Note: Descriptions are shown in the official language in which they were submitted.
WO93/01931PCT/~ISg2~0~978
211383il
COMPOSITE S~RUCT~RE WITH FOAM PLASTIC CORE
AND METHOD OF MAKING SAME
BACXGROUND OF THE IN~N~ION
FIELD OF INVENTION
5~he present invention generally relates to a
composite structural material and the method of making
the same and more specifically the inv~ntion relate~ to
a low cost, lightweight, fire resistant composite
material and the method of making the same in which the
composite consists of a core constructed from
lightweight expanded foam plastic such as expanded
polystyrene. The core is covered on one or more of its
surfaces with a high strength outer layer constructed
of a layer or layers of non-woven fabric webs
impregnated or infiltrated with cementitious slurry
binder with the fibers in the layers of non-woven
fabric material forming a three-dimensional
reinforcement matrix for the cementitious slurry. The
outer layer is formed and cured on one or more surfaces
of the lightweight plastic core resulting in a crack
resistant outer layer having greater ductility and
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toughness than ordinary cement or concrete. The cement
in the outer layer bonds directly to the lightweight
plastic core thus requiring no additional bonding
- agent. Outer layers can be formed and cured around
various shaped cores for variouC end uses.
DESC~I~TION OF THElaR~a~.AB~
Composite materials comprised of high strength
outer layers bonded to lightweight core materials are
utilized for several applications. The outer layers
serves to increase the strength, durability, ultra-
violet resistance, fire resistance, chemical
resistance, or combinations of thece properties of the
composite depending on the application.
Patent No. 4,764,238 discloses a composite
material made by applying heat and pressure to fabrics
preimpregnated with a thermosetting resin to bond the
fabrics to an open-celled foam core. The resulting
lightweight composite is claimed to be suitable for
energy absorbing, impact-resistant structures.
Patent 4,050,659 relates to an electrical
transformer equipment pad made with a fiberglass
reinforced exterior plastic surface formed around an
expanded foam core.
Patent 4,303,722 describes a panel constructed
of thin facings, comprised of a fabric or web of glass
fibers and a set composition of thermosetting
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condensation resin and gypsum, bonded to a rigid
substrate such as a foamed plastic material. In this
composite, the fibers in the reinforcing material are
essentially two-dimensional, advantageously placed as
near to the surface of the facing as possible.
Patent 4,963,408 relates to a unitary
composite laminate structure made by encapsulating a
foam core with a load bearing polymer matrix reinforced
with oriented fibers.~ This composite also utilizes a
bonding material to fuse the outer layer to the core.
Patent 4,559,263- de~cribed a cement-foam
composite board in which a concrete, made with
lightweight aggregate and a foaming agent is bonded on
one side of an expanded foam panel. This patent
further claims that an unspecified reinforcing means
may be included in the concrete.
Panels made in the above mentioned manners are
limited in their performance due to trade-offs involved
with the choice of materials utilized in the coatings
or facings. The resinous and polymeric coatings are
less fire resistant and more costly than the
cementitious ones. However, the cementitious facings
exhibit lower flexural strengths and are more prone to
cracking and brittle behavior.
Non-woven webs of fibers have been utilized as
reinforcement for cement matrices for thin sheet-like
materials.
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Patent 4,778,718 refers to a non-woven
reinforced cement sheet made by screeding dry cement
into the fiber matrix and then applying water to
hydrate the cement and form a sheet.
Patent 4,617,219 relates to a three-
dimensionally reinforced cement structure utilizing at
least one non-woven web a the fibrous reinforcement.
This patent further claims that layers of such non-
woven reinforced cement sheets can be formed together
10 to produce structural panels. ~-
Thin sheet~ made in the above manner~, with no
core material, do not po~ses~ sufficient overall
strengths to span typical panel lengths or support
loads such as wind or foot traffic. The thin, core- -~
less sheets do not exhibit i~sulative properties
significantly greater than those of ordinary concrete.
Panels made thick enough in the above manners to
support loads, without lightweight cores, are only
approximately 30~ lighter than equivalent panels made
with ordinary concrete.
Blocks of lightweight, foamed plastic, such as
polystyrene, are utilized for buoyant support of
floating structures ~uch as boat docks. When these
blocks are utilized without protective outer layers,
chemicals in the water, from outboard motor , for
example, can break down the block and pieces of the
block are then free to pollute the body of water.
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SUMMAR~ ~F THE INVENTION
It is the object of the present invention to
provide a lightweight, low cost, ductile and crack-
resistant composite material which also possesses fire
resistance.
- A further object of this invention is to
provide a method of manufacture of this compo~ite in -;~
suitable forms to ~eet such end uses as equipment pads,
floating docks, building panels,~ noise abatement -~
10 surfaces, and fire resistant self-cladded in~ulation. ~-
The composite consists of a high strength
outer layer formed and cured around one or more sides
of a lightweight core. This outer layer is a
cementitious matrix three-dimensionally reinforced with
a non-woven web of fibers. The fibers are present in
3-20% volume loadings, which imparts high flexural ~-~
strength, ductility, toughness, and crack resistance to
the outer layer. The fibers are completely
encapsulated in the cement matrix, giving the outer
20 layer the appearance, hardness, and durability of ~
ordinary concrete. The fibers are also protected from ~-
fire and ultra-violet radiation by the cement matrix.
