DK181889B1

DK181889B1 - Method for manufacturing a molded structure and a molded structure

Info

Publication number: DK181889B1
Application number: DKPA202330119A
Authority: DK
Inventors: Rytter Frederik
Original assignee: Leicon Aps
Priority date: 2023-07-07
Filing date: 2023-07-07
Publication date: 2025-03-06
Also published as: DK202330119A1; WO2025011717A1

Abstract

Method for manufacturing a molded structure (2), the method comprising: a) cutting one or more fibre reinforced composite structures (20) into a plurality of smaller pieces (12) comprising glass fibre reinforced composite material; b) filling the smaller pieces (12) and a binder material (10) into a mold (4) having an inner space (16); c) providing a pressure (P) during a predefined curing time (Δtc) towards the smaller pieces (12) in the inner space (16) of the mold (4); d) removing the molded structure (2) from the mold (4); e) the mold (4) and hereby the smaller pieces (12) and the binder material (10) are vibrated in a predefined period of time (T) and f) while temperature of the mold (4) is maintained in a temperature range of 40-90°C.

Description

DK 181889 B1 1

Field of invention

The present invention relates to a method for manufacturing a molded structure comprising glass fibre recycled from fibre reinforced composite structures.

Prior art

According to the European wind energy agency, around 14,000 blades could be dismantled across the continent in the next five years, which would amount to between 40,000 and 60,000 tonnes of waste. For this reason, recycling, especially of wind turbine blades, is seen as one of the key challenges for the industry.

The wind energy sector is experiencing tremendous growth due to the global need for a cleaner energy supply. The useful life of a wind turbine is around 25-30 years, depending on the level of maintenance. Most of its components are recyclable, although the challenge lies in recycling the wind blades efficiently. The materials from which they are made are mostly composites, such as fibreglass, carbon fibre or various resins, so separating them for recycling is particularly difficult and expensive.

Due to the speed at which wind energy is growing, it is necessary to develop other alternatives as the volume of retired blades will increase rapidly.

There are currently three main types of recycling applicable to wind blade components: - mechanical recycling involving shredding following a separation process. The materials are reused, often as filler material, mainly in building materials or plastics; - thermal recycling, in which the blades are incinerated, producing

DK 181889 B1 2 energy and decomposing the composites. This process is able to preserve certain characteristics of the fibrous materials, making them suitable for later use; - chemical recycling applying techniques such as fluidised bed or solvolysis, by means of solvents and thermal processes, separate the resins from the fibres so that both materials can be reused.

CN114619613A discloses a method for recycling waste wind turbine blades. The method comprises the following steps: mixing a waste wind power blade material and a thermoplastic material in a preset size range to obtain a molded material, and carrying out compression molding on the molded material to obtain a wind power matching product. The moulded structures produced by using this solution typically have pour mechanical properties due to a high content of air bubbles. Accordingly, it would be desirable to have an alternative method capable of solving this problem.

Thus, there is a need for an alternative method for manufacturing a floating foundation for wind turbines, which method reduces or even eliminates the above-mentioned disadvantages of the prior art.

There is, however, a need for a method that enables an improved, simpler and more efficient way of reusing fibre reinforced composite structures such as wind turbine blades.

It is an object of the invention to provide a method by which it is possible to recycle fibre reinforced composite structures and manufacture molded structures that can be used in various constructions.

Summary of the invention

The object of the present invention can be achieved by a method as

DK 181889 B1 3 defined in claim 1 and by a moulded structure as defined in claim 14.

Preferred embodiments are defined in the dependent subclaims, explained in the following description and illustrated in the accompanying drawings.

The method according to the invention is a method for manufacturing a molded structure, the method comprising: a) cutting one or more fibre reinforced composite structures into a plurality of smaller pieces comprising glass fibre reinforced composite material; b) filling the smaller pieces and a binder material into a mold having an inner space; c) providing a pressure during a predefined curing time towards the smaller pieces in the inner space of the mold; d) removing the molded structure from the mold, wherein e) the mold and hereby the smaller pieces and the binder material are vibrated in a predefined period of time and f) while temperature of the mold is maintained in a temperature range of 40-90°C, wherein the smaller pieces are shorter than 20 cm.

