Composite panel

Abstract

Composite panel, particularly for forming roof panels of cars and/or industrial vehicles, and method of manufacturing the composite panel, which composite panel includes a core of foamed material, at least one skin layer of nonwoven material, and at least one connecting layer between the core of foamed material and the skin layer of nonwoven material.

Claims

1. Composite panel comprising: a core layer, which comprises cross-linked foamed polyolefin; wherein the cross-linked foamed polyolefin comprises high-density polyethylene (HDPE); and a reinforcing layer on at least one of two faces of the core layer, wherein the reinforcing layer comprises a first non-woven layer comprising unidirectionally-oriented continuous thermoplastic polyester fibers and a non-woven web of randomly-oriented fibers; and the first non-woven layer and the non-woven web are joined together by at least one layer comprising a second thermoplastic polymer, which has a lower softening temperature than a first softening temperature of the unidirectionally-oriented continuous thermoplastic polymer fibers, such that the reinforcing layer is in the form of a sheet having said layers of fibers joined together by the second thermoplastic polymer with a three-dimensional fiber structure comprising a first side with randomly-oriented fibers and a second opposite side with unidirectionally-oriented fibers; and the composite panel has a total weight of less than 950 g/m.sup.2, a total thickness of less than 6.5 mm and a deflection value of less than 5 mm.

2. The composite panel according to claim 1, wherein said core layer comprises the HDPE in an amount ranging from 20 to 40% by weight of total weight of the core layer.

3. The composite panel according to claim 1, wherein the softening temperature of the second thermoplastic polymer ranges from 80 to 120 C. and the first softening temperature is at least 230 C.

4. The composite panel according to claim 1, wherein the reinforcing layer has a weight ratio of the unidirectionally-oriented continuous thermoplastic polyester fibers to the second thermoplastic polymer of 0.6:1 to 1:1.

5. The composite panel according to claim 1, comprising one or more of said reinforcing layers successively overlapped on both faces of said core layer.

6. The composite panel according to claim 1, wherein the unidirectionally-oriented continuous thermoplastic polyester fibers and the randomly-oriented fibers are embedded into a matrix of the second thermoplastic polymer.

7. The composite panel of claim 6, wherein the matrix of the second thermoplastic polymer adheres to the core layer.

8. The composite panel according to claim 1, further comprising an additional layer of a plastic material on an additional face of said first layer of unidirectionally-oriented fibers that does not face towards said core layer.

9. The composite panel according to claim 1, wherein the unidirectionally-oriented continuous thermoplastic polyester fibers comprise polyethylene terephthalate fibers.

10. The composite panel according to claim 1, wherein said first non-woven layer further comprises glass fibers.

11. The composite panel according to claim 10, wherein said glass fibers are sealed within said first non-woven layer by covering said first non-woven layer with a thermoplastic resin.

12. The composite panel according to claim 7, wherein the randomly-oriented fibers comprise basalt fibers.

13. The composite panel according to claim 12, wherein said basalt fibers are chopped.

14. The composite panel according to claim 12, wherein and said first non-woven layer comprises polyester fibers and glass fibers, said first non-woven layer and said non-woven web being joined together by the second thermoplastic polymer to form a three-dimensional fiber structure comprising randomly-oriented fibers on a first side and unidirectionally-oriented fibers on an opposite side.

15. The composite panel according to claim 1, wherein the at least one of the reinforcing layers successively overlap both faces of said core layer; each first non-woven layer being covered on a side that does not face towards said core layer with the non-woven web, the first non-woven layer and the non-woven web layers in the reinforcing layer on both sides of said core layer being joined together and to the core layer by the second thermoplastic polymer.

16. The composite panel according to claim 6, further comprising a bonding agent for adhesion between said core layer and said second thermoplastic polymer.

17. The composite panel according to claim 1, wherein said core layer has a basis weight of less than 100 g/m.sup.2; the first non-woven layer has a basis weight of less than 150 g/m.sup.2; and the non-woven web has a basis weight of less than 140 g/m.sup.2.

18. The composite panel according to claim 1, wherein the layer comprising the second thermoplastic polymer has a basis weight of less than 70 g/m.sup.2.

19. The composite panel according to claim 1, wherein said second thermoplastic polymer comprises a polyolefin.

20. The composite panel of claim 6, wherein the reinforcing layer comprises a layer of unidirectionally-oriented, continuous polyester fibers embedded into the polymer matrix, which includes thermoplastic polyolefin; wherein the thermoplastic polyolefin is adhered to the core layer.

