Hollow fiber-reinforced plastic body

The invention relates to a hollow fiber-reinforced plastic body comprising a curable resin-impregnated winding of high-strength fibers. To provide a strong hollow fiber-reinforced plastic body having a quick-to-make wall thickness the invention proposes that a double-walled shell which surrounds the hollow body interior is made by a first winding of one or more tapes of an uncut double pile cloth having a spaced-apart top cloth and bottom cloth and also binding pile threads which is covered by an outer winding, the windings being impregnated with a curable resin.

BACKGROUND OF THE INVENTION 
1. The Field of the Invention 
The invention relates to a hollow fiber-reinforced plastic body comprising 
a resin-impregnated winding of high-strength fibers to build up the 
plastic body wall. 
2. Description of the Related Art 
Hollow fiber-reinforced plastic bodies have been produced by winding 
resin-impregnated rovings or combinations of various glass filament 
materials on a rotating drum or core, the resins used being preferably 
thermosetting polyester and epoxy resins. The winding can take place in 
various patterns of selectable pitch angles and numbers of layers, to wall 
thicknesses which preferably range from 1 to 4 cm. Owing to their high 
strength, these hollow plastic bodies can be used as pressure pipes, tank 
containers, towers and the like. However, it takes a long time to build up 
to the wall thickness and there is a risk of seepage. 
It is therefore also known to wind hollow fiber-reinforced plastic bodies 
in two cover layers of resin-impregnated rovings between which a core 
layer of a plastics foam is placed by manual lay-up. The plastics foam is 
a quick way of achieving the desired wall thickness. However, the plastics 
foam is not resistant to ageing, since it decomposes in time. The use of 
such hollow plastic bodies for pipes or tanks for transporting and storing 
chemicals or oil therefore represents a danger to the environment.

SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a hollow 
fiber-reinforced plastic body which is strong, quick to make in the 
required wall thickness, and safe as regards the risk of seepage. 
This object is achieved when a winding of one or more tapes or strips of an 
uncut double pile cloth having a spaced-apart top cloth and bottom cloth 
and also binding pile threads is provided as a double-wall shell which 
surrounds the hollow body interior and builds up the wall together with a 
cover winding. 
The invention provides a hollow fiber-reinforced plastic body which, 
through the inlaying of a double-walled shell in the form of an uncut 
double pile cloth surrounding the hollow body interior, possesses a safety 
wall. As the resin hardens, the pile threads between the upper and lower 
part of the double pile cloth stiffen and leave a cavity in which leak 
detectors or other leak indicating devices can be fitted. The top and 
bottom cloths also form two successive stiffened walls which shield the 
hollow body interior off against the outside. In the event that fluid 
should seep through the inner wall, it is trapped in the cavity and 
prevented by the second wall from further seeping towards the outside. The 
double-walled shell thus not only permits early detection of a leak but 
also prevents egress of the leaked material, at least for a certain length 
of time. 
The double-walled shell comprising an uncut double pile cloth can be 
constructed, in particular in the case of cylindrical bodies, by winding 
one or more fabric tapes or strips, preferably with the edges of the tapes 
open towards the side. This wound layer thus permits the construction of 
an unbroken safety cavity which extends around the hollow body interior. 
The warp and weft threads making up the top and bottom cloths and also the 
pile threads can be made of high-strength fibers, for example glass. The 
fibers used can either be spun as staple fibers into yarns or take the 
form of monofilaments or multifilaments. 
The pile threads can be laid into a double pile cloth woven by the warp 
pile fabric velvet technique in a V- or W-binding. The length of the pile 
threads as spacers between the top and the bottom cloths can be 3 to 8 mm. 
The density can be 20 to 80 pile threads/cm.sup.2, depending on the cubic 
capacity of the safety cavity. 
A hollow fiber-reinforced plastic body of high stiffness is obtained by 
arranging the double pile cloth as a core layer between two 
resin-impregnated wound layers of high-strength fibers. To smooth the 
wound layer of high-strength fibers relative to the core layer it is 
possible to place glass mats in between. 
