The All Composite One Piece Bumper

1
The All Composite One Piece Bumper

• by
• Brian Knouff
• 3rd Annual SPE Automotive Composites Conference
• September 9 10, 2003
• Troy, MI

2
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

3
Challenging Sacred Cows

• Glass not Stiff Enough to Replace Steel
• Carbon Too Expensive
• Composites Cant be Attached
• adhesives work in some applications
• Composites Display Poor Fatigue Properties
• Process Cycle Time Too Long

4
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

5
First Application

• Aftermarket Class 8 Bumper

6
Background

• Metal bumpers account for about half of the market

7
Background

• Plastic bumpers make up the balance

SMC
Thermo Plastic Polyolefin
ABS Alloy
FRP
8
Design Requirements

• Natural Frequency gt50 Hz
• Deflect lt0.5 inches with 300 lb downward load at
  end
• represents large person stepping on bumper to
  clean hood, etc
• Deflect lt0.5 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 gt 50

9
Design Topology
10
Design Comparisons
11
Deflections
12
Weights (kg)
13
All Carbon and Ni/Carbon Hybrid Bumpers
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GATS Bumper
15
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
  todays 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

17
Production Launch
18
Old Production

• Very large volumes
• Huge investments in tooling
• Every part the same
• Part/Plant redesign every 10 years or so

19
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

20
Production Intent

• Aftermarket Class 8 Bumper
• Less than 40 lbs.
• Nf20 Hz
• 1 piece construction

• Charcoal gray or black color
• No visible fibers on front face
• Textured, non-painted surface

21
Part Design

• 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

• Optimized for Natural Frequency
• Topology dictated areas of critical mass.

22
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

23
Texturing CNC Plug
24
Production Process

• Vacuum Infusion
• Closed 2-sided mold
• No injection pressure
• Vacuum at exhaust pulls resin through inlet and
  through fabric

25
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
27
In Service
28
Micrography

• Microscopic analysis displays
• Excellent wetout
• Absence of voids
• Good fiber distribution
• Barrier coat thickness

29
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