21. The composite panel of claim 20 wherein the cross-linked foamed polyolefin comprises 20 to 40% by weight of the HDPE; the polyester fibers comprise polyethylene terephthalate fibers; and the thermoplastic polyolefin comprises polypropylene.

22. The composite panel of claim 1, wherein the reinforcing layer comprises a second layer including randomly-oriented basalt fibers and the first non-woven layer including unidirectionally-oriented thermoplastic polyester fibers reinforced with unidirectionally-oriented glass fibers.

23. The composite panel of claim 22 wherein the thermoplastic polyester fibers and glass fibers are embedded into a polymer matrix of the second thermoplastic polymer; and the polymer matrix is adhered to the core layer.

24. The composite panel of claim 22 wherein the polyester fibers comprise polyethylene terephthalate fibers; the thermoplastic polyolefin comprises polypropylene; and the core layer comprises the HDPE in an amount ranging from 20 to 40% by weight of total weight of the core layer.

25. Composite panel comprising: a cross-linked foamed polyolefin core layer; and a reinforcing layer on at least one of two faces of the core layer, the reinforcing layer comprising a first non-woven layer, which comprises unidirectionally-oriented continuous thermoplastic polyester fibers reinforced with unidirectionally-oriented glass fibers, and a non-woven web of randomly-oriented fibers; wherein the first non-woven layer and the non-woven web are embedded into a matrix of a second thermoplastic polymer having a lower softening temperature than the softening temperature of the unidirectionally-oriented continuous thermoplastic polyester fibers; and the composite panel has a total weight of less than 950 g/m.sup.2, a total thickness of less than 6.5 mm and a deflection value of less than 5 mm.

26. The composite panel of claim 25, comprising one or more of the reinforcing layers successively overlapped on both faces of the core layer.

27. The composite panel of claim 25, wherein the composite panel a deflection value of less than 3.5 mm.

28. The composite panel of claim 27, wherein the thermoplastic polyester fibers have a softening temperature of at least 230 C.

29. The composite panel of claim 25, wherein the cross-linked foamed polyolefin comprises 20 to 40% by weight high-density polyethylene (HDPE) and the core layer has a basis weight of less than 100 g/m.sup.2; the first non-woven layer has a basis weight of less than 150 g/m.sup.2; and the non-woven web has a basis weight of less than 140 g/m.sup.2.

30. The composite panel of claim 25, wherein the unidirectionally-oriented continuous thermoplastic polyester fibers comprise polyethylene terephthalate fibers; and the second thermoplastic polymer comprises polypropylene.

31. Composite panel comprising: a cross-linked foamed polyolefin core layer, which comprises 20 to 40 wt. % HDPE and has a basis weight of less than 100 g/m.sup.2; and a reinforcing layer on at least one of two faces of the core layer, the reinforcing layer comprising a non-woven layer, which has a basis weight of less than 150 g/m.sup.2 and comprises unidirectionally-oriented continuous thermoplastic polyester fibers reinforced with unidirectionally-oriented glass fibers, and a non-woven web of randomly-oriented fibers having a basis weight of less than 140 g/m.sup.2; wherein the first non-woven layer and the non-woven web are embedded into a thermoplastic polyolefin matrix adhered to the core layer; and the composite panel has a total weight of less than 950 g/m.sup.2, a total thickness of less than 6.5 mm and a deflection value of less than 5 mm.

32. The composite panel of claim 31, wherein the thermoplastic polyolefin matrix comprises polypropylene, the thermoplastic polyester fibers comprise polyethylene terephthalate fibers; and the randomly-oriented fibers comprise basalt fibers.

33. The composite panel of claim 31, wherein the each reinforcing layer is in the form of a sheet having said layers of fibers joined together by the thermoplastic polyolefin matrix to form a three-dimensional fiber structure comprising a first side with randomly-oriented fibers and a second opposite side with unidirectionally-oriented fibers.

