Method for manufacturing a structural beam, structural beam, and building comprising such a beam

Abstract

A method of manufacturing a structural beam comprising an elongate base part comprising a polymer. The base part has a length, a width and a height. The beam also comprises an elongate reinforcement part comprising a strip comprising a unidirectional polymer, bonded to the base part at an outer surface of the base part and extending in the length direction along the length of the base part. The strip has a higher Young's modulus than the base part. The method also relates to a beam and to a building comprising such a beam.

Claims

1. A method of manufacturing a structural beam comprising an elongate base part comprising a polymer, the base part having a length, defining a length direction of the beam, and having a width and a height and a thickness, and an elongate reinforcement part comprising a strip comprising a polymer and unidirectional fibers, bonded to the base part at an outer surface of the base part and extending in the length direction along the length of the base part, the strip of the elongate reinforcement part having a higher Young's modulus than the base part, the method comprising feeding a composition comprising the polymer for forming the elongate base part, via an extruder, to an extrusion die, feeding the elongate reinforcement part comprising the strip to the extrusion die, forming the beam by extrusion, while bonding the elongate reinforcement part to the base part by joining the elongate reinforcement part and the composition within the extrusion die, wherein the base part has a width in the range of 10-50 percent of the height.

2. The method according to claim 1, further comprising bonding a further elongate reinforcement part comprising a further strip comprising a polymer and unidirectional fibers to the base part at a further outer surface of the base part opposite the outer surface and extending in the length direction along the length of the base part.

3. The method according to claim 2, wherein the further elongate reinforcement part of the beam to be formed comprises multiple strips comprising a polymer and unidirectional fibers bonded to each other, wherein during the step of feeding, said further elongate reinforcement part comprising the multiple strips is fed to the extrusion die for the purpose of bonding said further elongate reinforcement part to said further outer surface of the base part.

4. The method according to claim 2, wherein a width of the elongate reinforcement part and/or the further elongate reinforcement part is at least substantially equal to the width of the base part.

5. The method according to claim 1, wherein the elongate reinforcement part of the beam to be formed comprises multiple strips comprising a polymer and unidirectional fibers bonded to each other, wherein during the step of feeding, said elongate reinforcement part comprising the multiple strips is fed to the extrusion die.

6. The method according to claim 1, wherein the polymer of the base part is chosen from the group consisting of thermoplastic polymers, including co-polymers, or blends thereof.

7. The method according to claim 1, wherein the polymer of the strip is chosen from the group consisting of thermoplastic polymers, including co-polymers, or blends thereof.

8. The method according to claim 1, the base part being constituted by a hollow profile.

9. The method according to claim 8, the hollow profile of the base part being filled with a foam.

10. The method according to claim 1, wherein the strip comprising a polymer and unidirectional fibers has a thickness in the range of 0.1-5 mm and the base part has an I shaped cross section half and a reversed L-shaped cross section half.

11. The method according to claim 1, wherein the base part has a height in the range of 50-700 mm.

12. The method according to claim 1, further comprising bonding a further elongate reinforcement part comprising a further strip comprising a polymer and unidirectional fibers to the base part at a further outer surface of the base part opposite the outer surface and extending in the length direction along the length of the base part; wherein the elongate reinforcement part of the beam to be formed comprises multiple strips comprising a polymer and unidirectional fibers bonded to each other; wherein during the step of feeding, said elongate reinforcement part comprising the multiple strips is fed to the extrusion die; wherein the strip comprising a polymer and unidirectional fibers has a thickness in the range of 0.1-5 mm; wherein the base part has a height in the range of 50-700 mm; wherein the base part has a width in the range of 10-50 percent of the height; wherein the further elongate reinforcement part of the beam to be formed comprises multiple strips comprising a polymer and unidirectional fibers bonded to each other; wherein during the step of feeding, said further elongate reinforcement part comprising the multiple strips is fed to the extrusion die for the purpose of bonding said further elongate reinforcement part to said further outer surface of the base part; and wherein a width of the elongate reinforcement part and/or the further elongate reinforcement part is at least substantially equal to the width of the base part.

13. The method according to claim 12, the base part being constituted by a hollow profile filled with a foam.

14. The method according to claim 1, wherein the strip comprising a polymer and unidirectional fibers has a thickness in the range of 0.2-2.5 mm.

15. The method according to claim 1, wherein the base part has a height in the range of 100-400 mm.

16. The method according to claim 1, wherein the elongate base part has a top outer surface extending in the length direction and at least one side outer surface extending in the length direction; wherein the strip is located on the top outer surface and wherein the strip is not located on the at least one side outer surface.

