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Formula Student Germany

Formula Student Germany. FSAE-CFRP monocoque. Contents. Motivation Concept Dimensioning Design Cuts Manufacturing. Motivation. mass-specific mechanical properties safety lightweight design possibilities integration of functions (new challenge). Why a Monocoque ?.

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Formula Student Germany

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  1. Formula Student Germany FSAE-CFRP monocoque

  2. Contents • Motivation • Concept • Dimensioning • Design • Cuts • Manufacturing

  3. Motivation • mass-specific mechanical properties • safety • lightweight design possibilities • integration of functions • (new challenge) Why a Monocoque? • time and cost (depends) • design complexity • maintenance and repair Hastobeansweredduring design event!

  4. Concepts – Basic Options • axle to axle ↔ front-only • more interaction • no additional load transmissions • one-piece ↔ multi-part • manufacturability • no joint • push- ↔ pullrod • considerable influence on MC-design • manufacturing method • wide influence on MC-design • influence on cost • joint ↔ integrated • manufacturability • no joint • ergonomy und package • tool  mock-up • shouldn‘t change too often

  5. Concepts – Geometry Variation • simplified FE-model  qualitative analysis of concepts • initially: isotropic material • presumed weaknesses: • upper wishbones • cockpit

  6. Influence on Torsional Stiffness

  7. 300 mm F = 177 kN Preliminary Design: Frontal Crash

  8. CLT http://www.klub.tu-darmstadt.de/forschung/download.php

  9. FE-Model • anisotropic material • align element coordinate system! • shell elements • Ansys: SHELL99, SHELL91 • Input of single plies enables CLT and Puck to be used in Ansys • reasonable results without tests?

  10. Design in Detail • Load Transmission • Bonded Joint • Cockpit Reinforcement 1 3 2

  11. Load Transmission • critical • safety seat belt • suspension • complex detailed calculations • tests are more reasonable • integration of functions • roll hoops

  12. Bonded Joint

  13. Cockpit Reinforcement

  14. Machine-Cut Plies each cut  CAD surface model 3d surface  2d contour  *.dxf NX4 • less wasted material • faster manufacturing • higher quality splines  lines and circular arcs reduce number of segments nesting Autocad (Vistagy Fibersim, CATIA Composite Design, NX Laminate Composites)

  15. Ply Book • ply book pages for overview and for each cut • in sequence of actual manufacturing steps • if necessary: exact position and alignment

  16. Manufacturing • Epoxy blocks cut • and bonded • 5 axis mill

  17. fine-grained abrasive paper • mould release agent • alignment pins • CFK tooling prepregs • (2x200gr | 3x650gr | 1x200gr)s

  18. autoclave curing of negative moulds • defrosting of prepregs • CNC cut plies

  19. labeling and arranging • first face • positioning via pins

  20. inserts are also nested • CFK panel  jet cutting • honeycomb core machine cut • insert positioning via pins

  21. vacuum • parts to be cured in autoclave • 2 or 3 shots

  22. removing alignment pins • demoulding • bonding • tension belts

  23. Tips for a Start • Material • high-tension fibres aren‘t beneficial for axial compression • high modulus fibres: brittle, low ultimate elongation! • fabric: fine, compact, not wavy  twill or sateen (e. g. 3k-yarn: 200g/m² for instance) • local UD reinforcements (e. g. for distinct, not varying state of stress) • core: e. g. fine aluminum honeycombs of low density • Concept • examine concepts and solutions of other teams • define manufacturing method early (depends on your options and those provided by partners) • Design • define package early • lightweight construction! • symmetrical ply layout • complete CAD model • avoid unnecessary joints

  24. See you at Hockenheim 05. – 09. August 2009

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