Technical field

The invention generally relates to the field of manufacturing composite components by automated tape or fiber laying technology. More specifically, the subject matter of the invention is a method of laying individual layers composed of multiple sets of unidirectional tapes or fibers, especially in the process of manufacturing components by the automatic tape or fiber laying technology using thermoplastic carbon fiber reinforced tapes with a matrix made, i.a., of PEEK, PAEK, PPS or PEK.

Background art

Automated Fiber Placement (AFP) or Automated Tape Lying (ATL) technologies, known in the art, consist in laying pre-prepared unidirectional tapes or fibers using a machine or industrial robot with a dedicated head equipped with a unidirectional tape or fiber feeding system, a laser heating the tapes or fibers to a temperature above the melting point of the thermoplastic material and a roller pressing the tapes or fibers being fed against the surface of the mould. The difference between the AFP technology and the ATL technology comes down mainly to the fact that AFP uses pre-impregnated single fibers in the form of narrow strips being laid simultaneously, while the ATL technology uses pre-prepared unidirectional tapes in the form of wider strips, being laid individually or in sets of several tapes, layer by layer.

Due to manufacturing tolerances of individual parts of the machine or the robot, the width and thickness tolerances of the input material itself and the additive nature of manufacturing (layer by layer), the production of components by the AFP and ATL technologies is prone to systematic incorporation of defects in line with increasing number of layers during the process, and appearance of a wavy, rough surface on the part facing the laying head.

Summary of the invention

The objective of the invention is to minimize the number of defects in the manufactured composite component during laying of the set of unidirectional tapes or fibers layer by layer, and to get rid of the wavy and rough surface on part of the component, and thus to improve the quality of the finished product by laying successive layers in a strictly defined manner while maintaining the best process parameters.

A method of manufacturing composite components according to the present invention consists in laying plurality of layers of a composite material, each layer being composed of plurality of unidirectional tapes or fibers in the form of parallel-oriented strips of the composite material. The unidirectional layers with the same orientation of tapes or fibers are being laid with a lateral shift between these unidirectional layers so that the individual tapes or fibers of at least two unidirectional layers with the same orientation are shifted relative to each other by the value x defined by the section running in the direction perpendicular to the tape or fiber lying direction and parallel to the plane of symmetry, wherein the value x is different than the multiple of the width of the single tape or fiber.

In a preferred embodiment, each layer is being laid using plurality of sets of the unidirectional tapes or fibers being laid simultaneously during one pass of a laying head, wherein each set comprises plurality of tapes or fibers in the form of parallel oriented strips of composite material.

The lateral shift between the unidirectional layers occurs in order according to the direction of layer growth.

In one embodiment, the unidirectional layers are being laid directly on top of each other.

In turn, in another embodiment, the unidirectional layers may be separated by at least one layer with different orientation of tapes or fibers.

The value of x is preferably 1.5 of the width of a single tape or fiber.

The layers are preferably being laid symmetrically with respect to the plane of symmetry.

Advantageous effects of the invention

The use of the automated method of laying unidirectional tapes or fibers according to the invention allows for obtaining high-quality composites using standard tooling for this process, i.e. a robot with a head, a positioner and a heated mould.

Brief description of the drawings The invention will now be illustrated in more detail in a preferred embodiment with reference to the accompanying drawings, in which:

Fig. 1 - shows an arrangement of layers and their directions according to one preferred embodiment of the invention.

Fig. 2 - shows another exemplary arrangement of layers according to another preferred embodiment of the invention.

Fig. 3 - shows yet another exemplary arrangement of layers according to another preferred embodiment of the invention.

Fig. 4 - shows a lateral shift between adjacent layers in the cross section through an arrangement of layers having the same orientation.

Detailed description of preferred embodiments of the invention

With reference to Figs. 1-4, below will be explained a method of laying composite material layers by the automated AFP laying technology, referred to as the automated (programmed) tape (fiber) laying, using thermoplastic carbon fiber reinforced tapes with a matrix made, i.a., of PEEK, PAEK, PPS or PEK.

Figs. 1, 2 and 3 show a typical sequence of laying the layers 1, 2, 3, 4 in a manufactured composite component, according to a preferred embodiment of the invention, wherein the arrangement of layers has symmetry with respect to the plane P, therefore each layer 1, 2, 3, 4 with a given direction (of orientation of tapes T) occurs at least twice in the arrangement. Thus, Fig. 1 shows an arrangement consisting of four layers 1, 2, where the individual layers la, 2a, 2b, lb have consecutively the following orientation, according to the direction of layer growth: 0°, 90°, 90°, 0°. On the other hand, Fig. 2 shows embodiments with an arrangement comprising six layers 1, 2 which are arranged in two directions: 0° and 90° in order according to the direction of layer growth la, 2b, lb, lc, 2b, Id, and Fig. 3 - an arrangement comprising ten layers 1, 2, 3, 4 arranged in four directions, 0°, 90°, 45°, -45°, respectively, and in the following order according to the direction of layer growth: la, 3a, 2a, 4a, 2b , 2c, 4b, 2d, 3b, lb. The layers 1, 2, 3, 4 are arranged symmetrically with respect to the symmetry plane P.

