RECYCLING OF FIBER-REINFORCED COMPOSITE MATERIAL USING ELECTROMAGNETIC RADIATION

Systems, methods, and devices for providing a recycling technique for fiber-reinforced composite material using electromagnetic radiation. The recycling technique comprising selecting one or more parameters for a microwave system, orienting the fiber-reinforced composite material within a microwave chamber of the microwave system, microwaving the fiber-reinforced composite material using electromagnetic radiation based on the selected one or more parameters to expel a plurality of fibers from the fiber-reinforced composite material, and collecting the expelled plurality of fibers and remaining matrix material from the microwave chamber.

BACKGROUND

Embodiments of the present disclosure generally relate to the recycling of fiber-reinforced composite material. More specifically, embodiments of the present disclosure relate to using electromagnetic radiation, such as radio frequency radiation or microwave radiation, to expel fibers from fiber-reinforced composite material.

2. Related Art

Fiber-reinforced composites such as carbon fiber-reinforced polymers have been used to make a variety of parts in many industries. For example, fiber-reinforced composites are used to make parts of aircrafts, boats, trains, cars, and wind turbines. Further, fiber-reinforced composites are expanding into other industries and are becoming prevalent in daily life. However, fiber-reinforced composites are difficult to recycle due to the fibers being interspersed within the matrix material. Current methods of dealing with fiber-reinforced composites include incineration or burying in a landfill. Said methods incur more expensive production costs of new fiber-reinforced composites, as well as the costs of disposing of old fiber-reinforced composites.

SUMMARY

Embodiments of the present disclosure solve the above-mentioned problems by providing systems, methods, and devices for recycling fiber-reinforced composite material by utilizing electromagnetic radiation to separate fiber materials from the composite materials that allows for the recycling of the fiber and composite materials. Embodiments of the present disclosure avoid the high costs of producing new fiber-reinforced composite material and the wastefulness of disposing of fiber-reinforced composite material through incineration or landfilling.

In some aspects, the techniques described herein relate to a method for removing fibers from a fiber-reinforced composite material via electromagnetic radiation to prepare for a recycling process, the method including: placing the fiber-reinforced composite material within a microwave chamber, the fiber-reinforced composite material including glass fibers within a polymer matrix; causing the glass fibers to be expelled from the polymer matrix by exposing the fiber-reinforced composite material to variable-frequency electromagnetic radiation; and separating the glass fibers from the polymer matrix to render the polymer matrix suitable for the recycling process.

In some aspects, the techniques described herein relate to a method, further including: prior to microwaving, processing the fiber-reinforced composite material to increase a surface area of the fiber-reinforced composite material.

In some aspects, the techniques described herein relate to a method, further including: prior to microwaving, covering the fiber-reinforced composite material with an electromagnetic-radiation-permeable cover to contain the glass fibers expelled from the polymer matrix.

In some aspects, the techniques described herein relate to a method, wherein the fiber-reinforced composite material is exposed to the variable-frequency electromagnetic radiation to increase a temperature of the fiber-reinforced composite material at a predetermined ramp rate until the fiber-reinforced composite material reaches a predetermined target temperature and held at the predetermined target temperature for a predetermined hold time.

In some aspects, the techniques described herein relate to a method, wherein the predetermined ramp rate is 5° C. per minute and the predetermined hold time is at least 7 minutes.

In some aspects, the techniques described herein relate to a method, wherein the variable-frequency electromagnetic radiation is within a frequency range of 27 MHz to 300 GHz.

In some aspects, the techniques described herein relate to a method, further including: after exposing the fiber-reinforced composite material to the variable-frequency electromagnetic radiation, reorientating the fiber-reinforced composite material within the microwave chamber; and after reorientating the fiber-reinforced composite material, exposing the fiber-reinforced composite material to further variable-frequency electromagnetic radiation.

In some aspects, the techniques described herein relate to a method for removing fibers from a fiber-reinforced composite material via electromagnetic radiation to prepare for a recycling process, the method including: placing the fiber-reinforced composite material within a microwave chamber, the fiber-reinforced composite material including reinforcing fibers within a polymer matrix; causing the reinforcing fibers to be expelled from the polymer matrix by exposing the fiber-reinforced composite material to variable-frequency electromagnetic radiation to increase a temperature of the fiber-reinforced composite material at a predetermined ramp rate until the fiber-reinforced composite material reaches a predetermined target temperature and held at the predetermined target temperature for a predetermined hold time; and separating the reinforcing fibers from the polymer matrix to render the polymer matrix suitable for the recycling process.

In some aspects, the techniques described herein relate to a method, wherein the reinforcing fibers are a material selected from a set consisting of glass fibers, carbon fibers, metallic fibers, nylon fibers, organic fibers, silicon oxide fibers, or Kevlar® fibers.

In some aspects, the techniques described herein relate to a method, wherein the polymer matrix includes diallyl phthalate.

In some aspects, the techniques described herein relate to a method, wherein the fiber-reinforced composite material is exposed to the variable-frequency electromagnetic radiation by passing it through the microwave chamber on a conveyor belt for a predetermined number of cycles.

In some aspects, the techniques described herein relate to a method, wherein the predetermined target temperature is within a range from 170° C. to 180° C.

In some aspects, the techniques described herein relate to a method, wherein the predetermined ramp rate is at least 5° C. per minute.

In some aspects, the techniques described herein relate to a method, wherein the variable-frequency electromagnetic radiation is in a frequency range of 5.85 Ghz to 6.65 GHz.

In some aspects, the techniques described herein relate to a method for removing fibers from a fiber-reinforced composite material via electromagnetic radiation, the method including: placing the fiber-reinforced composite material within a microwave chamber, the fiber-reinforced composite material including reinforcing fibers within a polymer matrix; causing the reinforcing fibers to be expelled from the polymer matrix by exposing the fiber-reinforced composite material to variable-frequency electromagnetic radiation; and collecting the reinforcing fibers expelled from the polymer matrix.

