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?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. material E|| E G Corresponding

1 E-Glas / EP 44480 13219 5562 0,25 2 0,62 HTA/MTM49-3 125650 9800 4580 0,335 1,55 0,63 T700S/MTM49-3 125300 9105 3830 0,33 1,55 0,6

no. material R||t R

c Rt R

c R||Corres

ponding 1 E-Glas / EP 1100 1000 54 150 75 0,62 HTA/MTM49-3 1810 1455 35,3 232 89,3 0,63 T700S/MTM49-3 2662 1386 28,3 180,2 56,8 0,6

loads

nx [N/mm] -147,5

laminate lay-uplamina tk [mm] material

1 0,116 0 0,49 8

2 0,116 90 0,49 8

3 0,116 45 0,49 8

4 0,116 -45 0,49 8

5 0,462 0 0,49 8

6 0,116 -45 0,49 8

7 0,116 45 0,49 8

8 0,116 90 0,49 8

9 0,116 0 0,49 8

lamina angle [] [%] [%] [%] [N/mm2] [N/mm2] [N/mm2] fE,FF fE,IFFFracture

modeFracture

angleweakening

1 0,00 -0,17 0,05 0 -179,6 0,5 0 0,15 0,01 A 0 32 90,00 0,05 -0,17 0 51,6 -12,9 0 0,03 0,06 C 51,22 23 45,07 -0,06 -0,06 0,23 -63,8 -6,2 8,6 0,05 0,08 B 0 24 -45,07 -0,06 -0,06 -0,23 -63,8 -6,2 -8,6 0,05 0,08 B 0 25 0,00 -0,17 0,05 0 -179,6 0,5 0 0,15 0,01 A 0 36 -45,07 -0,06 -0,06 -0,23 -63,7 -6,2 -8,6 0,05 0,08 B 0 27 45,07 -0,06 -0,06 0,23 -63,7 -6,2 8,6 0,05 0,08 B 0 28 90,00 0,05 -0,17 0 51,6 -12,9 0 0,03 0,06 C 51,2 29 0,00 -0,17 0,05 0 -179,2 0,5 0 0,15 0,01 A 0 3

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

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

Auto

cad

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