Creating a Future for Engineers Formula Student Germany FSAE-CFRP monocoque

Creating a Future for Engineers Contents  Motivation  Concept  Dimensioning  Design  Cuts  Manufacturing

Creating a Future for Engineers +mass-specific mechanical properties +safety +lightweight design possibilities +integration of functions +(new challenge) Motivation -time and cost (depends) -design complexity -maintenance and repair Why a Monocoque? Has to be answered during design event!

Creating a Future for Engineers  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 Concepts – Basic Options  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

Creating a Future for Engineers Concepts – Geometry Variation  simplified FE-model  qualitative analysis of concepts  initially: isotropic material  presumed weaknesses:  upper wishbones  cockpit

Creating a Future for Engineers Influence on Torsional Stiffness

Creating a Future for Engineers 300 mm F = 177 kN Preliminary Design: Frontal Crash

Creating a Future for Engineers no.materialE || EE G    Corres ponding  1E-Glas / EP ,2520,6 2HTA/MTM ,3351,550,6 3T700S/MTM ,331,550,6 no.materialR || t R  c RtRt RcRc R  || Corres ponding  1E-Glas / EP ,6 2HTA/MTM ,323289,30,6 3T700S/MTM ,3180,256,80,6 loads n x [N/mm]-147,5 laminate lay-up lamina t k [mm]  material 1 0,11600, ,116900, ,116450, , , ,46200, , , ,116450, ,116900, ,11600,498 lamina angle [  ]   [%]   [%]   [%]   [N/mm 2 ]   [N/mm 2 ]   [N/mm 2 ] f E,FF f E,IFF Fracture mode Fracture angle weakening 10,00-0,170, ,60,500,150,01A03 290,000,05-0,17051,6-12,900,030,06C51, ,07-0,06 0,23-63,8-6,28,60,050,08B ,07-0,06 -0,23-63,8-6,2-8,60,050,08B02 50,00-0,170, ,60,500,150,01A ,07-0,06 -0,23-63,7-6,2-8,60,050,08B02 745,07-0,06 0,23-63,7-6,28,60,050,08B02 890,000,05-0,17051,6-12,900,030,06C51,22 90,00-0,170, ,20,500,150,01A03 reserve factor laminate fracture 6,6 reserve factor first inter-fibre fracture 6,6 CLT

Creating a Future for Engineers 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?

Creating a Future for Engineers 1.Load Transmission 2.Bonded Joint 3.Cockpit Reinforcement Design in Detail 1 2 3

Creating a Future for Engineers Load Transmission  critical  safety seat belt  suspension  complex detailed calculations  tests are more reasonable  integration of functions  roll hoops

Creating a Future for Engineers Bonded Joint

Creating a Future for Engineers Cockpit Reinforcement

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

Creating a Future for Engineers Ply Book  ply book pages for overview and for each cut  in sequence of actual manufacturing steps  if necessary: exact position and alignment

Creating a Future for Engineers Manufacturing  Epoxy blocks cut  and bonded  5 axis mill

Creating a Future for Engineers  fine-grained abrasive paper  mould release agent  alignment pins  CFK tooling prepregs  (2x200gr | 3x650gr | 1x200gr)s

Creating a Future for Engineers  autoclave curing of negative moulds  defrosting of prepregs  CNC cut plies

Creating a Future for Engineers  labeling and arranging  first face  positioning via pins

Creating a Future for Engineers  inserts are also nested  CFK panel  jet cutting  honeycomb core machine cut  insert positioning via pins

Creating a Future for Engineers  vacuum  parts to be cured in autoclave  2 or 3 shots

Creating a Future for Engineers  removing alignment pins  demoulding  bonding  tension belts

Creating a Future for Engineers Tips for a Start  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  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

Creating a Future for Engineers 05. – 09. August 2009 See you at Hockenheim