.
The problem considered here is to characterise the design constraints for carbon-fibre wing boxes, in other words, to find which designs are straightforward to manufacture.
With carbon-fibre construction, the wing box is constructed as two separate components fastened together. Each part contains a wing surface (upper or lower) and a vertical spar that spans the cross-section of the wing. 
We consider that the wing surface profile is given, with a set curvature both in the span- wise direction, and the fore-aft direction. The typical wing is 14 m meters in length and has a radius of curvature of the order of 65 m. Moreover, the wing has a slope of 15◦ near the aircraft, 7◦ at a distance of 4 m from the aircraft and 3◦ at the wing tip.
A spar then joins to the wing cover, roughly at right-angles to the wing surface, with a height of the order of 1 m.
The carbon fibre fabric comprises a woven mesh of individual fibres. Typically the fibres are grouped together to form flat ribbons, which are then woven in some pattern. These mesh fabrics do not stretch but can be sheared freely up to a critical shear angle (about 7◦ for the fabrics considered). The critical shear occurs when the ribbons come into contact, and the weave then prevents further shearing. In the construction process, several layers of carbon fibre fabric much be laid over a mould of the wing and spar shape. For structural strength, each single sheet should smoothly cover the wing and spar, without needing cuts or leaving wrinkles.
The Gaussian curvature of the wing surface is sufficiently small to allow the carbon-fibre sheets to be laid smoothly over the surface. Laying the carbon-fibre sheets over the edge and onto the spar presents greater difficulties. Airbus already appreciate that if two devel- opable surfaces are joined by a so-called ‘origami fold’ (i.e. one in which the two surfaces could be flattened out into a single developable sheet) then the carbon fibre sheets can be applied without any problems. When attempting to construct wing box components with a deviation from such a fold, it has been found that is is difficult to get the sheets to lie smoothly over the surfaces without rucks appearing.
The design space of a wing box that comprises an origami fold is too small to be useful. Instead, the main problem is to determine if one can modify the curvature of the spar by some amount and still be able to cover the wing cover and spar smoothly with carbon fibre, only allowing shear deformation of the fabric and with a shear angle below a given bound.
The Study Group was therefore asked to investigate the laying of carbon fibre sheets over different edge geometries, with a particular focus on trying to quantify how much deviation is permitted from the ideal ‘origami fold’ given the critical shear angle of the fabric.
date: 2018
citation:   Barton, David and Ockendon, H. and Piette, Bernard and Whittaker, Robert and Campillo-Funollet, Eduard and Jeffrey, Mike and Ockendon, John and Walsh, E.  (2018) New Techniques for Composite Wing Manufacture.  [Study Group Report]     
document_url: http://miis.maths.ox.ac.uk/miis/754/1/esgi-airbus.pdf