WO2008151962A1

WO2008151962A1 - Fiber angle sensor and method for determining a prevailing main fiber direction

Info

Publication number: WO2008151962A1
Application number: PCT/EP2008/056800
Authority: WO
Inventors: Oliver Meyer
Original assignee: Eads Deutschland Gmbh
Priority date: 2007-06-14
Filing date: 2008-06-02
Publication date: 2008-12-18
Also published as: DE102007028014A1; DE102007028014B4

Abstract

The invention relates to a device and a method for measuring the main fiber orientation in a textile fabric (12). In a preferred embodiment, the orientation of fibers (14) in the textile fabric (12) is determined by determining the intensity of reflected radiation as a function of the angle of incidence and angle of reflection.

Description

Fiber angle sensor and method for determining a predominant

Main fiber direction

The invention relates to a fiber angle sensor and to a method which can be carried out, in particular using the same, for determining a main fiber direction prevailing in a textile fabric.

Recently, fiber-reinforced plastics are becoming increasingly widespread. In order to achieve desired mechanical properties of the components produced therefrom, the fibers are arranged in a force-oriented manner in certain orientations. For this purpose, for example, textile structures are formed with techniques of textile technology so that the fibers extend mainly in the desired direction. Corresponding semifinished products formed from the fibers are referred to in particular as preforms. Another approach, which has hitherto not yet been published, is to deposit individual fiber pieces in specific orientations.

Accordingly, in the production of dry carbon fiber textiles and in preforming processes, precise adherence to certain deposition angles is desirable in order to ensure the subsequent mechanical properties.

The invention has for its object to provide an apparatus and a method for detecting the position of filaments in a textile structure.

This object is achieved with a fiber angle sensor according to claim 1 and a method with the steps of claim 16.

Advantageous embodiments of the invention are the subject of the dependent claims. According to the invention, a fiber angle sensor is provided for detecting a main fiber orientation prevailing in a region of a surface of a textile structure. For the first time, an automatic measurement of fiber orientations in preforms or other textile semifinished products to be used in the production of components from fiber-reinforced materials can be carried out in order to verify the desired properties at a very early point in time.

The sensor can be used for quality control in various manufacturing processes. Possible fields of application are also the textile technology, but in particular and prefers the production of CFRP or GFRP components.

The fiber angle sensor can be constructed utilizing various physical effects that correlate to a particular fiber orientation. A fiber angle sensor can be constructed in a particularly simple and effective manner by exploiting the different optical behavior of fibers of different orientation when illuminated with appropriate radiation.

In particular, fibers oriented in a specific orientation at their boundary surfaces to the surroundings at a given angle of incidence reflect light of different intensity. The radiation is thus deflected more or less, depending on how the fiber is oriented to the radiation. If one measures the intensity in a certain way reflected radiation as a function of the direction of irradiation, this can be used to determine the fiber orientation. The reverse measurement (exchange beam source / beam detector) would also work. Likewise, depending on the application, it would also be possible to measure the radiation which is still passing through in a certain area so as to also find out which proportion has been correspondingly reflected and accordingly is missing in the measured radiation. A particularly preferred embodiment of the fiber angle sensor therefore has a radiation source for emitting radiation that can be reflected by the fiber material to be detected and a radiation detector for detecting radiation reflected by the fibers in the textile structure into a specific area.

From a dependence of the reflection / transmission on the relative orientation of the beam incidence or beam exit on the one hand and the textile surface on the other hand, it is thus possible to determine the predominantly predominant fiber orientation on the surface, more precisely the irradiated area thereof. Such a dependency can be determined particularly simply by a construction in which the radiation source is rotatably arranged relative to the surface to be measured in order to illuminate the surface over an angular range and to determine the reflected radiation as a function of the relative angle between irradiation and the surface to be measured. The relative rotatability can be generated by rotation of the radiation source with a fixed surface (for example a slide or in a manufacturing process located and held there textile semi-finished) and / or by rotation of the surface (for example, rotating the textile Gebild-).

In principle, the radiation source also suffices if only the beam itself rotates. In principle, this can also be achieved by a plurality of approximately circularly arranged, more or less stationary or only limitedly swiveling radiation sources, which are switched one after the other.

In principle, instead of the relative rotation of radiation and the object to be measured, it is also conceivable to move a sensitive area of the radiation detector so as to reflect or reflect accordingly in different directions otherwise as (eg diffraction) deflected radiation depending on the direction of radiation to measure. Again, this may be a measure of the orientation of the fibers at which the beam deflection occurs.

On the surfaces of carbon fibers or glass fibers in particular light rays are reflected more or less well depending on the angle of incidence. Therefore, in one embodiment it is preferred that the radiation source is a light source for emitting light which is reflectable at interfaces of carbon fibers or glass fibers, and the radiation detector is designed for measuring the intensity of light radiation reflected into a region.

