Reinforcement for wood-based structures

Abstract

Component consisting of a plate or a block or any geometry of one or more layers of wood, characterized in that one or more stone layers and one or more carbon layers as stabilizer layers are firmly connected to the layer(s) of wood.

Description

[0001] Wood consists of several main components, each of which plays an important role in the material's strength and stability. The most important components of wood are: Cellulose – is the main component of wood and makes up about 40-50% of the dry mass. Cellulose is a polysaccharide consisting of long chains of glucose molecules. These chains are organized into fibers that give wood its tensile strength, similar to steel in concrete.

[0002] Hemicellulose is a group of polysaccharides and accounts for approximately 20-30% of the dry mass of wood. Hemicelluloses are more branched and shorter than cellulose and contribute to the flexibility and interconnection of cellulose fibers.

[0003] Lignin is a complex polymer that makes up about 20-30% of the dry mass of wood. Lignin fills the spaces between the cellulose fibers and gives the wood its compressive strength. It acts as an adhesive, holding the cellulose fibers together and giving the wood its rigidity and strength. Extractives make up a small portion of the wood mass (about 1-5%) and include resins, fats, waxes, and other organic compounds. They influence the color, odor, and resistance of the wood to pests and decay.

[0004] The long cellulose fibers are primarily responsible for the tensile strength of wood. They can absorb large tensile forces because the chains of glucose molecules are very resistant to stretching.

[0005] Lignin provides wood's compressive strength by supporting the cellulose fibers and preventing them from yielding under pressure. The amorphous structure of lignin distributes compressive forces and helps keep the wood stable.

[0006] Wood fibers play a crucial role in the mechanical properties of wood. These fibers consist primarily of cellulose embedded in a matrix-like structure of hemicellulose and lignin. The orientation and arrangement of the cellulose fibers determine the direction and degree of wood's strength. In the longitudinal direction (parallel to the fibers), wood is particularly strong in terms of tensile forces, while compressive strength is supported by the compressive effect of lignin.

[0007] Cellulose fibers determine the tensile strength, while lignin ensures the compressive strength of wood. The combination of these components enables wood to effectively absorb both compressive and tensile forces, making it a versatile and resilient building material.

[0008] These circumstances mean that the material can absorb tensile and compressive forces simultaneously without immediately breaking under bending load or failing under static or dynamic compressive and tensile loads.

[0009] Only then does the material become suitable for use in the construction sector for the construction of buildings, bridges and other structures and their components, such as ready-made beams, walls, ceilings, floors or even railway sleepers.

[0010] The disadvantage of wood is its deformation due to forces, which can sometimes be sustained and permanent, and also occurs due to changes in temperature and humidity of the ambient air.

[0011] In order to be able to compete with other materials, new methods are being tried out, including additionally stabilising wood with different types of fibre materials in order to make it even more load-bearing, and also to protect it against changes in length and shape caused by forces, temperature and moisture, which can have unpleasant side effects, especially in building construction. This invention is concerned with the sustainable strengthening of wood for long-term use in building construction while at the same time saving the valuable resource wood, which must be used sparingly from a climate technology point of view.

[0012] The connection of reinforced concrete therefore works excellently under changing temperature conditions to which buildings are usually exposed during operation, because the thermal expansion coefficients are approximately 10-12 × 10 -6 / K of steel and concrete are virtually identical. The thermal expansion coefficients for the various materials are determined, for example, with a dilatometer, whereby the respective linear expansion coefficients are expressed in units (K -1 ) must be specified.

[0013] Wood and carbon fibers are a good match in terms of thermal expansion coefficients, even better than with glass fibers or stone fibers. However, wood is subject to shrinkage and creep over time, which are particularly influenced by humidity. This invention aims to counteract this by using the compressive strength of stone to partially relieve the wood's load and keep it dimensionally stable, since stone cannot be permanently deformed but always strives to return to its original shape. The carbon layer acts as an absolutely immutable structure when it comes to absorbing tensile loads.When used as an intermediate layer between carbon fiber and wood, the stone also improves force transmission between the carbon layer used, ensuring dimensional stability under tensile loads and preventing material deformation due to tension. As the stone layer acts as an interface between the carbon and the wood, it better transmits shear forces to the more flexible wood. This prevents the extreme stiffness of the carbon fiber from having to be fully absorbed by a thin wood boundary layer. The stone layer is softened by a modulus of elasticity that lies between that of the wood and the carbon fiber, and is also dampened under dynamic loads. This enables a much more durable and force-fitting connection between wood and carbon fiber, which, together with the stone, is better adapted to permanent loads than pure wood structures. The stone ensures a gradual decrease in the stiffness of the joined materials.The carbon fiber is significantly stiffer than the wood and the stone is also stiffer than the wood, but less stiff than the carbon fiber layer.

[0014] The versatility of the different woods and the fact that wood has very different characteristics of stiffness, compressive and tensile strength in the various axes along or parallel to the grain orientation, and that these ratios can vary extremely from one wood species to another, and in addition the expected expansion or shrinkage of the wood can cause the positioning of the carbon layer to vary, ultimately determines the best sequence of the three layers according to the respective application and in particular the grain direction of the wood.

