Properties and service performance

European Commission Directorate-General For The Information Society And Media Directorate-General For Research And Innovation

Description

Weight reduction of vehicle sub-assemblies using thin-walled adhesively bonded steel composite structures
Industrial research and development

Informations

• Publié par: EUROPEAN-COMMISSION-DIRECTORATE-GENERAL-FOR-THE-INFORMATION-SOCIETY-AND-MEDIA-DI
• Nombre de lectures: 17
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

Commission of the European Communities
technical steel research
Properties and service performance
Weight reduction of vehicle sub-assemblies using thin-walled
adhesively bonded steel composite structures Commission of the European Communities
technical steel research
Properties and service performance
Weight reduction of vehicle sub-assemblies using thin-walled
adhesively bonded steel composite structures
A. B. Haberfield, G. M. Davis
British Steel pic
9 Albert Embankment
London SE1 7SN
United Kingdom
Contract No 7210 - KC/806
(1.7.1985-30.6.1988)
Final report
Directorate-General
Science, Research and Development
1990 EUR 12770 EN Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Di recto rate-Genera I
Telecommunications, Information Industries and Innovation
L-2920 Luxembourg
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of then is responsible for the use which might be made of
the following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1990
ISBN 92-826-1475-1 Catalogue number: CD-NA-12770-EN-C
© ECSC-EEC-EAEC, Brussels · Luxembourg, 1990
Printed in Belgium WEIGHT REDUCTION OF VEHICLE SUB-ASSEMBLIES USING THIN
WALLED ADHESIVELY BONDED STEEL COMPOSITE STRUCTURES
British Steel/Austin Rover
ECSC Agreement No. 7210.KC/806
Summary Report
In recent years, a considerable amount of work has been carried out, under ECSC aegis,
to seek effective means of reducing the weight of vehicle structures primarily through
the use of certain high strength steels. These researches have involved the concept of
substituting steel sheet with increased strength to compensate for a reduction in sheet
thickness, for example, body panels of thickness down to 0.6/0.7mm and structural
members down to 1.2mm.
The possibility of enhanced weight reduction by reducing the thickness much more
significantly than in the earlier researches, was explored by using body panels of
thickness down to 0.3mm and compensating for this significants reduction by
inducing deliberate geometric changes in the plane of the sheet to enhance the
structural moduli of sub-assemblies. These changes included the use of
rigidized/embossed sheet, produced by rolling techniques, together with specially
designed composite panels made from rigidized/embossed sheet adhesively bonded to
equally thin flat "skins".
(a) Panel Applications
To assess the potential of rigidizing for panel type applications, corner to corner, print-
through, dynamic dent tests, static dent and bend tests were carried out on both
rigidized and non-rigidized panels. From the results obtained a number of basic rules
were established as follows:-
1. The stiffer the adhesive used the better the corner to corner deflection
performance and the better the denting performance.
2. The stiffer the adhesive, the more susceptible the assembly is to print-
through, although careful choice of outer and inner skin thickness can
overcome this effect.
3. The yield strength of both the outer and inner skins does not affect the corner
to corner deflection performance, although increasing the yield strength of
the outer skin improves the denting performance.
4. The yield strength of the outer skin compared to the inner skin does not
significantly improve print-through.
5. Increasing the thickness of the outer and the inner skins significantly
improves corner to corner deflection, although only the thickness of the outer
panel affects denting performance. Only the thickness of the outer panel
relative to the thickness of the inner skin affects print-through with best
results where the outer skin is thickest.
These concepts have been applied to an automotive bonnet (Rover 200 series). For this,
a composite system comprising a flat rephosphorised steel (0.55mm) outer with a CRI
rigidized (0.28mm) inner bonded with XB7265 adhesive was chosen for inclusion in the
finite element computer model to produce a feasible design. To facilitate this analysis,
an "equivalent thickness" of isotropic material was calculated and the elastic constants
were determined from strip bending and plate bending tests. Computer modelling of a current production bonnet skin was carried out and the torsion and bending behaviour
of the bonnet predicted. Compared to the measured values from a production bonnet, it
was predicted from the computer model that the composite bonnet would be stiffer as
well as lighter.
A number of composite bonnets were produced and their performance during bend and
torsion tests compared both with a current production bonnet and computer predictions
developed fore assemblies. The results obtained indicate a close correlation
between actual and predicted performance. In addition, the results indicated that there
is some potential for weight reduction compared to the existing assembly.
(b) Structural Applications
The applicability of composite panels incorporating rigidized steel skins to structural
applications was assessed in terms of bend properties, torsional rigidity and collapse
resistance of closed top-hat structures.
The results of torsion and bend tests indicated that increasing either the stiffness of the
adhesive or the sheet thickness led to a marked improvement in the rigidity of the
structure. Increasing the yield strength or using a rigidized sheet in place of non-
rigidized sheets led to little improvement. It was shown that, the stiffness of the closing
plate is the controlling factor determining the torsional stiffness of the structure. To
optimise torsional stiffness, it is necessary to use a closing plate which is much thicker
than the top-hat stiffener.
Of the adhesives investigated, the epoxy types proved to be the most suitable for
structural applications both in terms of stiffness and collapse resistance. However, the
epoxy type adhesives used in the current studies possessed insufficient collapse
resistance at high temperatures. In addition, their resistance to long term weathering
is inadequate and would not meet service requirements.
- IV CONTENTS
Page
SUMMARY III
1. INTRODUCTION 1
2. PRINCIPLE OF QUILTED LAMINATES 2
2.1. Rigidized sheet
2.2. Production of laminates 3
2.3. Formability 4
3. APPLICATION OF LAMINATES TO PANEL OR BONNET
APPLICATIONS 5
3.1. Basic properties
3.2. Computer modelling of Rover 200 bonnet 10
3.3. Costing evaluation 16
3.4. Composite bonnet build7
3.5. Corrosion testing 2
3.6. Conclusions
4. APPLICATION OF LAMINATES TO STRUCTURAL USES1
4.1. Crush resistance of structures
4.2. Side impact
4.3.e bend tests8
4.4. Torsion testing 29
4.5. Discussion 3
4.6. Conclusions2
5. OVERALL CONCLUSIONS
6. REFERENCES3
TABLES - FIGURES5
V List of Tables
IA Analysis of Steels Investigated
IB Tensile Properties of Steels Investigated
Π Corner to Corner Deflection Tests
ΒΊ Results of Print Through Tests
rV Static Dent Test Results
V Impact Velocity:Dent Depth Results
VI Linear Regression Analysis of the Dent Depth:Impact Velocity
Relationship
VU Influence of Configuration on Collapse Characteristics of
0.3mm CRI Material
Vm Summary of Side Impact Tests (XB7265 Adhesive - Test
Configuration F)
IX Influence of Test Direction on Bend Angle at a Constant
Kinetic Energy of 526J
X Results of Side Impact Tests*On Type D Structures involving Dissimilar
Steels
XI Summary of Side Bend Tests
ΧΠ Torsion Test Results on Adhesive Bonded and Spot Welded Closed-Hat
Sections
Xffln Test Results
VII -