WO2019166691A1

WO2019166691A1 - A method for reinforcement of a composite product

Info

Publication number: WO2019166691A1
Application number: PCT/FI2019/050143
Authority: WO
Inventors: Veikko Raivio
Original assignee: Fibrego Oy
Priority date: 2018-02-27
Filing date: 2019-02-22
Publication date: 2019-09-06
Also published as: FI20185184A1; EP3758904A4; EP3758904A1

Abstract

The object of the invention is a method to reinforce a composite product in which method a combination consisting at least a mold (1) and against it put composite product (2) is immersed into a liquid (11) in a vessel (10), the immersion depth (d) of the mentioned combination from the surface (11.1) of the liquid (11) is selected so that a desired hydrostatic pressure is achieved to the surface (2.1) of the composite product, which pressure is kept constant for a certain time or which pressure is varied during the immersion by changing the immersion depth (d) and the mentioned combination is kept immersed in the liquid (11) for a certain favorable time in order to reinforce the composite product (2). In another application of the invention, the mentioned combination is surrounded by a gas tight membrane (3) before the immersion and inside the membrane there will be led the vacuum channel (8) through the membrane, that channel is connected to the vacuum unit (15), inside the membrane 3 a vacuum is created with the vacuum unit (15) and via the vacuum channel (8) and the composite product (2) surrounded by the membrane (3) is kept under the effect of the vacuum the duration of the immersion of the composite product or a part of this time in order to reinforce the composite product.

Description

A METHOD FOR REINFORCEMENT OF A COMPOSITE PRODUCT

The object of this invention is a method for reinforcement of a composite product in which method the composite product that has been put against a mold in a vessel where an overpressure is directed to the surface of the composite product.

The reinforcement of the composite product can mean for instance hardening it, post hardening it, augmenting its density or some other treatment that reinforces it. A part of the resins that are used in the production of the composites require a final hardening by heat treatment or overpressure.

The invention is used to reinforce different with help of a mold made constructions of composite products. This kind of composite products can be for instance parts made of fiber and resins or rubber composite parts etc. The usages of them can be for instance cars and aircrafts, sports equipments, parts of electronic industry, building elements etc.

It is known that when producing high strength composite products they are treated with over pressure and with a temperature that is higher than ordinary room temperatures. This kind of treatment is made knowingly with an autoclave. The autoclave that is suitable for this purpose is a pressure vessel that can be closed airtight with a lid or a door where the composite product is heated usually with steam.

The known technology that is described above is used very commonly in the reinforcement of the composite products. The semi finished or almost finished products and its mold are closed into an autoclave, over pressure is made inside it and the inside temperature is raised for instance into a little over 100°C. The pressure and the temperature inside the autoclave influence the composite product so that the product is pressed against the mold and certain construction parts in the product change their appearance when heated and get loose. As a result of this, air and other harmful stuff get off the product and the strength of the product gets better. The composite product can also get its exact final shape in the treatment. When using the before mentioned known technology, the size of the autoclave must be suited to the size of the composite product that is treated there. The pressures used in autoclaves are typically from one bar up and the temperatures are 121- 123°C.

5 The greatest drawback of the known technology can be seen that it sets a limit for the size of the composite product treated using it. The larger the product is the larger the autoclave needs to be. The autoclave is a pressure vessel and it is very expensive to produce a large and safe autoclave. The maintenance costs like energy costs, inspection and control costs grow strongly as the size grows. The pressure vessel must meet0 the high safety requirements of the Pressure Vessel Act, like the multifold requirements of the strength. The safe construction of the lid/door of the autoclave complicates the construction of the equipment. The usage of the autoclave has always a safety risk. 5 The higher the pressure is that is desired to be used in the autoclave the greater are the risks that must be taken and the higher costs must be accepted.

The intension of this invention is to achieve such a method for reinforcement of a composite product that the drawbacks of the known technology can be avoided. It is0 characteristic for the solution according to the invention what has been presented in the characterizing part of the claim 1.

The method in accordance with the invention has many advantages in comparison to the known technology. In the method according to the invention the equipments that5 are used are of their structure very simple and cheap to build and maintain. They are also suitable for treating very large composite products and there is no explosion hazard when using them.