This outer layer is applied to the core,
preferably expanded polystyrene, while the cement
matrix is in its wet, uncured form. The outer layer
can be applied by hand or by mechanical pressing means
to insure that the wet cement mat~ix is uniformly
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distributed throughout the fiber web and evenly in
contact with the lightweight core to allow the outer
layer to b~nd to the core as the cement matrix cures.
The use of a lightweigh~, foamed plastic core
5 giveæ the composite material a high strength:we~ght
ratio. This is true in flexure due to the beam design
of the sandwich panel and the high flexural strength of
the outer layer. In compression, the composite
exhibits high strength due to the outer layer's
compressive strength, which i~ equivalent to ordinary
concrete.
When utilized for floating structure supports,
the outer layer of the compo~ite first protects the
polystyrene core from attacking ch~micals and further
prevents pieces of the plastic core from breaking away
and polluting the marine environment.
These together with other objects and
advantages which will become subsequently apparent
reside in the details of construction and operation as
more fully hereinafter described and claimed, reference
being had to the accompanying drawings forming a part
hereof, wherein like numerals refer to like parts
throughout.
2SBRIEF DES~RIPTION OF THE DRAWINGS
Figure l is a perspective view of a panel
utilizing the composite structural material of the
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present invention. :
Figure 2 is a sectional view, on an enlarged
scale, illustrating the specific arrangement of the
co~ponents forming the composite ~tructural material of
this invention~
Figure 3 is a perspective view of a buoyant
support for a floating structure such as a boat dock.
DESCRIPTION OF THE PREFERRED ~MBO~IMENT -~
Referring now specifically to the drawings, a
composite structural component in the form of a panel
is illustrated in Fig. 1 and generally designated by
reference numeral 10 and which includes a core
generally designated by reference numeral 12 and an
outer layer generally designated by reference nu~eral
14 which may extend over one surface of the panel, both
oppo~ed surfaces or around all of the edges and all of
the surfaces. The outer layer~ 14 form the interior
and exterior ~urfaces of ~he panel and they can be
textured or colored when being formed or finished with
various materials ~uch as plastic, sheathing, painting,
grooving or the like for appearance purposes to enable
any desired architectural finish characteristics to be
obtained.
Aæ illustrated in Fig. 2, the core 12 is
constructed of lightweight foam plastic such as
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expanded polystyrene in thé form of a board 16, block
or other structural entity.
The outer layer 14 includes a three-
dimensional web of non-woven web 18 which includes non-
woven fibers 20 in which the fiber volume rangesbetween 3 and 20%. A cementitious slurry binder 22
intimately surrounds, infiltrates and connects the
fibers 20 when the cementitious slurry binder is cured.
The cementitious slurry binder 22 in the outer layer is
cured with the cured and hardened slurry binder 22,
outer- layer 14 and non-woven fibers 20 and core 12
becoming a rigid, integral body thus providing a panel
with an ultra lightweight core which is reinforced and
rigidified by the outer layer or layers with the core
and layer or layers being rigidly formed into a ~ingle
rigid unit.
In one embodiment of the invention, a panel
was formed in accordance with the present invention by
providing an expanded polystyrene board 16. A cement
slurry was mixed in a portable mortar mixer with the
following ratios by wei~ht: lO partæ Portland cement,
l part microsilica, 5 parts fine sand, 4 parts water
and O.l parts water reducing superplasticizer. Sheets
of a non-woven web material in the form of a
needlepunched polypropelene weighing 8 ounces per sq.
yd. with a loft of l/4 n were cut into pieces of
appropriate size to cover the board and applied to the
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core after the cement slurry has been applied in its
wet uncured form by hand or mechanical press.
After curing for 24 hours, test beams were cut
from the panel with the test beams being 24" in leng~h,
5 6H wide and 2 1/2" thick. These test beams were tested -~
for flexural strength after a 7 day curing period by
using 3rd point loading on an 18n ~pan with the average
flexural strength being 500 psi. This flexural
strength is approximately equivalent to prior art
panels when constructed to be 4" thick which weigh
approximately 20 pounds per æq. ft. The lightweight,
low cost, insulative, fire resistant, chemical
-resistant, ultra-violet resistant and ductile structure
enables the composite material to be used as an
equipment supporting base or pad, fire resistant noise
abatement panels, building panels, self-cladded
insulation for pipe and ductwork and a float to support
a dock with the composite structural material providing
adequate buoyancy to floatingly support the dock at a
desired elevation in relation to the water and having
a high resistance to ultra-violet light deterioration.
The foregoing is considered as illustrative
only of the principles of the invention. Further,
since nu~erous modifications and changes will readily
occur to those skilled in the art, it is not deæired to
limit the invention to the exact construction and
operation shown and described, and, accordingly, all
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suitable modifications and equivalents may be resorted
to, falling within the scope of the invention.
