DE10205206A1 - prepreg - Google Patents

Abstract

A prepreg with a sheet-like scrim made of filaments and with a resin for impregnation is proposed. In order to enable optimum ventilation when evacuating and pressing prepregs stacked on top of one another, the scrim is only partially impregnated with the resin over its thickness.

Description

The present invention relates to a prepreg according to the preamble of Claim 1, a use of a prepreg according to the preamble of Claim 20 and a component according to the preamble of claim 24.

Under the name "prepreg" is a fiber mat, especially in shape a scrim to understand that with a particularly thermosetting resin is or can be impregnated. Prepregs in particular processed by hot pressing, u. a. to molded parts or semi-finished products. In particular, thick-walled prepregs can be made from one another Components are manufactured.

The term "resins" here includes in particular liquid to solid to understand organic products preferably according to DIN 55958, which for Solidification of the fiber mat can be hardened or crosslinked. Generally it can but also another binding agent to solidify it act impregnated fiber mat when curing.

Prepregs with fiber mats, unidirectional fabrics, multiaxial fabrics, Fabrics and the like are used especially in the manufacture of components used when it comes to defined mechanical properties. Through defined alignment and uniform loading of the filaments components that can withstand very high loads can be achieved.

Several prepregs are usually used to produce a component superimposed, compressed and evacuated under vacuum as well then heated to liquefy and harden the resin. It is problematic if in the individual prepregs themselves or between neighboring ones Air is trapped in prepregs and does not escape during evacuation can. This leads to an undesirable, undefined arrangement of the Filaments. In particular, an uneven load or Tension of the filaments and thereby a deterioration of the mechanical properties of the finished component.

In order to avoid air pockets, it is already known from practice alternating dry scrims, fabrics, mats etc. - i.e. layers without resin - and layering prepregs or resin films impregnated with resin, so that air can escape laterally through the dry layers during evacuation can.

The disadvantage of the aforementioned procedure is that the effort is relatively high and in particular on an appropriate stratification must be meticulously observed. It has also been shown that thicker Dry layers often liquefy and harden the resin not impregnated or impregnated properly. This leads to finished component with poor mechanical properties.

Sandwich-like prepregs are also already known from practice. For example, between a dry upper scrim and a a resin layer is arranged on the dry lower scrim.

In the above structure, it is disadvantageous that complex production of the prepreg is required. Furthermore, thicker ones are also used here Located which is particularly desirable in the manufacture of thick-walled components are, often an impeccable impregnation or impregnation of the individual filaments during the liquefaction and curing of the resin.

The present invention has for its object a prepreg and a Use of a prepreg and a component made from prepregs specify, so that a simple, simple preparation of the prepreg Cost-effective production of thick-walled components in particular while avoiding undesirable air pockets.

The above object is achieved by a prepreg according to claim 1 Use according to claim 20 or a component according to claim 24 solved. Advantageous further developments are the subject of the dependent claims.

A basic idea of the present invention is one Prepreg with a clutch of the latter only partially in the thickness direction - in one first thickness range - impregnated with resin, so that one over the entire area of the prepreg-reaching layer - in a second Thickness range of the scrim - that is not formed or at least much less than the first thickness range impregnated with resin (impregnated) is. The partial impregnation means that the dry or only filaments of the second slightly in contact with resin Thickness range form an air-permeable layer that allows lateral escape of Air when evacuating and / or compressing one another Prepregs enabled.

The proposed prepreg is very simple and inexpensive to manufacture.

Another advantage is that in particular thick walls of If necessary, components only from the proposed prepregs can be built.

For example, especially with high basis weights, Interlayers of prepregs that are impregnated with high resin content are used.

The only partial impregnation leads to surprisingly simple afterwards Way to a desired double function, namely on the one hand extensive impregnation of the scrim even before finishing the prepreg, as is required especially with thicker fabrics, and on the other hand, to secure ventilation to prevent undesirable air pockets when Layering and then pressing together or To be able to avoid evacuation. So far, a prepreg or a layup layer always at least essentially uniformly impregnated or not at all impregnated. However, the present invention is based on the idea that To vary the proportion of resin over the thickness of the scrim to the desired properties.

