This application claims the benefit of priority under 35 U.S.C. §119 to German Patent Application No. 102014202352.1, filed on Feb. 10, 2014, in the German Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.
The present disclosure relates to a method and an apparatus for manufacturing a fiber-reinforced thermoset composite, and more particularly to a method and an apparatus for manufacturing multi-curve fiber-reinforced thermoset composites by using a pultrusion process.
In the field of automobile construction, a variety of structural parts having multiple curves are commonly employed, such as, cowl cross bars, stabilizer bars, and coil springs. Conventionally, such parts are manufactured using steel shaped in a tube or coiled wire as a base material by a complex but well-manageable process which involves steps such as cold bending or drawing, quenching, and coating for corrosion protection. Since such steel based manufactured parts are main factors for the overall weight of an automobile, a significant reduction in the overall weight and the energy consumption of the automobile can be expected by substituting the steel with a material having similar strength with a lower weight, such as a fiber-reinforced plastic composite.
However, due to material property differences, processes used in manufacturing multi-curve shaped parts using steel cannot in general be used for fiber-reinforced composites. There is a method available for manufacturing general fiber-reinforced composite parts, especially thermoset composites, known as pultrusion, in which reinforcement materials, such as fibers, woven, or braided strands, are impregnated with a resin and pulled through a heated stationary die, and the resin undergoes polymerization. However, due to geometric difficulties, only straight or single curved shapes can be molded in the pultrusion die, such that the manufacturing of multi-curve shaped parts is impossible using the thermoset composites which need to be cured in the pultrusion die to obtain a desired shape.
EP0802851 B1 discloses a process comprising steps of pulling a reinforcing material impregnated with a heat curable thermosetting polymeric composition through a temperature controllable pultrusion die. The temperature of the pultrusion die and a drawing speed of the material are controlled, so that a predetermined length of material in the pultrusion die is substantially cured. The temperature of the pultrusion die is lowered, so that the predetermined length of the material which passes through the pultrusion die substantially remains being uncured. The uncured portion of the material emerging from the pultrusion die is reshaped, and the reshaped portion is cured. The pultrusion die is repeatedly heated and cooled, thus increasing energy consumption and limiting the speed during manufacturing. In particular, in order to provide a sharp transition between the cured and uncured portions, the step of pulling the material through the pultrusion die has to be discontinued or performed at a very slow rate while the die is being cooled.
The present disclosure provides a method of manufacturing a fiber-reinforced thermoset composite and an apparatus for manufacturing the same.
According to an embodiment of the present disclosure, a method of manufacturing a fiber-reinforced thermoset composite includes pulling a first portion of a continuous material comprised of reinforcement fibers which are impregnated with a heat curable thermosetting resin through a die. The first portion in the die is subjected to a field of electromagnetic microwaves to heat the first portion to at least a curing temperature of the thermosetting resin. A second portion of the continuous material is pulled through the die. The field of electromagnetic microwaves in the die is reduced such that the second portion is not heated to the curing temperature.
The field of electromagnetic microwaves is terminated in the step of reducing the field of electromagnetic microwaves.
The step of pulling the first portion and the step of pulling the second portion are performed by continuously pulling the continuous material through the die.
The method further comprises reshaping the second portion of the continuous material, and heating the second portion to at least the curing temperature of the thermosetting resin.
The step of reshaping is performed continuously.
The step of reshaping includes guiding the continuous material between a plurality of pulleys, and moving at least one of the pulleys in a reshaping direction perpendicular to a longitudinal direction of the continuous material.
The step of reshaping is performed by stamping at least the second portion of the continuous material in a stamping press.
The step of heating the second portion is performed concurrently with the step of reshaping the second portion.
According to another exemplary embodiment of the present disclosure, an apparatus for manufacturing a fiber-reinforced thermoset composite includes a die. A pulling device pulls a continuous material comprised of reinforcement fibers which are impregnated with a heat curable thermosetting resin through the die. A microwave generator is configured to subject a first portion of the continuous material, when the continuous material is pulled through the die, to a field of electromagnetic microwaves to heat the first portion to at least a curing temperature of the thermosetting resin. A controller is configured to control the microwave generator to reduce the field of electromagnetic microwaves such that a second portion of the continuous material is not heated to the curing temperature when the continuous material is pulled through the die.