17. The method according to claim 1, wherein the structural beam is configured to support a roof of a building.

18. A method of supporting a roof of a building comprising: manufacturing a structural beam according to the method of claim 1; and supporting the roof of the building with the structural beam.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The present teachings are described hereinafter with reference to the accompanying schematic drawings in which examples of the invention are shown and in which like reference numbers indicate the same or similar elements.

(2) FIG. 1 shows, in front perspective view, a first example of a beam according to the present invention,

(3) FIG. 2 shows, in front perspective view, a second example of a beam according to the present invention,

(4) FIG. 3 shows, in perspective view, the beam of FIG. 2,

(5) FIG. 4 shows, in perspective view, a part of a third example of a beam according to the present invention,

(6) FIG. 5 shows, in perspective view, a part of an example of a building according to the present invention, having a beam according to the present invention,

(7) FIGS. 6-8b show, in front view, a fourth, fifth and sixth example of a beam according to the present invention, respectively,

(8) FIG. 9a shows, in side view, an example of an extrusion die, shown highly simplified for the purpose of explaining the manufacturing process according to the invention,

(9) FIG. 9b shows section IXb-IXb of FIG. 9a, and

(10) FIG. 9c shows front view IXc-IXc of FIG. 9a.

(11) Throughout the figures, components which are equal, or at least function in a similar manner, have been indicated with the reference signs to which each time 100 is added. The figures are not to scale as to the thickness of any reinforcement parts (to be explained in detail below) relative to a height dimension of the respective beams.

DESCRIPTION OF EMBODIMENTS

(12) FIG. 1 shows a structural beam 1 for use as a building or civil engineering structural element, such as a roof beam. An example of a manner in which the beam 1, or any other example of a beam according to the present invention described above and/or below, may be used in practice is shown in FIG. 5. FIG. 5 shows part of a building 50. A pitched roof of the building is still to be provided. A support construction for the roof comprises two roof beams according to the present invention, more specifically purlins 1 as well as a ridge beam 1. The ridge beam 1 may have identical dimensions compared to purlins 1, optionally other than the length thereof, or may have different dimensions. Its height may for example be greater. Any of the beams according to the invention may be used as a roof beam such as a mentioned purlin or ridge beam as shown in FIG. 5, for example.

(13) The structural beam 1 as shown in FIG. 1 has an elongate base part 2 of a polymer. The beam has a length of 6 m, at least in the present example, defining a length direction of the beam 1 perpendicular to the plane of the paper. The base part has a width w of 100 mm and a height h of 400 mm. The base part 2 comprises polypropylene filled with 20 wt. % glass fiber. The beam 1 is of rectangular cross section having a height greater than its width. In use the beam 1 is intended to be used such that the beam is mainly subject to forces in the height direction. That means, the resistance to bending is greater in the height direction compared to the width direction. For weight reduction purposes the base part 2 is formed as a hollow profile, at least in the present example, having one central, vertical inner rib 8 and two horizontal inner ribs 9. In an embodiment, one or more cavities of the hollow profile of the base part 2 may be filled such as with a foam such as polypropylene foam.

(14) The beam 1 has an elongate reinforcement part 3 formed by a multiple, in the present example three, strips 10 comprising a polymer and unidirectional fibers, bonded to the base part 2 at its bottom outer surface 6. More specifically the three strips 10 are bonded to each other so as to form a stack of strips, and are each made of glass filled polypropylene, having a glass fiber content, for example in the range of 35 to 85 volume %. The stack of strips forming the elongate reinforcement part 3 extends in the length direction along the entire length of the base part 2. As FIG. 1 shows, a width of the stack 3 is equal to the width of the base part 2. In another example, the width of the stack may be slightly smaller than the width of the base part. In other examples, the stack may have less or more than three strips, such as 2, 4, 5, 6, 7, 8, 9 or 10 strips, the number depending on parameters such as the material properties and the thickness of individual strips. The presence of the elongate reinforcement part 3 on the bottom surface of the base part 2 of the beam 1 increases the bending stiffness, i.e. resistance to bending.

(15) The beam 1 also has a further elongate reinforcement part 4, also formed by a stack of three strips 10 comprising the same polymer and unidirectional fibers as the strips 10 of stack 3, bonded to the base part at its top outer surface 7. The stack of strips 4 extends in the length direction along the length of the base part 2 and is identical to the stack 3. Therefore the above description of stack 3 also applies to stack 4. In other embodiments the further elongate reinforcement part 4 may have more or less strips than the elongate reinforcement part 3.

