DE1704925A1 - Plastic pipe with fiberglass reinforcement and process for its manufacture - Google Patents

Description

Plastic pipe with fiberglass reinforcement, and process for its manufacture. Plastic pipes with glass fiber reinforcements are already known in various designs and for a variety of applications.The glass fibers embedded in polyester or epoxy resins are usually arranged in the form of fabrics and thus form a dense framework of longitudinal and transverse fiber elements, which are embedded in the Resin body are connected both among themselves and with the resin body itself. However, this arrangement of the individual fibers does not allow their elasticity properties to be fully exploited and either to open up possible applications for the pipes where they could not be used up to now due to insufficient elasticity, or to design them with the same dimensions for higher loads in general, because only one is always relatively smaller Part of the glass fibers are geared towards the main stress and then often break as a result of overload. In contrast, the present invention aims to create plastic pipes whose field of application is preferably where increased elasticity is required, for example for sports equipment or antenna masts. Such plastic pipes with glass fiber reinforcement contain an inner, at least one-layer glass fiber layer as a base layer, at least one section of pre-tensioned glass fibers arranged over it and running in the longitudinal direction of the pipe, which are essentially evenly distributed over the circumference of the pipe, and at least one outer layer above the pre-tensioned glass fibers single-layer glass fiber layer, the whole being embedded in and fixed in a hardened resin body forming the tube.

The manufacturing method for such pipes comprises according to the invention the steps of winding the glass fiber layer forming the base sheet onto one Winding mandrel, the application of a second, from essentially in the longitudinal direction of the pipe running glass fibers, the pre-tensioning of these glass fibers by means of clamping elements attached to the front ends of the tubular body, wrapping a third layer of fiberglass over the second under substantial Tension to the underlying, substantially longitudinally oriented second glass fiber layer to press firmly against the base layer and the third, outer fiber layer, the impregnation of said fiberglass layers with a curable synthetic resin, the thermal one Hardening of the synthetic resin impregnation, the loosening of the clamping elements for the now in the pipe fixed, prestressed, longitudinally directed glass fibers of said second Zage and the removal of the tube from the winding mandrel, as well as the final grinding the pipe surface.

The impregnation can be done in such a way that already the base layer a resin impregnation is obtained, this being in excess introduced resin as the fiber layers continue to build up, they are also impregnated, or impregnation including the subsequent curing can be carried out in a pressure vessel, wherein the glass fiber structure enclosed in the vessel: applied to the winding mandrel first evacuated, then, while maintaining the vacuum, soaked in resin and then is exposed to an overpressure that is maintained until the end of the polymerization phase in the Vessel is maintained.

While known plastic pipes with glass fiber reinforcement have modulus of elasticity of 200,000 kg / cm 2 can be achieved. can those of the invention pipes 350,000 - 400,000 kg / cm 2 can be achieved. They also show one, especially at Sports equipment such as B. high jump poles essential crack-free fracture point, while in known designs there is a risk of stab wounds, r The Invention. is explained below with reference to the drawing, for example. In this FIG. 1 shows a schematic, partially sectioned illustration of the pipe structure, the individual layers being exposed in their gradual sequence while FIG. 2 is a schematic representation of the winding device and the winding process conveyed.

The same reference numbers in both figures denote the same parts: _.

The pipe section shown in: Fig. 1 has an inner one on the left or first glass fiber layer.1, which is in the form of a glass fiber fabric or of Rovings is wound unidirectionally on a mandrel 21 shown in FIG. 2 and the base layer is: in the order of the manufacturing steps at In a first construction, this fiber layer receives an impregnation after winding with a curable synthetic resin that removes all of the spaces between each Fills up to the surface of the winding mandrel 21 without voids. As resin materials Thermosetting epoxides, polymethanes and polyurethanes are preferably suitable.

This first layer can also be applied in the form of a fiberglass mat be, in which a fiber fabric in a plastically deformable layer of an uncured Synthetic resin is embedded. Such semi-finished products are known as "Prepreg" known. However, rovings can also be wound that have the same or Similar coating to the "prepreg" mats, or they can be on the feed path run through an impregnation bath from which they absorb the synthetic resin in liquid form. Of course, fiberglass fabrics can also be impregnated in this way.

