GB2606977A

GB2606977A - Method

Info

Publication number: GB2606977A
Application number: GB2212106.5A
Authority: GB
Inventors: David Victor Maynard Jack
Original assignee: Darchem Engineering Ltd
Current assignee: Darchem Engineering Ltd
Priority date: 2022-08-19
Filing date: 2022-08-19
Publication date: 2022-11-23
Also published as: GB202212106D0

Abstract

The method comprises providing a starting material comprising constituent components of a composite material, the constituent components comprising a matrix component and a reinforcement component. The method further comprises applying electromagnetic radiation to the starting material to cure the starting material. The electromagnetic radiation may comprise microwave radiation, and the method may include holding the starting material against a forming tool, such as a mandrel tool, as the electromagnetic radiation is applied. Compression may be applied using negative pressure such as a vacuum. The starting material may comprise a fibre reinforced polymer (FRP) pre-preg material. The matrix component may comprise water, and the starting material may cure via a condensation reaction. The matrix may comprise a thermoset bioresin, polyfurfuryl alcohol (PFA) resin matrix. A cured composite and a component for an aircraft including the cured composite may be produced by the method.

Description

METHOD

FIELD

The present disclosure relates to a method of curing a starting material comprising constituent materials of a composite material. The disclosure also relates to a composite material produced by said method, and a component, in particular but not exclusively an aircraft component, comprising said material.

BACKGROUND

Modern aircraft typically include a large number of components made from composite materials. Widely used materials in aerospace today include CFRP prepreg materials and in many cases the majority of the airframe on modern airliners is composed of such materials.

Such composite materials are typically manufactured via a method comprising hand laying a prepreg composite material, placing in a vacuum bag and then placing in an oven or autoclave to cure. Often this is a timely and energy intensive process, often requiring purpose-built specialist and expensive hardware.

The build rate of an aircraft is often limited by the curing step of the required composite components. Accordingly, curing such components can be the rate-limiting step in aircraft manufacture.

It is an object of the present disclosure to overcome or substantially reduce the problems associated with the prior art.

SUMMARY

In a first aspect, a method of curing a starting material comprising constituent components of a composite material is provided, the method comprising: providing a starting material comprising constituent components of a composite material, the constituent components comprising a matrix component and a reinforcement component, and applying electromagnetic radiation to the starting material to cure the starting material.

Without wishing to be bound by any particular theory, it is believed that electromagnetic radiation heats water within the starting material e.g. within the matrix component. In this way, as the water in the starting material is heated by the incident radiation, the curing reaction rate of the starting material increases due to the increased temperature.

In this way, the starting materials are cured.

Furthermore, in some cases the starting material cures via a condensation reaction, thereby producing water, which can then also be heated by the incident radiation and in turn increase the temperature of the material. Additionally, in some cases, the condensation reaction is exothermic, thereby producing more heat as the reaction progresses, in turn further heating the starting material. This can create a runaway reaction in the starting material that greatly accelerates curing of the starting material in comparison to traditional methods.

It has been found that curing by the method disclosed herein can be carried out in seconds, rather than hours as is the case with traditional methods.

In this way, a manufacturing technique is provided by which cured composite articles or parts can be produced in much less time, at less expense, and with a much lower carbon footprint than is achievable using standard manufacturing techniques.

In the case where the curing cycle of the required aircraft parts is the rate-limiting step in an aircraft manufacturing process, the method disclosed herein enables this rate-limiting step in the manufacturing process to be accelerated, thereby speeding up the whole manufacturing process.

It will be appreciated that the method disclosed herein may be used to fully or partially cure the starting material.

In some embodiments, the matrix component comprises a continuous phase. In some embodiments, the reinforcement component is embedded in the matrix component. In some embodiments, the reinforcement component comprises a plurality of reinforcement components and the matrix component is arranged to bind the reinforcement components together.

In some embodiments, the matrix component comprises a binder. In exemplary embodiments, the matrix component may comprise a polymer, ceramic, metal or carbon matrix. In some embodiments the polymer matrix may comprise a resin.

In some embodiments, the matrix component may comprise a polymer matrix comprising at least one of: a thermoset polymer, polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, thermoplastic polymer, polypropylene, PEEK, poly(furfuryl alcohol) (PFA) and/or other suitable polymer.

In some embodiments, the reinforcement component(s) comprise continuous reinforcement, e.g. fibres, and/or ground minerals. In exemplary embodiments, the reinforcement component(s) comprise at least one of: carbon fibres, carbon fibre fabrics (e.g. woven, unidirectional), fibreglass fibres, fibreglass fabric, aramid fibres, fabric comprising aramid fibres, and/or other suitable materials.