The continuous material comprised of reinforcement fibers impregnated with the heat curable thermosetting resin may be provided in advance, or may be prepared just in time along with performing the method of the present disclosure. For example, the reinforcement fibers may be impregnated with the heat curable thermosetting resin before being drawn into the die or after being drawn by injecting the heat curable thermosetting resin into the die.
In the step of subjecting the first portion to the field of electromagnetic microwaves to heat the first portion according to the present disclosure, the continuous material is configured to be heatable by being subjected to the field of electromagnetic microwaves at least within the first portion. For example, the continuous material may, at least in the first portion, be configured with the reinforcement fibers including 30% or more of carbon fibers, and/or with the thermosetting resin including an admixture of an electrically conductive or a bipolar filler material such as carbon or iron powder.
As a result of performing the method of the present disclosure, since the first portion of the continuous material is heated to at least the curing temperature of the thermosetting resin, the first portion leaves the die in a permanently cured condition. On the other hand, the second portion is not heated to the curing temperature, and therefore leaves the die in an uncured condition, thus enabling it to be subsequently reshaped and cured to obtain a multi-curve shape as desired.
Because the heating of the first portion is effected by subjecting the first portion to the field of electromagnetic microwaves, heat is generated to cure the first portion within the first portion of the continuous material itself, in particular within the thermosetting resin comprised in the first portion. Thus, the die does not need to be heated in the present disclosure, and the die can be provided with a material that is not thermally affected by the field of electromagnetic microwaves.
Since the die does not need to be heated above the curing temperature for curing the first portion, there is no need to cool the die to below the curing temperature before the second portion is pulled through the die, which enables a low energy consumption to be achieved during manufacturing. Furthermore, since heating and cooling of the die are not necessary, a sharp transition between the cured condition of the first portion and the uncured condition of the second portion is possible even if the continuous material is pulled through the die at a high speed. Thus, a high manufacturing speed is achieved while manufacturing a highly accurate thermoset composite with the sharp transition between the cured first portion and the uncured second portion, such that subsequent reshaping and curing of the second portion to manufacture a highly precise multi-curve composite become possible.
According to the exemplary embodiment of the present disclosure, the sharp transition between the cured condition in the first portion and the uncured condition in the second portion of the continuous material is achieved, and thereby manufacturing a precise multi-curve shaped part using a thermoset composite. The termination of the field of electromagnetic microwaves can be simply achieved by using a switch, and the overall energy consumption for generating microwaves is reduced.
Further, simple and smooth manufacturing operations are possible while achieving a high manufacturing speed since the continuous material can be pulled through the die at a maximum speed for curing the first portion without slowing down.
In addition, a completely cured multi-curve particle is enabled directly result from carrying out the method. The second portion is heated by subjecting the second portion to a further field of electromagnetic microwaves. That is, the continuous material is configured within the second portion to be heatable by being subjected to the field of electromagnetic microwaves. For example, the continuous material may be configured with reinforcement fibers including 30% or more of carbon fibers, and/or with a thermosetting resin including an admixture of an electrically conductive or a bipolar filler material such as carbon or iron powder. In this way, the second portion can flexibly be reshaped, and the second portion is cured at a high speed with reduced energy consumption, thus achieving an improved manufacturing process. Furthermore, complex shapes can be achieved.
According to the exemplary embodiment of the present disclosure, the shape of the second portion can be modified by applying a reshaping process using a modifying control of the pulley movement, without having to provide a modified physical reshaping tool.
Further, according to the exemplary embodiment of the present disclosure a precise shaping is possible. More specifically, the stamping press can be moved with the continuous material. In this way, the continuous material does not have to be stopped during stamping, thus achieving higher manufacturing speeds.
Further, it is possible to achieve particularly complex shapes using the same reshaping tool by simply relocating the tool on the second portion during reshaping while curing the continuous material.
