DE4308370C2 - Process and core body for producing a hollow molded or profile body made of fiber-reinforced plastic - Google Patents

Description

The invention relates to a method for Production of a hollow molded body according to claim 1, on a core body for use in this process according to claim 16 and one according to the method producible two-wheel frame according to claim 20.

It is known in the processing of fiber reinforced Plastic to work with a core. This, e.g. B. from PU foam core is wrapped with fiber material, impregnated with reactive plastic and in a mold underneath Exposure to heat hardened. One disadvantage of this The method is that the remaining in the molded body Core additionally increases the weight of the molded body.

A method is also known in which a inflatable tube with impregnated fiber material is wrapped. The molding is cured in a shape with inflated hose and under action of warmth. A disadvantage of this method is that wrapping especially with more complex shaped bodies of the hose with fiber material due to the Flexibility of the hose made very difficult. Furthermore, when handling such Shaped body blanks, e.g. B. when placed in the mold, Defects such as kinks, bruises, etc. occur that too  a reduction in the strength of the composite body to lead.

The application of such processes to HIGH-TECH products such as for example off-road bike frames resulted in unsatisfactory results since the former known methods compared to the frame weight Was too high or when using the latter procedure is not the required Fatigue strength of the frame construction was achieved.

DE 27 46 173 B2 is one Device for the production of components fiber-reinforced plastics known, on a Base plate a rigid one made of a metallic material manufactured core is mounted. About this core is a rubber-elastic support body put on his The underside of the base plate rests, i.e. not the core completely enveloped. At the core is a supply line for Print medium trained that you on the one hand to Base plate out and on the other hand to the inside of the elastic support body opens so that the Pressure can be applied to the inner surface of the support body is. The outer surface of the elastic support body is surrounded with a laminate of fiber-reinforced synthetic resin. One constructed in this way on a base plate Shaped body blank is of a split shape enclosed on the side facing the base plate has an opening. This form is in turn with a Surround foil. For curing the fiber-reinforced Resin is made using the autoclave method a vacuum is applied between the film and the mold and through the supply lines formed in the core Pressurized inner surface of the support body. With this device is a method of manufacturing a pick molded body, the undercuts and complex Has outer contours, not possible, because then the fixed Core can no longer be removed.  

JP 56-30824 A shows one made of a metal alloy low melting point core manufactured with impregnated fiber material is wrapped. This Shaped body blank is then at a temperature below hardened to the melting temperature of the metal alloy. Then the core is at a temperature above melted the melting point of the metal alloy. This document can not indicate any Cover the mandrel with elastic material.

CH 148 560 shows a method for producing a Casting molds made from an easily meltable salt.

The registration is therefore the Task to provide a method in which the manufacture and handling of a fiber material wrapped around a complex shape Shaped body blanks or shaped body with minimized Dead weight can be done easily and reliably.

This object is achieved by the features of Claim 1 solved.

With the method according to the invention, it is possible to be complex to produce shaped hollow bodies, the cavity of which is merely must have an opening through which the interior of the elastic jacket a pressure medium can be supplied.

This procedure is made possible by using a massive fusible core, made entirely of one elastic sheath is wrapped, the opening of the Jacket is adapted to the opening of the molded body, so that the core of the molded body by melting and draining Will get removed. This makes it possible to create complex moldings, which have strong undercuts.  

Another advantage according to the invention Subject of the application lies in the fact that Print media directly into the gap between the massive core and the elastic jacket is fed. So that the be made very easily since none Supply lines must be trained in the core. Furthermore, the core is due to its massive design stable in handling, so that no risk of breakage when Handling and when building the molded body blank.

Claim 16 describes a specially adapted Core body for use in the method according to the invention and claim 20 describes one with the Two-wheel frame produced according to the method of the invention.

By the measure, one with the shape of the Core body provided on the inner surface of the shaped body create that from a fusible core and from a elastic core surrounding the core, for example in Form of a hose, it is suitable due to its strength and inherent rigidity are good for wrapping with yarn-like or fabric-like Fiber material. This makes it possible to take the fiber tissue underneath Avoid kinking and creasing cleanly and evenly to wrap the core body.

The fiber orientation can correspond to the Requirements and loads can be chosen arbitrarily. The blank produced in this way is by the Core body inherently stiff and can e.g. B. when inserted into a  divisible form can be handled well without the Shaped body blank is damaged.