In some embodiments, the starting material may comprise a partially cured material (e.g. a pre-preg material) and/or uncured material (i.e. wet material).

In some embodiments, the constituent materials may also comprise a core, e.g. an open-or closed-cell-structured foam e.g. polyvinylchloride, polyurethane, polyethylene and/or polystyrene foams; balsa wood; syntactic foams; materials comprising a honeycomb structure; and/or any other suitable core material.

In some embodiments, the starting material may be prepared via one or more of the following methods, or any other suitable method: pre-preg hand lay-up, pre-preg automated lay-up, composite wet lay-up, automated fibre placement, automated tape layup, filament winding, and/or vacuum resin infusion (any suitable variation thereof).

Optionally, wherein the electromagnetic radiation comprises microwave radiation.

The starting material (in particular the matrix component) has been found to readily absorb electromagnetic radiation, in particular electromagnetic radiation in the microwave region.

For example, the microwave radiation may comprise a wavelength in the range of about 0.3cm to 30cm.

Optionally, wherein the method comprises holding the starting material against a forming tool as the electromagnetic radiation is applied.

In this way, the starting material is cured whilst it is held against the forming tool. This enables a cured composite part to be formed which geometrically conforms to the shape of the forming tool.

In other words, the starting material is held against the forming tool as it cures.

Optionally, wherein the method comprises applying compression and/or negative pressure to the starting material as the electromagnetic radiation is applied.

In this way, compression applied to the starting material helps to prevent blistering of the starting material as it cures. For example, in some embodiments this acts to hold the matrix component (e.g. resin) within the reinforcement component (e.g. fabric) as the material cures.

In other words, compression is applied to the starting material as it cures.

Optionally, wherein the method comprises applying compression and/or negative pressure with an absolute pressure of 13 bara or less.

In some embodiments, an autoclave may be used. In some such embodiments, the pressure applied during compression may be in the range of 4-13 bara (commonly referred to as 3-12 bar i.e. the Gauge pressure).

Optionally, wherein the method comprises applying a vacuum to the starting material as the electromagnetic radiation is applied.

In other words, a vacuum is applied to the starting material as it cures.

Again, a vacuum applied to the starting material helps to prevent blistering of the starting material as it cures. For example, in some embodiments this acts to hold the matrix component (e.g. resin) within the reinforcement component (e.g. fabric) as the material cures.

Optionally, wherein the method comprises applying a vacuum to the starting material having an absolute pressure in the range of from about 0.01 bara to about to 0.5 bara, for example about 0.1 bara.

For example, where an autoclave is not used (e.g. out of autoclave (00A)), the absolute pressure applied during application of the vacuum may be in the range of approximately 0.01 bara (commonly referred to as -0.99 bar, i.e. the vacuum pressure) to 0.5 bara (commonly referred to as -0.5 bar, i.e. the vacuum pressure), for example 0.1 bara (commonly referred to as -0.9 bar, i.e. the vacuum pressure).

Optionally, wherein, application of electromagnetic radiation to the starting material produces a treated material, and wherein, following application of electromagnetic radiation, the treated material is allowed to cool while compression is applied to the treated material.

In some embodiments, the starting material cures to form the treated material, which may be fully or partially cured. In other words, the treated material may comprise the starting material which has fully or partially cured. In the case where the treated material is partially cured, it may continue to cure as it is allowed to cool.

In some embodiments, the treated material is passively allowed to cool, e.g. at room temperature. In some embodiments, the treated material is actively cooled e.g. by controlling the cooling rate of the material.

In some embodiments, the treated material is allowed to cool for up to about 60 minutes, for example up to about 45 minutes, for example up to about 30 minute, for example up to about 15 minutes, for example for about 5 minutes.

Optionally, wherein the method comprises providing a starting material comprising a fibre reinforced polymer (FRP) pre-preg material.

Optionally, wherein the starting material is configured to cure via a condensation reaction.

In this way, water is produced as the starting material cures. The produced water can then be heated by the incident radiation and in turn increase the temperature of the material, thereby increasing the curing reaction rate.

In this way, the starting material is not required to contain any water in order to be cured by the method disclosed herein.

Optionally, wherein the matrix component comprises water.

Optionally, wherein the matrix component comprises up to about 50% water.

In some embodiments, the matrix component comprises up to about 40% water, for example up to about 30% water, for example up to about 20% water, for example up to about 10% water, for example in the range of about 4 to 8% water, for example about 7.5% water.