Unless indicated otherwise, like reference numbers throughout the figures indicate like elements.
Hereinafter, a method and an apparatus of manufacturing a fiber-reinforced thermoset composite according to embodiments of the present disclosure will be described with reference to the accompanying drawings.
In the present disclosure, the continuous material 104 may be configured to be heatable by being subjected to a field of electromagnetic microwaves. For example, the reinforcement fibers may include 30% or more of carbon fibers, or the thermosetting resin may include an admixture of an electrically conductive or a bipolar filler material such as carbon or iron powder.
Hereinafter, the configuration of the pultrusion die 200 will be explained in more detail with further reference to
The pultrusion die 200 is equipped with first and second microwave generators 201, 202 for subjecting a portion of continuous material 104, which enters the die opening 230, to fields of electromagnetic microwaves 211, 212 in order to heat the portion of continuous material 104 to at least a curing temperature of the thermosetting resin 113. The first microwave generator 201 is externally mounted to the upper die half 221 with a first waveguide 234 at a top face 241 of the upper die half 221. Similarly, at a bottom face 242 of the lower die half 222, the second microwave generator 202 is externally mounted to the lower die half 222 with a second waveguide 235, which is vertically below the first microwave generator 202. Both die halves 221, 222 are made of a material that is substantially permeable to microwave frequency electromagnetic fields such as a ceramic material.
The first microwave generator 201 is configured to generate a first field of electromagnetic microwaves 211 which fills a cone-shaped region extending from a cone vertex at the top face 241 to a cone base at the bottom face 242 within the pultrusion die 200. Similarly, the second microwave generator 202 is configured to generate a second field of electromagnetic microwaves 212 which fill a cone-shaped region extending from a cone vertex at the bottom face 242 to a cone base at the top face 241 within the pultrusion die 200. Both first and second fields of electromagnetic microwaves 211, 212 overlap in the die opening 230, such that during activation of the microwave generators 201, 202, the die opening 230 is filled by a substantially homogeneous microwave field having sufficient strength to heat the portion of the continuous material 104 that is located inside the die opening 230 to above the curing temperature within a longitudinally extending microwave irradiation zone.
In
The manufacturing apparatus 116 further comprises a cooling device 130 for cooling the continuous material 104 to room temperature after receiving the continuous material 104 from the pultrusion die 200, which is heated in the pultrusion die 200. The cooling device 130 prevents heat spreading out from the portion of the continuous material 104, which is heated in the pultrusion die 200, to the neighboring portion of the continuous material 104. Thus, a boundary between cured portions and uncured portions is defined in the continuous material 104.
Furthermore, the manufacturing apparatus 116 comprises a pulling device 114 for continuously pulling the continuous material 104 formed of the reinforcement fibers 106 impregnated with resin 113 through the drying device 109, the resin tank 108, the pultrusion die 200, and the a cooling device 130, thereby driving the preparation process for the continuous material 104.
The manufacturing apparatus 116 further comprises a power source 132 for supplying electric power to the first and second microwave generators 201, 202, as well as a switch 126 for connecting and disconnecting the power source 132 with the first and second microwave generators 201, 202. In addition, a controller 124 is provided for controlling the switch 126. The controller 124 is configured to control the first and second microwave generators 201, 202 by switching the switch 126 on and off at regular intervals, in coordination with the pulling of the continuous material 104 by the pulling device 114, thereby providing alternating portions in the continuous material 104. Cured first portions 101 of the continuous material 104 alternate with uncured second portions 102 of the continuous material 104, each having a predetermined length controlled by the controller 124.