34. The composite panel of claim 33, wherein the composite panel has a reinforcing layer adhered to each face of the core layer such that the first side of the reinforcing layer with the randomly-oriented fibers facing towards the core layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other characteristics and advantages of the present invention will be more clear from the following description of some non limiting embodiments shown in annexed drawings wherein:

(2) FIG. 1A is a general diagram of a composite panel according to the present invention;

(3) FIG. 1B is a variant embodiment suitable for fields of application wherein a very high mechanical strength is required;

(4) FIG. 1C is a further variant of FIG. 1A;

(5) FIG. 2 is a diagram of an intermediate product comprising layers with randomly-oriented and unidirectionally-oriented fibers respectively;

(6) FIG. 3 is a general diagram of many embodiments, wherein the layer of nonwoven material is between two layers of plastic material;

(7) FIG. 4 is a diagram of an intermediate product composed of a layer of nonwoven material between two layers of plastic material.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(8) A panel according to the present invention comprises a core of foamed material 1, at least one reinforcing layer composed of a layer of thermoplastic fibers for example in the form of nonwoven 2 and at least one connecting film or layer 3 which is made of thermoplastic material and it is provided between the core of foamed material 1 and the nonwoven layer 2 or as an alternative on the face of the nonwoven layer opposite to the core 1 therefore said nonwoven layer 2 is interposed between the core 1 and the thermoplastic film 3 (FIG. 1 C).

(9) The layers of the panel can successively overlap both the faces of the core of foamed material 1, in symmetric or asymmetric relation to said core of foamed material 1, in particular to the plane 10.

(10) The core of foamed material 1 is composed of cross-linked polyolefin material, particularly cross-linked polyethylene with a high content of high-density polyethylene, preferably ranging from 20 to 40%.

(11) The layer of thermoplastic fibers 2 is composed of polyester, particularly polyethylene terephthalate.

(12) In particular the layer of thermoplastic fibers is in the form of nonwoven and it is composed of a mat of continuous filaments, so called spun bond nonwoven.

(13) In the embodiment shown in FIG. 1B there is provided a layer of fibers 4 composed of randomly-oriented basalt fibers and arranged between the core of foamed material 1 and the assembly of the layer of thermoplastic fibers 2 and the film 3 in the two possible arrangement variants of FIGS. 1A and 1C.

(14) The nonwoven layer 2 comprises unidirectionally-oriented and preferably continuous polyester fibers and it can possibly further comprise glass fibers, which glass fibers are unidirectionally-oriented.

(15) If the nonwoven layer 2 comprises unidirectionally oriented glass fibers the layer of mineral fibers, that is basalt 4, and said layer of thermoplastic fibers 2 are joined by said connecting film or layer 3 composed of a film of thermoadhesive material or thermoplastic material to form a three-dimensional fiber structure comprising randomly-oriented fibers in a first side and unidirectionally-oriented fibers in the opposite side.

(16) In the layer of fibers 4, the density of basalt fibers is such to form interstices for the passage of the thermoadhesive material or thermoplastic material once said material has been turned to a viscoelastic condition by heating.

(17) Thus the thermoadhesive material or thermoplastic material pass through the layer of fibers 4 and adhere on the one hand to the layer of thermoplastic fibers 2, and on the other to the core of foamed material 1, such as shown by arrows 30.

(18) In the embodiment shown in FIG. 1 the connecting layer 3 composed of the thermoadhesive film or the layer of thermoplastic material is placed between the layer of thermoplastic fibers 2 and the layer of basalt fibers 4, however it is possible to provide as an alternative to place the thermoadhesive film or the layer of plastic material between the core of foamed material 1 and the layer of basalt fibers 4.

(19) Advantageously the thermoplastic fibers of the nonwoven layer 2 are composed of a thermoplastic polymer having a softening temperature higher than the softening temperature of the thermoplastic polymer or thermoadhesive material of the connecting film 3, therefore by applying heating for softening or melting the material of the connecting film 3, thermoplastic fibers of the layer 2 maintain their shape and structure behaving as natural or mineral fibers and are embedded in the polymer of the film 3 that in the melted condition wets these fibers generating an embedding matrix that in the cooled condition embeds them and blocks them together and in relation to the matrix. As already highlighted above this action allows the best chemical/physical compatibility to be provided between fibers and impregnation or embedding matrix, therefore the mechanical connection between fibers and thermoplastic material containing them is the highest one, while it avoids using relatively heavy mineral or synthetic fibers, improving the mechanical strength and reducing the weight.

(20) The softening temperature of the film preferably ranges from 80 to 120 C. and that of thermoplastic fibers of the layer 2 is equal to or higher than 230 C.

(21) An embodiment provides the core to be composed of cross-linked foamed PE, preferably chemically cross-linked.

(22) Advantageously the core has a content of high-density PE (HDPE) ranging from 20 to 40% by weight of the total weight of the core 1.