Hereby, it is possible to recycle fibre reinforced composite structures and manufacture molded structures that can be used in various constructions.

Cutting one or more fibre reinforced composite structures into a plurality of smaller pieces comprising glass fibre reinforced composite material makes it possible to reuse the smaller pieces in a new molded structure.

Accordingly, the smaller pieces and the binder material can be filed into

DK 181889 B1 4 a mold having an inner space.

In an embodiment, the binding material is sprayed on the smaller pieces.

In an embodiment, the binding material and the smaller pieces are mixed through a stirring process.

In an embodiment, the binding material and the smaller pieces are mixed while maintaining the temperature in the range 10-40°C.

In an embodiment, the method comprises the step of preheating the mold.

In an embodiment, the method comprises the step of preheating the mold to a temperature in the range 20-90°C.

In an embodiment, a parting agent (mold release agent) is applied to the mold before the smaller pieces are filled into the mold.

In an embodiment, the parting agent is a layer of plastic.

In an embodiment, the parting agent is a layer of paper.

In an embodiment, the parting agent is a liquid parting agent.

In an embodiment, the mold comprises vent channels, wherein the vent channels are arranged and configured to evacuate air bubbles. In an embodiment, the mold comprises one or more sensors arranged and configured to detect the pressure in a vent channel.

In an embodiment, vacuum is applied to the mold in order to prevent

DK 181889 B1 air gaps.

In an embodiment, the relative humidity is maintained in the range 25- 60%. 5

The step of providing a pressure during a predefined curing time towards the smaller pieces in the inner space of the mold makes it possible to lower the air content of the molded structure and hereby increase the strength.

Removing the molded structure from the mold may typically be done after opening the mold (e.g. by removing a lid).

In one embodiment, the one or more fibre reinforced composite structures include wind turbine blades.

Hereby, the method makes it possible to recycle fiberglass from wind turbine blades and other fibre reinforced composite materials.

Accordingly, the method is environmentally freindly. It should be underlined that there an increasing number of wind turbine blades needs to be replaced and that the method according to the invention makes it possible to use scraped (discarded) fibre reinforced composite structures such as wind turbine blades in a new floating foundation for wind turbines.

The fibre reinforced composite structures may be any type of objects made by recyclable fibre reinforced composite.

The method comprises the step of cutting one or more fibre reinforced composite structures into a plurality of smaller pieces comprising fibres.

In one embodiment, the one or more fibre reinforced composite

DK 181889 B1 6 structures comprise one or more wind turbine blades.

This step may be done in a location different from the location, in which the additional steps of the method are carried out.

By the term cutting is meant a procedure by which one or more fibre reinforced composite structures (e.g. one or more wind turbine blades) are split into smaller portions. The cutting procedure may be done my using any suitable cutting tools.

In one embodiment, the method comprises the step of heating up the mold while the mold is closed and/or prior to closing the mold. Hereby, it is possible to accelerate the curing process.

In one embodiment, the method comprises the step of applying ultraviolet light to accelerate the curing process. Hereby, it is possible to accelerate the curing process.

By applying a pressure sufficiently large to evacuate air gaps from the mold during the molding process, it is possible to increase the strength of the molded structure. By providing the pressure for a sufficiently long time period it is possible to fill out all air gaps with the binder material.

Accordingly, the amount of air in the cured product can be minimized.

Therefore, a high strength of the molded structure can be achieved.

In an embodiment, the molded structure is a solid molded structure.

In an embodiment, the molded structure comprises a plate-shaped portion.

In an embodiment, the molded structure is a plate.

DK 181889 B1 7

In an embodiment, the molded structure comprises a box-shaped portion.

In an embodiment, the molded structure is box-shaped.

In an embodiment, the binder material is a polyester.

In an embodiment, the binder material is a glue.

In an embodiment, the binder material is epoxy.

In an embodiment, the mold and hereby the smaller pieces and the binder material are vibrated during at least 25 % of the curing time (Ato).

In an embodiment, the mold and hereby the smaller pieces and the binder material are vibrated during at least 50 % of the curing time (Ato).

In an embodiment, the mold and hereby the smaller pieces and the binder material are vibrated during at least 70 % of the curing time (Ato).

