FR3026669A1 - - Google Patents

Abstract

The invention relates to a clamping device (1) for fastening objects (3) by clamping, which comprises, in addition to a prestressing device (17) for producing a prestressing force, an additional adjusting member (18) depending on temperature, to compensate for settlement processes caused by temperature. The invention also relates to a method for manufacturing a fiber reinforced composite part, which is fixed by means of such a clamping device (1).

Description

The invention relates to a clamping device for tightening the fastening of objects, in particular fiber-based preforms for the manufacture of a workpiece, a fiber-reinforced composite. The invention also relates to a method for manufacturing a fiber-reinforced composite part which is formed from a fiber-based material into which a matrix material has been infused. 10 Parts made of fiber-reinforced composite material, called composite fiber-reinforced parts, are today essential in the aeronautical and aerospace field. But the use of such materials is also increasingly popular in the automotive field. In particular, critical structural elements are made of fiber-reinforced plastics which are of minimal weight because of their strength and rigidity, which are high for a given weight. Due to the anisotropic properties resulting from the fiber orientation of the fiber reinforced composite materials, the parts can be adapted to local loads or stresses, thereby enabling optimum material utilization in the light of lighter construction. In the manufacture of fiber-reinforced composite parts, it is common to introduce a fiber-based material into a shaping tool, whereby a matrix material, for example a resin system, having a diameter of 25 to 25 μm, is used. has been infused into the fiber-based material, is cured by being warmed up and, if necessary, under pressure, thereby forming an integral part. The fiber-based material used for producing the fiber-based preform, for example flat semi-products, may be a dry or pre-impregnated fiber-based material. If a dry fiber material is used, the matrix material is then infused at a later time into the fiber material, for example by a vacuum infusion process, and then cured. In the manufacture of fiber-reinforced composite parts, the so-called open-mold technology is often used, according to which the fiber-base material for the manufacture of the preform, including the auxiliary substances required under the form of flow aids, suction membranes and finishing of a vacuum film, is applied to a fixed side of tooling of a forming tool. The fiber-based preform is thus not formed and cured in a generally closed shaping tool. At the level of stiffening elements or geometrical connections, additional forming tooling parts are often applied as supports, under the vacuum envelope or on the vacuum envelope, so that they can also be maintained during operation. manufacture of the fiber-reinforced composite part the predefined geometry of the part within the tolerances.

During the actual manufacturing process, i.e. during the curing operation of the matrix material by heating and, if appropriate, pressure loading, the fiber-based preform between the tools is compressed, so that the shaping tools must follow this settling process or this packing effect. In practice, a prestressing clamp is used where the prestressing has been produced by means of a spring pin on a lever arm. In this case, however, it has been disadvantageous that due to the settling process or the settling effect during preform warm-up, prestressing was partially or totally lost, so that The tools are no longer pressed against each other, and as a result the required part tolerances can no longer be met. In fact, because of the high temperatures during the curing process itself, the spring tension decreases, so that the prestressing lost under the effect of the settling process can no longer be sufficiently compensated. Accordingly, it is an object of the present invention to provide an improved method for making a fiber reinforced composite part, in particular that of the Open-Mold-technology technology, as well as a clamping device for use in this application. This allows the process to compensate reliably for the settling effects of the fiber-based preform observed during the manufacturing process. In accordance with the invention, the object of the invention is achieved by means of a clamping device for fastening objects by clamping, comprising two clamping arms, each having at one clamping end a jaw by means of which an object can be fixed by clamping, and which are mounted movable relative to each other by means of a hinge, the clamping device also comprising a prestressing device for producing a Pre-adjustable preload force, which acts as a clamping force on the clamping jaws when an object is attached by means of the clamping device, characterized in that in addition to the prestressing device, there is provided minus a temperature-dependent adjusting member, which, when adjusting the preload force at the prestressing device, has a first state in which the temperature-dependent adjusting member does not produce no additional prestress, and which, in case of increase of the temperature of the environment surrounding the clamping device, goes into a second state in which the temperature-dependent adjustment member produces an additional prestressing force, based on the effect of thermal expansion and acting as a clamping force on the clamping jaws. Furthermore, the object of the invention is achieved by a method for producing a fiber-reinforced composite part which is formed of a fiber-based material infused with a matrix material, comprising the steps of: a) supply and preparation of a clamping device according to one of

Claims (11)

REVENDICATIONS1. previous b) introducing a fiber-based material into a forming tool and making a fiber-based preform; c) fixing the fiber-based preform by means of the clamping device by bringing at least one clamping jaw of the clamping device into interaction with the fiber-based preform, and adjusting, by means of the prestressing device, a prestressing force which acts as a clamping force on the fiber-based preform via the clamping jaws; d) manufacturing the fiber-reinforced composite part by heating the fiber-based preform in the forming tool during attachment by the clamping device. According to the invention, there is provided a clamping device for fastening objects by clamping, the clamping device comprising at least two clamping arms, which each have, at a clamping end, a clamping jaw. The clamping jaws are here configured to allow tight attachment of the object, for example by interposing the object between the two clamping jaws of the clamping arms. It is also conceivable to arrange the clamping jaws on the clamping arms in such a way that they produce a tight fit away from each other. The clamping jaws here are mounted movable relative to each other by means of a hinge, so that this movable mounting of the clamping jaws allows the transmission of a clamping force to the clamping jaws. to ensure a fixation. Thus, for example in the case of diametrically opposed clamping jaws, an object can be placed between these clamping jaws and secured by applying a clamping force to the object to be clamped. Furthermore, there is provided a prestressing device designed to produce a prestressed prestressing force, which acts as a clamping force on the 40 clamping jaws when an object is attached by means of the clamping device. Such a prestressing device may for example be a spring force mechanism, which produces an adequate prestressing force, which then acts as a clamping force on the clamping jaws. It is also conceivable that the prestressing device has a threaded spindle by means of which a prestressing force is produced by the movement of a screwed nut. Such a generic clamping device makes it possible to fix an object by clamping, the prestressing device making it possible to produce a pre-adjustable preloading force, which then acts as a permanent clamping force on the clamping jaws for fixing the object. It is thus possible to fix objects for a sufficiently long duration, in that the preset prestressing force acts, for the duration of use, as a clamping force on the clamping jaws for fixing. Now, in order to compensate for the decrease or loss of the preset prestressing force occurring due to settling or settling effects, it is proposed in accordance with the invention to additionally provide in the functional chain between the prestressing device for generating the prestressing prestressing force and the clamping jaws for producing the clamping force, a temperature-dependent adjusting member having a first state and at least a second state. In the first state, existing during the adjustment of the prestressing force at the prestressing device, the temperature-dependent adjustment member does not generate, on the clamping jaws, a clamping force in addition to the prestressing force of the prestressing device, so that it can be considered as neutral regarding the clamping force to be produced. In this case, the clamping force to be produced is generated exclusively through the prestressing device providing the preset prestressing force. During a temperature increase from the initial temperature during the adjustment of the prestressing force on the prestressing device, up to a set temperature, the temperature-dependent adjustment member moves from the first existing state. when adjusting the prestressing force, to a second state existing when the temperature of the set temperature rise is reached. The temperature rise here concerns the medium surrounding the clamping device, for example a gaseous or also liquid fluid. In the second state, the temperature-dependent adjustment member can no longer be considered as neutral with respect to the clamping force to be produced at the clamping jaws, the temperature-dependent adjusting member producing the opposite an additional prestressing force based on the effect of the thermal expansion and then acting as an additional clamping force on the clamping jaws. In the second state, the temperature-dependent control member has an enlarged dimension with respect to that of the first state, with respect to the transmission path of the prestressing force, thereby generating an additional prestressing force. According to the invention, the following advantageous effect is thus obtained, namely that in the case of an increase in the temperature and the settling processes or settling effects which result therefrom on the object to be fixed, it was possible to compensate for the loss of the preset preload force, by means of the temperature-dependent control member, since the adjustment member now has a function of the temperature produced itself, on the increase temperature, a corresponding prestressing force, which then acts as a clamping force on the clamping jaws. The loss of clamping force due to the loss of the preset preload force is then compensated for by an additional clamping force on the basis of an additional biasing force of the temperature-dependent adjuster. According to the invention, such a clamping device can thus be implemented in processes in which the objects to be fixed must be warmed up with, consequently, the risk of settling process during the warm-up, which must be compensated. On this occasion, the inventors have found that by means of the effect of the thermal expansion of a temperature-dependent control member, which in particular does not comprise any mechanical components and is arranged in the functional chain or the force transmission chain of the clamping device, the loss of a prestressing force having been adjusted, could be compensated, because following the thermal expansion of the material used for the temperature-dependent adjusting member, it is possible to produce an additional prestressing force. According to an advantageous embodiment, the two clamping arms are connected via the hinge and are mounted movably relative to each other so that the clamping jaws are movable. relative to each other. The clamping jaws are here arranged on the respective clamping arm, for example in a fixed manner or by means of a seat of a ball joint, for purposes of orientation compensation. With the aid of the clamping arms, which are movably mounted relative to each other via the hinge, the clamping jaws can be moved relative to one another. The clamping jaws are here arranged radially opposite on the clamping arms, so that for-de-clamping acting on the clamping jaws, acts in a common plane, namely on the same axis. The clamping force can here act in a direction towards the respectively opposite clamping jaw or in a direction away from the respectively opposite clamping jaw, according to the needs of the use and the embodiment of the clamping device. Thanks to the movably mounted clamping arms, on which the clamping jaws are arranged in a radially opposite manner, the clamping jaws can be moved relative to one another so that the distance between the clamping jaws can be adjusted. decreased or increased. In general terms, it is therefore within the scope of the present invention for the clamping jaws to be mounted movable relative to one another via the hinge, so that the clamping jaws can be moved closer together. 15 or spaced from each other, thereby to exert on the object the desired clamping force. According to an advantageous embodiment, the prestressing device is arranged at an operating end of the clamping arms, which is opposite to the clamping end, so that the prestressing force produced by the prestressing device is transmitted to the clamping jaws via the clamping arms acting as levers. Thus, the prestressing device could for example comprise a force-exerting adjusting member which is arranged at an actuating end of one clamping arm and bears against the actuating end of the other clamping arm. , the clamping arms being implemented as force transmission levers, placing between the actuating end and the clamping end the hinge for the rotational mounting of the clamping arms. But it is also conceivable that the clamping arms mounted movable relative to one another via the hinge, are arranged to be linearly movable relative to each other by means of a rotation joint, the rotation joint then simultaneously forming the prestressing device. According to an advantageous embodiment, the temperature-dependent adjustment member is provided between the prestressing device arranged on the first clamping arm, and the second clamping arm, so that in the first state, neutral of the temperature-dependent adjusting member, only a prestressing force produced by the prestressing device is transmitted. In another alternative or additional embodiment, the temperature-dependent adjusting member is provided at the clamping end between one of the clamping arms and the respective clamping jaw of the clamping arm so that here also, in the first neutral state of the temperature-dependent control member, the prestressing force produced by the prestressing device 5 is transmitted via the clamping arms of the adjusting the function of the temperature as well as the clamping jaw, and can thus act as a clamping force. It is only during said at least one second state of force generation that the temperature-dependent regulator produces, due to the effect of the thermal expansion, an additional prestressing force which then acts as a clamping force. According to another advantageous embodiment, it relates to the temperature-dependent control member of a body of material. This body of material may contain a material or be made of a material having a higher coefficient of thermal expansion than iron or steel. In the case of higher thermal expansion coefficients, a larger elongation is produced for the same quantity of material, so that in principle a larger path of travel can be obtained and more compaction processes can be compensated for. important. According to another particularly advantageous embodiment, the temperature-dependent control member is a body of material which contains aluminum or is made of aluminum. In accordance with the invention there is also provided a method for manufacturing a fiber reinforced composite part which is formed of a fiber material infused with a matrix material. According to the invention, a clamping device as previously mentioned is provided and firstly prepared, in particular a clamping device with an additional adjustment member, which is a function of the