Planar Composite Wood Element Bending Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wood composite elements for load-bearing ceilings are not suitable for high bending stresses and have limitations in using lower-quality sawn wood, with issues related to shear stress and aesthetic concerns due to narrow stripes.
Innovation Solution
A planar composite wood element with three layers of boards, where the outer layers are aligned normal to the bending axis and the intermediate layer parallel to it, with the compression side being thicker than the tension side to optimize bending resistance and utilize lower-quality wood effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If boards are aligned parallel to the bending axis in the intermediate layer, then manufacturing is simplified, but bending resistance is reduced
Solution Approach 1:
The wood composite element is divided into three distinct layers with different board orientations. The intermediate layer has boards aligned parallel to the bending axis for manufacturing simplicity, while the outer layers have boards aligned normal to the bending axis for enhanced bending resistance. This segmentation allows each layer to optimize for its specific function.
Solution Approach 2:
The invention creates a composite structure where layers with different wood board orientations are combined. The intermediate layer provides manufacturing simplicity and dimensional stability, while the outer layers provide bending resistance through their orientation normal to the bending axis. This composite approach resolves the contradiction by combining materials with different properties.
2Strength
If outer layers are made thicker to increase bending resistance, then bending strength is improved, but overall element height increases
Solution Approach 1:
The wood composite element applies different thicknesses to different layers based on their functional requirements. The outer layers are made thicker to provide bending resistance, while the intermediate layer maintains a thinner profile. This local differentiation of quality allows the element to achieve high bending strength without excessive overall height.
3Productivity
If lower-quality sawn wood is used in the intermediate layer, then material utilization is improved, but aesthetic quality deteriorates
Solution Approach 1:
The invention assigns different quality requirements to different layers based on their visibility and function. The intermediate layer, which is not visible and provides structural support, can use lower-quality sawn wood with knots and flaws, maximizing material utilization. The outer layers, which are visible and provide aesthetic quality, use higher-quality wood. This local differentiation resolves the contradiction between material utilization and aesthetic quality.
4Strength
If boards are aligned normal to the bending axis in outer layers, then bending resistance is improved, but shear stress vulnerability increases
Solution Approach 1:
The invention creates a composite structure where the intermediate layer has boards aligned parallel to the bending axis, providing resistance to shear stresses that act parallel to the board surfaces. The outer layers have boards aligned normal to the bending axis, providing resistance to bending moments. This composite arrangement with different orientations resolves the contradiction by having each layer specialize in resisting different stress types.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances bending resistance and shear stress handling, allowing for wider board usage and improved aesthetic appeal while effectively utilizing lower-quality wood for load-bearing ceilings with increased spacing between supports.
Implementation Method 1
three layers of boards (1, 2, 3) which are also glued to one another
Implementation Method 2
the annual rings (1.1) of the upper boards (1) are essentially normal to the plane at which the greatest shear stress occurs
Data Source
Figure 1
AI summary
The element has boards (1-3) that are aligned and arranged parallel to each other, where outer layers of the boards are oriented normal to an axis of expected bending loads. Rings (1.1) lie in a timber side of the boards that lie at a pressure side of the expected bending loads at a pressure side for a plane of the bending loads at an acute angle of 45 degrees. An outer layer at a discharge side formed by one of the boards is thicker than a stretch-side outer layer formed by the other board. A middle layer of the board is made of timber with low strength.