The base layer mentioned is followed by a second glass fiber layer 2, the individual fibers of which are approximately 8/1000 mm in diameter combined to form rovings, run essentially parallel to the longitudinal axis of the pipe and are evenly distributed over the entire circumference of the pipe. Their ends on both sides are inserted into clamping elements 22, 23 during the manufacture of the pipe, as can be seen in FIG. After this second glass fiber layer has been introduced, the latter are closed and all the fiber ends are clamped onto the respective pipe end. This is done, for example, by tightening clamps 22a and 23a, which hold the fiber layer between its inner surface and the related saddle piece 22b and 23b. The contact pressure is chosen to be so great that a shift between the individual fibers below and with respect to the saddle pieces during the subsequent pretensioning of these fibers is excluded. With those in Pig. 2, the saddle piece 22b of the element 22 sits firmly on the winding mandrel 21, as does the neck ring 24 on the side of the tensioning element 23, while the saddle piece 23b is displaceable on the mandrel 21. The distance between the neck ring 24 and the saddle piece 23b is set at the latest when the glass fiber strands are drawn in between the clamps and the saddle pieces to a length that is slightly greater than the stretching length of the fibers. The latter results from the tensile strength of the glass fibers, which are stressed with approx. 80% of their breaking load during prestressing. By evenly tightening nuts 25, which are seated on a number of bolts 26 arranged at regular intervals on the neck ring 24 and the flange 23, the prestressing force can be applied to the glass fibers of the fiber layer 2.

The fiber layer 2 can be introduced in the form of a fiber web, the weft threads 5 in is fixed in a suitable manner. By a suitable choice of adhesive tape or weft thread material non-removable markings or decorative elements can be incorporated will. However, it is also possible to use individual rovings between the tensioning elements 229 23 to be relocated.

A third layer is then placed over the now prestressed fiber layer 2 Wrapped fiber layer 3, which is preferably made from rovings, but also from a glass fiber fabric This layer has two main tasks: it is intended to be, on the one hand, the prestressed Bring layer 2 into close contact with both the base layer 1 and with it itself, as synthetic resin made from the layer 1 that is deliberately introduced in abundance squeeze out. Through this. will. perfect embedding of both layer 1, as well as layer 2. With a suitable viscosity of the synthetic resin impregnation mentioned and a sufficient excess of material can.- also the third, also-as a cover and protective layer Serving Zage 3 in reliable r * quietly soaked with resin material and embedded in it will. To be on the safe side, a top impregnation should be indicated in order to to ensure adequate resin coverage of the outermost fiber elements.

The pipe constructed in this way is now subjected to a heat treatment subject, in which the resin hardens and becomes intimate with the glass fiber insert connects. It is still stretched on its horizontally lying mandrel Tube rotates around its axis, around an all-round uniform resin layer or tube wall thickness to achieve.

To harden the resin, the pipe and its mandrel can be inserted into a provided with a drive device (not shown) heat space are brought. While the previous description concerns a structure in which the first-Glasfas: the layer or base layer experiences a synthetic resin impregnation, can A second construction can also be used "dry". This way of working is particularly indicated when impregnation and subsequent polymerisation of the resin in a substantially tubular .pressure vessel; takes place, the upright-den contains fiberglass structure applied to the winding mandrel .. The vessel is general so; designed that the mandrel is centered in the bottom and cover section and preferably has an inner diameter that allows the formation of an adequate Resin top layer over the outermost fiber sections allowed. After oversleeping the contents of the vessel are first »subjected to a high vacuum of approx. 0.1 Torr, to remove all air and moisture from the structure. Then, under Maintaining a vacuum, the impregnating resin preferably through a bottom on the vessel recessed opening until its level reaches a height of approx. 5 cm above the top fiberglass sections. This is therefore necessary in the following Phase to prevent air from penetrating the fiber structure. After filling of the impregnation resin, the vacuum is released and atmospheric air enters the vessel section introduced above the resin level. This section of the vessel faces the underlying, preferably the diameter calibration serving a much larger part Cross-section on. The air admitted above the resin level is at least an overpressure of approx. 10 kg% cm2 and the vessel is heated for the purpose of hardening the resin. As a result of the overpressure, a bubble-free solidification takes place during the volume contraction of the pipe structure ..

