Thin composite laminate and use thereof in making sports articles, especially boots
Laminated composite material usable to make articles of manufacture, such as boots or other sports articles in particular. The laminate is a new basic material particularly directed to articles of manufacture having drastic mechanical requirements and which are very inexpensive and lightweight. The laminate has a sandwich structure having a core between two layers. More particularly, the core and the two layers are composites, and at least a portion of the fibers of the core have a mechanical strength significantly lower than that of at least a portion of the fibers of one and/or the, other layers. In a particular embodiment, the laminate has a thickness of 3 mm or less. The layers are sheets of carbon fabric embedded in an epoxy resin, and the core is made from non-woven polyamide micro-fibers having a thickness equal to 0.32 mm. The invention also relates to the manufacture of the laminate.
1. A laminate comprising:
a sandwich structure comprising:
two layers of a composite material containing fibers;
a core consisting essentially of a fiber-reinforced composite material, said core being positioned between the two layers;
at least a portion of the fibers of the core having a mechanical strength lower than a mechanical strength of at least a portion of the fibers of at least one of the two layers;
the fibers of the core comprising a member selected from the group consisting of synthetic fibers, natural fibers, cellulose fibers, or a mixture of any of combination of synthetic, natural, and cellulose fibers, the synthetic fibers comprising a member selected from the group consisting of polyamide fibers, polyolefine fibers, polyester fibers, and polyesterimide fibers, and the natural fibers comprising a member selected from the group consisting of silk fibers, cotton fibers, linen fibers, jute fibers, and hemp fibers;
the laminate having a total thickness e less than or equal to 3 mm;
the core having a thickness e 2 and the two layers have a total thickness e 3 +e 4 , a ratio between the thickness of the core and the total thickness of the two layers being defined as follows:
e
2
/
e
3
+
e
4
2
≤
5.
2. A laminate according to claim 1 , wherein:
the ratio between the thickness of the core and the total thickness of the two layers are defined as follows:
e
2
/
e
3
+
e
4
2
≤
4.
3. A laminate according to claim 1 , wherein:
the ratio between the thickness of the core and the total thickness of the two layers are defined as follows:
e
2
/
e
3
+
e
4
2
≤
3.5
.
4. A laminate according to claim 1 , wherein:
the fibers of the core comprise fibers oriented within the composite material of the core.
5. A laminate according to claim 1 , wherein:
the fibers of the core comprise woven fibers.
6. A laminate according to claim 1 , wherein:
the fibers of the core comprise non-woven fibers.
7. A laminate according to claim 1 , wherein:
the fibers of the core comprise fibers randomly situated within the composite material of the core.
8. A laminate according to claim 1 , wherein:
the fibers of said at least one of the two layers comprise fibers made of a material comprising a member selected from the group consisting of polyolefine, oriented and stretched high-density polyethylene, polyamide, VECTRAN®, and SPECTRA®.
9. A laminate according to claim 1 , wherein:
the fibers of said at least one of the two layers comprise metallic fibers or metallic micro-fibers.
10. A laminate according to claim 9 , wherein:
the fibers of said at least one of said two layers comprise fibers made of a material comprising a member selected from the group consisting of aluminum, titanium, and boron.
11. A laminate according to claim 1 , wherein:
the fibers of the core comprise micro-fibers having a characteristic of rupture stress CR of less than or equal to 1,500 Mpa.
12. A laminate according to claim 1 , wherein:
the core comprises a plurality of superimposed plies of composite material.
13. A laminate according to claim 1 , wherein:
at least one of the two layers comprises a plurality of superimposed plies of composite material.
14. A laminate according to claim 12 , wherein:
at least one of the two layers comprises a plurality of superimposed plies of composite material.
15. A laminate according to claim 1 , wherein:
at least one of the two layers is transparent so that the core is visible, the core comprising decorating elements.
16. A laminate according to claim 1 , wherein:
the laminate has a tensile strength R in a bending test Tf relative to a specimen test piece made of a carbon fiber composite having the same shape and rigidity as those of the test pieces tested, such that R is greater than or equal to 50 N/mm.
17. A method of manufacturing a laminate according to claim 1 , wherein:
the core comprises at least one ply;
each of the two layers comprises at least one ply;
the core and at least the two layers are superimposed;
the plies of the core and each of the layers comprise plies of woven or non-woven micro-fibers, oriented or non-oriented micro-fibers, and fibers preimpregnated with resin or non-preimpregnated with resin.
18. A laminate comprising:
a sandwich structure having a total thickness no greater than 3 mm, said sandwich structure comprising:
a core consisting essentially of a composite, the composite comprising a polymer resin matrix reinforced with fibers, the fibers of the composite consisting essentially of fibers having a modulus M in longitudinal traction of less than or equal to 50,000 Mpa;
two fiber-reinforced composite layers, the core being positioned between the two layers, fibers of the two layers being different from the fibers of the core;
both of the two fiber-reinforced composite layers having a modulus M in longitudinal traction of less than or equal to 50,000 Mpa;
the core having a thickness e 2 and the two layers have a total thickness e 3 +e 4 , a ratio between the thickness of the core and the total thickness of the two layers being defined as follows:
e
2
/
e
3
+
e
4
2
≤
5.
19. A laminate according to claim 18 , wherein the fibers of the core have:
a rupture force in longitudinal traction of less than or equal to 1,500 Mpa;
an elongation at rupture in longitudinal traction of equal to or greater than 1.0%.
20. A laminate according to claim 18 , wherein:
the fibers of the core comprise micro-fibers having a modulus M in longitudinal traction of less than or equal to 30,000 Mpa.
21. A laminate according to claim 18 , wherein:
the fibers of the core comprise micro-fibers having a modulus M in longitudinal traction of less than or equal to 20,000 Mpa.
22. A laminate according to claim 18 , wherein:
the ratio between the thickness of the core and the total thickness of the two layers is defined as follows:
e
2
/
e
3
+
e
4
2
≤
4.
23. A laminate according to claim 18 , wherein:
the ratio between the thickness of the core and the total thickness of the two layers is defined as follows:
e
2
/
e
3
+
e
4
2
≤
3.5
.
24. A laminate according to claim 18 , wherein:
said core consists essentially of said composite.