DE102018111643B4 - Electrical resistance heating element and method for the material connection of fiber-plastic composite components - Google Patents

Abstract

Electrical resistance heating element (104, 200, 300) for plasticizing fiber-plastic composite components (100, 102) on a common joint contact surface in order to bond the fiber-plastic composite components (100, 102) to one another, the Resistance heating element (104, 200, 300) has electrically conductive heating sections (202, 306) forming heating resistors and electrically insulating insulating sections (204, 302) acting between the heating sections (202, 306), characterized in that the heating sections (202, 306) individually and/or can be electrically acted upon separately in groups.

Description

The invention relates to an electrical resistance heating element for plasticizing fiber-plastic composite components on a common joining contact surface in order to bond the fiber-plastic composite components to one another. In addition, the invention relates to a method for the cohesive connection of fiber-plastic composite components at a common joint contact surface.

From the document DE 10 2011 114 306 A1 a method is known for joining at least two FRP components lying one on top of the other in a joining area by means of a metal joining element, whereby to fix the FRP components lying on top of one another in the joining area, a setting bolt as a joining element is first passed through the FRP components and then through a metal sheet in contact with the joining area is driven, and then by means of resistance or friction welding a material connection between the fastener and the sheet metal is made.

From the document DE 10 2012 216 255 A1 a device is known for the integral connection of two plastic components with a pressing device with which the plastic components to be joined can be pressed against one another, and a heating device with which the surface of at least one plastic component can be heated at least in sections to a predetermined temperature, the two plastic components and the device being connected to one another are relatively movable and are movable in a direction of movement relative to the device, wherein the plastic components are first heated at the joint and then pressed together.

From the German patent application filed on March 12, 2018 with the file number 10 2018 105 690.7 An electrical resistance heating layer is known for plasticizing fiber-plastic composite components on common joint contact surfaces in order to bond the fiber-plastic composite components to one another, the resistance heating layer having a heating power distribution that is individually adapted to the joint contact surfaces. In addition, from the German patent application filed on March 12, 2018 with the file number 10 2018 105 690.7 a method is known for producing such an electrical resistance heating layer, wherein first of all an individually required heating power distribution is determined taking into account geometric data of the joining contact surfaces and/or material data of the fiber-plastic composite components. In addition, from the German patent application filed on March 12, 2018 with the file number 10 2018 105 690.7 a known method for joining thermoplastic fiber-plastic composite components, wherein the fiber-plastic composite components are plasticized using an electrical resistance heating layer for mutual material connection on joint contact surfaces, wherein for plasticizing the fiber-plastic composite components on the joint contact surfaces such an electrical resistance heating layer is used.

The document DE 10 2010 007 824 A1 relates to a method for joining and producing carbon fiber composite components. the document DE 10 2010 007 824 A1 According to the report, carbon fiber textiles are used as heating elements for resistance welding, which are impregnated on their surfaces with a thermoplastic or soaked throughout. Using an impregnated carbon fiber textile, either two duroplastic components or blanks are connected, or a duroplastic component is connected to a thermoplastic component or blank, with the duroplastic components or blanks carrying a thin intermolecularly bonded thermoplastic film as a connection film, at least on a duroplastic surface facing the deimpregnated carbon fiber textile. In the case of the heating elements, the insulating thermoplastic matrix is removed in the area of a current introduction in order to form numerous contact points, so that the heating behavior of the carbon fiber textile prepreg is very even and a welding result that is even over the area is achieved. In the document DE 10 2010 007 824 A1 it is pointed out that unidirectional C-fiber elements are unfavorable for non-planar geometries in the welding plane.

The document WO 93/19926 A1 relates to heating elements for thermoplastic bonding. The heating elements each include a resistive heating material and a pair of electrical leads. the document WO 93/19926 A1 Accordingly, it is proposed to use an expanded metal as the resistance heating material, to attach the electrical lines to the ends thereof, to insert the resistance heating material with the electrical lines between two layers of electrical insulation and to laminate this structure with a thermoplastic material. According to one embodiment, a plurality of electrical leads are provided, which are arranged for sequential heating along the heating element, it being understood that cold spots can occur in the process.