In an embodiment, the mold and hereby the smaller pieces and the binder material are vibrated during at least 95 % of the curing time (Ato).

In an embodiment, the mold and hereby the smaller pieces and the binder material are vibrated during the entire curing time (At.).

By vibrating the mold, the smaller pieces and the binder material it is possible to reduce the quantity of air bubble present in the binder

DK 181889 B1 8 material. Accordingly, it is possible to increase the mechanical strength of the molded structure.

In an embodiment, the pressure is in the range 10-200 N/mm?.

In an embodiment, the pressure is in the range 15-150 N/mm/.

In an embodiment, the pressure is in the range 20-100 N/mm?.

In an embodiment, the curing time is in the range 1-30 minutes.

In an embodiment, the curing time is in the range 2-25 minutes

In an embodiment, the curing time is in the range 4-20 minutes

In an embodiment, the curing time is in the range 5-10 minutes

In an embodiment, wherein the mold is heated to a temperature in the range 35-90°C.

In an embodiment, the mold is heated to a temperature in the range 40-80°C.

In an embodiment, the mold is heated to a temperature in the range 45-75°C.

In an embodiment, the temperature of the mold is maintained in the range 45-75°C.

In an embodiment, the the temperature range is 40-60°C.

In an embodiment, the the temperature range is at least 50°C.

DK 181889 B1 9

In an embodiment, the binder material is an epoxy resin. In an embodiment, the binder material is a heat-curing, one-component epoxy.

In an embodiment, the epoxy resin belongs to a class of prepolymers and polymers containing more than one epoxy group (e.g. a glycidyl or oxirane group). The epoxy resin contains a curing agent like e.g. polyamines, aminoamides and phenolic compounds.

In an embodiment, the epoxy resin is based on reacting epichlorohydrin with Bisphenol A. This reaction transforms the basic building blocks into a different chemical substance called Bisphenol A diglycidyl ether, which is a low-molecular resin more known as BADGE or DGEBA representing the smallest type of epoxy resin.

In an embodiment, the binder material is a polyester.

In an embodiment, the binder material is a thermoplastic polyester.

In an embodiment, the binder material is a vinyl ester. In an embodiment, the binder material is a bisphenol-A epoxy vinyl ester resin.

In an embodiment, the method comprises a shaping process, wherein after removing the molded structure from the mold the molded structure is put into another differently shaped mold before the molded structure is cured, wherein the molded structure is shaped into another shape and cured while being in the differently shaped mold.

It is an advantage that the smaller pieces are shorter than 20 cm.

DK 181889 B1 10

In an embodiment, the smaller pieces are in the range 0.05 mm to 200 mm.

In an embodiment, the smaller pieces are in the range 0.05 mm to 100 mm.

In an embodiment, the binder material constitutes at least 35% of the mass of the smaller pieces.

In an embodiment, the binder material constitutes at least 30% of the mass of the smaller pieces.

In an embodiment, the binder material constitutes at least 25% of the mass of the smaller pieces.

In an embodiment, the binder material constitutes at least 20% of the mass of the smaller pieces.

In an embodiment, the pressure is in the range 10-40 MPa.

In an embodiment, the pressure is in the range 15-30 MPa.

In an embodiment, the binder material constitutes less than 25% of the mass of the smaller pieces.

In an embodiment, the binder material constitutes less than 20% of the mass of the smaller pieces.

In an embodiment, the binder material constitutes less than 15% of the mass of the smaller pieces.

In an embodiment, the binder material constitutes 10-20% of the mass

DK 181889 B1 11 of the smaller pieces.

In an embodiment, the binder material constitutes 10-15% of the mass of the smaller pieces.

In an embodiment, wherein the method comprises: - selecting the smaller pieces in such a manner that the length of the smaller pieces has a mean in the range 5-15 cm.

In an embodiment, wherein the method comprises: - selecting the smaller pieces in such a manner that and the standard deviation of the smaller pieces is in the range 5-10 cm.

In an embodiment, wherein the method comprises: - selecting the smaller pieces in such a manner that the length of the smaller pieces has a mean in the range 5-15 cm and the standard deviation of the smaller pieces is in the range 5-10 cm.

