EP2509786A1

EP2509786A1 - Composite structure, method for manufacturing same and support element made with said composite structure

Info

Publication number: EP2509786A1
Application number: EP10787436A
Authority: EP
Inventors: Laurent Peyreaud
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-12-08
Filing date: 2010-12-03
Publication date: 2012-10-17
Also published as: FR2953446A1; FR2953446B1; CA2782987A1; WO2011069922A1

Abstract

The present invention relates to a composite structure including at least one first and one second layer of expanded and cross-linked polyethylene foam, which are assembled together by means of a stiffening adhesive, to a method for manufacturing said composite structure, to a support element and to a water craft (200) made with said structure.

Description

Composite structure, its manufacturing method and support element made with this composite structure

The present invention relates to a composite structure, its manufacturing method and a support element made with this composite structure.

In particular, it relates to a new nautical vehicle, in particular a kayak.

Kayaks are known as water vehicles that are increasingly popular with the general public.

However, these kayaks are generally made by roto-molding and quite heavy so that it is difficult to handle them alone.

In addition, their size combined with the heavy weight makes their handling tedious.

To solve these problems of size and weight, it has been proposed to make inflatable kayaks.

Indeed, these kayaks are generally light (about 15 kg) and not bulky in the deflated state.

However, in living waters, like rivers, their behavior is not stable enough and they do not have the rigidity necessary for good kayaking practice.

In addition, the draft in the rivers is weak in many places so that shocks against stones can damage the tubes, or even in extreme cases tear the canvas.

Furthermore, composite structures are known in the manufacture of various objects, such as for automobiles, for partitions, floors or panels, or for aeronautics.

A perfect example of this state of the art is known from WO2005030477.

These composite structures are generally made with two structural outer layers and an inner layer of foam for fill the space between the structural layers and to lighten the structure as a whole.

However, these composite structures are complex to manufacture and are restricted in the forms that can be achieved.

It is an object of the present invention to overcome, at least partially, one or more of these drawbacks known kayaks and to propose a new composite structure for making them fairly light.

For this purpose, the subject of the invention is a composite structure characterized in that it comprises at least a first and a second layer of an expanded and crosslinked polyethylene foam, assembled by means of stiffening glue.

This structure may comprise one or more of the following characteristics, taken alone or in combination: the stiffening adhesive comprises a resin,

the resin is an epoxy resin or a polyester resin,

the stiffening glue is a cyanoacrylate glue,

the stiffening glue is reinforced with fibers,

- the stiffening glue is reinforced with carbon fiber, a glass fabric, or Kevlar ™,

the thickness of a layer of foam is between 20 mm and 100 mm,

the density of the foam layers is between 25 kg / m ³ and 70 kg / m ³ , preferably between 30 kg / m ³ and 50 kg / m ³ , it comprises at least three layers, at least the end layers seen in the assembly direction of the layers are expanded and crosslinked polyethylene foam,

all the layers are made of expanded and crosslinked polyethylene foam,

at least one inner layer comprises a static reinforcing element,

- The reinforcing element is made of wood, or hard plastic material. The invention also relates to a method for manufacturing a support element, in particular a human element, in a composite structure, characterized in that

- Layers of expanded polyethylene foam and crosslinked by stiffening adhesive, - is machined by removing the composite assembly assembly to obtain a desired external shape.

This process may comprise one or more of the following characteristics taken alone or in combination:

the machining step is carried out by high speed machining; between the assembly step and the machining step, the glued layers are pressed under pressure until the hardening glue is hardened;

before assembly, the foam layers are precut to obtain a blank by stacking the final support element, a heat treatment is carried out on the external surface after the machining step,

the heat treatment comprises the projection of hot air at a temperature of between 80 ^° C. and 120 ^° C., preferably 100 ^° ; reinforcing fibers are incorporated in the stiffening glue during assembly.

The invention further relates to a support element characterized in that it comprises a composite structure as defined above. The invention further relates to a nautical vehicle, in particular a kayak, characterized in that it is made with a composite structure as defined above.

This nautical vehicle may comprise one or more of the following characteristics taken alone or in combination: the layer of expanded and crosslinked polyethylene foam forming the sole has a density greater than that of the adjacent layers, in particular equal to 70 kg / m ³ ,

- It includes a general U-shaped passenger housing whose branches are intended to house the legs of the passenger and the base is intended to house the trunk of the passenger,

- The bottom of the passenger housing has at the branches a rounded anatomical shape, lifting the leg at the knee,

- The stern has a flattened and widened shape to improve the lift and stability at the back of the kayak, it comprises a housing for receiving a sealed receptacle.