In some aspects, the techniques described herein relate to a method, wherein the reinforcing fibers are chopped-glass fiber fibers.

In some aspects, the techniques described herein relate to a method, wherein the reinforcing fibers are continuous fiber reinforcement fibers.

In some aspects, the techniques described herein relate to a method, wherein the variable-frequency electromagnetic radiation is in a frequency range of 10 MHz to 300 GHz.

In some aspects, the techniques described herein relate to a method, wherein the reinforcing fibers are collected from a sacrificial, microwave-permeable coating of the microwave chamber.

In some aspects, the techniques described herein relate to a method, wherein the fiber-reinforced composite material is exposed to the variable-frequency electromagnetic radiation for a time within a range of 5 minutes to 2 hours.

DETAILED DESCRIPTION

The following detailed description of embodiments of the present disclosure references the accompanying drawings that illustrate specific embodiments in which the present disclosure can be practiced. The embodiments are intended to describe aspects of the present disclosure in sufficient detail to enable those skilled in the art to practice the present disclosure. Other embodiments can be utilized, and changes can be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense. The scope of embodiments of the present disclosure is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

Recycling of composite materials is sought after due to the possibility of reusing the fiber material, which is usually complicated and expensive to manufacture. Reusing the fiber and matrix materials to manufacture new composite parts may substantially reduce the high costs associated with producing fiber-reinforced composite parts. By recycling fiber-reinforced composites, overall composite waste that is transported to landfills or incinerated is reduced. Further, recycling avoids the high-cost, high-energy demand, and pollution associated with the above-mentioned disposal techniques of waste composites.

Embodiments of the present disclosure allow the fiber and matrix material to be reused separately by separating the materials using electromagnetic radiation. Embodiments of the present disclosure contemplate each material having little to no degradation of properties after being microwaved. In this description, references to “microwaving,” “microwaved,” or “microwave” mean expelling electromagnetic radiation, such as radio frequency and/or microwave radiation. For example, microwaving a composite part means expelling electromagnetic radiation towards the composite part. Further, expelling electromagnetic radiation may cause the object being microwaved to increase in temperature. Therefore, in some instances, references to “microwaving,” “microwaved,” or “microwave” may include heating with electromagnetic radiation.

FIG.1depicts an exemplary composite part10comprising a fiber-reinforced composite material12. In some embodiments, the fiber-reinforced composite material12comprises a matrix material14and a fiber material16. Matrix material14may comprise polymers, metals, ceramics, combinations thereof, or any other suitable matrix material. For example, the matrix material14may comprise a diallyl phthalate (DAP) polymer. Embodiments are contemplated in which the composite part10may comprise a different form of base material instead of a matrix-based material, such as a standard polymer or other material without a particular material matrix.

In some embodiments, the fiber material16may comprise any combination of glass fibers (including chopped glass fibers and continuous fibers), carbon fibers, metallic fibers, nylon fibers, organic fibers, silicon oxide fibers, or Kevlar® fibers, as well as other suitable fiber-like reinforcements. For example, the fiber material16may be a carbon fiber material such that fiber-reinforced composite material12is a carbon fiber-reinforced composite material. In some embodiments, the fiber material16may comprise any of calcium carbonate, hydrous aluminum silicate, alumina trihydrate, calcium sulfate, or fiberglass filler, as well as combinations thereof. For example, the fiber material16may comprise a fiberglass filler and be added to the matrix material14. In some embodiments, the orientation of the fiber material16within the fiber-reinforced composite material12may comprise any of the following: randomly distributed, aligned, unidirectional, bidirectional, continuous, or any other suitable orientation. For example, the composite part10may comprise polymers with fiberglass reinforcement in an aligned orientation.

In some embodiments, the composite part10may be sourced from finished composite parts comprising fiber-reinforced composite material. For example, composite part10may be sourced from at least a portion of aircraft walls, boat hulls, train panels, truck hoods, or wind turbine blades, as well as other suitable products comprising a fiber-reinforced composite material. Embodiments are contemplated in which composite part10may be sourced from other forms of recycled components from various other industries such as, for example, pipes, aerospace components, or automotive components, as well as other suitable components made with fiber-reinforced composite material. For example, composite part10may be sourced from components of a product comprising carbon fiber-reinforced composite material.

In some embodiments, the composite part10may be a composite component recycled from any suitable industry or previous application. For example, the composite part10may comprise any of a recycled composite pipe, a recycled aerospace component (e.g., a plane wing or other component), a recycled vehicle component, or another suitable recycled composite component. In some embodiments, the fiber-reinforced composite material12may be cured or uncured. For example, composite part10may be sourced from a product comprising a cured fiber-reinforced composite material.

FIG.2depicts an exemplary microwave system18. Microwave system18may be utilized to microwave one or more objects, such as composite part10as described above. For example, microwave system18may provide electromagnetic radiation (e.g., radio frequency radiation and/or microwave radiation) to microwave composite part10. In some embodiments, the microwave system18may comprise a radiation emission source20for providing electromagnetic radiation and a microwave chamber22for receiving the electromagnetic radiation provided by radiation emission source20.

In some embodiments, radiation emission source20may provide electromagnetic radiation directly to microwave chamber22. For example, radiation emission source20may be within or proximate microwave chamber22such that the electromagnetic radiation emitted from radiation emission source20is received directly by microwave chamber22. Alternatively, or additionally, radiation emission source20may be redirected towards microwave chamber. For example, radiation emission source20may be a distance away from microwave chamber22such that the electromagnetic radiation is directed towards the microwave chamber22from the radiation emission source20via one or more wave guides.

In some embodiments, radiation emission source20may provide electromagnetic radiation in the form of radio frequency radiation and/or microwave radiation. For example, radiation emission source20may provide electromagnetic radiation within a range of 27 megahertz (MHz) to 300 gigahertz (GHz). Radiation emission source20may be a magnetron configured to provide electromagnetic radiation to microwave chamber22. For example, microwave system18may comprise a magnetron (e.g., a cavity magnetron) for providing electromagnetic radiation to microwave chamber22. Embodiments are contemplated in which radiation emission source20may be any suitable device configured to provide electromagnetic radiation to microwave system18.