The document DE 41 26 188 A1 relates to a method for attaching a heating element between an upper and a lower material, in which the upper material, the heating element and the Upholstery material are glued together using a thermoplastic adhesive and the heat required to melt and/or cure the adhesive is generated by means of the heating element. the document DE 41 26 188 A1 According to this, the heating element is made of textile knitwear, in which heating conductors running essentially parallel to one another are arranged, the average spacing of which is less than 10 mm. The heating element is constructed from a knitted textile fabric which consists at least partially of thermoplastic material.

The object of the invention is to improve a resistance heating element mentioned at the outset structurally and/or functionally. In addition, the invention is based on the object of improving a method mentioned at the outset.

The object is achieved with a resistance heating element having the features of claim 1. The object is also achieved with a method having the features of claim 7. Advantageous designs and developments are the subject matter of the dependent claims.

The fiber-plastic composite components can be vehicle components. The vehicle may be a land vehicle, automobile, aircraft, watercraft, or spacecraft. The fiber-plastic composite components can be fuselage parts of an aircraft. The fiber-plastic composite components can be wing parts of an aircraft.

The fiber-plastic composite components can be organic fibers such as aramid fibers, carbon fibers, polyester fibers, nylon fibers, polyethylene fibers, Plexiglas fibers and/or inorganic fibers such as basalt fibers, boron fibers, glass fibers, ceramic fibers, silica fibers, exhibit. The fibers may be woven, knitted, crocheted, braided or stitchbonded. The fibers can be present as a textile. The fibers can be single-layer or multi-layer. The fiber-plastic composite components can have a thermoplastic matrix material. The matrix material can have polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polysulfone (PSU), polyetherimide (PEI) and/or polytetrafluoroethene (PTFE). The fibers can be embedded in the matrix material.

The fiber-plastic composite components can each have at least one joint contact surface. The at least one joining contact surface can be flat. The at least one joining contact surface can be curved once or multiple times. The common mating pad may have a mating pad length and a mating pad width.

The resistance heating element can be used to arrange fiber-plastic composite components that are or are connected to one another between common joining contact surfaces. The resistance heating element can be used to plasticize the matrix material of the fiber-plastic composite components.

The heating sections can each have at least one electrical contact section individually or in groups. The at least one contact section can be arranged outside of the joining contact areas. A group of heating sections may comprise a plurality of heating sections arranged one after the other. A group of heating sections may comprise a plurality of heating sections arranged non-consecutively.

The heating sections may each have a thread-like or sheet-like shape. The heating sections can each extend along a path. The trajectory can be straight. The trajectory can be curvy. The heating sections can be oriented unidirectionally. The heating sections can be arranged parallel to one another, at least in sections. The heating sections may be spaced from each other. The heating sections can be at least approximately the same distance from one another. A density and/or orientation of the heating sections can be individually adjusted. The heating sections can have different distances from one another. The heating sections can extend in the longitudinal direction of the joining contact surface. The heating portions may extend in the mating pad width direction.

The resistance heating element can be permeable at least in sections for plasticized plastic material of the fiber-plastic composite components. The insulating sections can be plasticized. The heating sections can serve to plasticize the insulating sections. The heating sections can be made of a metal. The insulating sections can be made of a plastic. The insulating sections can be made of a thermoplastic material. The insulating sections can be made of a plastic that is compatible with a matrix material of the fiber-plastic composite components. In this context, “compatible” means in particular that the plastics can be connected to one another in a materially bonded manner. The insulating sections can be made of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polysulfone (PSU), polyetherimide (PEI) and/or polytetrafluoroethene (PTFE).

The resistance heating element can be designed as a hybrid fabric with thread-like heating sections and thread-like insulating sections. The hybrid fabric can have a first thread system with threads that are at least approximately parallel to one another and a second thread system with threads that are at least approximately parallel to one another. The first thread system and the second thread system can be crossed with one another. The first thread system can have heating sections. The first thread system can have heating sections and insulating sections. The first thread system can alternately have one or more heating sections and insulating sections. The second thread system can only have insulating sections.

