Note: Descriptions are shown in the official language in which they were submitted.
W() 9~/06~5 2 ~ ~ ~ 2 ~ ~ P~T/EP91/01419
PANEL OR SHELL-LIKE STRUCTURAL COMl?ONENT
The invention relates to a panel or shell-like structural component which can be subjected to
high loads.
In automobiles, there is often the need to expand the tmnk temporarily into the passenger
compartment, in order to transport unwieldy objects. In order to make it possible to
through-load, it is necessary to have a hinged rear seat back which is separate from the self-
bearing bodywork construction and therefore requires additional stabilization in order to meet
safety standards in the seat back area. For example, one of the safety standards prescribes
that, at a relative velocity of 40 km/h, a test dummy with a weight of 18 kg andgeometrically prescribed shape and edge measurements may not break through the upright
seat backs from the truck space into the passenger compartment. In order to meet this
standard, to date the proposals have been one or two panel constructions of crimped or
corrugated sheet metal which are given a decorative waU facing the trunk compartment.
The effective wall strength of these components lies between about 22 to 35 mm with a total
weight of about l0 kg for two hinged seat backs. Attempts have also been made to produce
the seat backs of a therrnoplastic synthetic material (polypropylene) with glass fibre
reinforcement in a one-shel1 construction. However, under the stated conditions of the
standard, this construction proved to be inadequate.
Another method used in RD~/I technology (Reaction-~njection-Molding - reaction foams) with
polyurethane is to insert flat reinforcing materials, such as glass fibre mats, into the forming
tool and to impregnate them with reaction mixture during the injection process.
The purpose of the invention is to develop a panel or shell-like structural component which
can be subjected to high static and dynamic loads.
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In order to acllieve this purpose in accordance with the invention, a structural component is
proposed which is made of a reaction plastic with a layer of stiffening of the following
construction embedded in it:
- a first and second outer layer of elastically extensible organic fibre fabric,- a first and second glass fibre layer on the inner surface of the f1rst and second outer
layers, and
- a compressible spacer layer placed between the two glass fibre layers,
all of the layers being impregnated with a low-viscosity reaction mixture formed upon the
foaming of the reaction plastic.
The primary purpose of the two outer layers, which will preferably consist of a weave or
hotley-colllbed fabric of elastically extensible organic fibres, such as polyethylene or
polyester fibres, will be to absorb shock loads elastically or plastically and thereby prevent
formation of a fracture or fissure. For this reason, for example, the organic fibres exhibit a
diameter of 0.3 to 0.8 mm, or in the case of polyethylenes, preferably from 0.5 mm up.
The glass fibre layers bordering on the inner surface of the outer layers have primarily a
stiffening function to absorb static loads. In order to be able to absorb high tension, at least
one of the two glass ~Ibre layers is made of two unidirectional mats sewn together crosswise,
a so-called Roving mat. If there is little demand made on the tensile forces, a glass fibre
t`abric can be used for this as well. On the other hand, on the side of the component exposed
mainly to compressive load, a glass fibre mat with an essentially isotropic (irregular) glass
fibre arrangement is used as the glass fibre layer.
The compressible spacer layer, composed of synthetic fibres advantageously bonded to each
other poiult-by-point as a loose fleece-like mat and preferably fused together, has the
purpose, especially during the manufachlre of the component, of holding the layer structure
against the form wall with a certain degree of frictional connection, so that it is not displaced
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within the forming tool by the fluid reaction mixture during the form-filling process. In
addition, it is intended to hold the statically and dynamically operating outer and glass fibre
layers outside the neutral flexing fibres of the component. As well, the component can be
varied by a greater or lesser compacting of the compressible spacer layer in its wall strength,
without a compensating loss of stability over a wide area, by corresponding construction of
the cavity of the forming tool. The compressible spacer layer is preferably composed of
polyamide fibres in a loose, irregular pattern, in which the fibres exhibit an effective
diameter of 0.5 to 1.3 mm, and preferably between 0.8 and 1 mm.
In order to obtain a high level of component stability, it is important that the reaction
mixhlre which forms the reaction plastic thoroughly impregnate the reinforcing layers. For
this purpose, the viscosity of the reaction mixture should not rise above 5,000 mPs initially,
alld preferably be between 100 and 1,000 mPs. This is the case for polyol and isocyanate as
raw products of polyurethane, for exarnple. It would be more advantageous to select a
reaction plastic from the polyurethane group, polyurea, epoxy resin, polyisocyanurate.