(16) At least in the present example the strips 10 each have a thickness of 0.5 mm, that means in the direction of the height of the beam 1.

(17) The elongate reinforcement parts 3 and 4 have been bonded to the polymer base part 2 while forming the base part 2 by means of extrusion, by feeding a polymer composition for forming the base part 2 via an extruder to an extrusion die, and feeding the strips 10 of the elongate reinforcement parts 3 and 4, to the extrusion die, thereby forming the beam 1 while bonding the elongate reinforcement parts 3, 4 to the base part 2 during the forming of the base part 2. Within the extrusion die, the polymer composition and the strips 10 are joined so as to bond them together. The polymer composition also flows between the individual strips, so as to firmly bond them together, and to the base part. Such a method will be explained below with reference to FIGS. 9a-9c.

(18) FIG. 2 shows a beam 100 which is highly similar to beam 1. Beam 100 also has a base part 102, identical to base part 2. However, instead of two stacks of (each) three strips 10 forming the respective elongate reinforcement parts 3, 4 of beam 1, beam 100 comprises elongate reinforcement parts 103, 104 each formed by a single strip 110 comprising a polymer and unidirectional fibers, bonded to the base part 102 at its bottom outer surface 106 and top outer surface 107, respectively. Like beam 1, the elongate reinforcement parts 103 and 104 of beam 100 have been bonded to the polymer base part 102 while forming the base part 102 by means of extrusion.

(19) FIG. 3 shows a beam 300 which is identical to beam 100, except for the fact that the cavities of the hollow profile base part 302 are filled with a polyurethane foam 311.

(20) FIG. 4 shows a base part 402 of a beam according to the invention. The base part is formed as a hollow profile base part but, other than the rectangular base parts 2, 102 and 302, it has a reversed T-shape cross section. At least one of the top outer surface 407 and the lower outer surface 406 of the base part 402 may be provided with an elongate reinforcement part comparable to reinforcement parts 3, 4; 103, 104.

(21) FIG. 6 shows a further example of a beam according to the invention, in the form of a beam 500 having a solid elongate base part 502 of rectangular cross section and, only at its bottom outer surface 506, an elongate reinforcement part 503 formed by a single strip comprising a polymer and unidirectional fibers. The strip may have been bonded to the base part by means of extrusion.

(22) FIG. 7 shows a further example of a beam, in the form of a beam 600 having a solid elongate base part 602 of rectangular cross section and, only at its bottom outer surface 606, an elongate reinforcement part 603 formed by a stack of two strips 610 comprising a polymer and unidirectional fibers, laminated onto the base part. The stack may alternatively have been bonded to the base part by means of extrusion.

(23) FIG. 8a shows a further example of a beam, in the form of a beam 700 having a solid elongate base part 702 of an I-shaped cross section. At the bottom outer surface 706, an elongate reinforcement part 703 formed by a stack of two strips 710 comprising a polymer and unidirectional fibers is provided. At its top outer surface 707, a further elongate reinforcement part 704 formed by a single strip 710 comprising a polymer and unidirectional fibers is provided. Both the reinforcement parts have been bonded to the base part by means of lamination. The reinforcement parts may alternatively have been bonded to the base part by means of extrusion.

(24) FIG. 8b shows a further example of a beam according to the invention, in the form of a beam 800 having a solid elongate base part 802 having, as lower half, an I-shaped cross section, and, as upper half, a reversed L-shaped cross section. At the bottom outer surface 806, an elongate reinforcement part 803 formed by a strip comprising a polymer and unidirectional fibers is provided. At its top outer surface 807, a further elongate reinforcement part 804 formed by a strip comprising a polymer and unidirectional fibers is provided. Both the strips have been bonded to the base part by means of extrusion.

(25) FIGS. 9a-9c show an example of an extrusion die 60 for use in a method of manufacturing of the beam 800 according to FIG. 8b. A similar process, using a similar die, adapted to the cross-sectional shape of the base part to be formed and adapted to the requirements as to the reinforcement parts (absent; single strip; stack of strips) to be bonded to the top and/or bottom outer surfaces of the base part to be formed, can be used for manufacturing any of the beams according to the invention as discussed throughout the present description. The method comprises the steps of feeding a polymer composition, such as (melted) polymer granules, via an extruder (not shown), to the extrusion die 60, via an inlet 61. Said polymer composition is used for forming by extrusion the base part 802 of the beam 800. Also, in the present example, two sets of four strips 10 (individual strips not shown in detail) comprising a polymer and unidirectional fibers are fed to the extrusion die 60, each set for forming a stack of strips within the die 60, forming the elongate reinforcement parts 803 and 804 respectively. Using the extrusion die 60, and the extrusion process, the base part 802 is formed while bonding the elongate reinforcement parts 803, 804, each formed in the extrusion die 60 from four strips 10, to the base part 802 during the forming of the base part 802. A feed speed of the strips 10 to the die 60 is set equal to the speed of extrusion. The polymer composition also flows between the individual strips of the respective reinforcement parts within the die 60, so as to firmly bond the strips together, and to the base part.

