Building panel with sections

Abstract

A building panel with a high degree of isotropy with regard to the load bearing capacity and flexural strength. The building panel includes a first section and a second section, each section including at least one layer, each of the at least one layer having fibers, whereby the fibers are distributed substantially homogeneously throughout each layer, substantially parallel to the main surfaces of the panel and oriented predominantly in the same direction and the sections are firmly joined in transverse direction, and the first section is thinner than the second section.

Claims

1. A building panel comprising: a first section and a second section, each section including at least one layer, each of the at least one layer comprising fibers mixed within a binding material; the fibers are distributed substantially homogeneously throughout each layer, substantially parallel to the main surfaces of the panel and oriented predominantly in the same direction; the first and second sections are firmly joined in transverse direction; the first section is thinner than the second section; the first section makes up at least 5% of the thickness of the panel and at most 30% of the thickness of the panel; the building panel has a fiber content of 5% to 25% by weight; the building panel comprises at least 50% by weight cementitious material, and the building panel has a degree of isotropy greater than or equal to 0.83 with regard to its load bearing capacity when determining the failure load according to EN 12825 (2001) with the first section beneath the second section.

2. The building panel according to claim 1, wherein the building panel is used in a floor.

3. The building panel according to claim 1, wherein the first section makes up at least 10% of the thickness of the panel and at most 18% of the thickness of the panel.

4. The building panel according to claim 1, wherein the second section has a 2.5 to 10 times greater thickness compared to the first section.

5. The building panel according to claim 1, wherein the at least one layer comprises a plurality of lamina comprising fibers in the same orientation.

6. The building panel according to claim 1, wherein the building panel is a gypsum fiberboard or a cement fiberboard and wherein the building panel has a monolithic appearance.

7. The building panel according to claim 1, wherein the fibers are of: mineral origin, synthetic origin, biological origin, or a combination thereof.

8. The building panel according to claim 1, wherein: the fibers have a mean length of 1 mm to 5 mm; the fibers have a mean diameter of 15 ?m to 50 ?m; or both.

9. The building panel according to claim 1, wherein the building panel has a degree of isotropy greater than or equal to 0.88 with regard to the flexural strength when determining the flexural strength according to EN 15283-2 (2009).

10. The building panel according to claim 1, wherein the building panel has a density greater than 1200 kg/m3 and less than 2000 kg/m3.

11. The building panel according to claim 1, wherein at least one of: the first section and the second section are joined by pressure before the binding material has set; or the first section and the second section are joined without the use of an adhesive.

12. The building panel according to claim 1, wherein the fibers are in the form of pulp which is prepared from recycled paper, cardboard, or a combination of paper and cardboard, and wherein the fibers comprise approximately 80% cellulose.

13. A building panel comprising: a first section and a second section, each section including at least one layer, each of the at least one layer comprising fibers mixed within a binding material; the fibers are distributed substantially homogeneously throughout each layer, substantially parallel to the main surfaces of the panel and oriented predominantly in the same direction; the first and second sections are firmly joined in transverse direction; the first section is thinner than the second section; the first section makes up at least 5% of the thickness of the panel and at most 30% of the thickness of the panel; the second section includes at least two layers oriented in the same direction relative to the orientation of the at least one layer of the first section; the building panel comprises at least 50% by weight cementitious material; and the building panel has a degree of isotropy greater than or equal to 0.83 with regard to its load bearing capacity when determining the failure load according to EN 12825 (2001) with the first section beneath the second section.

14. A building panel comprising: a first section, a second section, and a third section, each section including at least one layer, each of the at least one layer comprising fibers mixed within a binding material; the fibers are distributed substantially homogeneously throughout each layer, substantially parallel to the main surfaces of the panel and oriented predominantly in the same direction; the first and second sections are firmly joined in transverse direction, and the second and third sections are firmly joined in transverse direction; the first section is thinner than the second section; the first section makes up at least 5% of the thickness of the panel and at most 30% of the thickness of the panel; and the building panel comprises at least 50% by weight cementitious material; and the building panel has a degree of isotropy greater than or equal to 0.88 with regard to the flexural strength when determining the flexural strength according to EN 15283-2 (2009).