In some embodiments, microwave chamber22may have a volume of any shape. For example, the volume of the microwave chamber22may be cubic in shape, as depicted inFIG.2. Additionally, or alternatively, in some embodiments, microwave chamber22may be other suitable shapes such as a cylindrical shape, spherical shape, or shapes built on other polygons provided they are orthotropic in various x, y, z axis orientations. Embodiments are contemplated in which the microwave chamber22comprises any suitable shape with curved or straight interior walls.

In some embodiments, the shape of the microwave system18may be selected to achieve a particular level of microwave mode density as mode formation enhances the coupling of the power of the microwave system18to the composite part being heated. Additionally, or alternatively, the shape of the microwave chamber22is selected based at least in part on the frequencies expelled into the microwave chamber22. Embodiments are contemplated in which the shape and size of the microwave chamber22may be selected based at least in part on a shape and size of the composite part10such that the composite part10fits within microwave chamber22. In some embodiments, the microwave chamber22may be defined by one or more interior walls24encompassing a volume for receiving electromagnetic radiation. Further, in some embodiments, the number of interior walls24depends at least in part on the shape of the microwave chamber22.

Microwave chamber22may receive electromagnetic radiation (e.g., radio frequency radiation and/or microwave radiation) from microwave system18. In some embodiments, microwave system18may comprise a variable-frequency microwave (VFM) to provide electromagnetic radiation. A VFM is a type of microwave that utilizes varying frequencies of electromagnetic radiation to eliminate high microwave field strength locations on the surface of materials receiving the electromagnetic radiation due to the relatively uniform microwaving provided by the VFM across the substrate when compared to conventional fixed-frequency microwaving. A VFM also allows for the ability to microwave metallic materials due to the varied frequency of the electromagnetic excitation eliminating the charge buildup on edges of metallic materials that results in arcing from fixed-frequency microwaving. Embodiments are contemplated in which microwave system18may comprise a conventional fixed-frequency microwave. For example, microwave system18may comprise a fixed-frequency microwave to provide electromagnetic radiation to non-metallic composite parts.

In some embodiments, the volume of the microwave chamber22may be less than 5 cubic feet (ft3), less than 2 ft3, less than 1 ft3, within a range of 0.25 ft3to 30 cubic yards (yd3), within a range of 1 ft3to 10 yd3, within a range of 1 ft3to 5 yd3, or within a range of 1 ft3to 1 yd3. For example, the volume of microwave chamber22may be 1 ft3. However, it should be understood that other sizes and volumes not explicitly described herein are contemplated for the microwave chamber22. The microwave chamber22may be large enough such that at least a portion of aircraft walls, boat hulls, train panels, train panels, truck hoods, and wind turbine blades may be recycled. In some embodiments, the microwave chamber22may be large enough to fit entire composite parts as described herein into the microwave chamber22. For example, the microwave chamber22may be large enough to fit an entire boat hull into the microwave chamber22without any preprocessing.

In some embodiments, the frequency of the electromagnetic radiation provided by microwave system18to microwave chamber22may be anywhere from 27 MHz to 300 GHz. In some embodiments, the microwave system18may be configured to be pressurized. For example, one or more pumps may be coupled to the microwave chamber22to selectively alter a pressure within the microwave chamber22. Alternatively, or additionally, in some embodiments, the microwave system18may be configured to depressurize microwave chamber22to a pressure less than atmospheric pressure. For example, microwave system18may be configured to depressurize microwave chamber22to a vacuum state. Embodiments are also contemplated in which the microwave system18comprises an inert environment. For example, the microwave chamber22may be filled with inert gas to replace the air within the microwave chamber22.

In some embodiments, microwave system18further comprises an elevation mechanism25configured to elevate composite part10within microwave chamber22. In some embodiments, elevation mechanism25causes the composite part10to be a predetermined distance above the floor of microwave chamber22. Further, the elevation of composite part10within microwave chamber22may range on the floor (i.e., a bottom interior wall) of microwave chamber22to the ceiling (i.e., a top interior wall) of microwave chamber22. Accordingly, the elevation of composite part10within microwave chamber22may depend at least in part on the height of microwave chamber22. In some embodiments, elevation mechanism25may elevate composite part10to a high microwave field strength location within microwave chamber22. Elevation mechanism25may be any of a suspension device, an elevated platform, an elevation device, a turntable, as well as combinations thereof.

Embodiments are contemplated in which microwave system18may further comprise a turntable or conveyor belt configured to rotate or move composite part10within microwave chamber22. For example, microwave system18may comprise a turntable for receipt of composite part10such that composite part10rotates within microwave chamber22while receiving electromagnetic radiation from microwave system18. In some embodiments, using a turntable or other means of moving composite part10within microwave chamber22may reduce or eliminate low and/or high microwave field strength locations. Embodiments of a microwave system comprising a conveyor belt are described in more detail below atFIG.9.

FIG.3depicts an exemplary fiber-catching device26. Fiber-catching device26may provide one or more layers of protection between composite part10and one or more interior walls24of microwave chamber22. For example, fiber-catching device26may be positioned as a barrier between composite part10and one or more interior walls24of microwave chamber22. Accordingly, fiber-catching device may be utilized to intercept fiber material16expelled from fiber-reinforced composite material12as described in more detail below. Fiber-catching device26may be larger in size in comparison to composite part10such that the composite part10may be disposed or housed within a volume encompassed by fiber-catching device26. Additionally, the fiber-catching device26may be smaller than the microwave chamber22such that the fiber-catching device26may be inserted or disposed within the microwave chamber22. In some embodiments, fiber-catching device26may intercept expelled fibers to prevent at least a portion of the expelled fibers from escaping a microwave chamber. For example, fiber-catching device26may provide a barrier between an interior volume of a microwave chamber and the environment around the microwave chamber.