As resin for impregnating high-strength fibers, in particular rovings, it 
is possible to use a curable reactive resin, for example unsaturated 
polyester, epoxies, vinyl esters, phenolic, PUR, silicone (SI), polyimide 
(PI), polyamide-imide (PAI) resins or UV-curing resins. 
According to a further embodiment of the invention the double-walled shell 
made of an uncut pile cloth can be used as a passage for the flow of a 
temperature control material such as water or oil. Advantages are good 
heat transfer or dissipation of heat. The flow rate depends easily on the 
flow speed and distance between top and bottom cloth. 
Other objects, features and advantages of the invention will become more 
fully apparent upon consideration of the claims and the following 
description. 
DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 is a schematic view of a first embodiment of a hollow fiber 
reinforced plastic body 1 having a cylindrical or spherical wall which 
encloses an interior 2. The interior 2 is used for storing and/or 
transporting fluid, in particular chemicals. 
The wall of the hollow plastic body 1 comprises a cover winding 3 of 
high-strength fibers and a first winding 4 of one or more tapes of an 
uncut double pile cloth. The two windings 3, 4 have been wound on top of 
one another and densified by resin curing. The winding 3 of the 
high-strength fibers has been wound on top of the winding 4 of the double 
pile cloth according to a selectable pattern of selectable pitch angles 
and numbers of layers. The high-strength fibers used can be rovings or 
combinations of other glass filament products. 
The winding 4 of uncut double pile fabric forms a double-walled shell which 
lines the interior 2 of the hollow plastic body 1. The uncut double pile 
cloth includes top and bottom cloths 5, which are arranged spaced-apart 
from each other and are joined together by in-laid pile threads 6 which 
cross the between cloth space. The top and bottom cloths 5 thus form two 
spaced-apart walls which enclose a safety or detector cavity whose cubic 
capacity is only partly taken up by the pile threads 6, leaving a safety 
cavity. This safety cavity is subdivided, by rows of adjacent pile threads 
6, into a multiplicity of individual safety cavity compartments 7. The 
resin impregnation of the double pile cloth and hence the hardening of the 
double pile cloth brings about a densification of the top and bottom cloth 
5 and a stiffening of the pile threads 6 without filling up the safety 
cavity compartments 7. Within the safety cavity compartments 7 there are 
preferably arranged leakage detectors 8, which can be arranged disposed 
over the circumferential surface of the interior 2. Other leakage 
indicating devices can be used as well. 
The top and bottom cloths 5 consist of crossing warp and weft threads in a 
standard weave or derived weave. The double pile cloth has preferably been 
woven by the warp velvet technique, so that the pile threads 6 extend in 
the warp direction, specifically in a V- or W-binding. The length of the 
pile threads, which as spacers determine the distance between the top and 
bottom cloths, is between 3 and 8 mm. The density is between 20 and 80 
pile threads/cm.sup.2. The fiber material used for the top and bottom 
cloths 5 and the pile threads 6 are high-strength fibers, for example 
glass fibers, carbon fibers and aramid fibers. The fibers used can either 
be spun as staple fibers into yarns or take the form of monofilaments or 
multifilaments. If glass fibers are used, the weft may also include some 
fibers of a thermoplastic material, preferably up to 25%. 
To construct the double-walled shell, the winding 4 is produced with one or 
more tapes or strips of uncut double pile cloth, preferably with tape 
edges open at the side. A layer with the tape or tapes of double pile 
cloth is preferably wound with the tape edges side by side, the distance 
between adjacent tape edges being made small; preferably, the tape edges 
which are adjacent in the winding butt against one another. The tapes can 
have been brought to a desired width, preferably less than 90 cm, by 
cutting or directly, for example, by weaving. According to FIG. 1, the 
winding 4 consists of such a layer of double pile cloth. According to FIG. 
