prepared by brian knouff advanced composites engineering the all composite one piece bumper by brian...
TRANSCRIPT
Prepared by Brian Knouff Advanced Composites Engineering
The All Composite One Piece Bumper
by
Brian Knouff
3rd Annual SPE Automotive Composites Conference
September 9 – 10, 2003
Troy, MI
Prepared by Brian Knouff Advanced Composites Engineering
Introduction
Delphi Composites Center of Excellence set up to Affordably Integrate Composites into Transportation Industry
– ~ 1999– Stemmed from columns work done in Salt Lake City
Cost penalty realized Other benefits crucial Class 8 truck market benefits:
– Less road wear and tear– Fewer loads for those vehicles which gross out
» Less traffic» Less pollution
– Less maintenance for those which cube out» Better mileage
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Challenging Sacred Cows
Glass not Stiff Enough to Replace Steel Carbon Too Expensive Composites Can’t be Attached
– adhesives work in some applications
Composites Display Poor Fatigue Properties Process Cycle Time Too Long
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Strategy
Utilize Advanced Modeling Techniques to Optimize Composite Designs
Work with Government Labs, Universities and Commercial Partners to Investigate Alternative Precursors/Carbonization Techniques
Develop Novel Processes with Emphasis on Reduced Cycle Times
Work with Suppliers to Reduce Material Costs at High Volumes
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First Application
Aftermarket Class 8 Bumper
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Background
Metal bumpers account for about half of the market
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Background
Plastic bumpers make up the balance
Thermo Plastic Polyolefin
ABS Alloy
FRP
SMC
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Design Requirements
Natural Frequency >50 Hz Deflect <0.5 inches with 300 lb downward load at end
– represents large person stepping on bumper to clean hood, etc…
Deflect <0.5 inches with 50 lb forward load at end– represents hitting small object, windloads, etc…
Aesthetically pleasing with carbon fiber visible– Class A surface
Mass savings > 50%
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Design Topology
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Design Comparisons
Material RedThick
GreenThick
Weight,
NatFreq,
Deflection 1+,
Deflection2++,
Steel 4.55 4.55 82 54 .47 0.51 1.3
Aluminum 4.55 4.55 30 54 1.3 1.4 3.5
Composite 0 1* 1** 5.8 24 43 29 90
Composite 1 3* 1** 11 43 5.1 5.4 13.7
Composite 2 5* 1** 17 52 2.3 2.6 6.2
Composite 3 6* 1** 19 57 1.8 2.0 4.6
Composite 4 8* 1** 25 64 1.1 1.2 2.7
*represents 1 mm of carbon fabric and rest chopped glass**1 mm of carbon fabric+ deflection due to 50 lb load at end of bumper in z direction (pushing the bumperback)++ due to 300 lb downward load at end of bumper (both downward –y- and backward –z- deflections shown)
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Deflections
0
2
4
6
8
10
12
14
Steel 3mm 6mm
50 Lb Load
300 Lb y
300 lb z
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Weights (kg)
0
10
20
30
40
50
60
70
80
90
Steel 1mm 5mm 8mm
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All Carbon and Ni/Carbon Hybrid Bumpers
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GATS Bumper
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2000 GATS Display
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Conclusions
Composite bumpers can be designed to replace either steel or plastic bumpers
Composite bumpers can be commercialized in today’s market at high volumes (competitive piece price)
Versus Steel– lighter– increased design flexibility– lower tooling costs
Versus Plastic– stronger– stiffer– fewer parts (1 versus 40)– lower tooling costs
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Production Launch
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Old Production
Very large volumes Huge investments in tooling Every part the same Part/Plant redesign every 10 years or so
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New Production
Low to medium volumes as well as high volumes Minimal investments in tooling Parts constantly changing Plants fluid (modular) and lean Opportunity for structural polymer composites
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Production Intent
Aftermarket Class 8 Bumper Less than 40 lbs. Nf~20 Hz 1 piece construction
Charcoal gray or black color No visible fibers on front face Textured, non-painted
surface
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Part Design
Optimized for Natural Frequency Topology dictated areas of critical
mass.
Product Design– Math-based Optimization– Optimize with design responses,
variables, constraints, and objectives– Grid can be made dynamic– Typical design parameters include:
» thickness» fiber type» fiber orientation» fiber volume fraction» shape
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Process Development
Low-cost tooling– not steel or aluminum
Easy preform construction– no spray or robotic tooling– few piece construction– template cutting
» switch to more automated process in production
Minimize equipment $– vacuum infusion versus RTM
Experience showed that stitched fabrics too tight to vacuum infuse
– needed to use rollers for GATS bumpers
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Texturing CNC Plug
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Production Process
Vacuum Infusion Closed 2-sided mold No injection pressure Vacuum at exhaust pulls resin through inlet and through fabric
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Precut Preform
The pattern is cut from a single sheet of 3WEAVE fabric
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Tucking Preform
Single layer of 54oz is conformed into the mold
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In Service
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Micrography
Microscopic analysis displays:– Excellent wetout– Absence of voids– Good fiber distribution– Barrier coat thickness
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Make A Part
Today– Place several materials into
mold– Form materials into mold– Process materials into mold– Remove part– Trim and package– Ship
Future– Place net-shape preform into
mold
– Process into part– Remove part
– Ship