Performance analysis of a reduced cost manufacturing process for composite aircraft secondary structure

In the current, environmentally-aware, climate aircraft designers are under increasing pressure to<br/>produce fuel efficient vehicles. Weight reduction is an important method for increasing fuel<br/>efficiency. Fibre reinforced polymer (FRP) composites are known to offer weight savings over<br/>traditional metallic components, due to their excellent stiffness and strength to weight ratios.<br/>However, the major limiting factor for the use of aerospace quality composites is the<br/>manufacturing cost. The costs incurred in the conventional process of prepreg cured in an<br/>autoclave are well documented. The research in this thesis is concerned with reducing the cost of<br/>manufacturing aircraft standard carbon fibre composite sandwich panels, whilst maintaining<br/>mechanical performance.<br/><br/>The overall aim of the EngD is to provide a unified approach for assessing the performance of<br/>carbon fibre sandwich secondary structure that are manufactured using several different<br/>techniques. Cost and performance criteria are defined so that an optimal panel can be produced.<br/>The work has been motivated by the industrial sponsor, GE Aviation Systems. Five combinations<br/>of raw material and processing techniques, manufacturing options (MOs) were considered in<br/>incremental steps from the baseline of unidirectional prepreg cured in an autoclave to the noncrimp<br/>fabric (NCF) infiltrated using resin film infusion (RFI) and cured in a conventional oven.<br/>For cost and performance analysis a generic panel has been designed that is representative of<br/>secondary wing structure on commercial passenger aircraft. The cost was estimated by monitoring<br/>the manufacture of generic panels using each MO, whilst the performance was measured by both<br/>mechanical characterisation tests and by full scale tests on a custom designed rig. The rig applies a<br/>pressure load using a water cushion and allows optical access to the surface of the panel enabling<br/>the use of optical techniques, i.e. thermoelastic stress analysis (TSA) and digital image correlation<br/>(DIC). Feasibility tests on TSA and DIC demonstrated their use on the materials considered in<br/>this thesis, and were used to validate finite element (FE) models.<br/><br/>The RFI out-of-autoclave process was found to reduce generic panel manufacture time by almost<br/>30%, and the material cost was reduced by almost 40%. The mechanical characterisation tests<br/>suggested the ‘new’ process could produce laminates with a similar fibre volume fraction to that of<br/>the original process and similar in and out-of-plane mechanical properties. The in-plane stiffness<br/>was slightly reduced by 7 %, but the strength showed an increase of 12%. Full scale tests on the<br/>generic panels using point out-of-plane deflection measurements and full field TSA demonstrated<br/>the panel produced using the ‘new’ process has adequate performance. Moreover the full-field<br/>tests indicated an improvement in performance. Further work is required to optimise the design of<br/>the panel for weight, in particular the weight of the raw material, and investigating methods for<br/>modelling the NCF for certification.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2009

Author dc:creator

• Crump, Duncan Andrew

Advisor dc:contributor.advisor

• Barton, Janice