Prepared by Brian Knouff Advanced Composites Engineering The All Composite One Piece Bumper by Brian...

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


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


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


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


First Application

Aftermarket Class 8 Bumper


Background

Metal bumpers account for about half of the market


Background

Plastic bumpers make up the balance

Thermo Plastic Polyolefin

ABS Alloy

FRP

SMC


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%


Design Topology


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)


Deflections

0

2

4

6

8

10

12

14

Steel 3mm 6mm

50 Lb Load

300 Lb y

300 lb z


Weights (kg)

0

10

20

30

40

50

60

70

80

90

Steel 1mm 5mm 8mm


All Carbon and Ni/Carbon Hybrid Bumpers


GATS Bumper


2000 GATS Display


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


Production Launch


Old Production

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


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


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


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


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


Texturing CNC Plug


Production Process

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


Precut Preform

The pattern is cut from a single sheet of 3WEAVE fabric


Tucking Preform

Single layer of 54oz is conformed into the mold


In Service


Micrography

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


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

Prepared by Brian Knouff Advanced Composites Engineering The All Composite One Piece Bumper by Brian...

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