[0015] The porosity of stone is the reason for its relatively low elastic modulus compared to carbon, which can range between 40 and 80 GPa depending on the type of stone. The porosity of stone is also the reason for the strong bond between stone and wood, which is bonded to the stone by a force-fitting resin bond, with the resin anchoring itself in tiny cavities across the surface of the stone. The same applies to the bond between the intermediate stone layer and the fiber matrix, usually a two-component synthetic resin.

[0016] For improved stabilization through optimized force transfer between the wood and the carbon fiber matrix through a specifically configured stone geometry, so-called CFS lamellae (CFS - Carbon Fiber Stone) are described below. These lamellae have a layered structure in which the carbon layer is sandwiched between two stone layers and thus has no direct surface contact with the wood. The proposed connection is also suitable for use in the construction of house walls, ceilings, columns, and beams in building construction, as well as bridges made of wood and carbon fiber, which can be made permanently durable by bonding a stone-carbon bottom chord.

[0017] The Fig. shows an example of a plate or support made of wood (1) and firmly connected to a carbon layer (3) via an intermediate layer of stone (2).

[0018] The Fig. shows, by way of example, a plate or a support made of wood (1), the intermediate layer between wood and stone (2) being a carbon layer (3).

[0019] The Fig. shows an example of a plate or support made of wood (1) which forms the intermediate layer between the carbon layer (3) and the stone (2).

[0020] The Fig. shows an example of a wooden module (1a and 1b) consisting of two parts, which can be of equal or different thicknesses and are stabilized with a lamella made of granite (2) coated with fibers on both sides. The carbon fiber layer (3), which is arranged between the two stone layers (2a and 2b), has little or no direct contact with the wood. The thickness of the stone layer determines the expected bending load and / or expansion capacity of the wood under changing humidity and temperature. The tolerable temperature and humidity-dependent expansion range of the wood is greater the greater the ratio of the thickness of the stone layers to the thickness of the carbon layer, since the flexibility of the stone layer can compensate for the occurring change in length within certain limits.This reduces the shear load on the area of ​​the wood interface to the stone, which has to transfer the forces that arise from a bond that is as stiff as possible.

[0021] Fig. shows an example of a cross-section of a flat arrangement, such as a wall, in which the wood structure (1) is glued to the outside of two stone panels (3) coated with carbon (2). Here, too, the direct contact between the wood and the long carbon fiber is mechanically separated by a correspondingly thick stone layer. The wood layer improves the fire protection of the wall. Between the carbon layers is an insulation layer made, for example, from a fill of BioChar (4).

[0022] Fig. shows the same structure as Fig. , but with a different layer sequence. Layer (4) in the middle is the insulation layer. In this case, a layer of stone lies between the carbon layers and the wood layers.

[0023] Fig. shows the same structure as Fig. , but with an additional stone layer (5), which protects the carbon layer on one side of the wall from external mechanical and chemical influences and UV light.

[0024] In all cases, the matrix-bonded long-fiber layers made of carbon fibers can hold the stone material and the wood layers under prestress, as described in EP 08 850 003.8. Ideal adhesion between wood and stone, or between stone and carbon layer, is achieved when the stone has a rough surface. The matrix, which creates the bond between the fibers and the stone material, consists either of synthetic resins or water glass-based binders; here, too, a rough stone surface is helpful. All high-tensile long fibers suitable for reinforcing stone can be used as fibers. These can be a wide variety of fibers or a fiber mixture, preferably containing carbon fibers.

[0025] If the carbon fibers are produced from biomass and thus have a negative CO2 footprint, climate protection can be contributed to by giving wood a significantly more positive CO2 footprint. The weathering potential of the stone used increases the negative CO2 footprint, as cutting the stone leaves behind weatherable stone dust that can absorb and permanently bind CO2. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 08 850 003.8

[0024]

Claims

[1] Component consisting of a plate or a block or any geometry made of one or more layers of wood, characterized by that one or more stone layers and one or more carbon layers as stabilizer layers are firmly bonded to the wood layer(s). [2] Component according to claim 1, characterized by that the stone is arranged as a force-transmitting link between wood layers and carbon layers. [3] Arrangement according to claims 1 and 2, characterized by that the compressive elastic modulus of the stone is greater than that of the wood used and smaller than the tensile elastic modulus of the carbon layer used. [4] Arrangement according to claims 1 to 3, characterized by that the stone layer consists of granite, gabbro, basalt, sandstone, quartzite, limestone or any other rock or mineral material. [5] Arrangement according to claims 1 to 4, characterized bythat the stone is a natural stone and the wood can be of different nature. [6] Arrangement according to claims 1 to 5, characterized by that the carbon layer stabilizing the stone consists of either carbon fibers, carbon nanofibers or graphene. [7] Arrangement according to claims 1 to 6, characterized by that the stone layers are prestressed by the carbon layer. [8] Arrangement according to claims 1 to 7, characterized by that the carbon layer is bound with resin or water glass and connected to the stone. [9] Arrangement according to claims 1 to 8, characterized by that the composite layer of carbon and stone keeps the wood layer under tension. [10] Arrangement according to claims 1 to 9, characterized by that the stone slab used has a rough surface. [11] Arrangement according to claims 1 to 10, characterized bythat the carbon layer used is placed in the middle between two stone layers and these three layers are placed in the middle of two wood layers. [12] Arrangement according to claims 1 to 11, characterized by that the component has a negative CO2 balance.

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