In some embodiments, the fiber-catching device26may be configured to provide a barrier between composite part10and interior walls24of microwave chamber22. For example, fiber-catching device26may be a dome-shaped layer positioned over composite part10to intercept at least a portion of fiber material16expelled from composite part10. In some embodiments, the fiber-catching device26may be a coating or thin layer deposited onto interior walls24of the microwave chamber22such that the expelled fibers are intercepted by the fiber-catching device rather than the interior walls24. Alternatively, fiber-catching device may be a thin layer of material disposed between composite part10and one or more interior walls24of microwave chamber22. It should be understood that fiber-catching device26may comprise an internal surface28used for catching fibers that have been expelled. Further, internal surface28may intercept the expelled fibers such that the fibers are not expelled outside of a volume encompassed by fiber-catching device26. For example, an internal surface28of a dome may prevent expelled fibers from escaping the volume encompassed by the dome.

In some embodiments, fiber-catching device26may be any of removable, sacrificial, temperature-resistant, or microwave-permeable, as well as combinations thereof. For example, fiber-catching device26may be microwave-permeable such that microwaves penetrate fiber-catching device26to microwave composite part10therein. In some embodiments, the fiber-catching device26may comprise a glass material, a silicon material, or a fused quartz material, as well as any other suitable material. For example, the fiber-catching device26may comprise a silicon or fused quartz material. In another example, the fiber-catching device26may be a glass dome configured to allow electromagnetic radiation to pass therethrough and be received by a fiber-reinforced composite part therein.

In some embodiments, the fiber-catching device26may be configured to withstand any of the following: high-pressure, low-pressure, or vacuum conditions. Embodiments are contemplated in which the fiber-catching device26may be removably couplable to one or more interior walls24of microwave chamber22. For example, the fiber-catching device26may be mounted within microwave chamber22via any suitable fastener or mounting means, such as, bolts, clips, adhesive, or another suitable attachment means.

FIG.4AandFIG.4Bdepict exemplary side views of the microwave system18microwaving the fiber-reinforced composite material12via electromagnetic radiation30. As depicted inFIG.4A, microwave system18may microwave a composite part10comprising the fiber-reinforced composite material12. As described above, the composite part10may comprise at least a portion of any of an aircraft wall, a boat hull, a train panel, a truck hood, or a wind turbine blade, as well as other suitable parts comprising a fiber-reinforced composite material. Embodiments are also contemplated in which a plurality of composite parts10are placed within the microwave chamber22to receive the electromagnetic radiation30from microwave system18.

Alternatively, or additionally, microwave system18may microwave one or more preprocessed composite parts32comprising the fiber-reinforced composite material12, as depicted inFIG.4B. Preprocessed composite part32may be formed by preprocessing composite part10into one or more smaller pieces (i.e., preprocessed composite part32). In some embodiments, preprocessing may include one or more of the following: shredding, chopping, cutting, mulching, or any other process suitable for reducing a size and/or increasing a surface area of an object. For example, preprocessed composite part32may be formed by cutting composite part10into one or more smaller pieces. In some embodiments, a plurality preprocessed composite parts32may be placed within the microwave chamber22to receive the electromagnetic radiation30from microwave system18.

Microwave chamber22may microwave composite part10and/or preprocessed composite part32using electromagnetic radiation30emitted by radiation emission source20. Accordingly, microwave system18may provide electromagnetic radiation30within the microwave chamber22to microwave composite part10and/or preprocessed composite part32. The electromagnetic radiation30provided within microwave chamber22may be dependent on one or more parameters selected for microwave system18. In some embodiments, the parameters may comprise any of frequency, power level, ramp rate, temperature, as well as combinations thereof. However, it should be understood that other parameters not explicitly described herein are contemplated.

The frequency of electromagnetic radiation30provided within microwave chamber22may be within a range of 10 MHz to 300 gigahertz GHz, within a range of 20 MHz to 300 GHz, within a range of 100 MHz to 300 GHz, within a range of 300 MHz to 300 GHz, within a range of 1 GHz to 300 GHz, or within a range of 5.85 GHz to 6.65 GHz. For example, radiation emission source20may provide electromagnetic radiation within a range of 27 MHz to 300 GHz. The power level of microwave system18may be within a range of 0% to 100%, within a range of 20% to 100%, within a range of 40% to 100%, or within a range of 60% to 100% of the maximum power output of microwave system18. For example, microwave system18may be operated at a power level within the range of 40% to 100% of the maximum power output of microwave system18. In some embodiments, the maximum power output of microwave system18may be within a range of 50 W to 2,000 W, within a range of 100 W to 1,000 W, within a range of 150 W to 500 W, within a range of 175 W to 250 W, within a range of 600 W to 1,700 W, within a range of 600 W to 800 W, within a range of 800 W to 1,000 W, or within a range of 1,000 W to 1,200 W. For example, the maximum power output may be 200 W for microwave system18.

As used herein, “ramp rate” may refer to a rate of temperature change within the microwave chamber per unit of time. The ramp rate may be less than 15 degrees Celsius per minute (° C./min), less than 10° C./min, less than 5° C./min, within a range of 1° C./min to 15° C./min, within a range of 2° C./min to 10° C./min, or within a range from 2.5° C./min to 7.5° C./min. For example, the ramp rate may be 5° C./min. The temperature within microwave chamber22may be within a range of 20° C. to 300° C., within a range of 50° C. to 250° C., or within a range of 100° C. to 200° C. For example, the target temperature of microwave chamber22may be 175° C. As used herein, “target temperature” may refer to a temperature at which microwave system18is set to attempt to maintain. For example, having a target temperature of 175° C. may refer to microwave system18attempting to maintain a temperature of 175° C. and remain within a predetermined error range from the target temperature (e.g., within a range of 5° C. above and 5° C. below the target temperature).

