Patent ID: 12220864

DETAILED DESCRIPTION

The devices, systems, and methods disclosed herein provide for curing of composites without the need for an autoclave. The devices include a conductive layer that can be formed through additive manufacturing. When electrical current is passed through the conductive layer, the conductive layer “self-heats” by Joule heating to cause the resin of a composite placed on the conductive layer to cure. Because the device itself creates enough heat to cure the composite, the uncured composite and the tooling device do not need to be placed in an autoclave for curing.

The devices have a high glass transition temperature (Tg) for high-temperature curing of composites. This new tooling design offers rapid and flexible design and manufacturing of high-performance tooling, eliminates the need for expensive resources (i.e., ovens and autoclaves), and can make composite manufacturing more accessible, energy-efficient, and cost-effective.

The devices, systems, and methods disclosed herein include conductive nanoparticles (e.g., carbon nanotubes, carbon nanofibers, graphene, carbon black, carbon nanofibers, etc.) mixed with polymers to enhance their electrical conductivity and create printable conductive polymers that can conduct electrical current and produce heat by Joule heating (i.e., resistive heating) effect. Using a multimaterial design approach, where the conductive polymer is printed on a non-conductive 3D-printed polymer substrate, allows for preventing any current loss and minimizing heat losses from the tooling to the surfaces under the tooling.

Both thermoset and thermoplastic polymer materials with a high temperature stability (including but not limited to epoxies, polyurethanes, cyclic olefins, acrylates, PEEK, PEKK, polyimidies, PPS, PES) can be used in the design of self-heated tooling using the methods disclosed herein. Flash-curable, high-performance thermosetting resin system based on dicyclopentadiene (DCPD) and epoxies can be used to develop printable inks by modifying the base resin system with electrically conductive and non-conductive particles. This novel resin system can instantaneously polymerize and cure printed materials following deposition from the printing nozzle without an additional post-curing step. The inks can therefore be used to produce various tooling geometry without additional support materials (i.e., in-the-air printing) for curing fiber-reinforced polymer composites based on the integrated self-heating capability.

The tooling design comprises two main material systems, namely, electrically conductive, self-heating surface layer(s) and a non-conductive host material. The non-conductive layering is the base of the tooling to electrically isolate and protect the electrically conductive layer, which becomes the heating element. Both inks utilize the same matrix resin (e.g., DCPD) to minimize the difference in thermal expansion and to improve the interlaminar properties of printed tooling. Carbon nanotubes can be used in the conductive ink as a conductive nanoparticle and rheology modifier whereas fumed silica can be used in the non-conductive material as a rheology modifier (though other combinations of materials are envisioned). Upon printing and curing of the inks, the resulting polymeric materials have a high glass transition temperature, Tg, of ˜120° C., making the printed tooling suitable for curing composites at cure temperatures up to 100° C.

The self-heated tooling can be used to demonstrate out-of-oven curing of conventional composite materials using prepregs (i.e., pre-impregnated fabrics) or resin film infusion processing techniques. The self-heated tooling heats the composite layup directly via conduction as opposed to conventional convective heat transfer mechanisms, leading to energy-efficient curing of composites. In addition, this process is scalable and can be developed using inexpensive printers and a wide range of materials.

In addition to the demonstrated tooling design, this printing technique can be used to directly write/print functional materials (using various polymers, additives, particles, reinforcements, optical fibers) on exiting surfaces or printed structures for imparting multifunctional properties (including but not limited to electrical, electrothermal, electromagnetic shielding, piezoelectricity, structural health monitoring, and energy storage) to polymeric parts for use in various applications, including de-icing, wearable heaters, self-healing, shape memory polymers, and sensors.

Various implementations include a self-heating device. The device includes an electrically insulative layer, an electrically conductive layer, a first electrode, and a second electrode. The electrically insulative layer has a first surface and a second surface spaced apart from the first surface. The electrically conductive layer has a first surface and a second surface spaced apart from the first surface. The second surface of the conductive layer is coupled to the first surface of the insulative layer. The conductive layer includes a polymer. Conductive nanoparticles are embedded in the polymer. The first electrode and a second electrode are coupled to the conductive layer. The first electrode and the second electrode are spaced apart from each other and in electrical communication with each other through the conductive layer. The conductive layer produces heat through Joule heating when electrical current is passed through the conductive layer.