The insulating sections can be formed using a carrier foil. The heating sections can be applied to the carrier film in an additive manufacturing process. The heating sections can be applied to the carrier foil by selective laser melting. The heating sections can be printed onto the carrier foil.

For the cohesive connection of fiber-plastic composite components, the fiber-plastic composite components can first be arranged on one another with the joining contact surfaces. The resistance heating element can be arranged between the joining contact surfaces. Electrical power can then be applied to the resistance heating element in order to heat the resistance heating element in such a way that the fiber-plastic composite components are plasticized at the joining contact surfaces and/or the insulating sections. The resistance heating element can be heated until the matrix material heats above a crystallite melting temperature and/or until the matrix material and/or the insulating sections have at least a sufficiently reduced viscosity. The matrix material and/or the insulating sections can be liquefied in the process. The liquefied matrix material of the fiber-plastic composite components to be connected to one another can diffuse through the heated resistance heating layer, so that the matrix materials of the fiber-plastic composite components and/or insulating section material mix at least in sections. In order to support the joining of the fiber-plastic composite components to one another, the fiber-plastic composite components can be moved relative to one another and/or the joining contact surfaces can be pressed against one another. Subsequent application of electrical power to the resistance heating element can be terminated, so that the resistance heating layer cools down and the matrix material and/or the insulating section material solidifies again.

Different electrical power can be applied to the heating sections individually and/or in groups. Different electrical power can be applied to the heating sections individually and/or in groups in order to bring about a different heat input. The heating sections can be supplied with different electrical power individually and/or in groups in order to achieve a homogeneously distributed heat input within the joining surface during the joining process, to compensate for increasing heat dissipation towards edge sections of the joining surface, to avoid temperature gradients across the joining zone and/or Avoid places of elevated and/or reduced temperature.

Electrical power can be applied to the heating sections at the same time. Electrical power can be applied to the heating sections individually and/or in groups one after the other. Electrical power can be applied to several heating sections at the same time.

In summary and presented in other words, the invention results in, among other things, the use of unidirectionally conductive welding elements in electrical resistance welding for the joining of thermoplastic fiber composite components.

In static and continuous resistance welding, advantages can be achieved by using welding elements consisting of conductive and insulating components. Functionalized welding elements can be used in an electrical resistance welding process in static and continuous form. The welding elements can be functionalized by unidirectionally conductive components. The welding elements can have hybrid fabrics or conductors fixed to carrier foils or also SLM-printed carrier foils. Conductivity can only exist in one direction. A degree of freedom in constructive design is high, conductor density and orientation can be varied.

In the static welding process, energy can be introduced in a targeted manner and a homogeneous temperature distribution can thus be achieved. Cooling down in edge areas can be counteracted by applying higher power there. The targeted energy input can bring about high strengths over the entire surface and thus improved component performance. Welding time can be shortened. Contacting can take place in multiple phases in order to be able to deliver different power levels to the functionalized welding element.

An area of elevated temperature along the weld line can be increased. As a result, on the one hand, a process time can be significantly shortened, because an energy input to a large number of successive electrical conductors can enable a significant increase in the feed rate of a welding tool. Depending on the number of contact points, speeds can be increased by a factor of 10. In this way, the profitability of a continuous electrical resistance welding process can be increased for a wide range of applications. In addition, a targeted energy input can enable a flatter temperature gradient over the course of the weld seam. This can lead to slower heating and, above all, cooling behavior and thus avoid mechanical and morphological weakening due to internal stresses, vacuoles, porosity or cracks.

In particular, “may” denotes optional features of the invention. Accordingly, there is in each case an exemplary embodiment of the invention which has the respective feature or features.

With the invention, an energy input can take place in a targeted manner. An energy input can be adjusted. A temperature distribution can be homogenized. An area of elevated temperature can be enlarged. Process times can be shortened. A feed rate can be increased.