In some embodiments, the parameters may be based at least in part on one or more properties of the fiber-reinforced composite material12. Additionally, or alternatively, the parameters may be based at least in part on one or more properties of the microwave chamber22. In some embodiments, the parameters may be selected to minimize damage to the composite part10. Further, in some embodiments, the parameters may be selected to avoid excess heating of the fiber-reinforced composite material12. In some embodiments, the parameters may be selected to expel a maximum amount of the fiber material16from composite part10. For example, by minimizing damage and maximizing fiber expulsion, a polymer may be rendered suitable for recycling.

Embodiments are also contemplated in which one or more composite parts10and/or one or more preprocessed composite parts32may be placed on a turntable or conveyor belt configured to rotate or move one or more composite parts10and/or one or more preprocessed composite parts32within microwave chamber22. For example, one or more preprocessed composite parts32may be placed on a conveyor belt configured to move the one or more preprocessed composite parts32through microwave chamber22. Continuous microwave systems comprising one or more conveyor belts are described further below inFIG.9.

FIG.5AandFIG.5Bdepict an exemplary side view of the microwave system18after microwaving composite part10. The microwaving process at least partially expels the fiber material16from the composite part10. In some embodiments, the composite part10expels most or all the fiber material16leaving behind a post-process matrix part36. In some embodiments, composite part10may expel greater than 70%, greater than 75%, greater than 80%, greater than 85%, greater than 90%, greater than 95%, greater than 99%, or greater than 99.9% of fiber material16. Further, expelling fiber material16may leave behind only the matrix material14, such that post-process matrix part36comprising matrix material14is left behind. In some embodiments, the expelled fibers38are expelled toward the interior walls24of the microwave chamber22. Further, in some embodiments, the expelled fibers38may at least partially cover one or more interior walls24of the microwave chamber22, as depicted inFIG.5A. In some embodiments, the fiber material16is expelled due to a transient dipole effect on the fiber material16polarizing the fiber material to the interior walls24of the microwave chamber22.

In some embodiments, as depicted inFIG.5B, a fiber-catching device26may be used such that the expelled fibers38are at least partially intercepted when traveling toward the interior walls24of the microwave chamber22and contained within the fiber-catching device26.FIG.5Bdepicts the fiber-catching device26intercepting and containing the expelled fibers38to prevent them from reaching one or more interior walls24of the microwave chamber22. In some embodiments, the fiber-catching device26may be similar to the dome depicted inFIG.3. In some embodiments, the fiber-catching device26may be a coating or thin layer added to the interior walls24of the microwave chamber22. Further, in some embodiments, the fiber-catching device26may be at least one of the following: removable, sacrificial, temperature-resistant, and microwave-permeable. The fiber-catching device26may ease the collection and cleanup of the expelled fibers38in comparison to the collection and cleanup of the expelled fibers from the interior walls24of the microwave chamber22by reducing the total surface area receiving the expelled fibers.

The fiber-catching device26may be configured to cover any number of interior walls24of the microwave chamber22. In some embodiments, one or more interior walls24may be protected from the expelled fibers38. For example, the microwave chamber22may comprise sensitive equipment (e.g., a vent) on at least one interior wall, and require the fiber-catching device26to prevent the expelled fibers38from interacting with the sensitive equipment. Embodiments are contemplated in which fiber-catching device26does not prevent the expelled fibers from reaching every interior wall24of microwave chamber22. For example, walls not comprising sensitive equipment (e.g., a bottom wall and/or floor of microwave chamber22) may still receive the expelled fibers38while using fiber-catching device26.

FIG.6depicts exemplary post-process materials34collected after microwaving the composite part10with electromagnetic radiation30. The post-process materials34may comprise a post-process matrix part36and expelled fibers38. The post-process matrix part36comprises the matrix material14and little to no fiber material16. For example, post-process matrix part36comprises less than 30%, less than 25%, less than 20%, less than 15%, less than 10%, less than 5%, less than 1%, or less than 0.1% fiber material16. The expelled fibers38may be collected from the interior walls of the continuous microwave chamber42using at least one of a fiber-catching device26, a moving mechanical collection technique, acoustical vibrations, or any other suitable collection technique. Embodiments are contemplated in which expelled fibers38are collected from the internal surface28of fiber-catching device26using at least one of a moving mechanical collection technique, acoustical vibrations, or any other suitable collection technique. For example, expelled fibers38may be collected from interior walls24of microwave chamber22and/or interior surface28of fiber-catching device26via scraping interior walls24and/or interior surface28.

The post-process matrix part36may be reused to create different composite parts comprising the matrix material14. For example, post-process matrix part36may be recycled and reinforced with a different fiber material to create a new composite part. Similarly, the expelled fibers38may be reused to create different composite parts comprising the fiber material16. In some embodiments, the collected post-process matrix part36and expelled fibers38may have little to no damage (e.g., scorching or charring) after being microwaved using electromagnetic radiation30. Further, in some embodiments, most or all the properties of the post-process materials34remain unchanged in comparison to the properties of their respective matrix material14and fiber material16. For example, the matrix of the matrix material14may still be intact after being microwaved and expelling fiber material16.

FIG.7depicts an exemplary graph including a target temperature of the composite part10(depicted as Target T), a temperature of the composite part10measured using a fiber optic probe (depicted as FO T), an average power for the microwave system18(depicted as Avg P), an average forward power in the microwave system18(depicted as Avg FP), and an average reverse power in the microwave system18(depicted as Avg RP) for an exemplary microwaving of composite part10. As described above, a target temperature of the composite part10may refer to the temperature at which the composite part10is attempted to be maintained. Embodiments are contemplated in which the target temperature of the composite part10defines a ramp rate. As described above, the ramp rate may refer to the change in the target temperature of the composite part10over time. In some embodiments, the ramp rate may be within a range of 0° C. per second (° C./s) to 20° C./s, within a range of 0° C./s to 10° C./s, within a range of 0° C./min to 30° C./min, within a range of 0° C./min to 20° C./min, within a range of 0° C./min to 15° C./min, or within a range of 0° C./min to 10° C./min.