EXAMPLES

(26) It should be clear to the person skilled in the art that with the beam of the invention, it is possible to achieve a similar resistance to bending at a significantly reduced weight (such as a thinner beam, for example) by using elongate reinforcement parts.

(27) It should also be clear to the person skilled in the art that with the beam of the invention, at the same weight as compared to the beam without elongate reinforcement parts, the resistance to bending can be increased.

(28) For the purpose of demonstrating the effect of the elongate reinforcement parts in the structural beams according to the present invention, in an example, a calculation comparison was made between a beam with the shape as indicated in FIG. 8b with and without reinforcement parts. In addition, the material of the beam with reinforcement parts was varied.

(29) The beam of the comparative examples had the following characteristics:

(30) TABLE-US-00001 Width at top (w) 100 mm. Thickness of beam (B1) 4 mm. Height of beam (H1) 296 mm. Width at foot (B3) 100 mm. I (second moment of inertia) 1.32 * 10.sup.7 mm.sup.4 density of polypropylene A 900 kg/m.sup.3 density of polypropylene A filled with 30 wt % glass fiber B 1120 kg/m.sup.3

(31) As reinforcement, reinforcement parts were provided on the exterior and interior side as indicated in FIG. 8b. The reinforcement parts had the following characteristics:

(32) TABLE-US-00002 Width (B3) 100 mm. Total thickness (T4) 2 mm. Material polypropylene A, filled with unidirectional glass fibers (70 wt % glass based on the total of polypropylene A and glass fibers) density: 1670 kg/m.sup.3 Young's modulus of reinforcement 35000 N/mm.sup.2 part

(33) The bending resistance was calculated according to formula 1:
resistance to bending=E*I(formula 1)

(34) The resistance to bending per meter is the resistance to bending divided by the height of the beam (H1). The Young's modulus was determined according to ISO527/1B (version as in force as of Jan. 1, 2016).

(35) TABLE-US-00003 CE 1 Example 1 Example 2 material polypropylene A polypropylene A polypropylene A, (without glass (without glass filled with 30 wt % fiber B) fiber B) glass fiber B Reinforcement (elongate No Yes Yes reinforcement parts 480 and 483 of FIG. 13) Thickness of beam of 4 4 4 roof forming element (B1) (mm) Weight (kg) per meter 1.8 2.1 2.6 length E (Young's modulus) 1450 1450 7000 (N/mm.sup.2) of the elongate base part Resistance to bending 39 195 343 (per meter roof forming element) (kNm.sup.2)

(36) As can be seen from the above Table, the beams of the invention have a significantly increased resistance to bending at the same dimensions. In addition, it is shown that preferably the elongate base part comprises in addition to the polymer, also reinforced fibers.

(37) The calculations were repeated to compare the beam of an example 3, having a reduced total thickness (T4) of the reinforcing element of 1 mm, and having a reduced beam thickness (B1) of 2 mm, to the dimensions of a wood beam having the same resistance to bending as the beam of example 3.

(38) TABLE-US-00004 Example 3 CE 2 material Atlantic white cedar Density (kg/m.sup.3) 770 E-modulus 5200 Width at top (W) (mm) 100 100 Thickness of beam (B1) (mm) 2 4 Height of beam (H1) (mm) 296 296 Width at foot (B3) (mm) 100 100 Weight (kg) 1.4 1.5

(39) As can be seen from the above example, traditional wooden beams may be replaced by structural beams of the invention while maintaining the dimensions. In addition, the structural beams of the invention are lighter as compared to wood enabling easier construction.

(40) The structural beams of the invention have the advantage that they can be prepared in any dimension, whereas with wood, additional processing steps, such as gluing or screwing need to be performed. Therefore, the dimensional tolerance of the structural beams of the invention is extremely high. In addition, natural variances in E-modulus in the structural beam of the invention are almost non-existent, whereas in a wooden beam variances may be present for example due to the presence of knots and other irregularities.