(23) As regards thermoplastic material of the layer of fibers 2 and of the film 3 for obtaining the best stiffness to weight ratio, in the reinforcing layer the ratio of polymer having a higher softening temperature to the polymer having a lower softening temperature ranges from 0.6:1 to 1:1.

(24) The film of thermoplastic material (3) is advantageously a multi-layer film composed of at least one polyolefin layer or the like and at least one layer composed of polymers with a high modulus of elasticity in bending, preferably ranging from 2000 to at least 3500 MPa.

(25) The layer of thermoplastic fibers is preferably a layer of unidirectionally-oriented fibers and it is composed of polyester, particularly polyethylene terephthalate.

(26) The arrangement of the panel according to the general diagram shown in FIG. 1 is applicable to the several examples described below.

Example 1A

(27) Panel symmetric in relation to plane 10 in the order from the center to the outside of the panel composed of:

(28) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with basis weight of 70 g/m.sup.2 and thickness of 4 mm;

(29) a reinforcing layer on each side of the core 1 comprising

(30) a connecting layer 3 composed of a thermoadhesive or thermoplastic film with basis weight of 18 g/m.sup.2 and thickness of 20 m;

(31) a layer of thermoplastic fibers in the form of nonwoven 2 composed of polyethylene terephthalate with basis weight of 90 g/m.sup.2.

(32) Such panel has a total weight of 286 g/m.sup.2, a total thickness of 4.7 mm and it has deflection values ranging from 2.5 to 3.5 mm.

Example 1B

(33) Panel symmetric in relation to plane 10 in the order from the center to the outside of the panel composed of:

(34) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with basis weight of 70 g/m.sup.2 and thickness of 4 mm;

(35) a layer of fibers 4 composed of a web of basalt fibers with basis weight of 60 g/m.sup.2;

(36) a connecting layer 3 composed of a thermoadhesive film with basis weight of 18 g/m.sup.2 and thickness of 20 m;

(37) a skin layer of nonwoven material 2 composed of polyethylene terephthalate and reinforced with unidirectionally-oriented glass fibers with basis weight of 90 g/m.sup.2.

(38) Such panel has a total weight of 616 g/m.sup.2, a total thickness of 4.7 mm and it has deflection values ranging from 2.5 to 3.5 mm.

Example 2

(39) Panel asymmetric in relation to plane 10 composed of:

(40) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with basis weight of 70 g/m.sup.2 and thickness of 4 mm;

(41) and on a first side of the core of foamed material 1, in the order from the center to the outside of the panel, it is composed of:

(42) a layer of fibers 4 composed of a web of basalt fibers with basis weight of 60 g/m.sup.2;

(43) a connecting layer 3 composed of a thermoadhesive film with basis weight of 18 g/m.sup.2 and thickness of 20 m;

(44) a skin layer of nonwoven material 2 composed of polyethylene terephthalate and reinforced with unidirectionally-oriented glass fibers, with basis weight of 90 g/m.sup.2.

(45) and on the opposite side of the core of foamed material 1, in the order from the center to the outside of the panel, it is composed of:

(46) a layer of fibers 4 composed of chopped basalt fibers with basis weight of 90 g/m.sup.2;

(47) a connecting layer 3 composed of a layer of plastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(48) a skin layer of nonwoven material 2 composed of polyethylene terephthalate and reinforced with unidirectionally-oriented glass fibers, with basis weight of 90 g/m.sup.2.

(49) Such panel has a total weight of 682 g/m.sup.2, a total thickness of 4.7 mm and it has deflection values ranging from 3.5 to 4.0 mm with load placed on the side comprising the web of basalt fibers.

Example 3

(50) Panel symmetric in relation to plane 10 in the order from the center to the outside of the panel composed of:

(51) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with basis weight of 70 g/m.sup.2 and thickness of 4 mm;

(52) a layer of fibers 4 composed of chopped basalt fibers with basis weight of 90 g/m.sup.2;

(53) a connecting layer 3 composed of a layer of plastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(54) a skin layer of nonwoven material 2 composed of polyethylene terephthalate and reinforced with unidirectionally-oriented glass fibers with basis weight of 90 g/m.sup.2.

(55) Such panel has a total weight of 818 g/m.sup.2, a total thickness of 4.7 mm and it has deflection values of about 3.0 mm.