After the synthetic resin has hardened, the pipe is now stable Loosen the prestressing elements removed from the mandrel, the ends trimmed on both sides and optionally ground on the outside in order to achieve a smooth surface 4.

The device shown schematically in FIG mentioned elements a for driving the mandrel 21 serving chuck 30, which allows a comfortable tightening and loosening of the mandrel. On the other side it is mounted and centered in a cone tip 31, which in turn on a Tailstock 32 is seated. The figure shows analogous to the disposition example to the left of the break line in the middle of the mandrel, the layer-by-layer winding of a base layer of the roving 27 in the direction of arrow A, while the phase to the right of said break line is shown in which the pre-stressed fiber layer 2 through the glass fiber layer 3 is covered by rovings 28 being wound up in the direction of arrow B. The ones shown The directions of the arrows and the winding directions are only determined by the manner of representation in FIG. 2.

Claims (1)

Claims 1. Plastic pipe with glass fiber reinforcement, characterized by an inner, at least single-layer glass fiber layer as a base layer, at least one overlying it, running in the longitudinal direction of the pipe: layer of pre-stressed glass fibers that are distributed essentially evenly over the circumference of the pipe , as well as an outer, at least single-layer glass fiber layer lying over the prestressed glass fibers, the whole being embedded in a hardened resin body forming the tube and fixed therein. -2. Pipe according to Claim 1, characterized in that the inner fiber layer forming the base layer and the outer fiber layer lying over the prestressed, longitudinally directed glass fibers are unidirectionally wound glass fiber fabrics or rovings laid essentially in Zagen. 3. Pipe according to claim 1, characterized in that the prestressed longitudinally directed glass fibers are held by transverse fixing elements in order to ensure an even distribution around the pipe. -4. Pipe according to Claims 1 to 3, characterized in that the embedding compound is a 2olyester-p polyurethane or epoxy resin. 5. A method for producing a plastic pipe with glass fiber reinforcement according to claim 1, characterized by the steps of winding the glass fiber layer forming the base layer onto a winding mandrel, applying a second layer consisting essentially of glass fibers running in the longitudinal direction of the pipe, and prestressing these glass fibers by means of Tensioning elements attached to the front ends of the tubular body, winding a third glass fiber layer over the second under substantial tensile stress in order to press the essentially longitudinally directed second glass fiber layer underneath firmly against the base layer and the third, outer fiber layer, impregnating said glass fiber layers with a hardenable synthetic resin, the thermal hardening of the synthetic resin impregnation, the release of the clamping elements for the prestressed longitudinally oriented glass fibers of the said second frame fixed in the tube and the pulling of the tube from the winding mandrel, see above like the final blending of the pipe surface. 6. The method according to claim 5, characterized in that the first glass fiber layer forming the base layer is impregnated with a certain amount of synthetic resin during or after its construction and the glass fiber layers applied gradually thereon are soaked through the excess amount, and that the outermost glass fiber layer a final impregnation receives. 7. The method according to claims 5 and 6, characterized in that the first glass fiber layer is applied to the mandrel in the form of a fabric pre-impregnated with a plastic layer or of rovings, the plastic layer being plastically deformable and not hardened. B. The method according to claim 5, characterized in that while the isosynthetic resin is hardening, the pipe lies horizontally and is rotated about its axis. 9. The method according to claim 5, characterized in that the impregnation of the glass fiber structure and the hardening of the H.:,rzes in a vertically standing pressure vessel takes place in the following steps: a) rivacuating the vessel containing the glass fiber structure applied to the mandrel ; b) Filling in the resin while maintaining the vacuum up to a level which exceeds the uppermost glass fiber ends by approx. 5 cm; -c) Releasing the vacuum and allowing atmospheric air to flow into the vessel cavity above the resin level ;: d) Compress the air in the Void on 0a: 10 kg / cm 2; e) Heating the vessel, which is now under overpressure, and allowing the synthetic resin to harden. - 10. The method according to claim 9, characterized in that the resin is let into the pressure vessel from below.