Optionally, wherein the matrix component comprises a thermoset bioresin.

Bioresin is typically made from renewable sources (e.g. saccharidic feedstock) and so is beneficial for the environment. It is also typically beneficial in reusing waste (e.g. saccharidic feedstock that is a waste product from the sugar industry) and also in capturing carbon from the environment. In contrast, other matrix components (e.g. phenolic resins) are derived from fossil fuels.

Bioresin typically has high thermally stability with high service temperatures (e.g. of around 260°C but possibly up to 330°C and beyond for certain applications).

Bioresin is also typically cheaper than other resins.

Optionally, wherein the matrix component comprises a polyfurfuryl alcohol (PEA) resin matrix.

Optionally, wherein the electromagnetic radiation comprises electromagnetic waves, and wherein the method comprises varying the relative position and/or orientation of the starting material and the electromagnetic waves.

In this way, a more uniform application of electromagnetic radiation is provided to the starting material. In this way, the risk of the starting material burning is reduced.

Optionally, wherein the method is carried out in a curing volume and the electromagnetic radiation is applied in the curing volume, and wherein the method comprises rotating the starting material and the curing volume relative to each other.

Optionally, wherein the method is carried out in a curing volume, and wherein a radiation absorbing component is positioned in the curing volume.

In this way, the radiation absorbing component helps to diffuse hotspots in the curing volume by acting as a heatsink. This has been found to facilitate a more uniform application of electromagnetic radiation to the starting material. In this way, the risk of the starting material burning is reduced.

Optionally, wherein a plurality of radiation absorbing components are positioned in the curing volume.

Optionally, wherein the starting material defines a volume and at least one radiation absorbing component is provided in said defined volume.

Optionally, wherein the radiation absorbing component comprises a mandrel tool and wherein the method comprises positioning the starting material around the mandrel tool.

This arrangement has been found to be effective in diffusing hotspots in the curing volume by the mandrel tool acting as a heatsink. This has been found to facilitate a more uniform application of electromagnetic radiation to the material. In this way, the risk of the starting material burning is reduced.

In some embodiments, the starting material is wrapped around the mandrel tool.

Optionally, wherein the energy applied by the electromagnetic radiation to the starting material is 10.0 kJ/g or less, e.g. 5.0 kJ/g or less.

In some embodiments, the energy applied by the electromagnetic radiation is 2.5 kJ/g or less.

In an exemplary embodiment, electromagnetic radiation is applied at 350W for 100 seconds to a starting material of approximately 0.0288m2. In an exemplary embodiment, a 335gsm fabric is used, with a resin weight of 42%, giving a total weight of 475.7 gsm. In such embodiments, an energy of 2.5 kJ/g is applied.

In some embodiments, the electromagnetic radiation is applied at a power in the range of from about 200W to about 1000W, for example a power in the range of from about 300W to about 800W. In exemplary embodiments, a power of about 350W is used. In exemplary embodiments, a power of about 700W is used.

In some embodiments, the electromagnetic radiation is applied for about 100 seconds or less, for example about 80 seconds or less, for example about 60 seconds or less, for example about 30 seconds or less, for example about 60 seconds, for example about 30 seconds.

In some embodiments, the electromagnetic radiation is applied intermittently, and during each application, the electromagnetic radiation is applied for about 100 seconds or less, for example about 80 seconds or less, for example about 60 seconds or less, for example about 30 seconds or less, for example about 60 seconds, for example about 30 seconds.

In some embodiments, electromagnetic radiation may be applied for 30 minutes or less, e.g. 20 minutes or less, e.g. 10 minutes of less.

In a further aspect, a cured composite material produced by the method disclosed herein is provided.

In a further aspect, component (e.g. for an aircraft) is provided comprising a cured composite material produced by the method disclosed herein.

It will be appreciated that the optional features described herein may apply to any aspect disclosed herein. All combinations contemplated are not recited explicitly for the sake of brevity.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments disclosed herein will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates a flow diagram of a method in accordance with an embodiment of the invention; and Figure 2 illustrates a schematic diagram of a component comprising a cured composite material produced by the method of Figure 1.

DETAILED DESCRIPTION

With reference to Figure 1, a method 2 of curing a starting material including constituent components of a composite material is provided.

The method includes providing 4 the staffing material and applying electromagnetic radiation 6 to the starting material to cure the starting material. In the embodiment of Figure 1, the electromagnetic radiation includes microwave radiation.

The starting material includes constituent components of a composite material, including a matrix component and a reinforcement component. When fully cured, the starting material forms a cured composite material.