Example 4

(56) Panel symmetric in relation to plane 10 in the order from the center to the outside of the panel composed of:

(57) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with thickness of 4.7 mm;

(58) a layer of fibers 4 composed of a web of basalt fibers with basis weight of 60 g/m.sup.2;

(59) a connecting layer 3 composed of a thermoadhesive film with basis weight of 18 g/m.sup.2 and thickness of 20 m;

(60) a skin layer of nonwoven material 2 composed of polyethylene terephthalate and reinforced with unidirectionally-oriented glass fibers with basis weight of 90 g/m.sup.2.

(61) Such panel has a total thickness of 6 mm and it has deflection values of about 2.0 mm.

Example 5

(62) Panel asymmetric in relation to plane 10 composed of:

(63) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with basis weight of 70 g/m.sup.2 and thickness of 4 mm;

(64) and on a first side of the core of foamed material 1, in the order from the center to the outside of the panel it is composed of:

(65) a layer of fibers 4 composed of a web of basalt fibers with basis weight of 60 g/m.sup.2;

(66) a connecting layer 3 composed of a thermoadhesive film with basis weight of 18 g/m.sup.2 and thickness of 20 m;

(67) a skin layer of nonwoven material 2 composed of polyethylene terephthalate and reinforced with unidirectionally-oriented glass fibers, with basis weight of 90 g/m.sup.2.

(68) and on the opposite side of the core of foamed material 1, in the order from the center to the outside of the panel, it is composed of:

(69) a layer of fibers 4 composed of a web of basalt fibers with basis weight of 60 g/m.sup.2;

(70) a connecting layer 3 composed of a thermoadhesive film with basis weight of 18 g/m.sup.2 and thickness of 20 m;

(71) a skin layer of nonwoven material 2 composed of polyethylene terephthalate, not reinforced with glass fibers, with basis weight of 100 g/m.sup.2;

(72) Such panel has a total weight of 626 g/m.sup.2, a total thickness of 4.7 mm and it has deflection values ranging from 3.5 to 4.0 mm with load placed on both the sides.

(73) FIG. 2 shows a diagram of an intermediate product comprising a layer of randomly-oriented fibers 4 and a layer of unidirectionally-oriented fibers 2.

(74) The layer of randomly-oriented fibers 4 and the layer of unidirectionally-oriented fibers 2 are joined by a connecting layer 3 to form a three-dimensional fiber structure comprising randomly-oriented fibers on a first side and unidirectionally-oriented fibers in the opposite side.

(75) The layer of randomly-oriented fibers 4 comprises basalt fibers, the layer of unidirectionally-oriented fibers 2 comprises glass fibers and said connecting layer 3 is composed of a film of thermoadhesive material or a layer of plastic material, preferably as described in the above examples with reference to FIG. 1.

(76) Such intermediate product can be used alone or in combination with additional layers of any type, particularly in the arrangement shown in FIG. 1.

(77) FIG. 3 shows the general diagram of a further embodiment, wherein the connecting layer 3 is composed of a layer of plastic material, preferably comprising polyolefins, particularly polypropylene.

(78) An additional layer of plastic material 3 can be provided on the additional face of the layer of thermoplastic fibers in the form for example of nonwoven 2 which does not face towards the core of foamed material 1, such that the nonwoven layer 2 is embedded between two connecting layers or films 3 of thermoplastic material, which thermoplastic material, by heating, is softened such to permeate between the thermoplastic fibers in the nonwoven when heat pressing the panel, said fibers having a softening temperature higher than that of the thermoplastic material of the film 3.

(79) The total weight of the connecting layers 3 of plastic material is substantially equal to the weight of the skin layer 2 or anyway preferably ranging from 0.6:1 to 1:1 ratio of polymer of fibers of the nonwoven 2 having the higher softening temperature to the polymer of the film 3 having the lower softening temperature.

(80) The connecting layers or films 3 of thermoplastic material can each one comprise a multi-layer film composed of at least one polyolefin layer or another polymer with a low heat softening point and at least one layer composed of polymers with a high modulus of elasticity in bending, preferably ranging from 2000 to at least 3500 MPa.

(81) The arrangement of the panel according to the general diagram shown in FIG. 3 is applicable to the several examples described below.

Example 6

(82) Panel symmetric in relation to the plane 10 in the order from the center to the outside of the panel composed of:

(83) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with basis weight of 70 g/m.sup.2 and thickness of 4 mm;

(84) a first connecting layer 3 composed of a layer of thermoplastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(85) a layer 2 of unidirectionally-oriented thermoplastic fibers and for example in the form of nonwoven said fibers being made of polyethylene terephthalate and said layer being reinforced by adding unidirectionally-oriented glass fibers with basis weight of 90 g/m.sup.2;

(86) a second connecting layer 3 composed of a layer of plastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(87) Such panel has a total weight of 676 g/m.sup.2, a total thickness ranging from 4.9 mm to 5.3 mm and it has deflection values of about 4.5 mm.

