Patent Publication Number: US-2012038086-A1

Title: Method and Apparatus For Producing Parts of Fiber Reinforced Plastics

Description:
TECHNICAL FIELD 
     The invention relates to the manufacture of parts, in particular the manufacture of parts made of fiber-reinforced plastics. It relates to methods and apparatuses according to the opening clauses of the claims. 
     The invention can be applied in many fields, e.g., in the field of manufacturing rims or wheels, e.g., for vehicles, or in the field of aircraft production, in particular in the production of stringers used for reinforcing the fuselage. In electrical industry, the invention may be applied, e.g., for the production of glassfiber reinforced insulators from thermoplastic glassfiber prepregs. 
     BACKGROUND OF THE INVENTION 
     The automotive industry has a continuous demand for very lightweight parts and parts having a good fracture behaviour combined with a high stiffness and strength. This applies, e.g., to wheels and rims. Several ways of manufacturing rims or portions thereof are known in the art. 
     DE 101 45 630 A1 discloses a wheel made of fiber-reinforced plastics in which the major portion of fiber strands are oriented in circumferential direction in the rim and in radial direction in the wheel spider. This is achieved, e.g., through winding of unidirectional endless fibers. This makes it difficult to implement the production method in an industrial field, in particular in case of complex part geometries. 
     In DE 43 35 062 A1, a method for the production of curved fiber-reinforced thermoplastic profiles is proposed. Thermoplastic pre-impregnated fibers (commonly referred to as thermoplastic “prepregs”) are heated while exposed to pressure in a forming tool. The so-shaped prepreg profile is cooled after the shaping process. Subsequently, the prepreg profile is pushed in a gliding manner through a slot between two essentially fixed tool pieces. This way, the prepreg profile is again exerted to pressure, namely to the pressure resulting from the gliding interaction with the tool pieces. The profile thereby basically adopts the cross section of the slot between the fixed tool pieces and the curvature of the curved tool pieces. A drawback of this method is that the thermoplastic profile is treated while it is moving: The layers of the prepregs may slip or bend or displace during the treatment, thus compromising the final product. Applying this method, it is furthermore difficult to keep temperatures and pressures approximately constant. Furthermore, parts of certain shapes such as ring-like parts cannot be manufactured by this method. 
     In EP 842 757 B1, a method for producing a preformed component (preform) of a composite material is disclosed. A fibrous pre-assembly, namely a cloth having fibres in pre-defined orientations, is used. The deformable mesh of the cloth is placed on a preforming matrix or former and then wound around this former to a depth of several layers. The winding is fixed on a larger diameter of the former, such that the fibers are orientated in a prescribed manner. The so-obtained preform can have a ring-like shape. The preform can be put into a mold, and then, a resin can be transferred through the preform under vacuum and/or with a transfer pressure, and finally, the resin can be cross-linked at a suitable temperature. The injection of a thermoplastic resin is expected to be impossible or at least very problematic due to the high viscosity of thermoplastic materials. 
     GB 2 010 155 A discloses a method of manufacturing seamless metallic wheel rims. The desired cross section of the rim is impressed onto a basic ring-shaped piece of metal by two profiled circular molds. This method is not readily applicable to fiber composite material since the shaping mechanisms occurring in metals do not occur in materials containing fibers. 
     In WO 2008 050405 A1, a process for producing seamless ring-shaped structures made of thermoplastic composite materials is described. This rather simple process is based on inserting an annular preform made of several layers of a thermoplastic composite prepreg-material between an inner and an outer ring-shaped mold. At least one of the two mentioned molds rotates such that it locally exerts a pressure on a portion of the preform, wherein the preform is heated up to a process temperature at least in the region where the pressure is applied. Apparently, problems occur when trying to automate this dynamic process. Furthermore, realizing a constant process temperature distribution while applying an appropriate pressure in order to avoid slip or overlap effects of the layers of the prepreg material of the preform is rather difficult. Even with optimized process parameters such as temperature and pressure, the repeatability and quality required for industrial scale application is hard or impossible to assure, since a constant application of these parameters throughout the process is apparently impossible to achieve in industrial production. 
     SUMMARY OF THE INVENTION 
     One object of the invention is to create a method for manufacturing parts that does not show the disadvantages or problems mentioned above. In addition, the respective apparatus for manufacturing parts shall be provided. 
     Another object of the invention is to provide a possibility to produce parts, in particular lightweight parts with superior mechanical properties, in particular parts having a good fracture behaviour and/or a high stiffness and/or a high strength. 
     Another object of the invention is to provide a possibility to produce parts of reinforced plastics. 
     Another object of the invention is to provide a possibility to provide large process windows when producing parts, in particular parts of reinforced plastics, more particularly parts of reinforced thermoplastics. 
     Another object of the invention is to provide a possibility to produce parts showing a particularly safe behavior in case of abrupt rupture. 
     Another object of the invention is to provide a possibility to produce parts showing an improved failure behaviour. 
     Another object of the invention is to provide a possibility to provide an improved cycle time for producing parts. 
     Another object of the invention is to provide a possibility to produce parts having special shapes or geometries, in particular annular or ring-like shapes or similar shapes. 
     Another object of the invention is to provide a possibility to produce seamless parts, in particular seamless ring-like shaped parts. 
     Another object of the invention is to provide a possibility to produce parts having improved insulation properties, in particular thermal and/or electrical insulation, and/or parts showing an improved chemical inertness or resistance. 
     Another object of the invention is to provide a possibility to more easily produce parts, in particular parts substantially made of reinforced plastics. 
     Another object of the invention is to provide an improved possibility to produce parts substantially made of reinforced thermoplastic, in particular of glassfiber-reinforced thermoplastic or carbonfiber reinforced thermoplastic. 
     Another object of the invention is to provide an improved possibility to produce rims or wheels or portions thereof. 
     Another object of the invention is to provide an improved possibility to produce insulators, in particular reinforced insulators. 
     Another object of the invention is to provide an improved possibility to produce stringers for use in airplanes as reinforcing elements of the fuselage. 
     Further objects emerge from the description and embodiments below. 
     At least one of these objects is at least partially achieved by apparatuses and methods according to the patent claims. 
     The method for manufacturing parts comprises the steps of
     a) providing material;   b) providing a first tool comprising at least one set comprising at least one segment;   c) providing a second tool comprising at least one first and at least one second set of at least one segment each, said segments, when arranged next to each other in a predefined way, referred to as closed position, form a second-tool surface describing the shape of a portion of a surface of said part to be manufactured;   d) moving the at least one segments of said first set of said second tool into said closed position;   e) moving the at least one segments of said second set of said second tool towards and into said closed position;   f) compressing between at least said first and second tools at least a portion of said material, in particular at least substantially all of said material, by applying pressure to at least one of said first and second tools;
 
wherein said segments of said second tool are moved such that continually during moving of the at least one segments of said second set of said second tool towards said closed position, a momentary travel distance up to said closed position for the at least one segments of said second set of said second tool exceeds a momentary travel distance up to said closed position for the at least one segments of said first set of said second tool.
   