Hereby, it is possible to achieve final strength at least 60-70 % of the initial fibre reinforced composite structures, from which the smaller pieces are cut.

In an embodiment, the mold is an extruder mold comprising: - a extruder outlet channel; - a main body provided with an inlet and - a pressurising unit arranged and configured to provide a pressure towards material filled into the main body.

Hereby, it is possible to manufacture the molded structure via an extrusion process.

In an embodiment, the extruder outlet channel extends in extension of the main body.

DK 181889 B1 12

In an embodiment, the extruder outlet channel comprises a conical portion extending in extension of the main body.

In an embodiment, the pressurising unit is arranged to be moved along a longitudinal axis of the main body and hereby provide a pressure towards material filled into the main body.

In an embodiment, pressure is applied during curing the molded structure.

In an embodiment, the method comprises vibrating the smaller pieces while providing the pressure. Hereby, it is possible to evacuate air from the moulded structure while it is being pressurised. Vibrations makes it possible to remove even small air bubbles.

In an embodiment, the smaller pieces are vibrated with a frequency in the range 5-45 Hz.

In an embodiment, the smaller pieces are vibrated with a frequency in the range 10-20 Hz.

In an embodiment, the smaller pieces are vibrated with a frequency in the range 5-15 Hz.

In an embodiment, the smaller pieces are vibrated with a frequency in the range 15-25 Hz.

In an embodiment, the smaller pieces are vibrated with a frequency in the range 25-45 Hz.

In an embodiment, the smaller pieces are vibrated with a constant vibration frequency.

DK 181889 B1 13

In an embodiment, the vibration is provided by vibrating the entire mold.

In an embodiment, the method comprising adding additional glass fibers into the mold in order to increase the strength of the molded structure.

In an embodiment, a constant level of vibration is applied.

In an embodiment, a constant level of vibration is applied in at least 30 seconds.

In an embodiment, a constant level of vibration is applied in at least 1 minute.

In an embodiment, a constant level of vibration is applied in at least 2 minutes.

In an embodiment, a constant level of vibration is applied in at least 5 minutes.

In an embodiment, a constant level of vibration is applied in at least 10 minutes.

In an embodiment, a constant level of vibration is applied in at least 15 minutes.

In an embodiment, a constant level of vibration is applied in at least 20 minutes.

In an embodiment, a varying level of vibration is applied.

In an embodiment, a varying level of vibration is applied by applying a constant level interrupted by even periods with no vibrations.

DK 181889 B1 14

In an embodiment, the periods with a constant level vibration corresponds the duration of the period with no vibrations.

In an embodiment, the periods with a constant level vibration have a duration of 30 seconds.

In an embodiment, the periods with no vibrations have a duration of are 30 seconds.

In an embodiment, the periods with a constant level vibration have a duration of 10 seconds.

In an embodiment, the periods with no vibrations have a duration of are 10 seconds.

In an embodiment, the method comprises: - determining the mechanical properties of the smaller pieces prior to molding the molded structure, wherein the wall thicknesses of the molded structure are selected in such a manner that the mechanical strength of the molded structure is equal to or above a predefined selected level.

In one embodiment, the final mechanical strength of the molded structure is equal to or above 60-70 % of the mechanical strength of the initial fibre reinforced composite structures, from which the smaller pieces are cut.

In one embodiment, the final mechanical strength of the molded structure is equal to or above 60 % of the mechanical strength of the initial fibre reinforced composite structures, from which the smaller pieces are cut.

DK 181889 B1 15

In one embodiment, the final mechanical strength of the molded structure is equal to or above 65 % of the mechanical strength of the initial fibre reinforced composite structures, from which the smaller pieces are cut.

In one embodiment, the final mechanical strength of the molded structure is equal to or above 70 % of the mechanical strength of the initial fibre reinforced composite structures, from which the smaller pieces are cut.

Hereby, it is possible to ensure that the mechanical strength of the molded structure is sufficiently large.

In an embodiment, the molded structure is plate shaped.

In an embodiment, the molded structure is box shaped.

In an embodiment, the molded structure has a rectangular cross- section.

In an embodiment, the curing time is selected in dependency of the thickness of the molded structure. A larger thickness of the molded structure typically requires a larger curing time.