15. The building panel according to claim 14, wherein the building panel has a degree of isotropy greater than or equal to 0.83 with regard to its load bearing capacity when determining the failure load according to EN 12825 (2001) with the first section beneath the second section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: Schematic representation of a building panel according to the invention.

(2) FIG. 2: Schematic representation of an alternative embodiment of a building panel according to the invention.

(3) FIG. 3: Schematic representation of the set-up to test the load bearing capacity i.e. the failure load of a panel according to EN 12825 (2001).

(4) FIG. 4: Schematic representation of the set-up to test the flexural strength of a panel according to EN 15283-2 (2009).

DETAILED DESCRIPTION

Reference Number

(5) 1 first section 2 second section 3 fiber in cross section 4 fiber in longitudinal section 5 top main surface 6 layer 7 edge 8 steel cylinder 9 specimen 10 indentor 11 parallel support 12 platen 13 direction of applied force 14 sensor measuring deflection 15 adjacent edge

(6) FIG. 1 depicts a panel with two sections, whereby the first section 1 is thinner than the second section 2. In this embodiment each section 1 and 2 consists of one layer 6. The fibers of the first section are cut in cross section 3, while the fibers of the second section are cut in the longitudinal section 4, as can be seen below edge 7. This is reversed below the adjacent edge 15. The panel has two main surfaces. Here, the top main surface 5 is shown and the bottom main surface is hidden.

(7) FIG. 2 depicts a panel with two sections 1 and 2, wherein section 1 comprises one layer 6 and section 2 comprises two layers 6. To achieve a greater overall thickness of the panel two layers with fibers in the same orientation make up the second section 2 and only one layer 6 makes up the first section 1. All three layers 6 can be joined by pressure, such that sections 1 and 2 can be joined in transverse direction as can be seen by the orientation of the fibers 3,4.

(8) FIG. 3 and FIG. 4 depict the main aspects of the test set-ups for the measurements according to 12825 (2001) and EN 15283-2 (2009).

(9) The test set-up for the load-bearing capacity is pictured in FIG. 3. The specimen 9, typically sized 600 mm?600 mm, are placed on four steel cylinders 8 of equal height (90 mm diameter) instead of the usual pedestals. The four corners of a specimen 9 each cover a quarter of the circular surface of the cylinder. The indentor 10, a steel cube 25 mm?25 mm?25 mm, is pushed down on the specimen with a steadily increasing compressive force 13. The deflection sensor 14 measures the deflection or deformation of the specimen with increasing force until the panel cracks and the failure load is determined.

(10) The test set-up for determining the flexural strength is pictured in FIG. 4. Specimen, typically sized 550 mm?300 mm for a building panel thickness of more than 20 mm, are cut from a building panel in longitudinal and in transverse direction. A specimen 9 is placed on parallel supports 11. A platen 12 is pushed down on the center of the specimen with a compressive force 13. The deflection sensor 14 measures the deflection or deformation of the specimen with increasing force until the panel breaks and the failure load is determined. The flexural strength is then determined as described in EN 15283-2 (2009). For the degree of isotropy the flexural strength of a specimen cut in longitudinal direction is related to the flexural strength of a specimen cut in transverse direction.

(11) The examples are intended to further describe the present invention.

(12) The samples were tested according to EN 12825 (2001), EN 15283-2 (2009), FIG. 3 and FIG. 4. The failure load was tested on 600 mm?600 mm panels using steel cylinders instead of pedestals. Thus, the failure load for the load bearing capacity was determined substantially according to EN 12825 (2001). It is believed that this modification does not have an impact on the test results. All tests were conducted on gypsum fiberboard. The results for different relative thicknesses are summarized in Tables 2 and 3. From these results it appears that the degree of isotropy both with regard to the load bearing capacity and the flexural strength increases with decreasing thickness of the first section. However, it is expected that the degree of isotropy will decrease, if the first section is too thin.