The surface of the jacket offers compared to usual Solutions a particularly good primer for the Fiber material winding, so that creating the Shaped body blank is much easier.

Curing takes place with the jacket inflated and through Exposure to pressure and heat. By inflating the The casing is made of fiber material by means of compressed air detached from the core and against the wall of the mold pressed. This way, a clean separation between jacket with fiber material casing and mold core guaranteed.

After curing, the heat melted core drained and the coat out of the Pulled out or inside of the molded body leave. The process enables the production of coreless hollow molded parts made of fiber-reinforced plastic, the scrap rate in production caused by improper winding of the fiber material or improper Handling of the blank is minimized.

Because of the coreless hollow construction and the opposite known method reduced error rate is that The method according to the invention is particularly suitable for Application for making a bicycle frame that is characterized by low weight and high strength.

However, the method according to the invention is not only suitable for use on two-wheel frames, but it is suitable also for the production of all cavities highly stressed components such. B. two-wheel handlebars, Two-wheel frames, tennis rackets, swimming boards and the like Objects.  

By using wax as a meltable material for the core with a melting temperature of preferably 80 ° C. up to 140 ° C is a simple melting of the Kerns guaranteed and secondly the hardened Plastic material due to the relatively low Temperature only exposed to low thermal stress.

By providing multiple layers of wrap on stronger stressed areas of the molded body is a total high strength with minimized weight of the molded body reached.

By filling the inlaid in an auxiliary form pre-assembled jacket with melted core material the production of the core body is particularly special easily and exactly reproducible.

Since the sheath can be removed after the core has melted is, it can be reused so that the Manufacturing process can be done more economically.

Further advantageous embodiments of the invention are Subject of the other subclaims.

The invention will be more preferred hereinafter based on several Embodiments with reference to the drawings explained in more detail.

Fig. 1 shows a partially cut two-wheel handlebar with molded steering tube, which can be produced by the method according to the invention.

Fig. 2 shows a side view of a one-piece two-wheel frame, which is produced by the inventive method.

Fig. 1 is a two-wheel link blank with molded steering tube, as it is inserted for curing in a mold.

The interior of the two-wheel control arm is filled with a core body 1 , which consists of a fusible core 2 and a tube 3 surrounding the fusible core 2 . Fiber materials 4 , for example so-called prepregs, are wound around the core body 1 and later form the shaped body.

The method steps for producing a hollow molded body are described below using the example of the two-wheel handlebar shown in FIG. 1.

A divisible auxiliary form (not shown), the inner surface of which has the shape of the core 2 of the two-wheel link, is made with a fusible core material such as. B. poured hard wax. After the core 2 has cooled or solidified, it is removed from this auxiliary form.

In a further process step, the core 2 is covered with a gas-tight tube 3 . This is done, for example, by applying a suitable tube material, such as latex or silicone rubber, to the core 2 . However, a pre-assembled hose can also be used, which either originates from a previous application of the method according to the invention or which is obtained in a separate manufacturing process, which is not to be discussed here.

The core 2 surrounded by the tube 3 forms the actual core body 1 . The tube 3 surrounding the core body 1 is elongated on the handlebar tube of the two-wheel handlebar and has an opening 5 which can be closed by a valve (not shown).

The core body 1 is then wrapped with synthetic resin impregnated fiber fabric 4 , preferably carbon fibers, so-called prepregs.

Due to the inherent rigidity of the core body, the fiber fabric can be closely formed around the core body 1 . Areas subject to higher stress can be reinforced by multiple layers of fibers and / or stabilized by other materials etc. Furthermore, inserts such as fastening elements for fastening the handlebar can be molded in. The molded body blank produced in this way is easy to handle due to the rigidity of the core body 1 .

The molded body blank is now in a divisible mold (not shown) inserted, the inner surface of which Has shape of the outer surface of the molded body. By the stability of the blank is the danger of Wrinkling in the fiber material during insertion in the shape very small.

After the mold has been closed, the tube 3 is inflated so that the fiber material is pressed against the inner surface of the mold. The hose 3 and the fiber winding detach from the core 2 . The inner surfaces of the press mold can be heated so that the fiber-reinforced plastic hardens under the action of heat and pressure. After curing, the molded body is removed from the mold. The core can be melted by the action of heat during the pressing process or in a further process step and discharged as a liquid medium through the hose opening 5 . The draining of the liquid core material can be assisted by applying negative pressure to the hose opening 5 . The negative pressure further promotes the detachment of the hose 3 from the inner surface of the molded body. The hose 3 is thereby easier to pull out of the molded body.