In an embodiment, wall thicknesses of the molded structure are selected to be at least 3 mm.

In an embodiment, wall thicknesses of the molded structure are selected to be at least 4 mm.

In an embodiment, wall thicknesses of the molded structure are selected to be at least 5 mm.

DK 181889 B1 16

In an embodiment, wall thicknesses of the molded structure are selected to be at least 6 mm.

The molded structure according to the invention is a molded structure manufactured by using a method according to the invention.

Description of the Drawings

The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:

Fig. 1 shows a schematic view of the steps of a method according to the invention;

Fig. 2 shows a schematic view of a step of a method according to the invention;

Fig. 3A shows a step of the method according to the invention;

Fig. 3B shows another step of the method according to the invention;

Fig. 4A shows a first step of the method according to the invention;

Fig. 4B shows a second step of the method according to the invention;

Fig. 4C shows a third step of the method according to the invention;

Fig. 5A shows a step of the method according to the invention;

Fig. 5B shows another step of the method according to the invention;

Fig. 6A shows a first step of the method according to the invention;

Fig. 6B shows a second step of the method according to the invention;

DK 181889 B1 17

Fig. 6C shows a third step of the method according to the invention;

Fig. 7 shows a construction according to the invention and

Fig. 8 shows an example of a length distribution of the length of the smaller pieces according to the invention.

Detailed description of the invention

Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, a schematic view of the steps of a method according to the invention is illustrated in Fig. 1.

Fig. 1 illustrates a schematic view of the steps of a method according to the invention.

In the first step, a wind turbine blade 20 is cut into segments 22 by using a cutting device. In one embodiment, the cutting device is used to cut the wind turbine blade 20 into segments having a length that is 2 m or less. The cutting device may be any tool that is suitable for cutting the wind turbine into smaller pieces. In one embodiment, the cutting device is a power saw.

In the second step, the pieces that are cut during the first step are cut into smaller pieces 12 by using a cutting tool 24. In one embodiment, the smaller pieces 12 may have a length in the range 5-20 cm.

In the third step, the smaller pieces 12 that are cut during the second step are filled into the inner space 16 of the mold 4. In the same step a binding material 10 (e.g. polyester) is filled into the inner space 16 of the mold 4.

In the fourth step, pressure P is provided to form a molded structure 2.

Heating and/or ultraviolet light may be used to accelerate the curing process. Heating may be provided by using a heating element 8 integrated in the mold 4. A closing structure formed as a lid 6

DK 181889 B1 18 connected to a shaft 14. The shaft 14 is pressed towards the closing structure 6. Accordingly, the closing structure 6 is pressed towards the smaller pieces 12 so that the smaller pieces 12 are pressurised. The pressure P provided by the closing structure 6 towards the smaller pieces 12 is indicated.

In the fifths step, the molded structure 2 is removed from the mold 4 after the end of the curing process.

In one embodiment, glass fibers of a predefined length and thickness are added during the third step in order to increase the strength of the molded structure 2.

Fig. 2 illustrates a schematic view of a step of a method according to the invention. A planar plate-shaped molded structure 2 that have not yet been fully cured is inserted into a mold 104 and a lid 106 is used to close the mold 104. Pressure is applied to press the lid 106 towards the molded structure 2. When molded structure 2 has cured, the mold 104 is opened and the molded structure 2’ (now having an arced form) is removed from the mold 104. The method may comprise further steps, in which a plurality of molded structures 104 are joined to form a larger construction.

Fig. 3A illustrates a step of the method according to the invention. A plurality of smaller pieces 12 are filled into an open mold 4. The mold 4 comprises a bottom plate and walls protruding therefrom. In an embodiment, the mold 4 is box shaped.

A liquid binding material 10 is filled into the open mold 4 together with the smaller pieces 12. The mold 4 comprises a heating element 8 arranged and configured to heat the mold 4 and hereby increase the temperature of the smaller pieces 12 and the binding material 10 inside

DK 181889 B1 19 the inner space of the mold 4. Hereby, at faster curing can be achieved.