If the radiation source is designed to obliquely irradiate radiation onto the surface to be measured, then the radiation at the fibers, which are generally formed with approximately approximately a round cross-section, is reflected particularly well to the corresponding mirror-inverted angle if the fibers all orient in the direction of the radiation incidence are. Upwards, i. but then no radiation is reflected directly in the direction perpendicular to the surface. At an oblique incidence of radiation, reflection only takes place in this direction if the fibers are substantially at right angles to the radiation incident direction. If the radiation detector is then designed to measure radiation reflected in a direction perpendicular to the surface of the textile structure, then a relatively narrow maximum in the reflected radiation results over a very narrow angular range around the value 90 ° of the relative angle between fiber orientation and radiation incident direction. This results in a relatively accurate measure of the determination of the main fiber orientation.

The radiation effective for determining the reflectance can be increased, thus improving the sensitivity of the fiber angle sensor. If at least two radiation sources are provided. For example, a plurality of radiation sources may be aligned to emit radiation in a common plane crossing the textile formation - which may be relatively rotatable about a normal to the textile surface while detecting the relative rotation angle. For example, a mirrored arrangement of the radiation sources at a plane perpendicular to the surface plane to be measured is preferred. This arrangement is particularly advantageous in connection with the radiation detector which is sensitive precisely to the vertical emission direction. The latter will only detect reflection light from radiation sources radiating toward one another in an opposite direction and at an angle to the surface, if this radiation is reflected at the fibers, which will only be the case in the case of the fiber cross sections correspondingly rounded to a first approximation if these are oriented substantially perpendicular to the beam inflection plane and thus provide at least a small area for the reflection of radiation from the beam inflection plane exactly in the vertical direction.

In order to detect the angle dependence, it is preferred that, even with a plurality of radiation sources, these radiation sources are rotatable together relative to the surface to be measured. This includes a rotation of the pure radiation incidence with otherwise fixed beam generation and thus, in particular, the corresponding control of individual fixed, correspondingly aligned radiation generating devices of a beam source array.

The radiation source particularly preferably has a light line source or a laser. However, the radiation source can also have a pivotable point radiation source, in particular point light source, in order to generate a corresponding radiation incidence. In the case of light as detection radiation, the radiation detector preferably has a photodiode for detecting the intensity of the reflected light or, depending on the application, also the remaining light transmitted, for example.

In a preferred embodiment, the fiber angle sensor is further provided with an evaluation device by means of which the intensity of a reflected radiation from the surface in a certain range depending on their angle of incidence or the dependence of reflected radiation at a certain angle of incidence is determined depending on the angle of failure.

If, in the surface, the orientation of the fibers in projection perpendicular to the surface is of interest, it is mainly the angle of incidence projected onto the surface plane that is considered.

In a particularly preferred embodiment, a distance to the surface to be measured can be determined by a correlation between the height of a peak in the reflected radiation and the relative angle between radiation incidence or radiation failure. The corresponding design and calibration of the evaluation unit can be easily determined by carrying out some empirical experiments.

In a first alternative a) the method according to the invention for determining a predominant main fiber direction in a region of a surface of a textile structure comprises the following steps: irradiation of the surface by means of radiation falling preferably obliquely on the surface region, from different beam directions and measuring the intensity of the Fibers on the surface region of reflected radiation as a function of the beam direction. In a second alternative b), the method has the steps:

Irradiating the surface by means of a radiation incident on the surface region from a certain direction and

Measuring radiation reflected from the fibers at the surface area depending on the direction of failure.

In particular, in alternative a) it is preferred that the intensity of the radiation reflected substantially perpendicular to the surface is measured. There, the narrowest peak in the reflection radiation at a certain fiber orientation - namely when they are perpendicular to the radiation incidence - reach and thus the highest accuracy in the alignment measurement. In addition, the radiation detector can thus be arranged fixed on a relative axis of rotation, which simplifies the structure and facilitates the connection.

For determining the fiber orientation is further preferred - and this is applicable to both alternatives - the beam direction of a normal to the surface by an angular range continuously rotated or in lest possible small, the smaller the higher measurement resolution - rotation angle steps changed and by measuring the reflection to be detected there, that angle is determined in which an extreme value of the reflected radiation is detected. In this case, "beam direction" in alternative a) is understood to mean the emission direction of the radiation radiated onto the surface, and in alternative b) the reception direction, where the radiation reflected or otherwise emitted in this direction is detected. In particular, in alternative a), the direction which is perpendicular to the beam direction in the plane of the surface in which the maximum reflection can be determined is then more preferably determined as the main fiber direction.

The method can also be carried out fully automatically, for example in the context of an automated production of textile semi-finished products, for example for further processing in the production of CFRP or GFRP components.

The method could also be used as a sub-step in a control method for controlling the laying of fibers in certain orientations.

