Page 604 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Design and material utilization C HAPTER 18.1

Fig. 18.1-25 Saturn spaceframe showing polymer panels on a four-door sedan. 10

which could accommodate any differences in expansion the most effective type of corrosion protection allowing
between the two materials. The GM Saturn, shown in the encapsulation and full coverage of spot welds and cut
Fig. 18.1-25, has used the same type of pressed steel edges, although thickness control can be variable and
spaceframe (lower parts galvanized) for structural in- result in a weight penalty.
tegrity and strength while clad in thermoplastic skin
panels (doors, fenders, quarter panels and fascias) to
enhance corrosion resistance and reduce damage from 18.1.7.3 Examples of pressed aluminium
low speed impacts. The roof, bonnet and boot lid are spaceframes and associated designs
retained in steel and the skin assemblies are painted in
complete sets on support bucks in simulated on-car po- Again referring to examples of design innovation within
sitions. The design technology was carried forward and the Rover vehicle range, the experimental ECV3 vehicle
developed with the Renault Espace which featured had demonstrated that the base unit concept could be
a steel substructure (in reality unibody structures extended further to provide an even lighter structure
with non-structural plastic cladding panels), but the using aluminium pressed parts. The torsional stiffness in
distinction here was that the steel substructure was fully that case was improved by the use of adhesive in
hot-dip galvanized prior to cladding with a polymer ex- a weldbonding mode employing a specially developed
terior, the penetration of zinc into crevices adding to the pretreatment and prelubrication technology. The
torsional stiffness of the main frame. This is theoretically manufacturing feasibility of this approach was proven by

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