A vibration unit 40 is mechanically connected to the mold 4. The vibration unit 40 is arranged and configured to vibrate the mold 4 and hereby the smaller pieces 12 and the binder material 10. By vibrating the mold 4, the smaller pieces 12 and the binder material 10 it is possible to reduce the quantity of air bubble present in the binder material 10. Accordingly, it is possible to increase the mechanical strength of the molded structure. The vibration unit 40 may be actuated by any suitable activation unit including an electric, pneumatic or hydraulic motor or actuator.

Fig. 3B illustrates another step of the method according to the invention. Fig. 3B illustrates the mold shown in and explained with reference to Fig. 3A. A closing structure 6 formed as a lid has been inserted into the mold 4 in order to close the opening of the mold 4. A shaft 14 is connected to the upper side of the lid 6. The shaft 14 is connected to an actuator arranged and configured to provide a pressure towards the smaller pieces 12 and the binding material 10 inside the inner space of the mold 4.

It may be an advantage to vibrate the closing structure 6 in order to distribute the smaller pieces 12 and the binding material 10 inside the inner space of the mold 4 evenly. Moreover, vibration may facilitate removal of air bubbles inside the binding material 10. Accordingly, it is possible to evacuate air from the binding material 10 and hereby increase the density and the strength of the molded structure being molded by using the mold 4.

Fig. 4A illustrates a first step of the method according to the invention.

A molded structure 2 made by using the method of the invention is arranged above an additional structure 26. The additional structure 26

DK 181889 B1 20 may have a larger mechanical strength than the molded structure 2.

The additional structure 26 may be more abrasion-resistant than the molded structure 2. The additional structure 26 may be attached to the molded structure 2 by a welding process, by glue or by using mechanical attachment structures such as screws or bolts and nuts.

Fig. 4B illustrates a second step of the method according to the invention. This second step follows the first step shown in and explained with reference to Fig. 4A. In the second step, a second additional structure 28 is attached to the upper surface of the molded structure 2.

The additional structure 28 may have a larger mechanical strength than the molded structure 2. The additional structure 28 may be more abrasion-resistant than the molded structure 2. The additional structure 28 may be attached to the molded structure 2 by a welding process, by glue or by using mechanical attachment structures such as screws or bolts and nuts.

Fig. 4C illustrates a third step of the method according to the invention, in which the additional structure 28 has been attached to the upper surface of the molded structure 2. Accordingly, the molded structure 2 is sandwiched between the two additional structures 26, 28.

Fig. 5A illustrates a step of the method according to the invention. The step corresponds to the one shown in and explained with reference to

Fig. 3A. The smaller pieces 12 are filled into an open mold 4. The mold 4 comprises a bottom plate and walls protruding therefrom.

DK 181889 B1 21 the inner space of the mold 4. Hereby, at faster curing can be achieved.

A vibration unit 40 is mechanically connected to the bottom part mold 4. The vibration unit 40 may be placed in other positions (such as in a side portion or at the top portion of the mold 4). The vibration unit 40 is arranged and configured to vibrate the mold 4 and hereby the smaller pieces 12 and the binder material 10. By vibrating the mold 4, the smaller pieces 12 and the binder material 10 it is possible to reduce the quantity of air bubble present in the binder material 10. Accordingly, it is possible to increase the mechanical strength of the molded structure.

The vibration unit 40 may be actuated by any suitable activation unit including an electric, pneumatic or hydraulic motor or actuator.

Fig. 5B illustrates another step of the method according to the invention. Fig. 5B illustrates the mold shown in and explained with reference to Fig. 5A. A pressure mat 38 is, however, arranged between the closing structure 6 and the smaller pieces 12 and the binding material 10 inside the inner space of the mold 4. In an embodiment, the pressure mat 38 is attached to the underside of the closing structure 6.

In an embodiment, the pressure mat 38 is placed on the smaller pieces 12 and the binding material 10 inside the inner space of the mold 4 as a separate structure.

The closing structure 6 formed as a lid has been inserted into the mold 4 in order to close the opening of the mold 4. A shaft 14 is connected to the upper side of the lid 6. The shaft 14 is connected to an actuator arranged and configured to provide a pressure towards the smaller pieces 12 and the binding material 10 inside the inner space of the mold 4.