Various other implementations include a method of manufacturing a self-heating device. The method includes providing an electrically insulative layer as described above; disposing an electrically conductive layer onto the insulative layer as described above, wherein the conductive layer produces heat through Joule heating when electrical current is passed through the conductive layer; coupling a first electrode and a second electrode to the conductive layer as described above; and causing the conductive layer to cure.

Various other implementations include a method of manufacturing a polymer part using a self-heating tooling device. The method includes providing a self-heating tooling device, as described above; disposing a layer of resin onto the device and adjacent the first surface of the conductive layer such that the layer of resin is in thermal communication with the conductive layer; and causing electrical current to flow through the conductive layer to produce heat through Joule heating to cause the layer of resin cure into a polymer part.

FIGS.1-3show self-heating tooling devices100,200, according to various aspects of some implementations. The devices100,200each include a first electrically insulative layer110,210and an electrically conductive layer130,230. The device200shown inFIGS.2A and2Bfurther includes a second electrically insulative layer260but is shown prior to coupling electrodes to the device200, and the device100inFIGS.1A and1Bis shown with a first electrode152, a second electrode154but does not include a second insulative layer.

The first insulative layer110,210of the devices100,200shown inFIGS.1A-2Bhave a first surface112,212and a second surface114,214spaced apart from the first surface112,212. The first insulative layers110,210shown inFIGS.1A-2Bare made of dicyclopentadiene (DCPD) and have been created using additive manufacturing, as shown inFIG.3. The first insulative layer110shown inFIGS.1A and1Bis formed such that the first surface112defines a flat surface, however in implementations, such as the device shown inFIGS.2A and2B, the first insulative layer210of the device200is formed such that the first surface212defines a contour. This contoured shape defines the shape of the conductive layer230, and thus, the shape of the tooling device200and the at least the shape of the bottom surface of the part manufactured using the device200.

In some implementations, the first insulative layer is not created using additive manufacturing and is created using any other known technique of forming an electrically insulative part. In some implementations, the contour of the first surface of the first insulative layer is any other desired shape such that the device can be used to manufacture any other shape of a bottom surface of a part. In some implementations, the first surface of the first insulative layer does not define a contour and is flat. In some implementations, the first insulative layer is an electrically insulative surface and is not specifically manufactured for the device.

The electrically conductive layers130,230shown inFIGS.1A-2Bhave a first surface132,232and a second surface134,234spaced apart from the first surface132,232. The second surface134,234of the conductive layer130,230is coupled to the first surface112,212of the first insulative layer110,210, as shown inFIGS.1A-2B. The first surface132,232of the conductive layer130,230has a first portion142,242and a second portion144,244spaced apart from the first portion142,242.

Referring again toFIGS.2A and2B, because the second surface234of the conductive layer230is coupled to the contoured first surface212of the first insulative layer210, the first surface232of the conductive material230also defines a contoured shape. However, in implementations such as the device100shown inFIGS.1A and1B, the first insulative layer110does not include a contoured surface, and the first surface132of the conductive layer130includes a flat surface. In some implementations, the first insulative layer does not include a contoured surface, but the conductive layer has a variable thickness such that the first surface of the conductive layer includes a contoured surface. In some implementations, neither the first insulative layer nor the conductive layer include a contoured surface.

Like the first insulative layers110,210shown inFIGS.1A-2B, the conductive layers130,230also include DCPD. However, the conductive layers130,230also include conductive nanoparticles embedded within the DCPD. The nanoparticles embedded within the DCPD of the conductive layers130,230shown inFIGS.1A-2Bare carbon nanoparticles, but in other implementations, the conductive nano particles can include graphene, carbon black, carbon nanotube, carbon nanofiber, graphite, silver nanoparticles, copper nanoparticles, or any other electrically conductive material capable of being embedded within the polymer of the conductive layer and forming a continuously electrically conductive circuit through the conductive layer. In some implementations, the nanoparticles include nanotubes, nanofibers, or any other shape nanoparticles capable of being embedded within the polymer of the conductive layer and forming a continuously electrically conductive circuit through the conductive layer.