Other features and advantages of the invention will emerge from the following description, given by way of example, without limitation, with reference to the appended figures in which:

FIG. 1 shows a sectional view of a composite structure according to the invention according to a first example,

FIG. 2 shows a sectional view of a composite structure according to the invention according to a second example,

FIG. 3 shows a flowchart of the method according to the invention; FIG. 4 shows in a perspective view of a nautical vehicle, in particular a kayak, made with the composite structure according to the invention;

FIG. 5 is a top view of the kayak of FIG. 4,

FIG. 6 is a side view of the kayak of FIG. 4,

- Figures 7 to 15 show sectional views of different stages of realization of the kayak according to the invention.

In general, the identical elements carry the same reference numbers.

We will now describe the composite structure according to the invention, its manufacturing process and objects that can be made using this composite structure, in particular water vehicles, such as kayaks. 1. The composite structure

In order to be able to offer a support element for the human body, in particular a watercraft such as a kayak, it was first necessary to develop and invent a material that is both light, easy to assemble, easy to fashion while with sufficient stiffness properties, all with a pleasant touch during contact with the human body, including direct contact with the skin.

Figure 1 shows schematically in section a first example of a composite structure 1 according to the invention. This composite structure comprises at least a first 3 and a second 5 layers of an expanded and crosslinked polyethylene foam. These layers 3 and 5 are assembled by stiffening glue 7.

As stiffening adhesive, there may be mentioned as an example a resin, such as an epoxy resin or a polyester resin.

Alternatively, a cyanoacrylate glue can be used.

Surprisingly, the inventor of the present invention has discovered a "composite" effect of this assembly.

Indeed, the expanded and crosslinked polyethylene foam layers are generally flexible and deform under external stress.

By assembling one or more layers by a stiffening adhesive as described above, a very light composite structure is obtained, having a sufficient rigidity to withstand, for example, the human body and very pleasant in contact with the skin.

The hardness of these foams is greater than 40 shore and they can be used in a wide temperature range between -40 ^° C and +90 C.

It is a foam that is "hydrophobic" insofar as it absorbs in one month less than 1% of water in volume. Such foams are for example marketed as polyolefin foam under the trademark XPE from Cellutec (trademark). It is a foam made from polyethylene copolymers that is chemically cross-linked with closed cell and superfine cell structure. In addition, this foam exists in various colors such as white, anthracite gray, yellow, blue, red green and black, so that objects made with this structure can have aspects not only friendly, but also attract attention, as per example for a lifeboat on water (sea or lake) made using this composite structure.

Foam layers having a thickness of between 20mm and 100mm are usually used (once deconstructed), on average 50mm. It is clear that the rigidity of the composite structure is greater when the central layer is thick or, if the layers are thin, they are numerous.

The density of the foam layers is for example between 25kg / m ³ and 70kg / m ³ , or between 30kg / m ³ and 50kg / m ³ . For an object that is to be manufactured such as a support member, particularly for a human, a higher density will be used at the portions requiring greater static stiffness.

According to one development, it is possible to strengthen the fiber-stiffening glue, such as, for example, carbon fiber, glass fabric, or Kevlar ™. FIG. 2 shows another example of a composite structure according to the invention in which it comprises at least three layers 3, 7, 9, of which at least the end layers 3 and 5 seen in the assembly direction of the layers are expanded and cross-linked polyethylene foam.

Alternatively, the inner layer 9 is also made of expanded polyethylene foam and crosslinked.

According to another variant, it can be provided that the inner layer 9 comprises a static reinforcing element, for example made of wood, or of hard plastic material.

It is important that the outer layers that are potentially in contact with the skin or with water, be made of expanded polyethylene foam and crosslinked.

Thus, one gets a pleasant touch, quite similar to that of the human skin itself.

Finally, this foam is hypoallergenic.

As will be described in more detail later, this composite structure described above makes it possible to manufacture various objects, in particular support elements, in particular of the human body and intended to be in contact with it, such as for example seats , armchairs, sofas, mattresses (in the latter case, the rigidity is large enough not to need a support bed base) and more particularly water vehicles, such as a kayak or a canoe. The process of manufacturing the composite structure In addition to the properties of lightness, rigidity and feel, the Applicant has found that the composite structure can be easily shaped, in particular by machining by chip removal.

Thus, from a composite structure block or a preform / blank, there is virtually no limit to shaping desired objects.

Next, an exemplary method of manufacturing a support element, in particular for a human, in a composite structure, the various stages of which are represented in the flowchart of FIG. 3, will be described in detail.

It should be noted that some of the steps shown in Figure 3 are only optional and can for example increase the production rate, or improve the appearance of the manufactured object.

According to a step 110, expanded and crosslinked polyethylene foam layers are assembled with stiffening adhesive as described above.

To do this, the faces to be bonded are for example coated with a brush, spatula, roller or projection of the stiffening glue.