Example 7

(88) Panel symmetric in relation to the plane 10 in the order from the center to the outside of the panel composed of:

(89) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with basis weight of 80 g/m.sup.2 e thickness of 5 mm;

(90) a first connecting layer or film 3 composed of a layer of thermoplastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(91) a layer 2 of thermoplastic fibers for example in the form of nonwoven which thermoplastic fibers are composed of polyethylene terephthalate and the fibers being unidirectionally-oriented, moreover the layer being further reinforced by unidirectionally-oriented glass fibers with basis weight of 90 g/m.sup.2.

(92) a second connecting layer or film 3 composed of a layer of thermoplastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(93) Such panel has a total weight of 796 g/m.sup.2, a total thickness ranging from 5.9 mm to 6.2 mm and it has deflection values ranging from 3.0 to 4.0 mm.

Example 8

(94) Panel asymmetric in relation to plane 10 composed of:

(95) a core of foamed material 1 made of cross-linked polyethylene with a high content of high-density polyethylene with basis weight of 80 g/m.sup.2 and thickness of 5 mm;

(96) and on a first side of the core of foamed material 1, in the order from the center to the outside of the panel, it is composed of:

(97) a first connecting layer or film 3 composed of a layer of plastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(98) a layer 2 of thermoplastic fibers for example in the form of nonwoven whose fibers are composed of polyethylene terephthalate and are unidirectionally-oriented while said layer is reinforced with unidirectionally-oriented glass fibers, with basis weight of 90 g/m.sup.2.

(99) a second connecting layer or film 3 composed of a layer of thermoplastic material, in particular polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(100) and on the opposite side of the core of foamed material 1, in the order from the center to the outside of the panel, it is composed of:

(101) a first connecting layer or film 3 composed of a layer of plastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m;

(102) a layer 2 of thermoplastic fibers for example in the form of nonwoven whose fibers are composed of polyethylene terephthalate and are unidirectionally-oriented while said layer is not reinforced with glass fibers and it has a basis weight of 100 g/m.sup.2;

(103) a second connecting film or layer 3 composed of a layer of plastic material, particularly polypropylene, with basis weight of 54 g/m.sup.2 and thickness of 60 m.

(104) Such panel has a total weight of 806 g/m.sup.2, a total thickness ranging from 5.9 to 6.2 mm and it has deflection values of about 4.0 mm.

(105) It has to be noted that the examples described above can be modified such to provide on one of the two sides of the core or on both of them identical or different reinforcing layers and that is layers 2 of thermoplastic fibers in the form of nonwoven both reinforced with glass fibers and not reinforced with glass fibers, combined such to form panels symmetric or asymmetric in relation to plane 10.

(106) In a preferred embodiment glass fibers are spaced from each other by 5-10 mm.

(107) In particular the layer 2 of thermoplastic fibers for example in the form of nonwoven is composed of polyethylene terephthalate fiber, either virgin or regenerated, with a basis weight ranging from 90 to 100 g/m.sup.2, while for each skin layer 2 there are provided two layers of plastic material 3 with a basis weight ranging from 50 to 60 g/m.sup.2, thus observing the ratio by weight of the nonwoven material to the plastic material of about 1:1.

(108) FIG. 4 shows a diagram of an intermediate product composed of a layer of thermoplastic fibers, for example in the form of nonwoven 2, and at least two additional layers of thermoplastic material 3.

(109) The layers of thermoplastic material 3 overlap the layer 2 of thermoplastic fibers for example in the form of nonwoven on the opposite sides thereof.

(110) The layer 2 of thermoplastic fibers for example in the form of nonwoven is composed of fibers, preferably unidirectionally-oriented and possibly continuous ones, with such a density as to form interstices for the passage of the thermoplastic material of the film 3 of thermoplastic material, once said plastic material has been turned to the viscoelastic condition by heating, so that said thermoplastic material passes through said layer 2 of thermoplastic fibers and each fiber segment is isolated from contiguous fiber segments by said thermoplastic material and it is anyway blocked in position in the matrix of thermoplastic material once it becomes cold.

(111) Such intermediate product can be used alone or in combination with additional layers of any type, in particular in the arrangement shown in FIG. 3.