A connection between thermoplastic fiber-plastic composite components can be improved. A firmly bonded connection over the entire joint contact surface can be guaranteed. A firmly bonded connection can also be ensured on edge sections. A load-bearing capacity of a connection between thermoplastic fiber-plastic composite components can be increased. These advantages can be realized for any geometries of joint contact surfaces. These advantages can be realized for non-rectangular geometries of mating contact surfaces. Restrictions regarding joint geometries can be overcome.

Exemplary embodiments of the invention are described in more detail below with reference to figures. Further features and advantages result from this description. Specific features of these exemplary embodiments can represent general features of the invention. Features of these exemplary embodiments that are associated with other features can also represent individual features of the invention.

• 1 ein Fügen thermoplastischer Faser-Kunststoff-Verbund-Bauteile mithilfe eines elektrischen Widerstandsheizelements mit Heizabschnitten und Isolierabschnitten,
• 2 ein als Hybridgewebe mit fadenartigen Heizabschnitten und fadenartigen Isolierabschnitten ausgeführtes Widerstandsheizelement,
• 3 ein Widerstandsheizelement, bei dem Isolierabschnitte mithilfe einer Trägerfolie gebildet und Heizabschnitte an der Trägerfolie angeordnet sind und
• 4 einen Temperaturverlauf bei einem kontinuierlichen Widerstandsschweißen mithilfe eines Widerstandsheizelements mit Heizabschnitten und Isolierabschnitten.

They show schematically and by way of example:

• 1 joining thermoplastic fiber-plastic composite components using an electrical resistance heating element with heating sections and insulating sections,
• 2 a resistance heating element designed as a hybrid fabric with thread-like heating sections and thread-like insulating sections,
• 3 a resistance heating element in which insulating portions are formed using a base sheet and heating portions are disposed on the base sheet, and
• 4 a temperature profile in a continuous resistance welding using a resistance heating element with heating sections and insulating sections.

1 shows a joining of thermoplastic fiber-plastic composite components 100, 102 using an electrical resistance heating element 104 with heating sections and insulating sections.

The fiber-plastic composite components 100, 102 have organic fibers such as aramid fibers, carbon fibers, polyester fibers, nylon fibers, polyethylene fibers, Plexiglas fibers and/or inorganic fibers such as basalt fibers, boron fibers, glass fibers, ceramic fibers , silicic acid fibers embedded in a thermoplastic matrix material such as polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polysulfone (PSU), polyetherimide (PEI) and/or polytetrafluoroethene (PTFE).

The fiber-plastic composite components 100, 102 each have a joint contact surface. First, the fiber-plastic composite components 100, 102 are arranged with their joint contact surfaces on one another, with the resistance heating element 104 being arranged between the joint contact surfaces. Electrical power is then applied to the resistance heating element 104 in order to heat the resistance heating element 104 in such a way that the matrix material of the fiber-plastic composite components 100, 102 liquefies at the joint contact surfaces. The liquid matrix material penetrates the resistance heating layer 104 and the liquid matrix material of the plastic composite components 100, 102 mixes, possibly with movement of the plastic composite components 100, 102 relative to one another and/or with mutual pressing of the joining contact surfaces. Electrical power is subsequently applied to the resistance heating element, so that the resistance heating element cools down and the matrix material solidifies again. The plastic composite components 100, 102 are then at the Joining contact surfaces connected to each other in a materially bonded manner.

The insulating sections may be made of a thermoplastic material such as polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polysulfone (PSU), polyetherimide (PEI) and/or polytetrafluoroethene (PTFE). In addition, the insulating sections can then be liquefied when the resistance heating element is heated, so that the liquid matrix material of the plastic composite components 100, 102 and the liquid insulating section material mix.

2 12 shows a resistive heating element 200, such as resistive heating element 104 in FIG 1 , which is designed as a hybrid fabric with thread-like heating sections, such as 202, and thread-like insulating sections, such as 204. The hybrid fabric has a first thread system 206 with parallel threads and a second thread system 208 with parallel threads. The thread systems 206, 208 are crossed with one another. The first thread system 206 has alternating heating sections 202 and insulating sections 204 . The second thread system 208 only has insulating sections 204 . The heating portions 202 each have a thread-like shape and extend parallel to and spaced from each other as shown in FIG 1 unidirectional perpendicular. The resistance heating element 200 is permeable to plasticized plastic material from fiber-plastic composite components.