The detachment of the tube 3 from the molded body can be further facilitated by treating the outer surface of the core body 1 with a release agent before wrapping it with fiber material.

The two-wheel handlebar representing the molded body molded steering tube is essentially after pressing completed, the stable during the pressing process Kern ensures that the hollow body defined Wall thicknesses with a given interior surface structure has what compared to known solutions superior strength values and a Post-processing is largely unnecessary.

The hose 3 obtained in the above-described method can be used again to produce the next molded body. The core body 1 is produced by filling the tube 3 with molten core material in an auxiliary form.

In FIG. 2 is a partially sectioned bicycle frame is shown, which is constructed of an integrally formed hollow-profile structure with receiving portions for the bottom bracket 6, the steering head bearings 7, 8 and rear seat post. 9

The method steps for producing a hollow molded body are described below using the example of the bicycle frame shown in FIG. 2.

As can be seen from the dashed boundary lines, the core body 1 required for the two-wheel frame is made up of a plurality of partial core bodies 1 a, 1 b, 1 c, each of which has a fusible core 2 surrounded by a tube 3 and by joining the complete core body 1 surrender. The division chosen here is only an example. Of course, other divisions or a one-piece mold core are also conceivable. The partial core bodies 1 a, 1 b, 1 c lie close together at their abutment points and / or overlap one another. Butt joints should be avoided if possible, so that it is preferred for reasons of stability to overlap the transition areas between two partial core bodies 1 a, 1 b, 1 c, that is, that the transition areas can be joined together like two round rod ends cut off at an acute angle to the longitudinal axis.

The core body 1 constructed from partial core body 1 a, 1 b, 1 c is, as in the exemplary embodiment described above, also wrapped with prepregs, the materials used and the layer thickness being freely selectable depending on the strength, so that the winding layers are used several times at highly stressed locations can lie on top of each other.

The further processing of the molded body blank takes place in essentially in the same way as in the above described embodiment.

The two-wheel frame, which is a relatively complex shaped body, has a core body 1 , the partial core body 1 a, 1 b, 1 c of which does not encompass a closed profile structure of the bicycle frame, so that each tube 3 belonging to a partial core body 1 a, 1 b, 1 c after melting the respective core 2 through appropriate frame openings such. B. bottom bracket, steering head bearing or seat post opening 6 , 7 , 8 is removable.

In another variant of the method for producing a two-wheeled frame constructed from a hollow body profile, an integrally formed core body 1 is used. As described above, the core 2 , which consists of meltable material, is produced in a divisible auxiliary form and then coated with a thin, air-impermeable, elastic layer. The resulting tube 3 has extensions 5 for inflating the various frame openings such as bottom bracket, seat post and steering head bearing openings 6 , 7 , 8 . Following the above-described process steps, ie, wrapping with pre-impregnated fiber material, insertion into the mold, and curing under pressure and heat, the core material melted by the heat is discharged at the various frame openings.

Due to the one-piece design of the core body 1 with undercuts, the hose 3 must remain in the two-wheeled frame. So that the tube 3 forms a bond with the inner surface of the bicycle frame, the tube 3 can be treated on the outer surface with an adhesive agent. In this example, a composite body consisting of the hardened hollow plastic profile and the hose would result.

A is preferably used in the above-described methods Core material made of wax or hard wax or the like fusible material used, the melting point of a temperature of 40 ° C to 200 ° C, preferably at 80 ° C up to 140 ° C.

For better removal from the interior of the molded body after the plastic has hardened, the surface of the hose 3 can be treated with a release agent.

In the manufacture of the hollow molded body can in the divisible form, in which the curing of the molded body blank further shaping inserts are inserted. Furthermore, reinforcing elements can be made from others Materials such as B. Metal either in the divisible form be inserted with, so that they combine with the reactive plastic, or it will be on the molded body specially shaped receiving sections formed then the corresponding bearing bushes, recordings etc. are attached.

The described new method thus enables simple, precise production, even more complicated Hollow body geometries, which are characterized by low weight and excellent strength.