In some embodiments, the average power set for the microwave system is the power required to keep the temperature of the composite part10within a set error percentage of the target temperature of the composite part10. The range for the set power may range from 0% to 100% of the maximum power output of the microwave system18. For example, for a microwave system18having a maximum power output of 180 Watts (W), the power may range from 0 W to 180 W. In some embodiments, the maximum power output of microwave system18may be within a range of 50 W to 2,000 W, within a range of 100 W to 1,000 W, within a range of 150 W to 500 W, within a range of 175 W to 250 W, within a range of 600 W to 1,700 W, within a range of 600 W to 800 W, within a range of 800 W to 1,000 W, or within a range of 1,000 W to 1,200 W.

The average forward power may refer to the power coupled into the microwave system18. The average forward power in the microwave chamber22may depend at least in part on the set power of the microwave chamber22. In some embodiments, the average forward power may range from 0% to 100% of the maximum power output of the microwave system18. The average reverse power may refer to the portion of power not coupled into the microwave system18. In some embodiments, the average reverse power may range from 0% to 100% of the maximum power output of the microwave system18.

In some embodiments, the microwave chamber22may be run in an open loop configuration in which there is no feedback to correct the parameters of the microwave system18. Alternatively, or additionally, the microwave system18may be run in a closed loop configuration in which there is feedback to control the parameters of the microwave system18. For example, the power of the microwave system18may be controlled using a closed loop configuration by measuring the actual power expelled by microwave system18and correcting the set power of microwave system18to correct the measured power to be within a range of error percentages from the desired power of microwave system18. Further, for example, the power of the microwave may be adjusted such that the temperature of the composite part10is within a range of error percentages of the target temperature of the composite part10.

As depicted inFIG.7, the target temperature of composite part may be 175° C., the ramp rate may be 5° C./min, and the target temperature may be held for 7 minutes. The microwaving example depicted inFIG.7resulted in glass fiber expulsion from a composite part.

FIG.8depicts an exemplary method800of recycling fiber-reinforced composite material12. At step802, an optional preprocessing of the composite part10may be performed. In some embodiments, this preprocessing step may include one or more of the following: shredding, chopping, cutting, mulching, and any other process suitable for preparing material to be recycled. For example, an aircraft wall may need to be cut into smaller pieces in order to fit into the microwave chamber. Further, for example, a boat hull may be shredded to allow more surface area to be exposed for the fiber expulsion during microwaving, especially for a continuous microwaving process utilizing a conveyor belt system. Alternatively, in some embodiments, the microwave chamber22may be large enough to hold entire large parts. For example, the microwave chamber22may be large enough to fit an entire boat hull into the microwave chamber22without the preprocessing step.

At step804, one or more parameters for the microwave system18may be selected. In some embodiments, the parameters selected may include any of a time of microwaving, a time for holding a target temperature, a power of the electromagnetic radiation30, a target temperature the composite part10, a temperature within microwave chamber22, and a ramp rate. Composite part10may be microwaved for a time within a range of 1 minute to 3 hours, 5 minutes to 2 hours, 10 minutes to 1 hour, 15 minutes to 55 minutes, or 20 minutes to 50 minutes. For example, composite part10may be microwaved for 45 minutes. Embodiments are contemplated in which other microwaving times such as less than 1 minute and/or greater than 3 hours may be utilized if they expel at least a portion of fiber material16from composite part10. In some embodiments, the target temperature may be held for a predetermined time. For example, the target temperature may be held for a time of less than 1 minute, less than 2 minutes, less than 5 minutes, within a range of 1 minute to 20 minutes, within a range of 2 minutes to 15 minutes, within a range of 5 minutes to 10 minutes, or greater than 20 minutes. For example, the target temperature may be held for 7 minutes to expel fibers from a composite part.

The frequency of electromagnetic radiation30provided within microwave chamber22may be within a range of 10 MHz to 300 gigahertz GHz, within a range of 20 MHz to 300 GHz, within a range of 100 MHz to 300 GHz, within a range of 300 MHz to 300 GHz, within a range of 1 GHz to 300 GHz or within a range of 5.85GHz to 6.65GHz. For example, radiation emission source20may provide electromagnetic radiation within a range of 27 MHz to 300 GHz. The power level of microwave system18may be within a range of 0% to 100%, within a range of 20% to 100%, within a range of 40% to 100%, or within a range of 60% to 100% of the maximum power output of microwave system18. For example, microwave system18may be operated at a power level within the range of 40% to 100% of the maximum power output of microwave system18. In some embodiments, the maximum power output of microwave system18may be within a range of 50 W to 2,000 W, within a range of 100 W to 1,000 W, within a range of 150 W to 500 W, within a range of 175 W to 250 W, within a range of 600 W to 1,700 W, within a range of 600 W to 800 W, within a range of 800 W to 1,000 W, or within a range of 1,000 W to 1,200 W. For example, the maximum power output may be 200 W for microwave system18.

The ramp rate may be less than 15 degrees Celsius per minute (C/min), less than 10° C./min, less than 5° C./min, within a range of 1° C./min to 15° C./min, within a range of 2° C./min to 10° C./min, or within a range from 2.5° C./min to 7.5° C./min. For example, the ramp rate may be 5° C./min. The temperature within microwave chamber22may be within a range of 20° C. to 300° C., within a range of 50° C. to 250° C., or within a range of 100° C. to 200° C. For example, the target temperature of microwave chamber22may be 175° C. In some embodiments, the target temperature is within the range 170° C. to 180° C. In some embodiments, the target temperature is within the range 150° C. to 200° C. In still other embodiments, the target temperature is within the range 100° C. to 250° C.