Making the first insulative layer110,210and conductive layer130,230ofFIGS.1A-2Bout of the same material minimizes thermal expansion during use. Although the first insulative layers110,210and conductive layers130,230shown inFIGS.1A-2Bboth include DCPD, in other implementations, one or both of the first insulative layer and conductive layer can include any other polymer, such as a thermosets (e.g., epoxies, vinyl esters, phenolics, acrylates, polyimides, or a hybrid thereof) and/or a thermoplastic (e.g., PEEK, PEKK, PES, PBS, PLA, Nylon, PET, PETG, ABS). In some implementations, one or both of the first insulative layer and conductive layer include any other material suitable for making a tooling device.

The first electrode152shown inFIGS.1A and1Bis coupled to the first portion142of the first surface132of the conductive layer130, and the second electrode154is coupled to the second portion144of the first surface132of the conductive layer130. Because the conductive layer130is electrically conductive, the first electrode152is in electrical communication with the second electrode154through the conductive layer130. When electrical current is passed through the conductive layer130, the resistance of the conductive layer130causes the conductive layer130to produce heat through Joule heating.

As discussed above, the device200shown inFIGS.2A and2Bincludes a second insulative layer260that has a first surface262and a second surface264spaced apart from the first surface262. The second surface264of the second insulative layer260abuts the first surface232of the conductive layer230, as shown inFIGS.2A and2B. Although the second insulative layer260provides an electrical insulation barrier between the conductive layer230and the manufactured part being formed on the tooling device200, heat can still transfer through the second insulative layer260. The second insulative layer260can also prevent sticking of the manufactured part being formed and the conductive layer230.

In some implementations, the device does not include a second insulative layer. In some implementations, the second insulative layer is separate from the device, such as a sheet of electrically non-conductive polymer, as shown inFIGS.5A and5B.

FIG.3shows the manufacturing of the device100ofFIGS.1A and1B. To manufacture the self-heating device100ofFIGS.1A and1Bdescribed above, an electrically insulative layer110is disposed on a build plate198such that the second surface114of the first insulative layer112abuts the build plate and the first surface112of the first insulative layer110faces away from the build plate. The first insulative layer110is then caused to cure.

Next the electrically conductive layer130is disposed onto the insulative layer110such that the second surface134of the conductive layer130is coupled to the first surface112of the first insulative layer110and the first surface132of the conductive layer130faces away from the first insulative layer110. As discussed above, the conductive layer130includes a polymer that has conductive nanoparticles embedded in the polymer.

A first electrode152is then coupled to the first portion142of the conductive layer130and a second electrode154is coupled to the second portion144of the conductive layer130such that the first electrode152and the second electrode154are spaced apart from each other and in electrical communication with each other through the conductive layer. The conductive layer130is then caused to cure.

A second insulative layer can then be optionally added such that the second surface of the second insulative layer is coupled to the first surface of the conductive layer and the first surface of the second insulative layer faces away from the conductive layer. The second insulative layer is then caused to cure.

In the method discussed above, the first insulative layer110, the conductive layer130, and the second insulative layer are each manufactured by additive manufacturing, as shown inFIG.3. However, in other implementations, one or more of the first insulative layer, the conductive layer, and the second insulative layer are manufactured by any other known method of forming a polymer.

In some implementations, a first insulative layer is not deposited on a build plate, and the conduct is disposed directly onto any other insulative surface. In some implementations, the first insulative layer, or conductive layer where a first insulative layer is not included, is not disposed onto a build plate.

Although the first insulative layer110in the method above is caused to cure prior to the conductive layer130being disposed on the first insulative layer110, in some implementations, the conductive layer is disposed on the first insulative layer prior to causing the first insulative layer to cure, and then both the first insulative layer and the conductive layer are caused to cure at the same time. Although the first electrode152and the second electrode154in the method above are coupled to the conductive layer130prior the conductive layer130being caused to cure, in some implementations, the first electrode and the second electrode are coupled to the conductive layer after the conductive layer is caused to cure.

