Manufacture of long spars: Laminate design, experimental trials and non-destructive evaluation

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Although an enabler of high-rate manufacture, automated forming of components from flat laminates can result in fibre wrinkling. For the first time, fibre length is demonstrated to be a key driver of wrinkling defects when forming a C-spar with a central recess, at industrial length scales. Three such spars, of equal in-plane stiffness, were manufactured using Single Diaphragm Forming. Two contained standard ply angles (0°, 90° or ±45°) including 6 m long 0° fibres but had different stacking sequences, one shown to be formable in short spar trials, the other un-formable. A third spar also had a formable sequence but contained non-standard ply angles (angles other than 0°, 90° or ±45°) so that maximum fibre length was less than 0.6 m. Wrinkles occurred in both standard angle spars but did not occur in the non-standard angle case, demonstrating that use of formable, non-standard angle laminates can reduce scrappage of automatically formed aerospace parts, leading to significant time and cost savings in production.

Original languageEnglish
Article number110646
JournalComposites Part B: Engineering
Early online date23 Feb 2023
Publication statusPublished - 15 Apr 2023

Bibliographical note

Funding Information:
The authors gratefully acknowledge the financial support of the Engineering and Physical Sciences Research Council (EPSRC) , who fund the ADAPT project (EP/N024354/1), the Programme Grant “Certification for Design – Reshaping the Testing Pyramid” (CerTest, EP/S017038/1) and “Design simulation tools and process improvements for NCF preforming” (EP/P006701/1). Spar manufacture was undertaken at the National Composites Centre (using ADAPT funding) by Graham Clarke, Michael Bryant, Stuart Sykes and Andrew Bruton whose contributions are gratefully acknowledged. Richard Butler holds the Royal Academy of Engineering/GKN Aerospace Research Chair in Composites Analysis. The contributions of Yang Chen and Chrysoula Aza were supported by the Digital Engineering Technology and Innovation (DETI) programme. The authors are also grateful to Dr Kathryn Rankin and Prof. Ian Sinclair at the University of Southampton for X-Ray CT imaging, and to Steve Thomas at the University of Bath for his assistance with tooling and machining.

Data will be made available on request


  • Design for manufacture
  • Diaphragm forming
  • Length-effect
  • Non-standard ply angles
  • Wrinkling

ASJC Scopus subject areas

  • Ceramics and Composites
  • Mechanics of Materials
  • Mechanical Engineering
  • Industrial and Manufacturing Engineering


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