Optionally, it is possible to integrate a reinforcing fiber, as described above, into the stiffening glue during assembly.

When speaking of a layer, it may also be blocks of foamed polyethylene expanded and crosslinked.

Then, according to a step 114, the composite structure assembly is machined by chip removal to obtain a desired external shape. Machining is preferably done in HSC (for high speed machining) which is characterized by high cutting and feed speeds.This type of machining is advantageous on the one hand because of its speed and productivity increase. and on the other hand because the heat generated during the shearing of the chip does not have time to propagate in the workpiece and the tool, as a result of which most of this heat is removed by the chip (about 80% in UGV against 40% in conventional machining).

It is advisable to interpose between the assembly step 110 and the machining step 114, a step 112 during which the press-bonded layers are pressed until the hardening glue is hardened. The duration can be between 1h and 10h.

To increase the productivity, before assembly, the foam layers can be pre-cut according to an optional step 108 to obtain a stack blank of the final support member.

Finally, also optional, it is possible to carry out a finishing step 116 consisting in applying a heat treatment to the outer surface of the support element after the machining step.

This heat treatment comprises for example the hot air spraying at a temperature between 80 C and 120 C, preferably 100 ^° on the outer layers.

3. Nautical vehicle, in particular kayak, composite structure As already detailed above, the potential applications of the composite structure are numerous. By way of example, a specific example of an application relating to a nautical vehicle, more specifically a kayak made with the composite structure described above and according to the method described above, will be detailed.

The kayak is described here as an example for all kinds of watercraft, such as canoes, lifeboats, boats, sailboats etc., but also for all the support elements made with the composite structure .

Figure 4 shows a wired perspective view of the kayak according to the invention. Figure 5 is a top view and Figure 6 is a side view.

The watercraft 200, in particular kayak, is therefore made with a composite structure as described above and according to the method detailed above.

Thus, for a kayak with a height of 1.65m in length (child size), the total weight of the kayak is only about 1.8kg and for a height of 2.35m in length (adult size - man), the total weight of the kayak is only 6.5kg, which is about half the weight of the currently known inflatable kayaks.

This gives a considerable weight gain while having a rigidity and buoyancy sufficient to wear a person.

In addition, it should be noted that the kayak is made in "full", that is to say, it can not sink or turning, or during a shock with such a sharp stone, which significantly increases safety compared to kayaks and other known water vehicles. This kayak is further distinguished by a passenger housing 202 of generally U-shaped whose branches 204 are intended to house the legs of a passenger and the base 206 is intended to house the trunk of a passenger.

According to a development, the bottom 208 of the passenger housing 202 has at the branches 204 a rounded anatomical shape 210, an elevation, raising the leg at the knee, which increases the comfort, especially for long-term kayak hikes.

The feet of the passenger are in abutment against the inner wall of the housing 202 at the ends of the branches 204.

As seen in Figures 4 and 6, the stern 212 of the kayak has a flattened and enlarged shape to improve the lift and stability at the rear of the kayak.

It is convenient to provide at this flattened portion of the stern 212 a receiving housing 214 of a sealed receptacle (not shown), such as one or more sealed barrels.

This housing may have the form of a hollow semi-cylinder.

Furthermore, it is expected that the layer of expanded and crosslinked polyethylene foam forming the sole 216 (see Figure 6) has a density greater than that of adjacent layers, in particular equal to 70 kg / m ³ .

Figures 7 to 15 schematically show cross-sectional views of the kayak 200 at the seat, that is to say at the base 206 of the housing 202 U-shaped during the manufacturing process to illustrate the latter. In these figures, the dashed line shape 300 corresponds to the final transverse shape to be obtained.

As can be seen in these figures, the kayak is made from layers 302 made of expanded and cross-linked polyethylene foam which have been previously precut so that their superposition or stacking makes it possible to obtain a general shape exceeding the final shape 300.

It is therefore understood that these parts that protrude are to be removed later by machining.

These layers 302 are therefore assembled in pairs by a stiffening adhesive as described above.

Thus, in FIG. 8, a second plate 306 is adhered to the first 304, then in FIG. 9 a plate 308 serving as a kayak bottom on the plate 306.

These assemblies are for example using an epoxy resin. In FIG. 10, a reinforcing core 310 is assembled on the layer 308 by a stiffening adhesive. It is also an expanded and crosslinked polyethylene foam, but a little more dense than those of the layers 304, 306 or 308. In addition, this core 310 is surrounded by reinforcing glue 7 reinforced with fibers, as explained above. Then, on the sides of the core are added strips of expanded and cross-linked polyethylene foam of the same density as that of the layers 304, 306 or 308.