One important advantage in using the invention is achieved because it is possible to0 join easily to the setup according to the invention also such methods of reinforcing the composite products the joining of which to the autoclave is difficult. As a resume about the advantages of the invention it can be said that it can be used to produce high strength composite products almost without danger and without limiting its size.

5 The term“heat transfer liquid” means also material that is used to transfer cold.

The invention is described in more detail in the enclosed drawings, where

figure 1 presents an apparatus to be used in the method according to the invention, figure 2 presents in more detail the apparatus where the composite product is treated,0 figure 3 presents one way to perform the method according to the invention using the apparatus of the figure 1.

Next, there will be described one favorable way to use the method according to the invention and the function of the apparatus that is used in it by referring to the before5 mentioned figures:

In figure 1 there is given an apparatus to perform the method according to the invention. The apparatus includes a deep vessel 10 that is open at its top 10.1. The vessel has been filled with a liquid 11 that is water in this example. Above the surface 11.10 of the liquid there is a treating unit 13 fixed to the lifting organ 12 which unit is described in more detail in figure 2. There is firstly a mold 1 in the treatment unit 13 and around the mold there has been set the composite product 2 that includes in this example fiber bars and resin. The composite product has been surrounded by a gas tight membrane 3 and there has been installed around the mold, the composite product and5 the membrane a temperature insulation 4 that allows the pressure go through in such a way that there is a closed room 5 between the composite product and the membrane. Into the room 5, there has been led a feed channel 7a and an out channel 7b through the temperature insulation 4 into the heat transfer fluid 6 and inside the membrane 3 there has been led a vacuum channel 8 through the temperature insulation and the0 mentioned membrane. The feed channel 7a, the out channel 7b, and the vacuum channel 8 are flexible hoses in this example. The feed channel 7a and the out channel 7b have been connected to the feed unit 14 of the heat transfer liquid and the vacuum channel 8 has been connected to the vacuum unit 15. The method according to the invention functions when using the above described apparatus as follows: the treatment unit 13 is immersed into the liquid 11 in the vessel 10 to a certain depth of the surface 11.1 of the liquid and thus the room 5 gets filled through the temperature insulation 4 of the liquid flowing there and a hydrostatic pres- 5 sure comes to the surface 2.1 of the composite product 2 and the pressure depends on the depth d of the immersion. In the situation according to figure 3, the liquid 11 is water and the immersion depth d of the composite product is average 10 meters so that the over pressure to the surface 2.1 of the composite piece is about 1 bar (100 Kpa). The composite product gets pressed against the mold because of the over pressure and0 certain parts of material in the product like for instance air in the air bubbles get pressed to the surface of the product. At the same time as the hydrostatic pressure affects to the product the vacuum unit 15 is started and a vacuum is created by the vacuum unit in the vacuum channel 8 inside the membrane 3. The unfavorable material parts that come to the surface 2.1 of the composite product like for instance air get5 removed through the vacuum channel 8 from the composite product 2. The vacuum gives also extra effort to the unfavorable material parts to be removed from the mate rial of the composite product. As a result of this, gases and harmful substances get removed, the product gets tighter, and the strength values of the product get better. 0 In addition to measures that have been told above, it is possible according to the figure 3 to with the help of the feeding unit 14 and the feeding channel 7a and the out channel 7b circulate heat transfer liquid 6 that is warmer than the fluid 11 into the room 5 and away from there. As the heat transfer fluid gives heat energy in the room 5 the temperature of the composite product 2 increases. The heat insulation 4 prevents the5 heat energy from getting outside the treatment unit 13.

The heat transfer liquid 6 that is circulated in the before mentioned manner can be exploited in another application of this invention so that it is cooled lower than the liquid 11 before feeding it into the feed channel 7a and thus a cold treatment is made for the0 composite product 2 with the help of the heat transfer liquid together with the pressure treatment. The task of the heat insulation 4 is in this case to slow down the transfer of the heat energy from the liquid 11 to the heat transfer liquid 6, in other words to prevent the heat transfer liquid from warming up. The cooling down is a known way to harden the composite product and/or to strengthen it. The term“heat transfer liquid” consists in this document also the substance that is used to transfer coldness instead of the heat into the treatment unit 13.