In accordance with an advantageous embodiment of the invention, at least one of the outer
layers is bordered on the exterior by a decorative layer which is imperrneable to the liquid
reaction material. This decorative layer can be constructed as a synthetic foil, for example,
or as a textile carpeting layer which is coated to be water-tight on the inner side or
impregnated with a water-tight sealant.
For installation purposes, it is advantageous if at least one supporting structure is embedded
in the area of the glass fibre layers in the component, running parallel to the layers and
projectillg over the edge of the component. For example, the supporting structure can be
constMcted as a metal corrugation projecting over both sides of the edge of component,
\vhich in the case of a hinged seat back can be used as a storage well.
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Other advantageous installation possibilities emerge from the fact that one of the outer layers,
together with the glass fibre layer abutting it, overlaps the remaining layers on the side edge,
in which the overlapping edge of the outer and glass fibre layers can be bent away from the
other layers, leaving an open channel at the edge. The decorative layer placed on the
exterior of the other layers can then overlap the layers to hook onto the channel, while in the
channel a decorative or cushion cover can be wedged in the channel by means of an
elastomer piping on the side edge.
The component in accordance with the invention can be used to great advanlage as a
combined trunk barrier and hinged rear seat back of a motor vehicle, in which case the
decorative layer should face the trunk side to fulfil its purpose and the shock-absorbing
Roving mat or glass fibre fabric would face the passenger compartment.
The component in accordance with the invention can also be used as a roll-protection motor
vehicle roof, as an undercarriage protective panel or roof spoiler of a truck, as the flexing
base of a bumper, or as a bumper with an integrated flexible base for motor vehicles.
The invention is explained in greater detail below on the basis of an explanatory example
illustrated schematically in the drawing:
The single figure shows a section through the reinforcing $tructure of a component for
folding seat backs in motor` vehicles. In the upright position, folding seat backs of this type
simultaneously have the function of a trunk compartment barrier wall, which ensures that the
loose articles found in the trunk are kept from penetrating into the passenger compartment
even in the case of an accident.
The reinforcing structure of the component exhibits the following construction:
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- an outer layer 10 that, when the seat back is installed, fa~es the passenger
compartment and ;s constructed of a honey-combed fabric made of polyethylene ~Ibres
with a fibre diameter of about O.S mm, which can absorb shock loads -flexibly because
of the elastic characteristics of the polyethylene;
- a glass flbre layer 12 constructed as a Roving mat which, because of the
unidirectional orientation of its fibre bundles, sewn together crosswise, can tolerate
high tensile loads in the direction of the fibres;
- a spacer layer 14, composed of polyamide fibres in a fleece-like pattern and placed in
the centre, which permits the installation of various wall strengths in the component
and assumes a spacing function within the layered structure;
- a second glass fibre layer 16 with an essentially isotropic (irregular) arrangement of
the glass fibres, for stiffening, especially on the pressure side of the component;
- a second outer layer 18 constructed as a honey-combed fabric from polyethylene fibres with elastic shock-absorbing properties;
- a decorative layer 20, placed on the exterior of the outer layer 18 on the trunk
compartment side, which may be constructed, for example, as a synthetic film or as a
carpet provided with a water-tight coating or a corresponding impregnation.
In all the layers, the reinforcing structure exhibits sufficient porosity so that it can be
ssltul~ted with a low-viscosity reaction mixhlre which forms when the reaction plastic is
foamed.
Embedded additionally in the area of the first glass fibre layer is a metallic corrugation layer
22, the ends of which project over the component and form a storage well for the folding
seat back.
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The edges of the first outer layer 10 and the first glass fibre layer 12 together overlap the
remaining layers 14, 16, and 18 and are vertically bent toward the tmnk compartment in
such a way that an open channel 26 runs all the way around.
To manufacture the component, the reinforcing structure is set into the cavity of a forming
tool (not illustrated) in the described order and acted upon by a iiquid reaction mixture,
composed of polyol and isocyanate, for example, conducted through a spme located in the
central area of the outer layer 10, for example. This process saturates the layer structure in
the reaction mixture, so that during the subsequent foaming process a close bond with the
resulting reaction plastic is created. The wall strength of the component typically is about 12
to 14 mm, so that a total weight of about 6 kg results for the two folding seat backs.
E~periments llave shown that the component can withstand an acceleration of the standard
test dummy (18 kg) to 32 kg. The channel 26 remains open and can be used as a piping
channel to secure a covering or cushion overlapping the component on the side of outer layer
10, with the help of an elastomer piping.