The resin content of the proposed prepreg is preferred (Venting prepregs) so high or dosed that the entire process Scrim, also the second thickness range of the scrim, impregnated or is soaked. By adjusting the resin content of the According to the proposed prepregs, a desired resin content or Fiber content can be achieved in the finished component. In particular, at Manufacture of a particularly thick-walled component exclusively proposed, preferably relatively thick prepregs without intermediate layers of other resin films or layers, dry layers or the like be layered.

The second thickness range preferably adjoins one (outer) flat side of the scrim. In particular, according to one particularly preferred embodiment, the outer "loose" filaments on the outer flat side of the second thickness range by means of an exclusively fixed on the flat side arranged fixing element. For example the fixation according to DE 31 32 697 A1, EP 0 072 453 A2 or DE 197 07 125 A1. In a particularly preferred embodiment, this is Fixing element by a relatively large-mesh, very thin network or Grid formed, at least with some of the outer filaments is at least selectively connected. If necessary, a fixing element or a fixation can also be provided on both flat sides of the scrim.

Further advantages, properties, features and aspects of the present Invention emerge from the following description of a preferred Embodiment with reference to the drawing.

The only figure shows a schematic representation of a proposed prepreg.

The prepreg 1 , which is shown only very schematically and not to scale, has a scrim 2 made of filaments 3 .

The scrim 2 is of unidirectional design here, ie all the filaments 3 run parallel to one another, here in the longitudinal extension L of the prepreg 1 .

If required, however, the scrim 2 can also be multidirectional or multiaxial, that is to say have layers of filaments 3 lying one above the other with different directions of extension.

The layer thickness D is preferably at least 0.3 mm, in particular at least 0.5 mm. For example, the layer thickness is even 1 mm or more. This is particularly true in the manufacture of thick-walled components desired or advantageous.

Instead of a particularly non-directional scrim 2 , the filaments 3 can also be in the form of a Malimo scrim, fabric or the like.

The filaments 3 are preferably formed from glass fibers, plastic fibers and / or carbon fibers. In particular, filaments 3 made of carbon (carbon fibers), E-glass, R-glass or aramid are used.

The diameter of the filaments 3 is preferably 2 to 20 μm, in particular essentially 5 to 12 μm.

The filaments 3 preferably lie very tightly and evenly against one another, the filaments 3 preferably running in a very straight line with regard to uniform tension or loading when a component (not shown) made from the prepreg 1 is loaded.

The oblique hatching indicates a resin 4 with which the proposed prepreg 1 or its scrim 2 is only partially impregnated (impregnated) over the scrim thickness D. The part impregnated with the resin 4 forms a first thickness region 5 of the scrim 2 . The first thickness area 5 is followed by a second thickness area 6 of the scrim 2 , which is preferably not or possibly only slightly impregnated with the resin 4 or another resin or binder.

The resin 4 is in particular a thermoset or thermoplastic, preferably an epoxy resin.

The basis weight of the scrim 2 without resin 4 is preferably 200 to 5000 g / m ² , in particular 500 to 2000 g / m ² , for example essentially 1000 g / m ² .

An essential aspect of the present invention is that the second thickness range 6 of the scrim 2 forms a layer of "dry" or at least relatively loose, not airtightly bonded filaments 3 , which extends over the entire width B of the scrim 2 and along the Longitudinal extension L of the prepreg 1 , preferably extends over or on a flat side 7 of the scrim 2 and is air-permeable to a sufficient extent to prevent lateral escape of air or air between the prepregs 1 when evacuating and / or pressing together stacked prepregs 1 to allow from the first thickness range 5 of the scrim 2 .

The second thickness range 6 preferably has at least a thickness of one filament 3 , in particular at least 5%, 10% or 20% of the total laid thickness D. The thickness is preferably at most 50%, in particular at most 40%, of the layer thickness D.

Preferably, the prepreg 1 according to the proposal is formed only from a preferably "one-piece" scrim 2 , which can optionally also be multidirectional.

The scrim 2 in turn preferably consists only of the first thickness area 5 and the second thickness area 6 , which in particular define - as far as this is possible - merge into one another.

According to a very particularly preferred embodiment, the scrim 2 is impregnated with the resin 4 to a predetermined depth or thickness only from one side - in the example shown from the lower flat side. This depth or thickness thus determines the first thickness range 5 .

If necessary, a layer of pure resin 4 can follow on the outer flat side of the prepreg 1 directly adjoining the first thickness region 5 - in the example shown on the lower flat side. Preferably, however, the resin 4 is at least essentially completely contained in the scrim 2 , that is to say in the first thickness range 5 .

The proportion of resin 4 in the scrim 2 or prepreg 1 is selected such that the desired mechanical properties are achieved after processing into a component, in particular that the second thickness range 6 is then sufficiently impregnated or impregnated.

In particular, the prepreg (deaeration prepreg) 1 or scrim 2 contains essentially 35 to 60 vol.%, Preferably 40 to 45 vol.% Of resin 4, based on all filaments 3 of the scrim 2 . When the resin 4 is liquefied during the processing of the prepreg 1 , the resin 4 is then distributed at least substantially uniformly over the thickness of the scrim 2 , so that the often desired ideal fiber content of 55 to 60 vol.% Can be achieved.

When processing or during the manufacture of a component, the proposed prepregs 1 are preferably layered one above the other immediately, that is to say without the interposition of other layers, foils, mats or the like, in such a way that in the transition from one prepreg 1 to the next one first thickness range 5 and a second thickness range 6 come towards each other. This ensures that during the subsequent evacuation and / or compression of the prepreg stack, air can escape laterally through the respective second thickness region 6 between the flat sides of adjacent prepregs 1 , that is to say transversely to the longitudinal extent L. The same applies to the escape of air from the first thickness area 5 when the prepreg stack is evacuated and / or compressed. The second thickness range 6 thus prevents unwanted air inclusions in the prepreg stack, so that the consequences for the finished component which have already been explained and are caused by air inclusions can be avoided.

This is followed in particular by heating, for example to about 60 ° C. to 180 ° C., in particular 60 ° C. to 100 ° C., a liquefaction and curing or crosslinking of the preferably thermosetting resin 4 .

The proposed structure of the prepreg 1 enables the second thickness area 6 to be sufficiently impregnated or impregnated with the liquefied resin 4 before it cures, even in the case of a very thick scrim 2 , since the thickness of the second thickness area 6 is in relation to the total thickness D of the scrim 2 chosen relatively small and needs-based - for example, depending on the resin 4 used , the filament material, the filament diameter and. Like. - Can be adjusted.

For production or intermediate storage or for transport, the proposed prepreg 1 can be provided with a carrier (not shown), for example silicone paper, in particular on the impregnation side - in the example shown on the lower flat side.

Preferably, the prepreg 1 according to the proposal has a fixing element 8 on its flat side 7 , which is adjoined by the second thickness area 6 of the scrim 2 , or on the outside of the second thickness area 6 .

The fixing element 8 is preferably arranged exclusively on the flat side 7 so as not to disturb the course of the filaments 3 in the scrim 2 . In the example shown, the fixing element 8 is formed by a preferably coarse-meshed mesh or grid which, in order to stabilize the scrim 2 , in particular the second thickness range 6 of the scrim 2 , is at least selectively connected, for example glued, to at least some of the outer filaments 3 on the flat side 7 .

It is essential that, in the proposed prepreg 1, no elements, such as stitching or the like, reach through or constrict the scrim 2 , so that an optimal alignment and an optimal course of the filaments 3 in the component to be manufactured can be easily achieved.

Claims (24)