3 12 shows a resistive heating element 300, such as resistive heating element 104 in FIG 1 , in which insulating sections such as 302 are formed using a carrier film 304 and heating sections such as 306 are arranged on the carrier film 304. The heating sections 306 are printed onto the carrier film 304 by selective laser melting. The heating sections 306 each have a sheet-like shape and extend parallel to one another and at a distance from one another in the illustration according to FIG 1 unidirectional perpendicular. The carrier film 304 is made from a plastic that is compatible with a matrix material of fiber-plastic composite components and can be plasticized with the aid of the heating sections 306 .

The resistance heating element 200, 300 serves to plasticize fiber-plastic composite components, such as fiber-plastic composite components 100, 102 according to FIG 1 , on a common joining contact surface in order to bond the fiber-plastic composite components to one another. The heating sections 202, 306 can each be electrically charged individually or separately in groups. For example, the heating sections 202, 306 are electrically charged sequentially one after the other, with a plurality of overlapping heating sections 202, 306 being electrically charged at the same time.

4 FIG. 4 shows a temperature curve 400 during continuous resistance welding using a resistance heating element, such as resistance heating element 104 according to FIG 1 , resistance heating element 200 according to FIG 2 or resistive heating element 300 according to FIG 3 , with heating sections and insulating sections. The temperature curve 400 is shown in a diagram 402 in which a time or a distance of a welding tool is plotted on an x-axis and a temperature is plotted on a y-axis.

A broad energy input range 404 results from sequentially following and overlapping simultaneous electrical charging of several heating sections.

Reference List

100

Fiber-plastic composite component

102

Fiber-plastic composite component

104

resistance heating element

200

resistance heating element

202

heating section

204

insulating section

206

thread system

208

thread system

300

resistance heating element

302

insulating section

304

carrier film

306

heating section

400

temperature curve

402

diagram

404

energy input area

Claims (9)

Electrical resistance heating element (104, 200, 300) for plasticizing fiber-plastic composite components (100, 102) on a common joint contact surface in order to bond the fiber-plastic composite components (100, 102) to one another, the Resistance heating element (104, 200, 300) has electrically conductive heating sections (202, 306) forming heating resistors and electrically insulating insulating sections (204, 302) acting between the heating sections (202, 306), characterized in that the heating sections (202, 306) individually and/or can be electrically acted upon separately in groups. A resistance heating element (104, 200, 300) according to at least one of the preceding claims, characterized in that the heating sections (202, 306) are unidirectionally oriented. Resistance heating element (104, 200) according to at least one of the preceding claims, characterized in that the resistance heating element is permeable at least in sections for plasticized plastic material of the fiber-plastic composite components (100, 102). Resistance heating element (104, 200, 300) according to at least one of the preceding claims, characterized in that the insulating sections (204, 302) can be plasticized. Resistance heating element (104, 200) according to at least one of Claims 1 until 4 , characterized in that the resistance heating element (104, 200) is designed as a hybrid fabric with thread-like heating sections (202) and thread-like insulating sections (204). Resistance heating element (104, 300) according to at least one of Claims 1 until 4 , characterized in that the insulating sections (302) are formed using a carrier film (304) and the heating sections (306) are arranged on the carrier film (304). Method for materially connecting fiber-plastic composite components (100, 102) on a common joining contact surface, characterized in that a resistance heating element (104, 200, 300) according to at least one of the preceding claims between the fiber-plastic composite to be connected - Components (100, 102) are arranged and the heating sections (202, 306) are electrically charged in order to plasticize plastic material of the fiber-plastic composite components (100, 102) and/or the insulating sections. procedure after claim 7 , characterized in that the heating sections (202, 306) are supplied individually and/or in groups with different electrical power. Method according to at least one of Claims 7 until 8th , characterized in that the heating sections (202, 306) are supplied with electrical power individually and/or in groups in succession.

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