When all the before mentioned measures are made at the same time, serially, partly se¬

5 rially, the over pressure directed to the composite product 2, the vacuum inside of the membrane 3 and the heat and/or cold treatment cause together an interaction that lightens, strengthens, and hardens the composite product.

The invention can also be applied differently from what has been told so that only the0 before mentioned overpressure treatment is made for the composite product 2 and then the combination of the mold 1 and the composite product 2 as they are or placed to the treatment unit 13 and immersed to the liquid 11.

The invention can also be applied so that the mentioned over pressure and the under5 pressure treatments are made for the composite product 2 but not heat or cold treatment. In this case, the combination of the mold 1, the composite product 2, and membrane 3 is immersed into the liquid 11 as they are or placed to the treatment unit 13.

The invention can also be applied in such a way that the composite product 2 under¬0 goes the mentioned over pressure and heat and/or cold treatments but not the under pressure treatment. In this case, the treatment unit 13 having inside the combination of the composite product 2 and the mold 1 is immersed into the liquid 11.

In the method according to the invention the apparatus that is used can always be5 adapted to be suitable to the desired phases of the method.

The presented over pressure, under pressure, heat or cold treatments can thus be made in the method according to the invention at the same time, in turns, serially, or gradually. The pressure directed to the composite product 2 can be changed during the0 treatment by changing the immersion depth d, and the warming or cooling effect directed to the composite product 2 can be changed by changing the temperature of the heat transfer liquid 6 that is fed to the feeding channel 7a. The duration of the over pressure treatment for the composite product 2 when using the invention at hand can be for example 1- 2 hours or 1- 5 hours but its duration is not limited to only these times when using the invention. The under pressure and/or heat/cold treatment can last the whole time of the over pressure treatment or only a

5 part of it.

The liquid 11 that is used in the invention can be water or a mixture of water and some other substance, like cold substance. The hydrostatic pressure caused by the liquid 1 is directly relational to the immersion depth d and the density.

0

As an example in the method according to the invention used favorable immersion depths d can be mentioned 10- 50 meters, when the hydrostatic pressure is about 1- 5 bar when the liquid 11 is water. 5 The vessel 10 can be realized for instance as a tower or as a well and when making it the differences of height in the terrain can be exploited. The vessel 10 can also be a nature water reservoir like a lake or sea. When using a before mentioned nature water reservoir as a vessel 10, the immersion of the composite product 2 can be made from for instance a ship and thus it is possible to easily make even a great immersion depth0 d. Using these before mentioned solutions it is possible to attain favorably even over hundred meter immersion depths d.

The membrane 3 can be a vacuum bag or a flexible membrane that is made by spraying method that is especially suitable of the shape for the complicated composite5 products 2. It is characteristic for the membrane 3 that it is gas tight. The membrane can be made in many known ways.

As the heat transfer liquid 6, it is possible to use for instance Globaltherm products the usage temperatures of which are depending on the product -90 °C (Globaltherm C) -0 600 °C (Globaltherm Omnistore MS-600). Other alternatives are for instance water and different kind of oils and their mixtures. The heat transfer liquid 6 can also be a not poisonous and unbumable alternative. The temperature of the heat transfer liquid can be when fed for example -90- +600 °C. The temperature of the heat transfer liquid can be chosen case by case suitable The feeding unit 14 can be equipped with an apparatus of the heating or cooling of the heat transfer liquid 6 or the cooling/heating of the heat transfer liquid 6 can be made in an apparatus elsewhere from where it is led in certain temperature into the feeding unit

5 14 and to where it is led back after it has circulated in the room 5.

All the before mentioned realization forms of the method according to the invention can be combined with the rotation of the composite product 2 and thus the effect of the pressure and the other effects are secured to be even in all parts. The rotation can0 be made for instance by rotating the treatment unit 13 horizontally back and forth.

The heat insulation 4 can be realized in a separate box construction like the above examples show or it can be joined to the mold 1. It is characteristic for it that it lets through hydrostatic pressure, prevents the heat to get in or out of it and that there will5 be formed a room 5 for the heat transfer liquid 6.between it and the composite product 2. As an example about the heat insulation in connection of the mold 1 it can be mentioned a flexible or stiff heat insulation layer inside of which situated room 5 is a cavity/are cavities that reaches at least to a part of the surface 2.1 of the composite product 2.

