Creating a Future for Engineers

Formula Student Germany

Wet laminated CFRP monocoque

Manuel Baumann amz.ethz.ch

Creating a Future for Engineers

Introduction

Creating a Future for Engineers

Mold manufacturing

Part manufacturing

Additions

Potential

Bill of Material

Timeline

Index

Creating a Future for Engineers

Positive molds

Laminated negativ molds

Wet laminated monocoque

Bonded halves

Mold manufacturing – Concept

Creating a Future for Engineers

Mold manufacturing – Molding material

MDF PU Aeroboard 70

Density 800 kg/m ³ 630 kg/m ³

Thermal expansion 7.5*10-6 46.8*10-6

Thermal resistance >100° 93°

Cost 500 EUR/m³ 8000 EUR/m³

Disadvantage MDF

Inhomogeneous density over thickness

Sensitive to humidity

Creating a Future for Engineers

Mold manufacturing – Positive molds Bonding

Creating a Future for Engineers

Mold manufacturing – Positive molds Milling

Creating a Future for Engineers

Mold manufacturing – Positive molds Sanding

Creating a Future for Engineers

Mold manufacturing – Positive molds Priming

Creating a Future for Engineers

Mold manufacturing – Positive molds Bolts for insert positioning

Internal thread

Creating a Future for Engineers

Material choice: CFRP

Alternative material: GFK

Mold manufacturing – Negative molds

Creating a Future for Engineers

Formenharz P

Mold manufacturing – Negative molds

Creating a Future for Engineers

Formenharz P

Connection layer:

Epoxy

Fibreglas

Flocs

Thixotropiermittel

Mold manufacturing – Negative molds

Creating a Future for Engineers

Formenharz P

Connection layer

6 Layers carbon fibre

600 gr/m²

Mold manufacturing – Negative molds

Creating a Future for Engineers

Formenharz P

Connection layer

6 Layers carbon fibre

Vacuum

Mold manufacturing – Negative molds

Creating a Future for Engineers

Formenharz P

Connection layer

6 Layers carbon fibre

Vacuum

Demoldi

Mold manufacturing – Negative molds

Creating a Future for Engineers

Formenharz P

Connection Layer

6 Layers Carbon Fibre

Vacuum

Demold

Finished mold

Mold manufacturing – Negative molds

Creating a Future for Engineers

Core material:

Divinycell HP 60 foam

Insert material

Carbon and wood

Part Manufacturing – Material choice

Creating a Future for Engineers

2 core layers of 5mm

Heat bending

Part manufacturing – Monocoque halves

Creating a Future for Engineers

2 core layers of 5mm

Heat bending

Vacuum bonding

Sanding

Part manufacturing – Monocoque halves

Creating a Future for Engineers

Mold release agent

Frecote

Part manufacturing – Monocoque halves

Creating a Future for Engineers

Mold release agent

Frecote

Resin: Hexion L 235

Hardener L236

Microballons for filling the gaps

Part manufacturing – Monocoque halves

Creating a Future for Engineers

Procedure

4 layers CFRP

Placing core / inserts

12 h vacuum

4 inner layers CFRP

15 h vacuum

12-20 h curing at 80°

Part manufacturing – Monocoque halves

Creating a Future for Engineers

Bonding

the halves

Part manufacturing – Joining upper and lower halves

Creating a Future for Engineers

Roll hoop

Part manufacturing – Additional structural parts

Creating a Future for Engineers

Roll hoop

Rib

Part manufacturing – Additional structural parts

Creating a Future for Engineers

Weight: 21kg (without rollhoops)

Part manufacturing – Result

Creating a Future for Engineers

Painting

Degreasing

Primer

Sanding

White color

Sanding

White color

Clear varnish

4kg

Part manufacturing – Additional structural parts

Creating a Future for Engineers

Prepreg Monocoque: -Temperature resistant resin for negative molds

-Same manufacturing process

Advantage: Less weight, better surface, no painting needed

Additions – Potential

Creating a Future for Engineers

Additions – Bill of material

Material Amount Price

CFRP 600g/m2 for negative molds 30m2 1200EUR

CFRP 250g/m2 for monocoque 40m2 1400EUR

Foam Core 5mm 6m2 300EUR

MDF 0.8m3 500EUR

Resin 35kg 600EUR

Vacuum material 300EUR

Total 4300EUR

Creating a Future for Engineers

Important:

Well organiced workspace for laminating and sanding

2-4 people needed during laminating (due to little pot-life)

We used 8 weeks, mostly one person for positive molds, negative molds and monocoque

Additions – Timeline

Creating a Future for Engineers

05. – 09. August 2009

See you at Hockenheim