     Said first and second tools can also be considered and, accordingly, can be referred to as first and second pressing tools or first and second molds. 
     In one embodiment, the method is a method for manufacturing parts of reinforced plastics, in particular a method for manufacturing parts of fiber-reinforced plastics, in particular of fiber-reinforced thermoplastics. 
     In one embodiment which may be combined with the before-addressed embodiment, said method is a method for industrially producing said parts. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said material comprises a resin, and said compressing is carried out for promoting a cross-linking of the resin. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts are finished products or intermediate products to be subjected to one or more finishing manufacturing steps. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said method is a method for manufacturing seamless parts. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the segments are moved along a predefined way or path. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said segments of said first and second tools, when arranged in a predefined way, referred to as closed position, form a tool surface describing the shape of a portion of a surface of said part to be manufactured; in particular, wherein said segments of said first and second tools, when arranged in a predefined way, referred to as closed position, form a tool surface substantially describing the shape of the complete surface of said part to be manufactured. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, step f) is carried out for forming said material (or a portion thereof) in a desired shape; the pressure applied to the material is also referred to as forming pressure. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the applied pressure mentioned in step f) causes a moving relatively to each other at least of the segments of said first tool with respect to segments of said second tool. 
     In fact, one can in some embodiments distinguish two phases during the compressing in step f): A compressing of the material before the closed position of all tools is reached; in this phase, at least the segments of said second set are moved; this phase can be helpful for removing from the material gases (typically air) inside the material. And a compressing while the segments of the first set and the segments of the second set of the second tool are already in the closed position; during this phase, there is no relative movement anymore of segments of said first set with respect to the segments of the second set. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, in step d) the at least one segments of said first set of said second tool are moved from an initial position towards and into said closed position. 
     In one embodiment which may be combined with the before-addressed embodiment, at least one of said segments of said second set of said second tool is, when said second tool is in said closed position, arranged between more than one neighboring segments of said first set of said second tool, and an opening between said more than one neighboring segments of said first set of said second tool is, from said initial position up to an intermediate position reached by the first set before reaching said closed position, too small for said at least one of said segments of said second set of said second tool to penetrate on its way towards said closed position. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the direction of pressure applied to a segment of said second tool at least substantially coincides with the direction of the moving of the respective segment mentioned in step d) and e), respectively, at least when close to said closed position. In particular, wherein said moving mentioned in step d) and e), respectively, is accomplished at least substantially along a straight line, and wherein said direction of pressure at least substantially coincides with the respective direction of the moving. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts are predominantly, in particularly substantially, continuous-fiber reinforced parts (and said material correspondingly comprises continuous-fiber reinforced plastics). Parts reinforced with such substantially uninterrupted fibers have extraordinary properties. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts comprise fibers which are predominantly, in particularly substantially, oriented fibers (and said material correspondingly comprises oriented fibers). Parts reinforced in such a way can have extraordinary properties. The orientation of the fibers is selected according to desired properties of the part to be manufactured. E.g., calculations/simulations can be carried out for finding an optimum fiber orientation. Usually, there are comprised in the material several layers one or more of which will have the same and one or more of which will have a different fiber orientation. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts are rims or wheels or portions thereof. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts are insulators, in particular reinforced insulators, in particular substantially cylindrically-shaped insulators. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts are stringers used in airplanes as reinforcing elements of the fuselage. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said first set of said second tool is brought into contact with said material before said second set of said second tool is brought into contact with said material. In particular, pressure is applied to said material by said second set of said second tool only after pressure has been applied to said material by said first set of said second tool. And more particularly, said first and second sets of said second tool are structured and arranged and moved in such a way that whenever pressure is applied to said material by said second set of said second tool, pressure is also applied to said material by said first set of said second tool. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said first tool is an outer tool and said second set is an inner tool, or vice versa, in particular wherein the inner tool is, during said moving steps, located generally inside a shape generally described by said outer tool. 
     Usually, said first tool, more particularly its segments, are kept in position during the movements of the sets of the second tool. This can be accomplished by applying corresponding forces to the segments of said first tool and/or by fixing the segments of the first tool with respect to one another. Particularly interesting is the case that the first tool is the outer tool and the second tool is the inner tool. In this case, fibers, in particular continuous fibers comprised in the material will, at least predominantly, be stretched during the described compressing action, which usually leads to particularly advantageous material properties. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, at least one of (in particular each of) said sets of segments comprises at least two, in particular at least three, more particularly at least four segments. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the method comprises moving all segments of one of said sets (be it a set of said first tool or a set of said second tool) at least substantially simultaneously during said compressing, in particular wherein this applies to each of the sets of an inner tool or to each of the sets. In particular wherein for said moving of all segments of said one of said sets is driven by one and the same drive. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the method comprises moving all segments of one of said sets (be it a set of said first tool or a set of said second tool) at substantially the same speed during said compressing, in particular wherein this applies to each of the sets of an inner tool or to each of the sets. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said material is provided, in particular inserted between said first and second tools, substantially in form of foils or sheets or stripes. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said material as well as said part comprise or are at least substantially made of reinforced plastics, in particular of fiber reinforced plastics. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said material inserted between said first and second tools comprises a thermoplastic. Thermoplastics enable a more rapid production (shorter production cycle time), they have a high fracture toughness and a good recycleability and some show a high temperature resistance. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said material substantially is a preform or a prepreg material. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said material is inserted manually between said first and said second tools. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments except for the before-mentioned embodiment, said material is inserted automatically between said first and said second tools, in particular by a robot. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the method comprises heating said material before said compressing, and in particular after inserting the material between said first and said second tools. For thermoplastics, heating is important, whereas in case thermosets and elastomeres, it can be possible to dispense with heating. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the method comprises heating said material during said compressing. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the method comprises monitoring, in particular controlling the temperature of said material, in particular before and/or during said compressing. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts comprise a portion describing
         a substantially closed-shape; or   a nearly closed-shape; or   an open shape having a generally or at least partially concave inner side and a generally or at least partially convex outer side;
 
or wherein said parts substantially describe
   a substantially closed-shape; or   a nearly closed-shape; or   an open shape having a generally or at least partially concave inner side and a generally or at least partially convex outer side.       

     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts comprise a portion having a substantially ring-shaped or ring-like structure, or wherein said parts substantially have a ring-shaped or ring-like structure. 
     Such kinds of parts are difficult to produce otherwise, in particular when the material substantially is reinforced thermoplastics, in particular thermoplastics reinforced with fibers, in particular reinforced with continuous fibers. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said parts comprise a portion having a substantially annular shape, or wherein said parts substantially have an annular shape. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, during said compressing said material, an area of said material which is in contact with said first set of said second tool is larger than, in particular is at least two times, more particularly at least three times as large as the area of said material which is in contact with said second set of said second tool. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said first and second tools are tools the shape of which determines the shape of said parts, in particular wherein the shape of said first and second tools are tools describing, when they are arranged in a predefined way referred to as closed position), a shape corresponding to the shape of the part to be produced. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the tools form, when arranged in a predefined way, a cavity corresponding at least substantially to the shape of said part to be manufactured. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, for said first set of said second tool and/or for said second set of said second tool, the segments of the respective set are moved such that a pressure onto said material to be compressed exerted by one of the segments of said respective set is at least approximately the same for each of said segments. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, at least one of said segments of said second set of said second tool is tapered in the direction of the movement of said segment. In particular, each of said segments of said second set of said first tool is tapered in the direction of the movement of respective segment. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, at least one of said segments of said second set of said second tool is shaped such that when compressing said material, forces are exerted by said segment onto at least one segment of said first set of said second tool. In particular, wherein each of said segments of said second set of said second tool is shaped such that when compressing said material by moving said segments, forces are exerted by said segments onto at least one segment of said first set of said second tool, in particular onto each segment of said first set of said second tool. 
     In one embodiment referring to the before-addressed embodiment, said exerted force is transferred from said segment or from said segments onto said at least one segment of said first set of said second tool or onto each segment of said first set of said second tool via—in particular substantially solely via—at least one contact surface of said segment or segments interacting with at least one contact surface of said at least one segment of said first set of said second tool or interacting with contact surfaces of said segments of said first set of said second tool. In particular, such interacting contact surfaces are mating surfaces. 
     In one embodiment referring to the last-mentioned or to the before-last mentioned embodiment, said exerted forces are directed substantially in the direction of said movement of said segment or nearly perpendicularly thereto or a superposition of such forces. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, by said compressing, a pressure of at least 5 bar and in particular of at most 50 bar is exerted on said material. More particularly, a pressure of between 10 and 30 bar is exerted on said material by the segments of the tools. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, the method comprises the step of heating said material before and/or during and/or after said compressing, in particular heating at least substantially all of the material inserted between said first and second tool. In particular, namely most prominently in case of (reinforced) thermosets, said material comprises a resin, and said heating is carried out for promoting a cross-linking of the resin. In case of (reinforced) thermoplastics, said heating brings the thermoplastic into a well-formable state. 
     The apparatus for manufacturing parts (in particular of parts substantially made of reinforced plastics) comprises
         a first tool and a second tool, said first tool comprising at least one set comprising at least one (in particular at least two) segments, and said second tool comprising at least one first and one second set of at least one (in particular at least two) segment each;   a drive unit for driving at least said first set and said second set of said second tool.       

     Such an apparatus can allow to carry out the above-described methods. 
     In one embodiment, said drive unit is a drive unit for driving at least said first set and said second set of said second tool towards said first tool; in particular, said drive is structured and configured for said driving. 
     In one embodiment of the apparatus which may be combined with one or more of the before-addressed embodiments, the segments of said first tool are shaped such that, when arranged in a predefined way referred to as closed position, they form a an at least substantially continuous surface corresponding to a first partial surface of a part to be manufactured, and wherein the segments of said second tool are shaped such that, when arranged in a predefined way referred to as closed position, they form an at least substantially continuous surface corresponding to a second partial surface of said part to be manufactured, in particular wherein these two partial surfaces complement each other such that they form substantially the whole surface of said part to be manufactured. 
     In one embodiment of the apparatus which may be combined with one or more of the before-addressed embodiments, the segments of said first tool are shaped such that, when arranged in a predefined way, they form a continuous surface, and the segments of said second tool are shaped such that, when arranged in a predefined way, they form another continuous surface, and wherein these two continuous surfaces complement each other such that they form substantially the whole surface of a pre-defined volume when arranged with respect to each other in a predefined way. 
     In one embodiment of the apparatus referring to one or both of the two last-addressed embodiments, said at least one segments of said first set of said second tool comprise at least one mating surface each, mating, when said second tool is in said closed position, with at least one mating surface of said at least one segment of said second set of said second tool, wherein the mating surfaces of said first set of said second tool each form, in said closed position, an acute angle with said second partial surface. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said apparatus comprises a control unit configured to control a movement of said first and of said second set of said second tool in such a way that said segments of said second tool are moved such that continually during moving the at least one segments of said second set of said second tool towards said closed position, a momentary travel distance up to said closed position for the at least one segments of said second set of said second tool exceeds a momentary travel distance up to said closed position for the at least one segments of said first set of said second tool. In particular, the control unit controls said drive unit in the described way. 
     In one embodiment which may be combined with one or more of the before-addressed embodiments, said apparatus comprises a temperature change unit structured and configured for heating or cooling or for both, heating and cooling, material inserted between said first and second tools. In particular, at least a portion of said temperature change unit is integrated in at least one of said tools. 
     The invention comprises apparatuses with features of corresponding methods according to the invention, and vice versa. 
     The advantages of the apparatuses basically correspond to the advantages of corresponding methods and vice versa. 
     In one aspect of the invention, the method for manufacturing parts comprises the steps of
         inserting material between a first tool and a second tool, said first tool comprising at least one set comprising at least two segments, in particular wherein said segments are separable from each other, and said second tool comprising at least one first and one second set of at least one segment each, in particular wherein said segments are separable from each other;   compressing at least a portion of said material, in particular at least substantially all of said material, by
           moving at least said first set of said second tool towards said first tool; and then   moving at least said second set of said second tool towards said first tool.   
               