Claims (21)

1. A process for producing a hollow molded body from fiber-reinforced plastic with the process steps:

• - Forming a solid fusible core ( 2 ) in an auxiliary form with the shape of the inner surface of the desired shaped body,
• Applying an elastic gas-tight jacket material to the core ( 2 ) to produce a core body ( 1 ) provided with a jacket ( 3 ) by completely enveloping the core ( 2 ) with an elastic gas-tight jacket material,
• - Creating a shaped body blank by wrapping the core body with a fiber material ( 4 ), which is soaked either before or after wrapping with reactive plastic;
• - inserting the molded body blank into a divisible mold;
• Feeding a pressure medium directly into the gap between the surface of the solid core ( 2 ) and the inner surface of the jacket ( 3 ) via a jacket opening ( 5 ), so that the impregnated fiber material ( 4 ) is pressed against the inner wall of the mold,
• - hardening of the molded body blank by the action of pressure and heat;
• - Melting the core ( 2 );
• - Drain the molten core ( 2 ) and remove the molded body from the mold.

2. The method according to claim 1, characterized in that the core ( 2 ) consists of wax or similar fusible Ma material whose melting point is at a temperature of 40 to 200 ° C, preferably 80 to 140 ° C. 3. The method according to claim 1, characterized in that more heavily used areas of the molded body are wrapped several times with impregnated fiber material ( 4 ). 4. The method according to claim 1, characterized in that further shaping inserts into the divisible form be inserted. 5. The method according to claim 1, characterized in that reinforcing elements with either in the divisible form be inserted so that they bond with the reacti vene plastic, or after curing intended places are attached. 6. Method according to one or more of the above Claims, characterized in that as a reinforcement fa glass, aramid, polyester or carbon fibers in fabric form or used as a single fiber. 7. Method according to one or more of the above Claims, characterized in that as plastics Re action resins, preferably epoxy, polyurethane, polyester, Phenol or vinyl esters can be used. 8. The method according to one or more of the preceding claims, characterized in that the core body ( 1 ) is produced by filling the pre-assembled jacket ( 3 ) inserted in an auxiliary mold with molten core material. 9. The method according to one or more of claims 1 to 7, characterized in that the prefabricated jacket ( 3 ) is pulled over a fusible core ( 2 ) produced in an auxiliary mold. 10. The method according to one or more of claims 1 to 7, characterized in that sheath material, preferably latex or silicone rubber applied or sprayed onto a fusible core ( 2 ) produced in an auxiliary form and thus a core body provided with a sheath ( 3 ) ( 1 ) is generated. 11. The method according to one or more of the preceding claims, characterized in that the jacket ( 3 ) is removed after the core ( 2 ) has melted out. 12. The method according to claim 11, characterized in that the jacket ( 3 ) is treated for better removal on the outer surface with a release agent. 13. The method according to one or both claims 11 and 12, characterized in that the jacket ( 3 ) is used again in a subsequent shaping process. 14. The method according to one or more of claims 1 to 10, characterized in that the jacket ( 3 ) remains after melting the core ( 2 ) in the cavity of the molded body. 15. The method according to claim 14, characterized in that the jacket ( 3 ) is pretreated with remaining in the cavity of the molded body with a means or consists of a material that enters into a bond with the inner surface of the molded body. 16. core body for use in the method according to any one of claims 1 to 15, characterized in that the core body ( 1 ) consists of a plurality of partial core bodies ( 1 a, 1 b, 1 c) be, each one with a jacket ( 3rd ) surrounding the fusible core ( 2 ) and by assembling the entire core body ( 1 ). 17. Core body according to claim 16, characterized in that the partial core body ( 1 a, 1 b, 1 c) of the core body ( 1 ) lie closely together at their abutment points and interlock overlap pend. 18. Core body according to claim 16, characterized in that each partial core body ( 1 a, 1 b, 1 c) does not encompass a closed profile structure of the molded body, so that each belongs to a partial core body ( 1 a, 1 b, 1 c) Sheath ( 3 ) can be removed after the respective core ( 2 ) has melted out via corresponding shaped body openings ( 6 , 7 , 8 ). 19. core body for use in the method according to any one of claims 1 to 15, characterized in that the core body ( 1 ) is integrally formed and the integral body jacket ( 3 ) belonging to the core body remains in the molded body. 20. Two-wheel frame made of plastic, made by the method according to any one of the preceding claims, characterized in that it is constructed from an integrally formed hollow profile structure with receiving sections for bottom bracket ( 6 ), steering head bearing ( 7 ), satellite tel support ( 8 ) and rear wheel ( 9 ) is. 21. Two-wheel frame according to claim 20, characterized in that the jacket ( 3 ) enters into a bond with the inside of the two-wheel frame.