The provided starting material is positioned against a forming tool such that the starting material adopts a corresponding geometric shape as the forming tool as the starting material cures. In the exemplary embodiment of Figure 1, the starting material is wrapped around a forming tool 8 (e.g. a mandrel). In some embodiments, a forming tool may not be used.

Once the starting material is in a desired position, a vacuum is applied to the starting material 10 and the microwave radiation is applied 6.

In the embodiment of Figure 1, the vacuum acts to hold the starting material against the forming tool, and also to inhibit the matrix component (e.g. polymer resin) from seeping out of the reinforcement component. In other embodiments, any suitable means of holding the starting material against a forming tool may be used.

In the embodiment of Figure 1, in order to apply a vacuum to the starting material, the starting material is placed in a sealed vacuum bag, in accordance with techniques known in the art.

Microwave radiation is then applied to the starting material. As microwave radiation is applied to the starting material, the starting material cures such that it can be thought of as a "treated material". The treated material may comprise the starting material which has been fully cured, and/or may comprise the starting material which has been partially cured.

Following application of the microwave radiation, i.e. after application of microwave radiation has ceased 12, the treated material is allowed to cool 14 at room temperature. Alternatively, the treated material may be actively cooled at a temperature lower than room temperature. As the treated material is cooled, application of vacuum compression to the material is maintained. In cases where the treated material is partially cured after application of microwave radiation, it continues to cure as it cools.

In this way, a cured composite material can be produced.

Any suitable matrix component and reinforcement component may be used. For example, the matrix component may include a thermoset bioresin, for example a polyfurfuryl alcohol (PFA) resin matrix.

In some embodiments, the starting material includes a fibre reinforced polymer (FRP) pre-preg material. This type of material is typically easy to handle. Of course, alternative starting materials may be used.

In exemplary embodiments, the provided starting material includes an amount of water, e.g. the matrix component includes water.

In exemplary embodiments, the starting material is configured to cure via a condensation reaction.

Without wishing to be bound by any particular theory, it is believed that microwave radiation heats water within the starting material e.g. within the matrix component. In this way, as the water in the starting material is heated by the incident radiation, the curing reaction rate of the starting material increases due to the increased temperature. In this way, the starting material is cured.

In cases where curing is via a condensation reaction, i.e. which produces water, the produced water can then also be heated by the incident radiation and in turn increase the temperature of the material. Additionally, in some cases, the condensation reaction is exothermic, thereby producing more heat as the reaction progresses, in turn further heating the starting material and increasing the curing reaction rate. This can create a runaway reaction in the staffing material that greatly accelerates curing of the starting material in comparison to traditional methods.

In order to facilitate even application of the microwave radiation to the starting material, the method further comprises varying the relative position of the starting material with respect to the electromagnetic waves applied to it. In this way, the creation of hot spots in the starting material is diminished.

In the exemplary embodiment of Figure 1, the method is carried out in a curing volume and the microwave radiation is applied in the curing volume. The method further comprises rotating the starting material with respect to the curing volume. In such an embodiment, the microwave field applied in the curing volume may be fixed.

It will be appreciated that, for the purposes of safety, the curing volume may be surrounded by a cage or shield to prevent escape of microwave radiation.

Also in order to help diffuse hot spots in the curing volume, one or more radiation absorbing components may be placed in the curing volume. In the embodiment of Figure 1, the mandrel (or forming tool) itself acts as a radiation absorbing component, to facilitate a more uniform application of the microwave radiation to the starting material.

In some embodiments, any suitable number or form of radiation absorbing components may be used. In some embodiments, the radiation absorbing component and/or forming tool may be made from layered prepreg material. In other embodiments, any suitable material may be used to create the forming tool and/or the radiation absorbing component.

Following the method of Figure 1, a cured composite material is produced. For example, with reference to Figure 2, a component (e.g. an aircraft component) 16 including the cured composite material 18 may be produced. ii

EXAMPLE

The method disclosed herein will now be explained with reference to the following non-limiting example.

The method disclosed herein was used to create a monolithic composite shroud, used as a ducting insulation shell for the aerospace sector.

The starting material used was a PFA bioresin infused prepreg. In other words, the matrix component was a PFA bioresin. The PFA bioresin contained 5-7.5 wt% water and cures via a condensation reaction, which is also strongly exothermic.

The reinforcement component used was an aramid fabric.

Specifically, the prepreg material sold as A335 by SHD composites was used, with a weight of 335GSM.