     The subsequent movements of said first set of said second tool and said second set of said second tool (which movements are typically carried out exerting pressures of at least 5 bar) makes it possible to form ring-shaped and ring-like shaped parts from preforms such as prepreg material. It is possible to apply pressures very homogeneously to the material. 
     In one embodiment of this aspect, said moving at least said first set of said second tool towards said first tool takes place still (i.e. continuedly) or again (i.e. renewedly) during said moving at least said second set of said second tool towards said first tool. 
     This aspect may be combined, as far as principally compatible, with any other herein disclosed embodiment and with any feature of any other herein disclosed embodiment. 
     Further embodiments and advantages emerge from the dependent claims and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Below, the invention is described in more detail by means of examples and the included drawings. The figures show schematically: 
         FIG. 1  a top view onto a detail of an apparatus with inserted preform, while first tool (outer tool) and second tool (inner tool) are in closed position; 
         FIG. 2  a top view onto a detail of an apparatus, with inserted preform and open tools; 
         FIG. 3  a top view onto a detail of an apparatus, with inserted preform and closed outer tool; 
         FIG. 4  a top view onto a detail of an apparatus, with inserted preform and closed outer tool secured with clamps; 
         FIG. 5  an illustrative cross-section-like side view of a detail of an apparatus with inserted preform, while rods of a first set of pull rods are being connected; 
         FIG. 6  an illustrative cross-section-like side view of a detail of an apparatus with inserted preform, while rods of a first set of pull rods are connected and in action exerting forces on segments of the first set of the inner tool; 
         FIG. 7  a top view onto a detail of an apparatus with inserted preform, while rods of a first set of pull rods are connected and in action exerting force on segments of the first set of the inner tool, and segments of the second set of the inner tool are also shown; 
         FIG. 8  an illustrative cross-section-like side view of a detail of an apparatus with inserted preform and displacing mechanism, while segments of a second set of the inner tool are moving into the preform; 
         FIG. 9  an illustrative cross-section-like side view of a detail of an apparatus with inserted preform and displacing mechanism, while segments of the second set of the inner tool have been moved into the preform, and rods of a second set of pull rods are being connected; 
         FIG. 10  an illustrative cross-section-like side view of a detail of an apparatus with inserted preform, while segments of the second set of the inner tool have been moved into the preform, and rods of a second set of pull rods are being connected; 
         FIG. 11  an illustrative cross-section-like side view of a detail of an apparatus with inserted preform, while segments of the second set of the inner tool have been moved into the preform, and rods of a second set of pull rods are connected and in action exerting forces on segments of the second set of the inner tool; 
         FIG. 12  a top view onto a detail of an apparatus with inserted preform, while rods of the first set of pull rods are connected and in action exerting forces on segments of the first set of the inner tool, and rods of the second set of pull rods are connected and in action exerting forces on segments of the second set of the inner tool; 
         FIG. 13  a top view onto the inner tool in closed position; 
         FIG. 14  a top view onto the inner tool in closed position, with forces applied; 
         FIG. 15  a top view onto a detail of an apparatus, while segments of the second set of the inner tool are being released; 
         FIG. 16  an illustrative cross-section-like side view of a detail of an apparatus with displacing mechanism, while segments of the second set of the inner tool have been released and pull rods of the second set of pull rods are being disconnected; 
         FIG. 17  an illustrative cross-section-like side view of a detail of an apparatus with displacing mechanism, while the pull rods of the second set of pull rods have been disconnected and the segments of the second set of the outer tool have been moved away; 
         FIG. 18  a top view onto a detail of an apparatus, while the segments of the second set of the outer tool have been moved away, and the segments of the second set of the inner tool are released by moving the rods of the first set of pull rods; 
         FIG. 19  a top view onto a detail of an apparatus, while the segments of the set of the outer tool have been moved away after the clamps have been released; 
         FIG. 20  a very schematic illustration of various cross-sections perpendicular to a part axis, namely closed shapes on the left, nearly-closed shapes in the middle and open structures on the right; 
         FIG. 21  an illustrative partially sectioned side view of a detail of an apparatus with inserted preform and a pantograph mechanism as a drive for driving the segments of the inner tool; 
         FIG. 22  an illustration of a curved profile manufacturable using an apparatus of  FIG. 23 ; 
         FIG. 23  an illustrative cross-section-like side view of a detail of an apparatus with an outer tool having a set of two segments and an inner tool having a first set of one segment and a second set of two segments; 
         FIG. 24  an exemplary cross-section along the line A-A′ of the profile of  FIG. 22 ; 
         FIG. 25  another exemplary cross-section along the line A-A′ of the profile of  FIG. 22 ; 
         FIG. 26  a schematic illustration of a cross-section along the part axis of a detail of an apparatus for manufacturing a ring-shaped (cylinder-surface-like) part, with inserted material being compressed; 
         FIG. 27  a detailed view of an interface between a segment of the first and a segment of the second set of the second tool. 
     
    
    
     The reference symbols used in the figures and their meaning are summarized in the list of reference symbols. The described embodiments are meant as examples and shall not confine the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Parts, for instance ring-shaped structures, made of reinforced plastics can be manufactured since overlapping layers of a preform, usually made of prepreg material, merge during a production process involving pressing and usually also heating such that no more relevant intersections between the layers exist in the so-produced (seamless) part. Forces applied to a so-obtained part are transferred from one fiber strand to the next in the overlapping areas through shear forces in the matrix, and thus, the resulting structural impairment is very small compared to weld seams or glued surfaces. 
     Various semi-finished products can be used as a preform to be processed afterwards. For example: different fiber matrix combinations, or pre-impregnated (prepreg) non-consolidated fiber semi-finished products, or non-impregnated semi-finished products combined with films of not-reinforced polymer. Even thermoset or elastomer matrix systems can be processed in the proposed method. 
     For example, the following fiber materials can be used: carbon fibers, glass fibers, aramide fibers, basalt fibres, Poly p-phenylene benzobisoxazole (PBO) fibers, boron fibres, polyamide fibres, flax fibres, hemp, cotton, or combinations thereof. In general, as long as process pressure, time and temperature do not deteriorate the properties of the fibers in the produced part, any type of fiber can be used. Selection is made by most importantly considering by means of which fiber the desired properties of the produced part can be achieved. 
     There are various ways for manufacturing a preform, in particular a ring-like shaped preform. Here are some examples:
     i) A tape-shaped semi-finished product such as prepregs is provided in stripes, e.g., by cutting it into stripes. The stripes are positioned in such a way, that the desired preform, in particular a ring-shaped preform is obtained. The stripes can be flush to each other, overlapping, or in multiple layers.   ii) The preform, in particular a ring-shape, is formed by coiling up a semi-finished product such as prepregs to a spiral.   iii) A tape-shaped semi-finished product such as a prepreg is provided in stripes, e.g., by cutting it into stripes. The preform, in particular the ring-like shaped preform, is formed by gradually inserting the stripes into a pressing tool (cf. the examples and Figs. of tools below, in particular the outer tools). Cutting and/or inserting can be accomplished manually or automatically.   iv) Incisions are cut into a semi-finished product such as prepregs, such that the incisions do not divide it into completely separated portions. The purpose of these incisions is to cut through the reinforcing fibers inside the semi-finished product layers. The incisions are preferably inserted in such a manner that there is an offset between incisions in neighboring layers of the semi-finished product. The so-prepared preform is inserted into a tool (cf. the examples and Figs. of tools below, in particular the outer tools), e.g., as proposed in ii). The incisions facilitate a sliding movement of the reinforcing fibers during the process of forming the preform shape and therefore decrease the internal stress in the resulting preform, thus facilitating filling the preform into the tool.   v) Likewise, a semi-finished product cut to stripes (cf. i) or iii)) is provided with incisions as described in iv) prior and/or after being cut to stripes. Then, the preform is shaped like described in i), or the stripes are inserted into a tool as described in iii).   