(13) The degree of isotropy with regard to the load bearing capacity appears to be one directional, which means that the first section has to be the bottommost section in the test according to EN 12825 (2001), ideally also in the installed panel. The optimum ratio of the thickness of the first section to the thickness of the thin section appears to be close to the 84%/16% ratio. Test results also indicate that if the section makes up approximately 16% of the thickness of the panel, the weak and strong edge are reversed compared to all other examples. So far it is unclear, if this is due to experimental error or that the optimum ratio was surpassed slightly.

(14) Unexpectedly, the degree of isotropy with regard to the flexural strength improved regardless of the configuration of the panel i.e. whether the first section was the bottom or top section in the test. It is expected that the degree of isotropy in flexural strength will also increase regardless of the configuration, for the 68%/32% and 84%/16% panels.

(15) TABLE-US-00001 TABLE 1 Average failure load [N] for different panel thicknesses of gypsum fiberboard determined according to EN 12825 (2001). All panels have two equally thick sections that are joined in transverse direction (50%/50%); fibers of the bottom section are oriented substantially parallel to the A and C edges in FIG. 1; sample size in brackets. To guarantee identical measuring conditions, the building panels were tested on their production day. Average failure load [N] (sample size) Sampling point in Sampling point in Total panel the center of the center edge Degree of thickness (mm) edge 7 15 Isotropy 28 4222 (347) 5707 (66) 0.74 30 4720 (685) 6387 (127) 0.74 34 6250 (738) 8274 (104) 0.75 36 6744 (879) 9013 (130) 0.74

(16) TABLE-US-00002 TABLE 2 Average failure load [N] determined according to EN 12825 (2001) for different proportions of gypsum fiberboard sections joined in transverse direction; fibers of the bottom section are oriented substantially parallel to the edges 7 as depicted in FIG. 1; sample size = 10; panel thickness = 30.0 mm; panels were tested seven days after production. Relative thickness Average failure load [N] of the top Sampling section to the Sampling point point in the section layer in in the center of center edge Degree of a building panel edge 7 15 Isotropy 68%/32% 5258 6217 0.846 79%/21% 5369 6011 0.893 84%/16% 5539 5452 0.984

(17) TABLE-US-00003 TABLE 3 Average flexural strength [N/mm.sup.2] determined according to EN 15283-2 (2009) for different proportions gypsum fiberboard sections joined in transverse direction; sample size = 10; panel thickness = 30.0 mm; T = bottom section transverse to machine direction and parallel to the platen, P = bottom section in machine direction and perpendicular to the platen, SD = standard deviation. Relative thickness of the top section to the bottom section Flexural strength Degree of in a building panel [N/mm.sup.2] ? SD isotropy 50%/50% T 13.10 ? 0.5 0.81 50%/50% P 16.10 ? 0.4 79%/21% T 13.74 ? 0.5 0.90 79%/21% P 15.32 ? 0.5 21%/79% T 13.51 ? 0.3 0.89 21%/79% P 15.19 ? 0.3

(18) Descriptions of terms of degree such as approximately or about as used herein should be understood as a reasonable amount of deviation of the term of degree such that the result is not significantly changed. These terms of degree should be construed as including a deviation of at least ?5% or at least ?10%.

(19) As used herein, the term substantially and predominantly are intended to be understood as sufficient for the effect or to obtain the same overall result as if absoluteness were present. However, both terms may include a deviation of up to 40%, preferably up to 20%, more preferably up to 10%, most preferably up to 2%.

(20) The degrees of isotropy according to the invention may include a tolerance of ?0.02.