It may be an advantage to vibrate the closing structure 6 in order to distribute the smaller pieces 12 and the binding material 10 inside the

DK 181889 B1 22 inner space of the mold 4 evenly. Moreover, vibration may facilitate removal of air bubbles inside the binding material 10. Accordingly, it is possible to evacuate air from the binding material 10 and hereby increase the density and the strength of the molded structure being molded by using the mold 4.

Fig. 6A illustrates a first step of the method according to the invention in which an extruder mold 4 is applied. The extruder mold 4 comprises a cylindrical main body 32 provided with an inlet 34 and an extruder outlet channel 30. The inlet 34 is arranged and configured to receive smaller pieces 12 and binding material 10 filled into the main body 32.

A pressurising unit 36 is moveably arranged inside the main body. The pressurising unit 36 is arranged and configured to pressurise the smaller pieces 12 and binding material 10 filled into the main body 32.

Once a sufficient quantity of smaller pieces 12 and binding material 10 has been filled into the main body 32, the pressurising unit 36 is moved to the right. During the curing of the smaller pieces 12 and the binding material 10 a pressure is applied by the pressurising unit 36. An actuator (not shown) is used to move the pressurising unit 36 and hereby provide a pressure towards the smaller pieces 12 and the binding material 10. The extruder outlet channel 30 is conical and hereby facilitates the compression of the receive smaller pieces 12.

In an embodiment, the actuator is configured to vibrate the pressurising unit 36 and hereby provide vibrations towards the smaller pieces 12 and the binding material 10.

The extruder outlet channel 30 extends in extension of the main body 32. The cross-sectional area of the extruder outlet channel 30 is smaller than the cross-sectional area of the main body 32. The cross-sectional area of the extruder outlet channel 30 gradually decreases along the length of the portion of the extruder outlet channel 30 shown in Fig. 6A.

DK 181889 B1 23

Fig. 6B illustrates a second step of the method according to the invention. Fig. 6B illustrates the extruder mold 4 shown in and explained with reference to Fig. 6A. It can be seen that the pressurising unit 36 has been moved further to the right in order to pressurise the smaller pieces 12 and the binding material 10. Extruder outlet channel 30 is being filled while the inlet 34 has been emptied.

Fig. 6C illustrates a third step of the method according to the invention.

The third step follows the second step illustration and explained with reference to Fig. 6B. The pressurising unit 36 has been moved even further to the right in order to pressurise the smaller pieces 12 and the binding material 10 in the extruder outlet channel 30. It can be seen that the inlet 34 has been completely emptied.

A pressure is applied by the pressurising unit 36 towards smaller pieces 12 and the binding material 10 during the curing process. This may be accomplished by using an actuator (not shown) arranged and configured to move the pressurising unit 36 and hereby provide a pressure towards the smaller pieces 12 and the binding material 10.

The actuator may be arranged and configured to vibrate the pressurising unit 36 and hereby provide vibrations towards the smaller pieces 12 and the binding material 10.

Fig. 7 illustrates a construction according to the invention. The construction comprises three integrated elements I, II, III: a molded structure 2 (I), an intermediate structure II and another molded structure 2 (III). The three integrated elements I, II, III are attached to each other. The attachment may be accomplished in various ways including welding, clueing and by using mechanical fastening structures such as screws, bolts and nuts.

DK 181889 B1 24

In an embodiment, the first element I has a first level of mechanical strength, while the second element II has a level og mechanical strength different from the first element I. The third element III has a level og mechanical strength different from the second element II.

Fig. 8 illustrates an example of a length distribution of the length of the smaller pieces according to the invention. The lengths of the smaller pieces are selected in such a manner that the mean w and standard deviation oy corresponds to the one show in Fig. 8. Hereby, it is possible to ensure that the strength of the molded structure to meet predefined requirements.

In an embodiment, the lengths of the smaller pieces are selected in such a manner that the mean wis 12.08 cm and standard deviation oi is 3.02 cm.

In an embodiment, the thicknesses of the smaller pieces are detected before filling the smaller pieces and a binder material into the mold.

In an embodiment, the smallest thickness of the smaller pieces is detected before filling the smaller pieces and a binder material into the mold.