     Monitoring and/or controlling the temperature of the preform before and/or during exposing it to pressure in an apparatus with tools is recommended at least for thermoplastics in order to have a well-defined and stable process. The tolerance of the process temperature may be 10° C. to 20° C. or even around 50° C., or even more, depending on the material to be processed and with the process temperature chosen sufficiently high above T M  and T G , respectively. 
     In case of reinforced thermoplastics as matrix material in which the fibers are embedded, it is the thermoplastic material which basically defines the relevant process temperatures. 
     For semi-crystalline thermoplastic materials, the crystalline melting temperature T M  (e.g., 162° C. for polypropylene) and the crystallization temperature T C  are relevant. T C  can be more than 40° C. lower than T M , depending on the specific thermoplastic material. 
     A preform has to be heated at least up to its crystalline melting temperature T M . This can be accomplished by direct heating, e.g., using strip heaters, by radiation, e.g., using infrared radiators, by hot air convection, or by indirect heating through a tool in which the preform is pressed. A combination of two or more of these heating methods is also possible. 
     The arrangement of the heating devices is preferably chosen such that the preform is heated uniformly and quickly to a temperature higher than T M , in particularly to a process temperature clearly above T M , in most cases it will be chosen at least 20°, at least 50° C., or at least 75° C. above T M . 
     In the case of amorphous thermoplastic materials, there are no distinct temperature limits aside from the so-called glass transition temperature T G . The processing temperature has to be above T G , in particularly clearly above T G , in most cases it will be chosen at least on 20° C., at least 50° C., at least 100° C. or at least 150° C. above T G . Likewise, there is also no crystallization temperature T C  for amorphous thermoplastic materials (because they remain amorphous). For the solidification of the material, the solidification temperature T s  (which usually is slightly higher than T G , typically by between 10° C. and 40° C.) is of importance. 
     The principles of the processing methods are the same for amorphous and for semi-crystalline thermoplastic materials; but definitions and denotations of the temperature limits vary. 
     The following table shows some exemplary thermoplastic polymer materials usable in the proposed process. The temperature ranges are merely a reference for the corresponding bulk polymers. Depending on the specific modification of the polymers, the values can strongly deviate from the values in the table. 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 polymer 
                 T M  [° C.] 
                 T G  [° C.] 
                 T C  or T S  [° C.] 
               
               
                   
               
             
            
               
                 poly ether imide 
                 — 
                 210-220 
                 220-250 
               
               
                 (PEI) 
               
               
                 poly ether ether 
                 335-345 
                   
                 290-310 
               
               
                 ketone (PEEK) 
               
               
                 poly ether sulphone 
                 — 
                 210-220 
                 220-250 
               
               
                 (PES) 
               
               
                 poly sulphone (PSU) 
                 — 
                 175-185 
                 185-200 
               
               
                 poly phtalamide 
                 310-330 
                   
                 270-290 
               
               
                 (PPA) 
               
               
                 poly ethylene 
                 250-270 
                   
                 210-230 
               
               
                 terephtalate (PET) 
               
               
                 poly butylene 
                 200-230 
                   
                 160-190 
               
               
                 terephtalate (PBT) 
               
               
                 poly amide 12 
                 175-185 
                   
                 135-150 
               
               
                 (PA12) 
               
               
                   
               
            
           
         
       
     
     Elastomers and thermosetting plastics have a low viscosity, allowing to inject them into a mold cavity (formed by tools of the apparatus), e.g., in a resin transfer molding (RTM)-like process. It is also possible to use prepregs based on thermosets or elastomers as a preform. 
     The apparatus (equipment) suitable to perform the proposed method comprises an inner and an outer tool (or inner and outer “mold”), wherein the total number of segments comprised in both tools is at least three. In a very simple configuration, this means that either the outer tool comprises exactly one segment and the inner tool comprises exactly two segments, or the outer tool comprises exactly two segments and the inner tool comprises exactly one segment. 
     At least one of said tools is arrangeable in an open position in which a preform can be inserted into the apparatus before the preform is pressed in a pressing step and/or in which a pressed part can be released from the apparatus after said pressing step, and arrangeable in a closed position in which the pressing step/the forming process takes place. The outer and inner tools are reciprocally movable with respect to one another either by moving only one of them or by moving both. 
     In particular, if parts shall be produced having more complex shapes, like for instance open or closed ring-shaped structures, the inner and the outer tools are preferably each composed of two or more tool segments. This enables or facilitates to remove the part from the tools. 
     The tools can be made of the same or of different material. Metals and alloys, e.g., steel or aluminum, are suitable as materials for tools, because they are resilient and at the same time cost-effective and easily workable into the needed shape required in order to obtain the desired part. 
     If necessary, adhesion between matrix material of the preform and a tool surface can be avoided in that the surface of the tool is treated, e.g., with a commercial grade releasing agent. 
     In case of too little adhesion between matrix material of the preform and a tool surface, gluing substances or the like can be applied between matrix material of the preform and the tool surface in order to avoid uncontrolled/undesired mutual sliding of different layers comprised in the preform. 
     Since some materials and/or geometries may require a controlled cooling procedure or a thermal post-treatment, the presence of at least one heating and/or cooling device is recommended not only during pressing and/or before pressing has started (in order to reduce the pressing time), but also afterwards. E.g., a heating and/or cooling device can be incorporated directly into the apparatus, more particularly into one or both tools. And/or another heating and/or cooling device can be provided separately from the tools. Ways of accomplishing heating have been cited above. With respect to cooling, the same principles can be applied, but inversely, e.g., by using cold water serpentines or similar means well-known in the art. 
     In order to achieve a forming pressure suitable for both, the employed preform matrix material (mainly composing the preform), and for the shape of the part to be produced, different methods can be used, e.g., mechanically, hydraulically or electromechanically exerting a force on an external surface of at least one of the inner and outer tools. In order to achieve a very good fit between all of the tool segments and/or between the tools and the preform arranged between the tools, and in order to ensure a suitable direction of the applied force and a suitable pressure distribution, it is advisable to suitably guide the applied force, e.g., by using push rods or pull rods, wherein many alternatives are known to a person skilled in the art. 
     The process, or at least the pressing step (and therefore the movement of the segments) and preferably also the heating, is preferably automatically controlled, e.g., using a suitable software running in a controller or in a computer, e.g., the software controlling important parameters as for instance times for cooling, for heating and for pressing, temperature and pressure. 
       FIGS. 1 to 19  illustrate a first example of a method and of an apparatus for manufacturing parts. It is a method and an apparatus for manufacturing a ring-shaped structure of fiber-reinforced plastics, for instance a rim for a car wheel made of carbon fiber reinforced polyetherimide (PEI). 
     In particular, oriented continuous fibers are used as reinforcement. The  FIGS. 2 to 19  illustrate subsequent process steps and, in some cases of subsequent Figures, illustrate different views of approximately the same process step. But the so-implied order of process steps does not exclude that a different order of steps could be chosen or that steps could be added or deleted. 
       FIG. 1  illustrates a top view onto a detail of an apparatus for manufacturing parts, more precisely, it illustrates a cross-section through the apparatus. The apparatus comprises a first tool which is an outer tool or outer mold and a second tool which is an inner tool or inner mold. 
     The outer tool comprises a set of segments comprising four segments  1  which are pair-wise clamped to each other by clamps  6 . 
     The inner tool comprises a first set of segments comprising four segments  2   a  and a second set of segments comprising four segments  2   b.    
     First tool (outer tool) and second tool (inner tool) are shown in closed position. 
     In  FIG. 1 , the apparatus is shown with a preform  3  inserted between inner and outer tool. The shape of the cavity between segments  1  of the outer tool and segments  2   a , 2   b  of the inner tool corresponds to the shape of the part to be produced, such as a rim. 
     In  FIG. 2 , a detail of the apparatus is illustrated with outer tool and inner tool in opened position, with inserted preform  3  therebetween. The preform  3  can be a substantially cylindrical arrangement of suitable prepregs. 
       FIG. 3  illustrates that now, the outer tool is closed by application of forces F (illustrated by open arrows), e.g., applied against the outer surface of the outer tool. Reference  4  denotes the outer tool in closed position. The closed position can be considered a pressing-ready geometry of the outer tool as will become clear further below. 
     In order to increase the stiffness of the outer tool in the closed position  4 , clamps  6  are applied to the outer tool, see  FIG. 4 . By the clamps  6 , pressure is applied driving contacting interfaces  5  of the outer tool pairwise towards each other. Screws or others could be used instead of clamps  6 . 
     It is possible to start at this point a heating of the inner and/or of the outer tools (preferably both). A person skilled in the art will recognize that the heating process and the start of the heating can be scheduled earlier or later depending in particular on requirements given by the process and by the material or materials of the preform  3 . 
       FIG. 5  shows an illustrative cross-section-like side view of a detail of an apparatus with inserted preform  3 , with outer tool  4  in closed position, while rods  8  of a first set of pull rods are being connected. 
       FIG. 6  shows an illustrative cross-section-like side view of a detail of an apparatus with inserted preform, while the rods  8  of the first set of pull rods are operationally connected to the segments  2   a  of the first set of segments of the inner tool. The rods  8  are in action exerting forces on the segments  2   a , as illustrated by the small arrows. This way, the preform  3  is pressed (with low pressure) between the first tool and the segments  2   a  of the first set of the inner tool. 
       FIG. 7  illustrates the same situation as  FIG. 6 , but in a top view-like view onto a cross-section of a detail of the apparatus. The segments  2   b  of the second set of the inner tool are already illustrated in  FIG. 7 . As can be seen, by the movement of the segments  2   a  towards the outer tool and the preform  3 , space is created between neighboring segments  2   a . This space will be used for introducing the segments  2   b  between the segments  2   a  such that segments  2   b  can apply pressure against preform  3 , too (see below). The segments  2   a  have mating surfaces  13   a  and the segments  2   b  have mating surfaces  13   b . In closed position of the second tool, the mating surfaces  13   a  and  13   b  will mate, pairwise, see  FIGS. 1 ,  12 ,  13  and  14 . 
       FIG. 8  shows an illustrative cross-section-like side view of a detail of an apparatus with inserted preform and a displacing mechanism  10 . The situation is like illustrated in  FIGS. 6 and 7 , but the rods  8  of the first set of pull rods connected and in action exerting (low) forces on the segments  2   a  of the inner tool are not drawn. But rods  11  of a second set of pull rods are shown. Driven by displacing mechanism  10 , e.g., a lift actuated by an electrical motor, the segments  2   b  of the second set of the inner tool are being moved into the preform  3 . 
     In  FIG. 9 , which is illustrated like  FIG. 8 , the segments  2   b  of the second set of the inner tool are located inside the preform  3 , and the rods  11  are being connected. 
       FIG. 10  illustrates the situation of  FIG. 9 , but the driving mechanism is not shown. 
     In  FIG. 11 , the rods  11  are connected and in action exerting forces on segments  2   b  of the second set of the inner tool. Note that still the rods  8  of the first set of pull rods are connected and in action exerting forces on segments of the first set of the inner tool. Note further, that segments  2   b  not only press against preform  3 , but also against the segments  2   a , namely at their mutual contacting interfaces, i.e. at the mating surfaces  13   a , 13   b.    
       FIG. 12  illustrates the situation of  FIG. 11  in a top-view-like view. The preform  3  is pressed against the outer tool by segments  2   a  and, in those regions of its inner surface which are not in contact with segments  2   a , by the segments  2   b . The temperature of the now consolidating preform  3  shall be between 217° C. (which is T G  for the depicted material) and 400° C., preferably between 300° C. and 350° C. 
     It shall be mentioned that the contacting interfaces  13  (cf.  FIG. 13  illustrating a top view onto the inner tool) between segments  2   a  and  2   b  formed by the mating surfaces  13   a  and  13   b  (cf.  FIG. 7 ) do not only result in a particularly efficient process. They also provide an excellent distribution of the forces exerted on the preform  3  by segments  2   a  and  2   b . This is because there is not only force-fitting but also form-fitting of all the segments  2   a , 2   b  of the inner tool. 
     The contact interfaces  13  (cf.  FIG. 13 ) between segments  2   a  and  2   b  are angled with respect to the moving directions of the segments  2   a  and  2   b , respectively (cf. force vectors  14  and  15  in  FIG. 14  illustrating a top view onto the inner tool) in the direction indicated in  FIG. 4 , namely in such a way that the segments  2   b  can be moved into and fit into the spaces left between the segments  2   a . This leads to an acute angle α for segments  2   a  and an obtuse angle β for segments  2   b  (cf.  FIG. 27 ). Preferable, the angle α is chosen at least 1°, at least 2° or at least 4° smaller than the angle geometrically given by the insertability of the segments  2   b  next to (or between) segments  2   a  along the moving path of segments  2   b.    
     Segments  2   a  and  2   b  are pulled (by pull-rods  8  and  11 , respectively) toward the preform  3  until they reach a preset position (closed position). In that position, the cavity between outer tool and inner tool equals the shape of the part to be manufactured, i.e. the rim shape. Together, the outer surfaces of the segments  2   a  and  2   b  now have the shape of and form the inner surface of the part to be manufactured. 
     The pressure (forming pressure) exerted onto the preform  3  through segments  2   a  and  2   b  is upheld for between 2 seconds and 2 minutes, preferably between 20 seconds and 1 minute, for a consolidation of the thermoplastic resin in the layers of the preform  3 . In the present example, the process pressure has to be between 5 bar and 50 bar, preferably between 8 bar and 20 bar. These wide time and pressure ranges are one of the great advantages of the presented process, making it easier to run-in a new part geometry, and a new part geometry usually has one main variable: the number of prepreg material layers. 
     For example, in case of a rim for a bike wheel, only very few layers are needed, and therefore 10 seconds pressing time can already be sufficient, whereas in case of a wheel for a car, the number of layers is substantially higher, e.g., a few dozens, and thus, the pressing time rises to, e.g., 20 or 30 seconds. 
     The pressing time and the pressure are roughly proportional to the number of layers in the preform  3 , although other factors such as the complexity of the geometry of the part to be formed do also influence these parameters, but usually less strongly. 
     At this point, cooling of the inner and outer tool usually will be commenced, while still maintaining the pressure of the tools on the preform  3 . From now on, the preform  3  can be referred to as part  16 , in the present example: the rim  16 . Cooling can of course be accelerated by, for example, cooling serpentines in the tools. 
     While cooling, after having reached a temperature where the chosen material is solid, the pressure on the rim  16  will be reduced by loosening the rods  11 . The segments  2   b  are moved away from the rim  16 .  FIG. 15  depicts this in a top view onto a detail of the apparatus. The segments  2   b  of the second set of the inner tool are released (by moving the rods  11 , see the open arrows in  FIG. 15 ) at the end of the solidification of the material. The axis A of part  16  is perpendicular to the drawing plane 
       FIG. 16  illustrates in a cross-section-like side view of a detail of an apparatus that the segments  2   b  are in an opened position again, and the rods  11  are being disconnected. The same displacing mechanism  10  as in  FIGS. 8 and 9  is prepared to move the segments  2   b  out of the outer tool, but in the opposite way with respect to  FIGS. 8 and 9 . 
     In  FIG. 17 , pull rods  11  have been removed, and segments  2   b  have been moved out of the outer tool by means of displacing mechanism  10 . 
       FIG. 18  illustrates that after the segments  2   b  of the second set of the outer tool have been moved away, the segments  2   a  of the second set of the inner tool are released by moving the rods  8  of the first set of pull rods in the direction of the open arrows. The part  16  is now not in contact anymore with the second (=inner) tool. 
       FIG. 19  illustrates that the segments  2   a  of the set of segments of the outer tool have been moved away after the clamps  6  have been released. When moving segments  2   a  away from the part  16  preferably, an external robot, an operator or other means will hold the rim  16  so that it cannot fall. 
     With the rim  16  removed from the tools, the apparatus is ready for the next production cycle. 
     A short simplified version of the proposed process can be roughly summarized by the following steps in the following order:
         inserting the preform into the closed outer tool (which is pre-heated or not);   moving inner tool into pressing-ready position (in contact with the inserted material or nearly so);   heating the material (via the tools) to above T M  (in case of semicrystalline thermoplastics) and T G  (in case of amorphous thermoplastics), respectively, in particular to at least 20° C., more particularly to at least 50° C., even more particularly to at least 100° C. above T M  and T G , respectively;   compressing the material by means of the tools, at a pressure (forming pressure) of at least 10 bar, in particular at least 20° bar, typically at a pressure of between 25 bar and 50 bar;   passively or, preferably, actively cooling the material to below T M  and T G , respectively, in particular to at least 20°, more particularly to at least 40° below T M  and T G , respectively;   reducing the applied pressure;   opening/removing at least one of said tools;   removing the so-obtained part from the tools.       