Lastly, a sole 314 made of expanded polyethylene foam, for example 70 kg / m ³ , is glued to the core 310 and the strips 312. Thus, the assembly of the layers was completed by a stiffening glue to obtain a kayak blank.

Then, this assembly is put under a press to wait for the hardening of the glue for a time between 1h to 10h. Then, after hardening of the glue, the high speed machining is carried out on the faces to obtain the desired contour, which is shown in FIGS. 14 and 15.

Finally, heat treatment by blowing hot air to about 100 ^° is applied to give a surface finish to the kayak 200. Of course, the invention is not limited to the embodiments described above and many variants are conceivable without departing from the scope of the present invention.

It is easy to understand the advantages of the present invention, that is to say a particularly lightweight composite structure, pleasant in contact with the skin while having a good rigidity to support totally or partially a person.

Claims

1. Composite structure (1) characterized in that it comprises at least a first (3) and a second (5) layers of an expanded and crosslinked polyethylene foam, assembled by stiffening adhesive (7).

2. Composite structure according to claim 1, characterized in that the stiffening adhesive (7) comprises a resin.

3. Composite structure according to claim 2, characterized in that the resin is an epoxy resin or a polyester resin.

4. Composite structure according to claim 1, characterized in that the stiffening adhesive (7) is a cyanoacrylate adhesive.

5. Composite structure according to any one of claims 1 to 4, characterized in that the stiffening adhesive (7) is reinforced with fibers.

6. Composite structure according to claim 5, characterized in that the stiffening adhesive (7) is reinforced with carbon fibers, a glass fabric, or Kevlar ™.

7. Composite structure according to any one of claims 1 to 6, characterized in that the thickness of a layer of foam is between 20mm and 100mm.

8. Composite structure according to any one of claims 1 to 7, characterized in that the density of the foam layers is between 25kg / m ³ and 70kg / m ³ , preferably between 30kg / m ³ and 50kg / m ³ .

9. Composite structure according to any one of claims 1 to 8, characterized in that it comprises at least three layers (3, 5, 9), at least the end layers seen in the assembly direction of the layers. are expanded and crosslinked polyethylene foam.

10. Composite structure according to claim 9, characterized in that all the layers (3, 5, 9) are made of expanded polyethylene foam and crosslinked.

11. Composite structure according to claim 9, characterized in that at least one inner layer (9) comprises a static reinforcing element.

12. Structure according to claim 11, characterized in that the reinforcing element is made of wood, or hard plastic material.

13. A method of manufacturing a support element, in particular a human, in a composite structure, characterized in that

- Layers (110) expanded and crosslinked polyethylene foam layers, by stiffening glue,

the chip assembly (114) is machined off the composite structure assembly to obtain a desired external shape.

14. The manufacturing method according to claim 13, characterized in that the machining step (114) is performed by high speed machining.

15. The manufacturing method according to claim 13 or 14, characterized in that between the assembly step (110) and the machining step (114), the press-bonded layers are pressed until hardening. the stiffening glue (112).

16. Manufacturing method according to any one of claims 13 to 15, characterized in that before the assembly (110), is precut (108) the foam layers to obtain a blank stacking of the support member final.

17. The manufacturing method according to any one of claims 13 to 16, characterized in that carries out a heat treatment (116) on the outer surface after the machining step (114).

18. The manufacturing method according to claim 17, characterized in that the heat treatment (116) comprises the projection of hot air at a temperature between 80 C and 120 C, preferably 100 ^° .

19. Manufacturing method according to any one of claims 13 to 18, characterized in that it incorporates reinforcing fibers in the stiffening adhesive during assembly.

20. Support element characterized in that it comprises a composite structure (1) according to any one of claims 1 to 12.

21. Nautical vehicle, in particular kayak (200), characterized in that it is made with a composite structure (1) according to any one of claims 1 to 12.

22. The watercraft as claimed in claim 21, characterized in that the layer of expanded and crosslinked polyethylene foam forming the soleplate (216) has a density greater than that of the adjacent layers, in particular equal to 70 kg / m ³ .

23. Watercraft in the form of a kayak according to the claim

21 or 22, characterized in that it comprises a passenger housing (202) of generally U-shaped whose branches (204) are intended to house the legs of the passenger and the base (206) is intended to house the trunk of the passenger .

24.Nautical vehicle in the form of a kayak according to claim

23, characterized in that the bottom (208) of the passenger housing (202) has at the branches (204) a rounded anatomical shape (210), lifting the leg at the knee.

A water kayak vehicle according to any one of claims 21 to 24, characterized in that the stern (212) has a flattened and enlarged shape to improve the lift and stability at the rear of the kayak.

26.Nautical vehicle in the form of a kayak according to claim 25, characterized in that it comprises a housing (214) for receiving a sealed receptacle.