In some embodiments, the parameters may be based at least in part on properties of the fiber-reinforced composite material12. Additionally, or alternatively, in some embodiments, the parameters may be based at least in part on properties of the microwave system18, such as the shape and/or size of microwave chamber22. In some embodiments, the parameters may be selected to minimize or prevent damage (e.g., scorching or charring) to the composite part10. Additionally, or alternatively, the parameters may be selected to expel a maximum amount of the fiber material16from composite part10. For example, by minimizing damage and maximizing fiber expulsion, the leftover matrix material and expelled fibers may be suitable for recycling into new composite parts. In some embodiments, the parameters for the microwave system18are selected such that the microwaves interact with a particular material. For example, parameters such as microwave frequency may be selected such that the microwaves interact with the fiber material16without affecting the matrix material14or other base material.

At step806, the composite part10is placed into the microwave chamber22of microwave system18. The orientation of the composite part10may include any combination of an elevation of composite part10within microwave chamber22, a position of composite part10within microwave chamber22, or a rotation of composite part10and may be selected at least in part on properties of the microwave system18. For example, composite part10may be orientated at a high microwave field strength location within microwave chamber22. In another example, composite part10may be orientated at a center point within microwave chamber22such that the surface area of composite part10equally receives the electromagnetic radiation30from microwave system18. The orientation of the composite part10may be selected at least in part on properties of the composite part10. For example, based on the size and shape of the composite part10, the possible orientations of composite part10may be limited within the space of the microwave chamber22. In some embodiments, the composite part10may be placed in the center of the microwave chamber22to receive most of the electromagnetic radiation30. Alternatively, in some embodiments, the composite part10may be oriented in a non-central position of the microwave chamber22.

In some embodiments, the composite part10may be elevated from a bottom wall and/or floor of the microwave chamber22. Embodiments are contemplated in which the composite part10may be elevated using elevation mechanism25such as, for example, any of a suspension device, an elevated platform, an elevation device, a turntable, as well as combinations thereof. For example, the composite part10may be elevated using a grated ceramic platform such that the composite part10may be elevated to a high microwave field strength location within microwave chamber22. In some embodiments, elevating composite part10within microwave chamber22causes the composite part10to be a predetermined distance above the floor of microwave chamber22. Further, the elevation of composite part10within microwave chamber22may range on the floor (i.e., a bottom interior wall) of microwave chamber22to the ceiling (i.e., a top interior wall) of microwave chamber22. Accordingly, the elevation of composite part10within microwave chamber22may depend at least in part on the height of microwave chamber22.

At step808, the fiber-reinforced composite material12is microwaved using electromagnetic radiation30. The microwaving provided to fiber-reinforced composite material12during step808may be determined by the one or more parameters selected in step804. In some embodiments, the parameters selected may include any of a time of microwaving, a time for holding a target temperature, a power of the electromagnetic radiation30, a target temperature the composite part10, a temperature within microwave chamber22, and a ramp rate as described in step804. Microwaving the composite part10in the microwave chamber22, expels the fibers from the fiber-reinforced composite material12until most or all of the fibers within fiber-reinforced composite material12are removed. In some embodiments, fiber-reinforced composite material12may be microwaved until a predetermined amount or percentage of fibers are removed from fiber-reinforced composite material12. For example, fiber-reinforced composite material12may be microwaved until greater than 70%, greater than 75%, greater than 80%, greater than 85%, greater than 90%, greater than 95%, greater than 99%, or greater than 99.9% of fiber material16. In some embodiments, the fiber expulsion may be due to a transient dipole effect on the fiber material16polarizing to the interior walls24of the microwave chamber22. Expelling the fiber material16from the fiber-reinforced composite material12separates fiber-reinforced composite material12into a post-process matrix part36and the expelled fibers38.

At step810, the post-process matrix part36and expelled fibers38are collected separately. The expelled fibers38may be collected from the interior walls of the continuous microwave chamber42using at least one of a fiber-catching device26, a moving mechanical collection technique, acoustical vibrations, or any other suitable collection technique. The post-process matrix part36may be reused to create different composite parts comprising the matrix material14. For example, the matrix material14may be combined with a different fiber material to create a new composite part. Similarly, the expelled fibers38may be reused to create different composite parts comprising the fiber material16. For example, the expelled fibers38may be inserted into a different matrix material to make a new composite part. The collected post-process materials34may have little to no damage after being microwaved by the electromagnetic radiation30.

Further steps may be implemented in which after composite part10is microwaved, the composite part10may be repositioned and further microwaved. In some embodiments, the repositioning may include rotating the composite part10within the microwave chamber22. For example, the composite part10may be rotated partially or continuously to expose the side previously face-down during the first microwaving step. Additionally, or alternatively, in some embodiments, the repositioning may include changing the location of composite part10within the microwave chamber22. For example, the elevation or horizontal position of the composite part10within the microwave chamber22may change such that the composite part10may receive a different amount of electromagnetic radiation after repositioning compared to the first microwaving step. In some embodiments, the repositioning of the composite part10may be done manually by a user. Additionally, or alternatively, in some embodiments, the repositioning of the composite part10may be done automatically via computer program code.

In some embodiments, composite part10may be rotated or moved within microwave chamber22during the microwave process. For example, the bottom wall of the microwave chamber22may comprise a movable floor such that the composite part10may be moved during the microwaving process using a computer interface. In another example, microwave system18may comprise a turntable (e.g., elevation mechanism25) to rotate and/or move composite part10within microwave chamber22. In some embodiments, elevation mechanism25may change the elevation of composite part10during the microwave process. Embodiments are contemplated in which composite part10may be reorientated to then receive further microwaving from microwave system18.