temperature. Then, the fiber-based material (dry or pre-impregnated) is introduced into a forming tool, so that a corresponding fiber-based preform can be produced. At this stage, to fix the fiber-based preform in accordance with the geometry of the workpiece, the clamping device having been prepared is clampingly arranged on the fiber-based preform, at least one clamping jaw of the clamping device. being brought into interaction with the fiber-based preform, and a prestressing force being adjusted by means of the prestressing device and acting as a clamping force on the preform, via the clamping jaws. For the manufacture of the fiber-reinforced composite part, this arrangement consisting of the fiber-based preform, the forming tool and the clamping device is warmed up, whereby the material of matrix having been infused into the fiber-based material of the fiber-based preform cures, and constitutes the fiber-reinforced composite part. The arrangement comprising the fiber-based preform, the forming tool and the clamping device, as well as, if appropriate, other components, is advantageously introduced into an autoclave, and the manufacturing process for manufacturing the fiber reinforced composite part, implement the heating and, if necessary, the pressure loading is then performed. According to an advantageous embodiment, the size and / or the material of the temperature-dependent control element, for example in the form of a body of material, preferably in the form of a spindle, are chosen according to the temperature of the manufacturing process and a packing effect or compaction process expected of the fiber-based preform during manufacture of the fiber-reinforced composite part. The expected settlement effect here can be the reduction of the clamping path for the tight fixing of the object by means of the clamping device. With regard to the temperature of the manufacturing process and the adjustment of the prestressing force previously carried out at ambient temperature, the difference in temperature can then be determined. The size and / or the material of the temperature-dependent control member can then be chosen according to these components, so as to optimally compensate for the expected compaction process of the fiber-based preform. In this case, it is particularly advantageous if the size and / or the material of the temperature-dependent control element are, moreover, chosen as a function of a coefficient of thermal expansion of the material under consideration. The invention will be explained by way of example, with reference to the appended figures. 30 which show: Figure 1 a schematic representation of a clamping device in a first embodiment; Figure 2 is a schematic representation of the clamping device in a second embodiment. Figure 1 shows schematically a clamping device 1 with which a fiber-based preform 3 formed in a forming tool is to be attached. 2. The clamping device 1 has for this purpose a first clamping arm 11 and a second clamping arm 12, which are rotatably mounted relative to each other by means of a hinge 13. The first clamping arm 11 and the second clamping arm 12 are here rotatably mounted non-crosswise, via the hinge 13. At a clamping end 14 of the clamping device 1, on the clamping arms 11 and 12 are arranged respectively clamping jaws 15, which, for fixing the fiber-based preform 3 in the forming tool 2 can be brought into contact therewith, to thereby act the clamping force on the preform to fiber base 3. The clamping jaws 15 are here arranged on the respective clamping arms 11 and 12 so as to be radially opposite, the clamping jaws 15 being movably mounted relative to one another, using of the hinge 13, so as to be mutually close together or discarded. In the embodiment of Figure 1, a prestressing device 17 is arranged on the first clamping arm 11 at an actuating end 16 opposite the clamping end 14. The prestressing device 17 is designed to establish a prestressing force, and thus be able to produce a clamping force on the clamping jaws 15. The prestressing force of the prestressing device 17 is here also transmitted via the second clamping arm 12. When setting the temperature of the fiber-based preform 3, settling effects or packing processes may occur which result in a decrease in the thickness of the fiber-based preform 3 in the clamping area. The clamping distance D between the two clamping jaws 15 is consequently reduced, which leads to a loss of the prestressing force. To compensate for this packing effect, there is provided between the prestressing device 17 and the second clamping arm 12, an adjusting member 18 depending on the temperature, intended to compensate for this packing process. The adjustment member 18 depending on the temperature here has a first state and a second state. In the first neutral state, which exists for a temperature at which the prestressing device 17 is set with respect to the prestressing force, the temperature-dependent adjusting member 18 has a neutral behavior and transmits to the second arm clamping 12 the prestressing force applied by the prestressing device 17. The adjustment member 18, which is a function of the temperature, thus acts, in the first state, in the manner of a stop against which the prestressing device 17 rests against to produce the prestressing force. During the heating and settling of the fiber-based material (reduction of the clamping distance D), which results therefrom, the temperature-dependent adjusting member 18 moves into a second state which is