The starting material was wrapped around a forming tool using a hand layup process, then placed in a vacuum bag using standard techniques. The forming tool was constructed from layered prepreg material (e.g. a phenolic or epoxy prepreg) and acted as a radiation absorbing component. The starting material in the vacuum bag was then placed in a cavity of a microwave oven, and a vacuum line attached to the vacuum bag.

The starting material in the vacuum bag was arranged to rotate with respect to the cavity of the microwave oven.

A vacuum of approximately 0.05 bara (commonly referred to as 0.95 bar, i.e. the vacuum pressure) was applied to the starting material. Microwave radiation was then applied to the starting material whilst under vacuum compression. Microwave radiation was applied at an average power output of 350W for 120 seconds. After which, the application of microwave radiation was ceased and the treated material was allowed to cool under vacuum for about 5 minutes.

Following cooling, the starting material was fully cured.

The overall weight reduction from curing the prepreg was found to be around 20°/o, a large proportion of which is believed to be water.

On visual inspection, the cured part was found to be identical to a part made using a standard oven cured production process, in which an oven is run over 8.5 hours in a ramped cure cycle, in which the temperature is increased at approximately 2°C/min up to a plateau of 180°C for curing, the temperature is held at approximately 180°C for curing, and then ramped down at the end of the cure cycle at a rate of approximately 3°C/min.

Although this disclosure has been made with reference to one or more embodiments, it will be appreciated that various changes or modifications can be made without departing from the scope of the disclosure, as described in the appended claims. For example, it will be appreciated that the method disclosed herein could be used to make any number of articles or component parts comprising a composite material.

Claims

CLAIMS1. A method of curing a starting material comprising constituent components of a composite material, the method comprising: providing a starting material comprising constituent components of a composite material, the constituent components comprising a matrix component and a reinforcement component, and applying electromagnetic radiation to the starting material to cure the starting material.
2. The method of claim 1, wherein the electromagnetic radiation comprises microwave radiation.
3. The method of any preceding claim, wherein the method comprises holding the starting material against a forming tool as the electromagnetic radiation is applied.
4. The method of any preceding claim, wherein the method comprises applying compression and/or negative pressure to the starting material as the electromagnetic radiation is applied.
5. The method of claim 4, wherein the method comprises applying compression and/or negative pressure with an absolute pressure of 13 bara or less.
6. The method of claim 4 or 5, wherein the method comprises applying a vacuum to the starting material as the electromagnetic radiation is applied.
7. The method of claim 6, wherein the method comprises applying a vacuum to the starting material having an absolute pressure in the range of from about 0.01 bara to about to 0.5 bara, for example about 0.1 bara.
8. The method of any preceding claim, wherein, application of electromagnetic radiation to the starting material produces a treated material, and wherein, following application of electromagnetic radiation, the treated material is allowed to cool while compression is applied to the treated material.
9. The method of any preceding claim, wherein the method comprises providing a starting material comprising a fibre reinforced polymer (FEW) pre-preg material.
10. The method of any preceding claim, wherein the starting material is configured to cure via a condensation reaction.
11. The method of any preceding claim, wherein the matrix component comprises water.
12. The method of any preceding claim, wherein the matrix component comprises up to about 50% water.
13. The method of any preceding claim, wherein the matrix component comprises a thermoset bioresin.
14. The method of any preceding claim, wherein the matrix component comprises a polyfurfuryl alcohol (PFA) resin matrix.
15. The method of any preceding claim, wherein the electromagnetic radiation comprises electromagnetic waves, and wherein the method comprises varying the relative position and/or orientation of the starting material and the electromagnetic waves.
16. The method of claim 15, wherein the method is carried out in a curing volume and the electromagnetic radiation is applied in the curing volume, and wherein the method comprises rotating the starting material and the curing volume relative to each other.
17. The method of any preceding claim, wherein the method is carried out in a curing volume, and wherein a radiation absorbing component is positioned in the curing volume.
18. The method of claim 17, wherein a plurality of radiation absorbing components are positioned in the curing volume.
19. The method of claim 17 or 18, wherein the starting material defines a volume and at least one radiation absorbing component is provided in said defined volume.
20. The method of claim 19, wherein the radiation absorbing component comprises a mandrel tool and wherein the method comprises positioning the starting material around the mandrel tool.
21. The method of any preceding claim, wherein the energy applied by the electromagnetic radiation to the starting material is 10.0 IC/g or less, e.g. 5.0 Idig or less.
22.A cured composite material produced by the method according to any of claims 1 to 21.
23.A component (e.g. for an aircraft) comprising a cured composite material produced by the method according to any of claims 1 to 21.