     Note that applying the full forming pressure only after the material has reached a process temperature above T M  and T G , respectively, will usually result in better quality parts than applying that full forming pressure already before the material reached that temperature. 
     While the first example presented above in conjunction with  FIGS. 1-19  is only one way to carry out the process, there are still other possibilities. E.g., outer and inner tools could work in chronologically reversed order: The inner tool could firstly be positioned in a closed position (cf.  FIGS. 12 ,  13 ,  14 ) and hold the preform  3 , and then, the segments of the outer tool approach and enclose the preform  3 . 
     Also another process is possible: A robot keeps the preform  3  in position, and both, the inner tool and the outer tool, substantially simultaneously move from the opened position into the closed position represented by  FIG. 12 . 
     In case of the tools and a ring-like part according to the first example, the minimal number of segments of the inner tool ( 2   a  and  2   b , together) is four. In general, if a perfectly cylindrical or conical part has to be produced, one single cylindrical segment for the outer tool is in principle sufficient. But if the radial cross section of the rim presents at least one undercut in axial direction, at least two segments have to be used for the outer tool in order to remove a manufactured stiff part from the tools. 
     In case of the aforementioned chronologically inversed or simultaneous movement of the segments of the tools, these minimal numbers of segments may change accordingly. 
     If the cross-section of the preform  3  perpendicular to its axis is not perfectly circular, as for instance in an open ring-shaped structure or in an elliptical structure, the process can be adapted by replacing the perfectly circular inner and outer tools with correspondingly shaped other inner and outer segments having the suitable curvature and/or shape, cf. the various examples illustrated in  FIG. 20 . 
       FIG. 20  is a very schematic illustration of various cross-sections perpendicular to a part axis, namely closed shapes (ring-like shapes) on the left, nearly-closed shapes in the middle and open structures on the right. Note that a part axis can be bent/curved, e.g., a part can describe the shape of the surface of a portion of a torus. And note further that a part cross-section may vary along the part axis, e.g., a part can describe a portion of a cone. 
       FIG. 21  illustrates another example of a method and of an apparatus for manufacturing parts.  FIG. 21  shows an illustrative partially sectioned side view of a detail of a corresponding apparatus with inserted preform and a pantograph mechanism  17  as a drive for driving the segments  2   a , 2   b  of the inner tool (only segments  2   a  or segments  2   b  are drawn). In this second example, a pantograph  17  is used for moving segments of the inner tool. Accordingly, a different pressing principle is employed. 
     The segments  2   a  and  2   b  of the inner tool are mounted on pantograph  17 . While turning pantograph bolt  18 , the segments  2   a  and  2   b  move, since mounted on one and the same pantograph  17 , towards the closed outer tool, thus applying the desired pressure on the preform  3 . E.g., the segments  2   a , 2   b  are moved such that firstly, segments  2   a  get into contact with the inserted material, and then segments  2   b  get into contact with the inserted material, or segments  2   a  are moved earlier and/or at a different speed than segments  2   a . Generally, segments  2   b  will never be closer to the material  3  than segments  2   a  on their respective way towards and into the closed position. Suitably designing the pantograph arms allows to achieve such movements. After heating and pressing, the part can be extracted from the tools by turning the pantograph bolt  18  in the opposite way. 
     A third example of a method and of an apparatus for manufacturing parts is described in conjunction with  FIGS. 22 and 23 .  FIG. 22  is an illustration of a curved profile  19  manufacturable using an apparatus sketched in  FIG. 23 .  FIG. 23  is an illustrative cross-section-like side view of a detail of an apparatus with an outer tool having a set of two segments  22  and an inner tool having a first set of one segment  20  and a second set of two segments  21 . 
     This third example refers to a method and an apparatus for manufacturing carbon fiber reinforced polyetheretherketone (PEEK) open profiles  19 , for instance a stringer for reinforcing aircraft fuselages (cf.  FIG. 22 ). Profile  19  may present, e.g., an I-, a T- or a C-shaped or an approximately Z-shaped cross-section (along the line marked A-A′ in  FIG. 22 ), and, moreover, the cross-section may vary along the length extension of the profile.  FIGS. 24 and 25  illustrate exemplary cross-sections along the line A-A′ in  FIG. 22 , namely a T-shaped and an approximately Z-shaped cross-section, respectively. 
     And profile  19  can have continuously changing bending radii (cf. R 1  and RN in  FIG. 22 ). By means of the described process and apparatus, it is possible to manufacture profiles with locally variable radii and a locally variable cross-section. 
     The process parameters of temperature, pressing time and pressure of the first example (see above) can also be applied in this case. 
     In general, the process also works in substantially the same way as the above-described first example and with a principally equivalent or at least similar apparatus. A main difference is the number of segments: in this case, the inner tool has to comprise at least one central segment  20  and two lateral segments  21 , while the outer tool has to comprise at least two segments  22 . 
     The particular example of  FIGS. 22 to 25  (third example) may work with only two internal segments instead of the described three ones (one central one 20 and two symmetric ones  21 ) if there is only one internal radius R 1  or if the length of the profile allows to do it (not shown). 
     In general, in practice the minimal number of segments is basically given by two factors:
         the segments have to be designed in such a way that they do not collide with each other while moving back and forth from opened to closed position and vice versa;   the preform and the pressed part, respectively, have to be easily placeable into and removed from the tools and/or their segments.       