1. Prepreg ( 1 ) with a web-shaped scrim ( 2 ) made of filaments ( 3 ) and with a resin ( 4 ) for impregnation, characterized in that the scrim ( 2 ) over the scrim thickness (D) in a first thickness range ( 5 ) impregnated and impregnated in a second thickness range ( 6 ), or that it is substantially less impregnated, and that the first and second thickness ranges ( 5 , 6 ) each extend over the entire scrim width (B), so that the filaments ( 3 ) in the second thickness range ( 6 ) are permeable to air transversely to the longitudinal extent (L) of the prepreg ( 1 ). 2. Prepreg according to claim 1, characterized in that the second thickness region ( 6 ) adjoins a flat side ( 7 ) of the scrim ( 2 ). 3. Prepreg according to claim 2, characterized in that the prepreg ( 1 ) has an exclusively on the flat side ( 7 ) arranged fixing element ( 8 ) which arranged on the flat side ( 7 ) arranged filaments ( 3 ) of the second thickness range ( 6 ) fixed at least partially and / or selectively. 4. Prepreg according to claim 3, characterized in that the fixing element ( 8 ) is formed like a net. 5. Prepreg according to claim 3 or 4, characterized in that the fixing element ( 8 ) has a weight per unit area of 0.5 to 4 g / m ² , in particular of 1 to 1.5 g / m ² . 6. Prepreg according to one of the preceding claims, characterized in that the filaments ( 3 ) of the scrim ( 2 ) run undisturbed, in particular no elements extending through the scrim ( 2 ) are provided. 7. Prepreg according to one of the preceding claims, characterized in that the filaments ( 3 ) run unidirectionally or multidirectionally. 8. Prepreg according to one of the preceding claims, characterized in that the filaments ( 3 ) have a diameter of 2 to 20 µm, in particular essentially 5 to 12 µm. 9. Prepreg according to one of the preceding claims, characterized in that the filaments ( 3 ) are formed from glass fibers, plastic fibers and / or carbon fibers. 10. Prepreg according to one of the preceding claims, characterized in that the prepreg ( 1 ) has only a single scrim ( 2 ). 11. Prepreg according to one of the preceding claims, characterized in that the second thickness range ( 6 ) has at least a thickness of one filament ( 3 ). 12. Prepreg according to one of the preceding claims, characterized in that the second thickness range ( 6 ) based on the total layer thickness (D) has a thickness of 5% to 50%, in particular from 10% to 40%. 13. Prepreg according to one of the preceding claims, characterized characterized in that the layer thickness (D) at least 0.3 mm, preferably is at least 0.5 mm, and in particular essentially 1 mm or more. 14. Prepreg according to one of the preceding claims, characterized in that the scrim ( 2 ) without resin ( 4 ) has a weight per unit area of 200 to 5000 g / m ² , in particular 500 to 2000 g / m ² . 15. Prepreg according to one of the preceding claims, characterized in that the first thickness region ( 5 ) immediately adjoins the second thickness region ( 6 ), in particular wherein the scrim ( 2 ) is formed only from the first and second thickness regions ( 5 , 6 ) is. 16. Prepreg according to one of the preceding claims, characterized in that the resin ( 4 ) is arranged at least substantially exclusively in the scrim ( 2 ), in particular in the first thickness range ( 5 ). 17. Prepreg according to one of the preceding claims, characterized in that the prepreg ( 1 ) 35 to 60 vol .-%, in particular 40 to 45 vol .-%, resin ( 4 ) based on all filaments ( 3 ) of the scrim ( 2nd ) contains. 18. Prepreg according to one of the preceding claims, characterized in that the scrim ( 2 ) is impregnated on one side with the resin ( 4 ). 19. Prepreg according to one of the preceding claims, characterized in that the resin ( 4 ) is thermally curable and / or is a thermoset and / or a thermally crosslinkable thermoplastic. 20. Use of a prepreg ( 1 ) with a web-shaped lay-up ( 2 ) made of filaments ( 3 ), the lay-up ( 2 ) being impregnated with a resin ( 4 ) in a first thickness range ( 5 ) in a first thickness range ( 5 ) and in one the second thickness range ( 6 ) is not impregnated or substantially less impregnated with the resin ( 4 ) and the first and second thickness ranges ( 5 , 6 ) each extend over the entire laid width (B), so that the filaments ( 3 ) are in the second thickness range ( 6 ) are permeable to air transversely to the longitudinal extent (L) of the prepreg ( 1 ), for producing a component, characterized in that
that several prepregs ( 1 ) are stacked one on top of the other, that the stacked prepregs ( 1 ) are evacuated and / or compressed, air enclosed between prepregs ( 1 ) escaping through the second thickness range ( 6 ), and
that subsequently, in the evacuated and / or compressed state, the resin ( 4 ) is liquefied over the thickness ranges ( 5 , 6 ) to even out the impregnation and is finally cured or crosslinked. 21. Use according to claim 20, characterized in that only prepregs ( 1 ) according to one of claims 1 to 19 are used. 22. Use according to claim 20 or 21, characterized in that the resin ( 4 ) is liquefied by heating and / or cured. 23. Use according to one of claims 20 to 22, characterized in that the prepregs ( 1 ) are layered one above the other in such a way that a first thickness range ( 5 ) and a second thickness range ( 6 ) are in each case transferred from one prepreg ( 1 ) to the next. lie on top of one another or that a completely impregnated prepreg lies between the second mutually facing thickness regions ( 6 ) of two prepregs ( 1 ). 24. Component made of prepregs ( 1 ), characterized in that the prepregs ( 1 ) are designed according to one of claims 1 to 19 and / or that the component is manufactured according to one of claims 20 to 23.