Tissue Web Negative Poisson's Ratio Pattern
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Solution Overview
Problem
Wet-laid tissue webs typically exhibit inferior cross-machine direction properties compared to machine direction properties, with high Poisson's ratios that complicate manufacturing and increase costs due to the need for compensating for positive Poisson's ratio effects during formation and conversion.
Innovation Solution
A topographical pattern comprising substantially machine direction-oriented line elements with specific height and angle is introduced to the tissue web, resulting in a negative Poisson's ratio, enhancing cross-machine direction properties such as stretch and tensile energy absorption while maintaining balanced machine direction properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a topographical pattern with line elements having element angle of about 8 to about 12 degrees and height greater than about 0.5mm is imparted to the tissue web, then the Poisson's ratio becomes negative (from about 0 to about -0.60), but the manufacturing process complexity increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the element angle (8-12 degrees) and height (>0.5mm) of the topographical pattern line elements to transform the Poisson's ratio from positive to negative range (0 to -0.60). This specific parameter optimization enables the tissue web to exhibit auxetic behavior without requiring fundamental manufacturing process changes.
Solution Approach 2:
The invention introduces a topographical dimension to the otherwise planar tissue web by adding line elements with specific height (>0.5mm) and angle (8-12 degrees). This third dimension (z-height) creates the negative Poisson's ratio effect, transforming a 2D material into a 3D structured material that exhibits auxetic properties.
2Strength
If bonding materials are applied in a pattern to enhance cross-machine direction strength and stretch, then cross-machine properties improve, but machine direction properties are not similarly enhanced
Solution Approach 1:
The patent applies local quality by creating a topographical pattern with line elements that are substantially machine-direction oriented rather than randomly distributed. This localized structural arrangement specifically enhances cross-machine direction properties (stretch and tensile energy absorption) while maintaining machine direction properties, achieving anisotropic enhancement without compromising handling efficiency.
3Productivity
If the tissue web structure is strained in the machine direction during formation and converting, then the positive Poisson's ratio causes width decrease in cross-machine direction, but this effect complicates manufacturing and increases cost
Solution Approach 1:
The patent inverts the conventional positive Poisson's ratio behavior by creating a negative Poisson's ratio structure. Instead of the width decreasing when strained in machine direction, the topographically patterned tissue web with line elements (8-12 degrees angle, >0.5mm height) causes the width to increase in cross-machine direction during machine direction straining. This inversion eliminates the need for compensatory measures and simplifies manufacturing process control.
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
The tissue webs exhibit improved cross-machine direction properties, including high stretch and tensile energy absorption, with a negative Poisson's ratio from about -0.10 to -0.50, which simplifies handling and manufacturing, and results in well-balanced machine and cross-machine direction properties.
Implementation Method 1
the line elements having an element angle from about 8 to about 12 degrees, the tissue web having a Poisson's ratio from about 0 to about -0.60
Data Source
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AI summary
The present invention relates to tissue webs and products having a topographical pattern comprising a plurality of substantially machine direction orientated line elements disposed on at least one surface of the tissue web. Preferably the line elements having an element angle (α), measured relative to the machine direction axis, from about 1 to about 20 degrees resulting in a tissue web having a Poisson's ratio from about 0 to about -0.60 and more preferably from about -0.10 to about -0.50 and still more preferably from about -0.20 to about -0.40. In addition to having a negative Poisson's ratio, the inventive tissue webs have desirable cross-machine direction properties, such as high CD Stretch and high CD TEA at relatively modest Tensile Ratios.