0

The vacuum unit 15 that makes the vacuum into the vacuum channel and further in- side the membrane 3 is for instance an aspirator.

The effects of the pressure, the vacuum, and temperature changes to the composite5 product 2 can be controlled during the process for instance using pressure sensors and the temperature sensors and infrared sensors and cameras. It is possible to use for the control also other known technology control equipments and methods. Relying on the control results the process can be regulated in the desired way either manually or automatically. When using the automated adjustment it is possible to use a computer or0 corresponding data handling equipment.

It should be noticed that even though this explication sticks to only one type for the invention favorable application example this does not, however, desire to limit the us- ages of the invention only to this type of solutions, instead, many variations are possi- ble in the scope of the invention idea of the claims.

Claims

5 1. A method for reinforcement of a composite product in which method the composite product has been put against a mold where an over pressure is directed to the surface of the composite product and which method is performed as follows: a. a combination consisting at least of a mold (1) and a composite product (2) is immersed into a liquid (11) in a vessel (10),

0 b. the immersion depth/s (d) of the mentioned combination from the surface

(11.1) of the liquid (11) is selected so that a desired hydrostatic pressure to the surface (2.1) of the composite product is attained and which pressure is kept constant for a certain time or which pressure is changed during the immersion by varying the immersion depth (d),

5 c. the mentioned combination is kept immersed in the liquid (11) a certain favorable time to reinforce the composite product (2),

characterized thereof that

d. around the mentioned combination there will be adapted a heat insulation (4) that lets pressure go through so that there will be formed a closed room (5)0 between the combination and the heat insulation,

e. into the room (5) through the heat insulation, there will be led a feed channel (7a) and an out channel (7b) of the heat transfer liquid (6) which channels are connected to the feed unit (14) of the heat transfer liquid which unit is situated outside the vessel (10).

5 f. via the room (5) there will be circulated by the mentioned channels heat transfer liquid (6) that is warmer or colder than the liquid (11) in order to heat or cool the composite product (2).

2. The method according to the claim 1 characterized thereof that

0 a. the mentioned combination includes also the mold (1) and the gas tight membrane (3) surrounding the composite product (2) and inside this mem- brane (3) there will be led a vacuum channel (8) going through this membrane which channel will be connected to the vacuum unit (15), b. inside the membrane (3) there will be created a vacuum with the help of the vacuum unit (15) and by the vacuum channel (8),

c. the composite product (2) surrounded with the membrane (3) is kept under the effect of vacuum the duration of the immersion of the composite product

5 or part of that time in order to reinforce the composite product

3. The method according to the claim 1 or 2 characterized thereof that the immersion depth (d) of the composite product (2) is changed during the immersion. 0

4. The method according to some of the claims 1- 3 characterized thereof that the heat transfer liquid 6 is circulated via the room

(5) the whole duration time of the immersion or a part of that time.

The method according to some of the claims 1- 4 characterized thereof that the5 liquid (11) is water, a mixture of water and cold substance or some other liquid that is suitable to the circumstances.

6. The method according to some of the claims 1- 5 characterized thereof that the immersion depth (d) is 10- 100 meters.

0

7. The method according to some of the claims 1- 6 characterized thereof that the immersion time is 1- 5 hours.

8. The method according to some of the claims 2- 7 characterized thereof that the5 membrane (3) is a plastic bag or a plastic membrane that has been made to the surface of the composite product (2) by spraying.

9. The method according to some of the claims 2- 8 characterized thereof that the vacuum unit (15) is an aspirator.

0

10. The method according to some of the claims 1- 9 characterized thereof that the heat insulation (4) forms a separate box or it will be adopted to the mold.

11. The method according to some of the claims 1- 10 characterized thereof that the heat transfer liquid (6) is water or oil or some their mixture.

12. The method according to some of the claims 1- 11 characterized thereof that

5 the feed channel (7a), the out channel (7b), and the vacuum channel (8) are flexible hoses.

13. The method according to some of the claims 1- 12 characterized thereof that feed unit (14) includes the apparatuses to heat and/or cool the heat transfer liquid0 (6).

14. The method according to some of the claims 1- 13 characterized thereof that ihe temperature of the heat transfer liquid (6) is -90 °C - +600 °C. 5