The process of manufacturing composite components, including the method of laying unidirectional tapes T according to the invention, comprises shifting the layers 1, 2, 3, 4 being laid in the perpendicular direction, the so-called lateral shift (displacement), and occurs between the layers 1, 2, 3, 4 with the same orientation of tapes T, referred to as unidirectional (otherwise single-name or parallel) layers.

The unidirectional layers 1, 2, 3, 4 with the same orientation can follow directly one after the other, including in between also the layers 1, 2, 3, 4 running in other directions, i.e. with a different orientation of tapes T. The so called lateral shift occurs between the unidirectional layers 1, 2, 3, 4, regardless of the position they are located in the sequence the layers 1, 2, 3, 4 are being laid and how many of them there are in the manufactured composite component.

The lateral shift consists in that each tape T of the subsequent unidirectional layer 1, 2, 3, 4 (i.e. the upper layer with respect to the direction of layer growth) is shifted relative to the tape T of the previous unidirectional (lower lying) layer 1, 2, 3, 4 by the value x, which can be defined as a vector or section with a direction running perpendicular to the direction the tapes T are being laid and parallel to the symmetry plane P, wherein the length of this section must always be different from the width of a single tape T (different than its multiple). Such a method of laying results in each tape T of the subsequent unidirectional layer 1, 2, 3, 4, when viewed in the cross-section in the direction the layers are being laid (in the direction perpendicular to the symmetry plane P), overlaps two tapes T of the lower laying layer 1, 2, 3, 4 at the their joint running parallel to the direction in which the T-tapes are being laid. As a result, the outer surface of the manufactured component is less wavy and rough. For example, the value x may be less or greater than the width of a single tape T, but cannot be equal to it, as then the tapes T of the upper laying unidirectional layer 1, 2, 3, 4 would be aligned with the lower lying tapes T, so the condition that the tape T of the upper laying unidirectional layer 1, 2, 3, 4 overlaps partially two adjacent tapes T of the lower laying unidirectional layer 1, 2, 3, 4 will not be fulfilled.

The width of the individual layers 1, 2, 3, 4 depends on the technology being used. For example, in the AFP technology, single and unconnected strips of fibers (tape) arranged in a wider band can have a width of 3 mm to 10 mm. On the other hand, in the ATL technology, the width of the unidirectional tape is as a rule greater, because the tape made of fibers has already been properly pre-prepared, i.e. joined from many smaller strands or strips of fibers (so-called composite fiber prepregs) into one whole, and may be, for example, from 50 mm to 250 mm.

It is to be noted here that the terms tape or fibers used above are interchangeable and are not limiting, unless otherwise indicated in the text, and generally mean a material in the form of a strand/strip of fibers generally referred to as tape, which, as in the case of the AFP technology, can be a single strand or strip (tow), which - earlier unconnected - are being arranged at the same time to form a wider band, or as in the case of the ATL technology - can be a wider tape that has been pre-prepared from composite fibers.

A layer arrangement comprising four layers 1, 2, 3, 4 consisting of unidirectional tapes T with the same orientation with lateral shift, according to a preferred embodiment of the invention, is illustrated in detail in Fig. 4, wherein EOL denotes the edge of the composite (laminate) being laid, and EOP stands for the edge/contour of the component.

The shift between the unidirectional layers 1, 2, 3, 4 occurs in order according to the direction of layer growth (arrow shown in Figs. 1-3).

As seen in Fig. 4, each layer 1, 2, 3, 4 includes multiple unidirectional tapes T which are being laid as multiple sets S. Each set S includes multiple tapes T, in this example eight tapes T in set S, and the tapes T of a single set T are being laid simultaneously during one pass of the robot head for automatic tape laying. In each subsequent unidirectional layer 1, 2, 3, 4, the sets S of tapes T are being laid with a lateral shift with respect to the previous layer 1, 2, 3, 4 by the shift value x, which in the presented example is 9.525 mm (which corresponds to a section equal in length to one and a half width of the tape T).

The introduction of the lateral shift of unidirectional tapes during manufacturing of the composite components reduces the defects occurring inside the material and reduces the waviness and roughness of the outer surface of the component, and thus results in an overall increase in the quality of the manufactured element.