An embodiment of the invention will be explained in more detail with reference to the accompanying drawings. It shows:

Figure 1 is a schematic cross-sectional view through a textile structure (transverse to the textile plane) with essential elements of a preferred embodiment of a fiber angle sensor in an orientation of 0 ° to a main fiber direction.

Figure 2 is a schematic cross-sectional view through the textile structure (transverse to the textile plane) with the essential elements of the preferred embodiment of a fiber angle sensor in an orientation of 90 ° to the main fiber direction.

3 shows a schematic view of a measurement setup of the preferred embodiment of the fiber angle sensor in a plan view of the textile plane to be measured; and 4 shows a schematic view of an oscilloscope as an evaluation device for measuring setup according to FIG. 3 with an exemplary curve for indicating the prevailing fiber orientation.

1 and 2, a measuring principle for measuring a fiber direction in a region of a surface 10 of a textile structure, using the example of a preform 12 as a textile semifinished product for the manufacture of a CFRP component, will be explained in the following text.

The preform 12 is formed of carbon fibers 14 aligned on the surface in accordance with a main orientation. For ease of discussion, the arrangement in a Cartesian coordinate system is explained below, the plane spanned by the x and y directions being defined by the plane of the surface 10 and the z direction being the direction perpendicular to the surface 10.

A fiber angle sensor designated overall by 16 has a radiation source, here in the form of a light source 18 for emitting a light line (light line source), in particular with a laser 20, and a radiation detector sensitive to the emitted light, here in the form of a photodiode 22.

The light source 18 emits light at an angle β to the xy plane (ie at an angle to the plane of the surface 10, in the following elevation angle) between about 10 ° and 80 ° to the surface 10. The light thus falls obliquely on the surface 10th ,

In the illustrated example, the carbon fibers 14 extend substantially in the x direction. In Fig. 1, the light is irradiated in the xz plane and thus perpendicular to the main fiber orientation, and in Fig. 2, the light is irradiated in the yz plane and thus parallel to the main fiber orientation.

In the case of the parallel alignment according to FIG. 2 (the angle α in the x-y plane between light incidence and main fiber direction is 0 ° or 180 °), the light is reflected on the approximately approximately cylindrical surface of the carbon fibers 14. A significant portion of the light is reflected in a region 24 which is arranged in mirror image to the direction of irradiation. However, there is no region of the surface of the carbon fibers 14 which would reflect the light from the direction incident at an oblique elevation β directly in the z direction (elevation angle 90 °).

In the vertical orientation (the relative angle α in the x-y plane between the light incident direction and the main fiber direction is 90 °), at the round surface of the carbon fibers 14, there is at least a line-like region where the light is directly reflected in the z-direction. This is obviously only the case when the angle α is equal to or very close to 90 °.

In principle, one could now also arrange the photodiode 22 in the reflection region 24 in order to determine the maximum reflection at exactly α = 0 °. However, a narrower peak or a narrower peak is obtained if, as shown, the photodiode is aligned exactly perpendicular to the surface 10 in order to measure the light reflected exactly in the z direction. In this case, a narrow peak is obtained only when the main fiber orientation is aligned exactly at α = 90 ° to the incidence of light.

3 shows a possible arrangement of the fiber angle sensor 16 in plan view of the surface 10. There are two light sources 18 which are arranged in a common position. seed plane directed towards each other on a central region 26 of the surface 10 radiate. The photodiode 22 is directed exactly in the z-direction perpendicular to this area.

By means of a rotating device 28, the light sources 18 can rotate together about the normal through the central axis of the photodiode 22 normal to the surface 10 as a rotation axis relative to the surface 10. The rotating device 28 is provided with a rotation angle sensor, not shown, which detects the rotation angle.

As a result, the range 0 ° <α <360 ° can be traced, wherein α represents the relative rotation angle in the x-y plane, more precisely the angle of the projection of the beam direction in the x-y plane to the x-axis. In this case, the intensity of the light reflected in the z-direction is measured by the photodiode 22 and recorded via the angle α-the signal of which is supplied by the rotation angle sensor.

An oscilloscope 30, connected as an example for an evaluation unit, to which the outputs from the photodiode 22 and the rotation angle sensor are connected, is shown in FIG. It results exactly at α = 90 °, a relatively narrow peak; i.e. the main fiber direction is α = 0 ° (perpendicular to the value with the peak); Accordingly, it can be determined from this that the main fiber direction in the region 26 of the preform 10 measured here runs in the x-direction.

The special reflection properties of the carbon fibers 14 thus allow the determination of the storage angle. If the surface 10 of a textile to be examined (in this case preform 12) is irradiated at a certain angle (here: β) with a light line source or a laser 20 and this light source 18 is rotated about the normal to the surface 10, then occurs in the direction of the normal in the- Then the strongest reflection on when the light line is 90 ° to the filament axis.