characterized in that the adjustment member 18 depending on the temperature, relative to the first state, increases its dimensions relative to the transmission path of the prestressing force. This increase in the size of the temperature-dependent regulating member 18 then leads, in the area of the actuating end 16, to the production of an additional prestressing force, which is in addition to the force This compensates for the settlement process, since now the path is enlarged in the area of the actuating end 16, so that the clamping distance D decreases and so the process of settlement is compensated. FIG. 2 schematically shows another embodiment where the hinge 13 is made in the form of a screw joint. The adjustment member 18, which is a function of the temperature, is here provided between a wing nut 15 forming pretensioning device 17 and the first clamping arm 11, so that, during the warm-up, an additional prestressing force can be exerted. on the clamping arm 11. Claims: 1. Clamping device for fastening objects by clamping, comprising two clamping arms (11, 12), which each have, at a clamping end (14), a jaw clamping device (15), by means of which an object can be fixed by clamping, and which are mounted movable relative to each other by means of a hinge (13), the clamping device also comprising a device preloading member (17) for producing a presettable biasing force, which acts as a clamping force on the clamping jaws when an object is attached by means of the clamping device, characterized in that in addition to the precontact device (17) at least one temperature-dependent adjusting member (18) is provided which, when adjusting the prestressing force at the prestressing device, has a first state in which the prestressing member (18) temperature-dependent adjustment does not produce additional prestressing, and which, in the event of an increase in the temperature of the environment surrounding the clamping device, changes to a second state in which the temperature-dependent adjustment member produces a force additional prestressing based on the effect of thermal expansion and acting as a clamping force on the clamping jaws. 2. Clamping device according to claim 1, characterized in that the two clamping arms (11, 12) are connected via the hinge (13) and are mounted movably relative to one another. other, so that the clamping jaws are movable relative to each other. 3. Clamping device according to claim 1 or 2, characterized in that the prestressing device (17) is arranged at an actuating end (16) of the clamping arms, which is opposite to the clamping end (14). ) clamping arms, so that the prestressing force produced by the prestressing device is transmitted to the clamping jaws via the clamping arms acting as levers. Clamping device according to one of the preceding claims, characterized in that the temperature-dependent adjusting member (18) is provided between the prestressing device (17) arranged on the first clamping arm (11). , and the second clamping arm (12). 5. Clamping device according to one of the preceding claims, characterized in that the temperature-dependent adjusting member is provided at the clamping end between one of the clamping arms and the respective clamping jaw of the clamping device. clamping arm. 5 Clamping device according to one of the preceding claims, characterized in that the temperature-dependent adjusting member (18) is a material body, which contains a material or consists of a material having a coefficient of thermal expansion higher than iron or steel. 10 7. Clamping device according to one of the preceding claims, characterized in that the adjusting member (18) is a temperature-dependent material body, which contains aluminum or is made of aluminum. 8. A process for producing a fiber-reinforced composite part which is formed of a fiber-based material infused with a matrix material, comprising the following steps: a) supply and preparation of a clamping device (1) according to one of the preceding claims; b) introducing a fiber-based material into a forming tool (2) and producing a fiber-based preform (3); c) fixing the fiber-based preform by means of the clamping device (1) by feeding at least one clamping jaw (15) of the clamping device in interaction with the fiber-based preform (3), and adjusting by means of the prestressing device (17), a prestressing force which acts as a clamping force on the fiber-based preform via the clamping jaws (15); d) manufacturing the fiber-reinforced composite part by heating the fiber-based preform (3) in the forming tool (2) during fixing by the clamping device (1). 30 Method according to claim 8, characterized in that the fiber-based preform (3) is introduced into an autoclave together with the forming tool (2) and the clamping device (1). , the fiber-based preform being brought to temperature by the autoclave and being, if necessary, stressed under pressure, to manufacture the fiber-reinforced composite part. Method according to claim 8 or 9, characterized in that the size and / or the material of the temperature-dependent adjusting member (18) of the clamping device are selected according to the temperature of the process of And the expected compaction effect of the fiber-based preform during manufacture of the fiber-reinforced composite part. 11. A method according to claim 10, characterized in that the size and / or the material of the adjusting member (18) depending on the temperature are, moreover, chosen according to a coefficient of thermal expansion of the material. .