4 the winding 4 may consist of a plurality of superposed layers, in which 
case the tape or tapes of the following wound layer cover the butted edges 
of the previous wound layer. The winding 4 is finally covered by the 
winding 3 produced from optionally pre-resinated finishing material, for 
example a flat woven fabric or nonwoven fabric. The side edges of the 
winding 4 can be closed by the cover winding 3. 
The resin used for impregnating the windings 3, 4 is a curable reactive 
resin, for example unsaturated polyester, epoxies, vinyl esters, phenols, 
PUR, silicones (SI), polyimides (PI) or polyamide-imides (PAI). It is also 
possible to use UV-curing resins. The resin defines a polymer matrix 
having the windings 3 and 4 embedded as reinforcing component to form a 
composite material. 
To produce the hollow fiber-reinforced plastic body of FIG. 1, a rotating 
drum or core is wound with one or more tapes of uncut double pile cloth, 
producing the winding 4, and then with a finishing layer, for example 
resin-impregnated rovings, nonwovens, mats, woven fabrics, etc. to produce 
the winding 3. The resin impregnation carried out in this way also leads 
to an impregnation of dry-wound tapes of the double cloth. However, 
depending on the method of winding, it is also possible for the tape or 
tapes of double pile cloth to be wound in the resin-impregnated state. 
Furthermore, after winding, the tapes of double pile cloth may be sprayed 
with a reactive resin and, after curing, be sheathed with a finishing 
layer which hides the butted edges of adjacent tapes, for example with a 
resin-impregnated nonwoven, mat, fabric, etc. 
In the case of hollow plastic bodies, preferably tanks having a so-called 
flat bottom and top, the cylindrical part can comprise a winding 4 to 
which has been attached a sheetlike bottom and/or top part, composed of a 
double pile cloth, wherein the curved angle-sections are covered by an 
outer finishing layer and hence forms a cavity connection between the 
cylindrical section and the bottom and/or top section. The finishing layer 
is preferably formed of a hardenable flat woven fabric or nonwoven fabric. 
To construct the double-walled shell in the case of spherical hollow 
plastic bodies 1 the double pile cloth can consist of individual joined 
segments. 
FIG. 2 shows a second illustrative embodiment of a hollow fiber-reinforced 
plastic body 1 wherein the winding 4 of uncut double pile cloth has been 
arranged as a core layer between an outer winding 3 of high-strength 
fibers and an inner winding 9 of high-strength fibers, this wound 
composite having been densified with a curable resin impregnation of the 
type mentioned. Otherwise the above observations concerning FIG. 1 and 
FIG. 4 apply. 
FIG. 3 shows a third illustrative embodiment of a hollow fiber-reinforced 
plastic body which differs from the second embodiment shown in FIG. 2 in 
that additional glass fiber mats 10, 11 have been placed between the 
windings 3, 9 of the high-strength fibers and the winding 4 of uncut 
double pile cloth and co-densified. Otherwise, the above observations 
concerning FIG. 1 and FIG. 4 apply once more. 
In a further illustrative embodiment, the double pile cloth can also 
consist of a knitted top and bottom cloth 5. 
FIG. 5 shows a fifth embodiment of a hollow fiber-reinforced plastic body 1 
which differs from the one shown in FIG. 2 in that the winding 4 is used 
as a passage for the flow of a solid, fluid or gaseous medium to control 
the temperature of the interior 2 of the hollow plastic body 1. The edges 
of the winding 4 are closed for this purpose. Then, the leakage detectors 
are replaced by temperature and/or charging control devices. Outboard 
inlet 13 and outlet 14 devices are provided for introduction and removal 
of the temperature control medium. 
Although the invention has been described in connection with what is 
presently considered to be the most practical and preferred embodiments, 
it is to be understood that the invention is not limited to the disclosed 
embodiments, but rather, is intended to cover various modifications and 
equivalent arrangements included within the spirit and scope of the 
appended claims.