Further steps may be implemented in which the composite part10may be oriented on a conveyor belt that moves through the microwave chamber22in a continuous process. Additionally, or alternatively, multiple composite parts may be continuously oriented on the conveyor belt by hand or autonomously. The expelled fibers38may be collected from the interior walls24of the microwave chamber22using at least one of a fiber-catching device26, a moving mechanical collection technique, acoustical vibrations, or any other suitable collection technique. Alternatively, or additionally, the expelled fibers38may be collected continuously or after a selected time period has passed ranging from30minutes to a few days. The post-process matrix part may be collected at the end of the conveyor belt via the use of collection bins or other suitable collecting techniques. Embodiments are contemplated in which the composite part10may take multiple trips through the microwave chamber22to expel most or all fibers within composite part10. Alternatively, or additionally, embodiments are contemplated in which the composite part10may go through multiple microwave chambers of varying or similar parameters along the conveyor belt system. Continuous microwave systems are further described below inFIG.9.

Further steps may be implemented in which after composite part10is microwaved, one or more parameters described herein may be altered in preparation for further microwaving of composite part10. For example, a first microwaving step may be done at a lower power to the composite part10followed by a second microwaving step at a higher power to finish expelling the fibers from the composite part10. In some embodiments, a first set of parameters may be selected for a first microwaving step and a second set of parameters may be selected for a subsequent microwaving step. In some embodiments, altering the parameters may be done manually by a user. Additionally, or alternatively, in some embodiments, altering the parameters may be done automatically via computer program code. Further, in some embodiments, the parameters may be changed during the microwave process.

Further steps may be implemented in which fiber-reinforced composite parts made of recycled materials may be recycled again using the steps listed above. In some embodiments, the recycled materials may be recycled multiple times. For example, a boat hull made from recycled matrix material with new fiber reinforcement may be preprocessed and microwaved to separate the matrix material again to recycle the matrix material into another composite part.

FIG.9depicts an exemplary continuous microwave system40comprising a continuous microwave chamber42and a conveyor belt44to move one or more composite parts (e.g., composite part10and/or preprocessed composite part32) through the continuous microwave chamber42. In some embodiments, continuous microwave chamber42may be similar to microwave chamber22. For example, continuous microwave chamber42may be defined by one or more interior walls. In some embodiments, continuous microwave chamber comprises one or more openings for allowing fiber-reinforced composite material12to enter and/or exit through. For example, conveyor belt44may lead through an opening to move fiber-reinforced composite material12through continuous microwave chamber42. In some embodiments, continuous microwave chamber42may comprise one or more openings that in response to a force pushing against the one or more openings. For example, continuous microwave chamber42may comprise one or more flaps configured to flex or hinge and open when pushed against by fiber-reinforced composite material12moving along conveyor belt44. As depicted inFIG.9, fiber-catching device26may be one or more flaps configured to intercept fibers expelled towards an opening of continuous microwave chamber42. Accordingly, fiber-catching device26may flex or hinge when pushed by fiber-reinforced composite material12moving along conveyor belt44.

The conveyor belt44may move the one or more composite parts from a loading point of conveyor belt44to an end point of conveyor belt44in direction46through the continuous microwave chamber42. In some embodiments, the conveyor belt44may extend past the continuous microwave chamber42and be utilized for other processes and transportation purposes. For example, the conveyor belt44may first lead to a preprocessing system that preprocesses one or more composite parts before being transported through the continuous microwave chamber42. Further, for example, the conveyor belt may lead to a post-processing step that further prepares one or more post-process matrix parts36to be recycled into new fiber-reinforced composite material.

In some embodiments, multiple conveyor belts may travel through the continuous microwave chamber42. Embodiments are contemplated in which the preprocessed composite parts32may take multiple trips through the continuous microwave chamber42to expel most or all fiber material16from fiber-reinforced composite material12. For example, the preprocessed composite parts32may go through the continuous microwave chamber42in direction46and then go back through the continuous microwave chamber42in a direction opposite of direction46. In some embodiments, the preprocessed composite parts32are passed through the microwave chamber for a predetermined number of cycles. Alternatively, or additionally, embodiments are contemplated in which the preprocessed composite parts32may go through multiple continuous microwave chambers of varying or similar parameters along the conveyor belt44. In some embodiments, the conveyor belt44may divide into different tracks to sort different types of composite materials and direct them towards separate continuous microwave chambers with tuned parameters selected for the type of composite materials. Further, in some embodiments, the conveyor belt system may comprise multiple input sections where composite materials are placed onto the conveyor belt44and multiple output sections where the post-process materials34are removed from the conveyor belt44.

In some embodiments, the conveyor belt44may stop for a period of time to allow the preprocessed composite parts32to remain within the continuous microwave chamber42for the period of time. In some embodiments, the time between stops may depend at least in part on the fiber-reinforced composite material12. In some embodiments, this period of time may range from a few seconds to multiple hours. For example, the conveyor belt44may stop movement of the preprocessed composite parts32for an hour before continuing movement again. In some embodiments, the time between the stopping of the conveyor belt44may depend at least in part on the spacing of the preprocessed composite parts32. Additionally, or alternatively, the time between the stopping of the conveyor belt44may depend at least in part on the fiber-reinforced composite material12. In some embodiments, the speed of the conveyor belt may range from 0 meters per second to 10 meters per second.

The expelled fibers38may be collected from the interior walls of the continuous microwave chamber42using at least one of a fiber-catching device26, a moving mechanical collection technique, acoustical vibrations, or any other suitable collection technique. For example, brushes may be utilized to remove the expelled fibers38from the continuous microwave chamber42. In some embodiments, a tube insert may be placed at least partially within the continuous microwave chamber42such that the tube intercepts and contains the expelled fibers38. Further, in some embodiments, the tube may move in direction46with the conveyor belt44such that the expelled fibers38may be collected continuously as the conveyor belt44moves in direction46. The expelled fibers38may be collected continuously or after a selected time period ranging from 30 minutes to 5 days. For example, a thin layer deposited onto the inside walls of the continuous microwave chamber42may be used to catch the expelled fibers38and may be replaced after a predetermined amount of time has passed to prevent over-accumulation of the expelled fibers38.

Although the present disclosure has been described with reference to the embodiments illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the present disclosure as recited in the claims.

Having thus described various embodiments of the present disclosure, what is claimed as new and desired to be protected by Letters Patent includes the following: