Class A Carbon Fibre Reinforced Plastic (CFRP) Body Panels on The MG Rover SV
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Transcript of Class A Carbon Fibre Reinforced Plastic (CFRP) Body Panels on The MG Rover SV
Class A Carbon Fibre Reinforced Plastic (CFRP) Body Panels on
The MG Rover SV
SPE 2003
Class A CFRP on a OEM Supercar
Customer requirements
Manufacturing solution for 250 units per year
Design freedom to develop a visually striking car
Low body weight to aid performance
Class A finish for vehicle life
Short lead time from concept to production
Design flexibility / niche production volumes
Design factors lead to a carbon fibre reinforced plastic (CFRP) solution Allows for a faster prototyping cycle while maintaining realistic development costs
The car consists of 32 composite components that vary in both size and complexity
Design flexibility / niche production volumes
Prototype phase was to last 5 months and produce a full set of male masters, a full set of female production tools and the first 5 prototype car sets
Nov 2002 – Car Unveiled at the British motor show
Dec 2002 – Orders placed to machine male masters
Jan 2002 – Tooling manufactured
Feb 2002 – Composite layup designs generated
March 2002 – First car set delivered
April 2002 – Cars sets delivered 2-5
The budget assigned to complete this phase was approximately $1.5m
History of lightweight CFRP in automotive (light, stiff, strong)
CFRP prepreg application
Tool Face
Carbon Prepreg (280g 4x4 Twill)Glue Film
Honeycomb Core
Advantages Extremely light weight High Stiffness High Strength Short Lead Time Cost effective tooling for limited No. parts
Disadvantages Limited cycle time due to labour intensive process
Premium material costs Expensive autoclave curing Surface needs significant work to achieve Class A
Attributes of CFRP prepreg
Material developments
Breathable Prepregs
Dry fibres extract air from laminate prior to curing
Eliminates the need for debulks, autoclave and allows for multiple plies to be laid up at once
Faster lay-up due to heavier more frequent plies
A single ply material capable of a CPT from 0.04” > 0.1” Designed to have a Tg1 > 260oF for stability in high
ambient temps Process can be adapted for different fibre architecture Syntactic core is currently manufactured at 0.04” and 0.03” Minimise weight/ maximise stiffness by increasing
thickness remove fibre from neutral axis,replace with low density resin
Car Body Sheet (CBS)
Woven Carbon
& Epoxy Skins
Low density
syntactic core
SPRINT CBS micrograph
0.011”
0.011”
0.04”
Advantages Combination of fibre and syntactic resin provides a
laminate that weighs 20% of steel (0.04”) for equivalent stiffness
Or weighs 35% (0.06”) of aluminium for equivalent stiffness
Dry fabrics aids air evacuation, typically void content 0 – 0.5 %
Zero bleed process therefore possible to accurately control component tolerances +/- 0.005”
Attributes
Issues effecting Class A
Pin holes caused by entrapped air, leads to surface defect
Surface Void Primer LayerColour Coat
Will require rework before repainting
Issues effecting Class A
Fibre read through caused by different CTE of resin system and fibre
Hard to conceal with a paint process Typically remerges with time/temperature/humidity
Issues effecting Class A
Mould Quality – Components ultimately reflect the tools from which they were removed
Air entrapment is eliminated by fine fibre structure sandwiching a catalysed resin film, on curing this forms a homogeneous surface layer
Class A surface films
The resin system is engineered with a Tg in excess of 260oF and additives to reduce the CTE
(Carbon 3 x 10–6/oC , Epoxy 70 x 10 –6/oC, SF 30 x 10 –6/oC )
The fabric used is a specially selected thermoplastic to ensure its mechanical properties does not distort the surface resin layer in service. (Low Modulus)
Finely woven thermoplastic
Resin Matrix has Tg > 260oF
Resin is formulated with
easy sand fillers to aid prep.
Woven Carbon
& Epoxy Skins
Low density
syntactic core
Class A surface film
Class A surface film
BlisteringPanel Primer Initial 240h hum. Initial 240h hum. Initial 240h hum. 240h hum.
SP CBS 830R 88,9 88,3 Gt 0 Gt 0 10 9 fewhigh build 87,2 86,2 Gt 0 Gt 0 10 10 microhigh build+flex 86,4 85,3 Gt 0 Gt 0 10 10 none
Competitor Y
830R 88,6 88,5 Gt 0 Gt 0 10 10 few high build 86,9 85,9 Gt 0 Gt 0 10 10 nonehigh build+flex 87,3 85,8 Gt 0 Gt 0 10 10 none
Competitor Z
830R 87,5 87,8 Gt 0 Gt 0 9 9 fewhigh build 87,1 85,1 Gt 0 Gt 0 9 9 nonehigh build+flex 86,6 85,2 Gt 0 Gt 0 9 10 none
Gloss Adhesion (#) Adhesion (X)
Class A surface film
ChipPanel Primer Initial 240h hum. Temp. cycle - 4°F
Fibre read through
SP CBS 830R slight slight slight Gr 2high build slight slight slight Gr 1high build+flex OK OK OK Gr 1
Competitor Y
830R moderate moderate severe Gr 2high build moderate moderate severe Gr 1high build+flex moderate severe severe Gr 2
Competitor Z
830R moderate severe moderate Gr 3high build moderate severe moderate Gr 2high build+flex moderate severe moderate Gr 2
Class A panels under Defracto analysis
Typical Component
Thin aerofoil requires increased stiffness through addition of syntactic cores
Indicator cut out, syntactic core must be removed
Mounting point on perimeter of part requires reinforcement
Meeting productivity
Still a manual process dependent of operators with some composite experience Productivity is a function of the number of components fabricated in tool over a period of time Minimise manual operations both in and out of the tool, decrease cost and increase productivity
Pre kit materials to form just one structural ply
Meeting productivity
Kits are delivered to the customer with surface film and CBS ready for application.
The prototyping phase was completed on time with the first 5 test vehicles produced within the 5 month cycle within budget
With in the next 2 months a further 10 production prototypes were produced
Currently from 1 tool set and a single shift production stands at 5 car sets a week (250 units per annum)
Paint lines are reporting a 80% increase on productivity over previous composite vehicle
Current programs are based around manufacturing 3000 parts per annum
Summary