The manufacturing apparatus 116 further includes a reshaping device 118 for reshaping the uncured second portions 102 of the continuous material 104, a heating device 120 for heating the reshaped second portions 102 to at least the curing temperature of the thermosetting resin, and a cutting device 122 for cutting the continuous material 104 into separate fiber-reinforced thermoset composites 100. For convenience of display, these components 118, 120, 122 are shown in the bottom half of
The reshaping device 118 includes a stamping press comprising a stamp 117 and a correspondingly shaped stamping form 119. The reshaping device 118 is shown in
The reshaping device 118 is configured to move along the continuous material 104. In the operation, a reshaping controller that may be part of the controller 124 described above controls the reshaping device 118 to first assume the open position (dotted lines). When the uncured second portion 102 passes between the stamp 117 and stamping form 119, the stamp 117 is controlled to gradually move toward the stamping form 119 while both the stamp 117 and the stamping form 119 are controlled to simultaneously move together with the continuous material 104 in the same direction and at the same speed as the continuous material 104 itself. In this way, the reshaping device 118 gradually reshapes the second portion 102 while traveling together with the same until the closed position of the reshaping device 118 (solid lines) is reached. The heating device 120 is fixedly arranged at the closed position of the reshaping device 118 (solid lines).
The reshaping device 118 of the manufacturing apparatus 116 of the present disclosure includes three pairs of pulleys 301-303. As can be seen in an additional detailed view given in
A first pulley arm 321 of the three pulley arms 321-323, which bears a first pair of pulleys 301 of the three pairs 301, 302, 303, is fixed by the moving device 314. A second pulley arm 322 of the three pulley arms 321-323, which bears a second pair of pulleys 302 of the three pairs 301-303, is held by the moving device 314 such as to be protractible and retractable in a further reshaping direction 312 that is perpendicular to the longitudinal direction 310 of the continuous material 104, and additionally to be rotatable in a rotational direction 313 around a rotation center 315 located in the moving device 314. A third pulley arm 323 of the three pulley arms 321, 322, 323, which bears a third pair of pulleys 303 of the three pairs 301-303, is held by the moving device 314 such as to be protractible and retractable in a reshaping direction 311 that is perpendicular to a longitudinal direction 310 of the continuous material 104.
The heating device 120 of the manufacturing apparatus 116 of the present disclosure is, as shown in
In the operation, the moving device 314 is controlled by a controller (not shown), which may be implemented by the controller 124 shown in
A method of manufacturing a fiber-reinforced thermoset composite by the embodiment of
In the first phase 521, steps 500, 502 are performed. In step 500, the first portion 101 of the continuous material 104 comprised of the reinforcement fibers 106 which are impregnated with a heat curable thermosetting resin is pulled through the pultrusion die 200. The continuous material 104 is configured to be heatable by being subjected to a field of electromagnetic microwaves, e.g. by including an appropriate amount of electrically conductive reinforcement fibers or/and including an appropriate amount of electrically conductive or bipolar filler material in the thermosetting resin. Step 502 is carried out concurrently with step 500 as a part of the first phase 521, the first portion 101 is subjected in the pultrusion die 200 to the fields of electromagnetic microwaves 211, 212 to heat the first portion 101 to at least a curing temperature of the thermosetting resin.
Next, a second phase 522 is performed which includes carrying out two steps 504, 506. In step 506, the fields of electromagnetic microwaves 211, 212 used in step 502 of the first phase 521 is switched off. Then, in step 504, the second portion 102 of the continuous material 104 is being pulled through the pultrusion die 200. Because the fields of electromagnetic microwaves 211, 212 have been switched off, the second portion 102 is not heated to the curing temperature, which is different from the first portion 101 in step 502 of the first phase 521.
Subsequently, in step 508, the second portion 102 of the continuous material 104 is reshaped. In step 510, the second portion 102 is heated to at least the curing temperature of the thermosetting resin. In alternative embodiments, steps 508 and 510 may also be performed simultaneously. After the second portion 102 has been cured, the fiber-reinforced thermoset composite that includes both the first portion 101 and the second portion 102 is removed from the remaining continuous material 104.
The method as described with reference to
Furthermore, such continuous pulling action on the continuous material 104 may continue after step 504 after the second portion 102 leaves the pultrusion die 200. In this way, while performing steps 508-510 for the first and second portions 101, 102 as described above, a next process using the method as described above may be started, in order to produce a further fiber-reinforced thermoset composite. According to the method of the present disclosure, a sequential manufacturing of fiber-reinforced thermoset composites is possible.
Number | Date | Country | Kind |
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10 2014 202 352.1 | Feb 2014 | DE | national |