The intensity of the reflection may be measured via a photodiode 22 and plotted against the angular position with a suitable instrument (e.g., oscilloscope or measuring computer).

Furthermore, a pivoted point source can be used instead of a line light.

Furthermore, the distance to the surface 10 can additionally be determined by correlation of the pivot angle or angle of rotation with the reflection peak.

The fiber angle sensor 16 can be used for quality control in various production processes. In the production of fiber preforms, errors in filing are detected and can be corrected before exclusion components.

LIST OF REFERENCE NUMBERS

10 surface

12 preform (textile structure)

14 carbon fibers 16 fiber angle sensor

18 light source (radiation source)

20 lasers

22 photodiode (radiation detector)

24 Reflection range with parallel alignment 26 Measuring range of the surface 10

28 turning device

30 Oscilloscope α Rotation angle (orientation to x-axis in x-y-plane) ß Elevation angle (alignment to surface 10)

Claims

claims

A fiber angle sensor (16) for detecting a main fiber orientation prevailing in a region (26) of an upper surface (10) of a textile structure (12).

2. fiber angle sensor (16) according to claim 1, characterized by a radiation source (18) for emitting by fibers (14) of the textile structure (12) reflectable radiation and a radiation detector (22) for detecting by the fibers (14) in the textile structure (12) in a certain range (z) of reflected radiation.

3. fiber angle sensor according to claim 2, characterized in that the radiation source (18) for illuminating the surface (10) from different angles, in particular over an angular range, is provided to the reflected radiation depending on the relative angle between irradiation and surface (10). capture.

4. fiber angle sensor according to claim 3, characterized in that the radiation source (18) relative to the surface (10) is rotatably arranged.

5. fiber angle sensor according to one of claims 2 to 4, characterized in that the radiation detector (22) for measuring the radiation reflected in different radiation directions is capable of the reflected radiation depending on the relative angle between radiation (24) and surface to be measured (10 ) capture.

A fiber angle sensor according to any one of claims 2 to 5, characterized in that the radiation source is a light source (18) for emitting light which is reflectable at interfaces of fibers (14), and the radiation detector (22) for measuring the intensity of is formed in a region of reflected light radiation.

7. fiber angle sensor according to one of claims 2 to 6, characterized in that the radiation source (18) for the oblique irradiation of radiation on the surface (10) is formed.

8. Fiber angle sensor according to one of claims 2 to 7, characterized in that the radiation detector (22) for measuring in a to the surface (10) of the textile structure (12) perpendicular direction (z) reflected radiation is formed.

9. fiber angle sensor according to one of claims 2 to 8, characterized in that at least two radiation sources (18) are provided, which are aligned for emitting radiation in a common, the textile structure (12) crossing plane.

10. fiber angle sensor according to claim 9, characterized in that the radiation sources (18) are rotatable together relative to the surface (10).

11. Fiber angle sensor according to one of claims 2 to 10, characterized in that the radiation source (18) has a light line source and / or a laser (20).

12. fiber angle sensor according to one of claims 2 to 11, characterized in that the radiation detector comprises a photodiode (22).

13. fiber angle sensor (16) according to one of claims 2 to 12, characterized in that the radiation source (18) has a pivotable point source.

14. Fiber angle sensor according to one of the preceding claims, characterized by an evaluation device (30), by means of which the intensity of an incident upon incidence of radiation on the surface (10) reflected radiation depending on the angle of incidence of the incident radiation and / or the angle of reflection of the reflected radiation is.

15. fiber angle sensor according to claim 14, characterized in that the evaluation unit (30) is formed such that a distance from the surface (10) can be determined by a correlation between the height of a peak in the reflected radiation and the direction of incidence.

16. A method for determining a predominant main fiber direction in a region (26) of a surface (10) of a textile structure (12) a) with the steps: Irradiating the area (26) of the surface (10) by means of a radiation, preferably oblique, incident on the surface area (26) from different beam directions and

Measuring the intensity of radiation reflected from fibers (14) of the textile structure (12) on the surface region (26) as a function of the beam direction or b) with the steps:

Irradiating the region (26) of the surface (10) by means of a radiation incident on the surface region (26) from a specific direction and

Measuring radiation reflected from fibers (14) on the surface region (26) as a function of their failure direction.

17. The method according to claim 16, characterized in that the intensity of a substantially perpendicular to the surface (10) reflected radiation is measured.

18. The method according to claim 16 or 17, characterized in that the beam direction in a rotation angle range about a normal to the surface (10) is changed as an axis and that relative rotation angle (α) between the beam direction and surface (10) is determined in the an extreme value of the reflected radiation is detected.

19. The method according to claim 18, characterized in that as the main fiber direction that direction is determined which is perpendicular to the beam direction in which the maximum reflection is detected.