FIGS.4-5Bshow the device ofFIGS.1A and1Bin use. To use the self-heating device100described above as tooling to manufacture a polymer part190, composite resin190is disposed onto the device100and adjacent the first surface132of the conductive layer130such that the composite resin190is in thermal communication with the conductive layer130. If the device200includes a second insulative layer260, such as the device200shown inFIGS.2A and2B, the composite resin is disposed directly onto the second insulative layer260. However, for implementations like the device100shown inFIGS.1A and1Bin which the device100does not include a second insulative layer, the composite resin190is disposed directly onto the first surface132of the conductive layer130. The tooling and composite resin190can be optionally placed within a flexible, vacuum sealed compartment, as shown inFIG.5A, to urge the composite resin190to conform the shape of the first surface132of the conductive layer130.

As shown inFIG.5B, the first electrode152and the second electrode154are coupled to an electricity source192such that the first electrode152and the second electrode154are in electrical communication through the conductive layer130. Electrical current is then caused to flow from the first electrode152, through the conductive layer130, and to the second electrode154to cause the conductive layer130to produce heat through Joule heating to cause the composite resin190cure into a polymer composite part190.FIGS.1B and2Bshow thermal images of each device100,200being heated to cure a composite resin190to form a part.FIG.5Bshows the composite part190after the resin has cured.

Although the above implementation of the device100is used as tooling for manufacturing of polymer parts, in some implementations, the devices disclosed herein can be used for any other purpose, such as in heat exchangers where controlled flow of heat is desired.

Examples

For proof of concept, a flat 40 mm×60 mm tool (effective heating area=40 mm×40 mm) was additively manufactured using both non-conductive and conductive materials. Two copper electrodes were attached to the tooling using a conductive adhesive to allow for connection to the power source (FIG.1A). The electrothermal performance (i.e., heat-generation capability) of the printed tooling were determined by measuring the temperature distribution of the tooling using an infrared thermal camera as a function of applied electric power (FIGS.1B and2B). As shown inFIGS.1B and2B, a uniform heat distribution is observed within the tooling.

The new multimaterial printing approach was also used to additively manufacture a non-flat tool (FIGS.2A and2B) to demonstrate the ability to fabricate self-heated tooling with complex geometries.

To demonstrate composite fabrication using self-heated tooling, a 3D-printed flat tool was used to cure a composite panel (40 mm×40 mm) via conventional vacuum-bagging of an out-of-autoclave carbon fiber/epoxy prepreg system (FIGS.5A and5B). Upon preparation of the layup and applying vacuum, electric current was applied to the tooling to heat it up at 80° C. for four hours and cure the composite material according to the manufacture's recommended cure cycle. The resulting composite panel was fully cured (degree of cure=98.6% determined from differential scanning calorimetry, DSC, measurement), indicating the effective and successful heating and curing of composite materials using the 3D-printed self-heated tool.

A number of example implementations are provided herein. However, it is understood that various modifications can be made without departing from the spirit and scope of the disclosure herein. As used in the specification, and in the appended claims, the singular forms “a,” “an,” “the” include plural referents unless the context clearly dictates otherwise. The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. Although the terms “comprising” and “including” have been used herein to describe various implementations, the terms “consisting essentially of” and “consisting of” can be used in place of “comprising” and “including” to provide for more specific implementations and are also disclosed.

Disclosed are materials, systems, devices, methods, compositions, and components that can be used for, can be used in conjunction with, can be used in preparation for, or are products of the disclosed methods, systems, and devices. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed that while specific reference of each various individual and collective combinations and permutations of these components may not be explicitly disclosed, each is specifically contemplated and described herein. For example, if a device is disclosed and discussed each and every combination and permutation of the device are disclosed herein, and the modifications that are possible are specifically contemplated unless specifically indicated to the contrary. Likewise, any subset or combination of these is also specifically contemplated and disclosed. This concept applies to all aspects of this disclosure including, but not limited to, steps in methods using the disclosed systems or devices. Thus, if there are a variety of additional steps that can be performed, it is understood that each of these additional steps can be performed with any specific method steps or combination of method steps of the disclosed methods, and that each such combination or subset of combinations is specifically contemplated and should be considered disclosed.