In an embodiment, the mechanical properties of the smaller pieces are determined prior to molding the molded structure, wherein the thicknesses of the smaller pieces are selected in such a manner that the mechanical strength of the air pontoon is equal to or above a predefined selected level.

In an embodiment, the mechanical properties of the smaller pieces are determined prior to molding the molded structure, wherein the smallest wall thickness of the molded structure is selected in such a manner that

DK 181889 B1 25 the mechanical strength of the air pontoon is equal to or above a predefined selected level.

In an embodiment, the mechanical properties of the smaller pieces are determined prior to molding the molded structure, wherein the smallest wall thickness of the molded structure is selected in such a manner that the smallest wall thickness of all the smaller pieces of the air pontoon is equal to or above a predefined selected level.

DK 181889 B1 26

List of reference numerals 2 Molded structure 4 Mold 6 Closing structure (e.g. lid) 8 Heating element

Binder material 12 Smaller pieces 10 14 Shaft 16 Inner space 20 Fibre reinforced composite structure 22 Segment 24 Cutting tool 26 Additional structure 28 Additional structure 30 Extruder outlet channel 32 Main body 34 Inlet 36 Pressurising unit 38 Pressure mat 40 Vibration unit 104 Mold 106 Closing structure (e.g. lid)

P Pressure

At: Curing time

Wu Mean ol Standard deviation/spread

T Period of time

Claims

DK 181889 B1 27 Patent claims

1. A method for producing a molded structure (2), the method comprising: a) cutting one or more fiber-reinforced composite structures (20) into a plurality of smaller parts (12) comprising the glass fiber-reinforced composite material; b) filling the smaller parts (12) and a binder material (10) into a mold (4) having an interior space (16); c) applying a pressure (P) for a predefined curing time (Δt) against the smaller parts (12) in the interior space (16) of the mold (4); d) removing the molded structure (2) from the mold (4), wherein: e) the mold (4) and thus the smaller parts (12) and the binder material (10) are vibrated for a predefined time period (T), and f) while maintaining the temperature of the mold (4) in a temperature range of 40-90 °C, wherein the smaller parts (12) are shorter than 20 cm.

A method according to claim 1, wherein the smaller parts (12) are vibrated at a frequency in the range of 5-45 Hz.

3. A method according to claim 1 or 2, wherein the curing time (Δt) is in the range of 1-30 minutes. 4. A method according to any one of the preceding claims, wherein the method comprises a shaping process, wherein, after removing the molded structure (2) from the mold (4), the molded structure (2) is placed in another differently shaped mold (104) before the molded structure (2) is cured, wherein the molded structure (2) is formed into another shape and cured while in the differently shaped mold (104).

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5. A method according to any one of the preceding claims, wherein the binder material (10) constitutes 10-30% of the mass of the smaller parts (12).

A method according to any one of the preceding claims, wherein the binder material (10) constitutes at least 20% of the mass of the smaller parts (12).

7. A method according to any one of the preceding claims, wherein the pressure (P) is in the range 10-200 MPa, 15-150 MPa or 20-100 MPa.

8. Method according to any one of the preceding claims, wherein the method comprises: - selecting the smaller parts (12) such that the length of the smaller parts (12) has a mean value (w) in the range of 5-15 cm, and the standard deviation (si) of the smaller parts (12) is in the range of 5-10 cm.

9. A method according to any one of the preceding claims, wherein the mold (4) is an extruder mold (4) comprising: - an extruder outlet channel (30); - a main body (32) provided with an inlet (34) and - a pressurizing unit (36) arranged and configured to provide a pressure against material filled in the main body (32).

A method according to any one of the preceding claims, wherein the method comprises vibrating the smaller parts (12) while applying the pressure (P).

A method according to any one of the preceding claims, comprising adding additional glass fibres into the mould (4) to increase the strength of the moulded structure (2).

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12. Method according to any one of the preceding claims, wherein the method comprises: - determining the mechanical strength of the smaller parts (12) before casting the cast structure (2), wherein the wall thicknesses of the cast structure (2) are selected such that the mechanical strength of the cast structure (2) corresponds to or is above a predefined, selected level.

Method according to claim 12, wherein the wall thicknesses of the molded structure (2) are selected to be at least 6 mm.

A molded structure (2) produced by a method according to any one of the preceding claims.