       FIG. 26  shows a schematic illustration of a cross-section of a detail of an apparatus for manufacturing a ring-shaped (cylinder-surface-like) part, with inserted material  3  being compressed. The cross-section is a cross-section along the axis of the part. The open arrow symbolizes force applied to material  3  via segment  2   a  of inner tool such that material  3  is compressed within the cavity formed between inner and outer tools thus assuming the shape defined by the tools. Guidances  7  such as pins attached to segment  2   a  interacting with holes (dotted lines in  FIG. 26 ) in segment  1  can be used for ensuring a suitable alignment of inner and outer tool. Reference  12  denotes the inner surface of the outer tool and therefore also the outer surface of part to be produced. In the cross-section illustrated in  FIG. 27 , this surface  12  shows up as a line, the part to be manufactured substantially describing a cylinder jacket. More complicated shapes are possible, e.g., varying the cylinder radius along the cylinder axis. By appropriate variations of that radius (and of the corresponding inner radius of the part), a rim for an automobile can be the produced part. The principle explained in  FIG. 26  can well be applied, e.g., to the first example illustrated in  FIGS. 1 to 19 . 
       FIG. 27  shows a detailed view of an interface  13  between a segment  2   a  of the first set of the second tool and a segment  2   b  of the second set of the second tool, e.g., as it can be used in the first example illustrated in  FIGS. 1 to 19 . The interface  13  is more particularly formed by mating surface  13   a  of segment  2   a  (cf. also  FIG. 7 ) and mating surface  13   b  of segment  2   b  (cf. also  FIG. 7 ). Segment  2   a , more particularly its mating surface  13   a  (cf. also  FIG. 7 ), forms an acute angle α with the local tangent of the inner tool. That local tangent is indicated as a dashed line in  FIG. 27 . Correspondingly, segment  2   b , more particularly its mating surface  13   b  (cf. also  FIG. 7 ), forms an obtuse angle β with the local tangent of the inner tool. Acute angle α usually will amount to between 89° and 40°, more particularly between 88° and 60°, even more particularly between 86° and 70°. 
     Note that the interface  13  and the mating surfaces  13   a  and  13   b  do not necessarily have to be plane. As indicated by the dotted line in  FIG. 27 , curved interfaces  13  and surfaces  14  are possible, too. The provision of an acute angle α leads to better arranged and better shaped fibers in the finished part. 
     It will be appreciated that the segment(s)  2   b  (first and second example) and  21  (third example) of the second set are (is), on their way towards the closed position always farther away (along their travel path) from their (its) position when in closed position than—at the same time—the segment(s)  2   a  (first and second example) and  20  (third example) of the first set (along their travel path) from their (its) position when in closed position. 
     One can, somewhat sloppily, say, the segment(s)  2   b ,  21  of the second set cannot pass by or “overtake” the segment(s) of the first set on their respective way into the closed position. 
     This allows to form parts with narrow concave surfaces. A limited space available for the segments is cleverly used. Different sets of segments are moved at different times and/or at different speeds to overcome geometrical limitations. Note that, similarly to what was discussed above in conjunction with the second example (cf.  FIG. 21 ), it is also in case of the first example (cf.  FIGS. 1-19 ) possible to have the segments  2   a  still moving and still not yet in the closed position while segments  2   b  are already on their way moving towards the closed position; in the description of the first example in conjunction with  FIGS. 1-19 , segments  2   b  are moved into their initial position only after segments  2   a  are already in their closed position. 
     The described method and apparatus is excellently suited for the manufacture of pressure-formed fiber-reinforced plastics parts from preforms, in particular for such parts which have or comprise a portion having a shape which is ring-like or nearly-closed or is rather complex with concave portions, in particular wherein continuous fibers and/or oriented fibers are used as reinforcement. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  segment, segment of first tool, outer mold segment 
           2   a  segment, segment of first set of second tool, inner mold segment 
           2   b  segment, segment of second set of second tool, inner mold segment 
           3  preform, prepregs 
           4  first tool in closed state, outer mold in closed state 
           5  contacting interfaces of segments of first tool, contacting interfaces of segments of outer mold 
           6  clamp 
           7  guidance, guiding means, guiding pin 
           8  pull rod, rod of first set of pull rods 
           10  displacing mechanism 
           11  pull rod, rod of second set of pull rods 
           12  outer surface of part to be produced, inner surface of outer tool 
           13  contacting interface, interface between a segment of the first and a segment of the second set of the second tool 
           13   a  mating surface of a segment of the first set of the second tool 
           13   b  mating surface of a segment of the second set of the second tool 
           14  force vector 
           15  force vector 
           16  part, rim 
           17  pantograph 
           18  pantograph bolt 
           19  part, profile 
           20  segment, segment of first set of second tool, inner mold segment, central mold segment 
           21  segment, segment of second set of second tool, inner mold segment, lateral mold segment 
           22  segment, segment of first tool, outer mold segment, segment of external mold 
         A axis, part axis 
         R 1  . . . R N  bending radius 
         α angle, acute angle 
         β angle, obtuse angle