Wavy Network Structures in Hard Phase for Auxetic Materials
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Solution Overview
Problem
Conventional materials with positive Poisson's ratio do not effectively exhibit auxetic properties, which are beneficial for specific mechanical applications, as they do not change dimensions in response to applied forces in a desirable manner.
Innovation Solution
A network structure comprising three wavy segments with a Young's modulus value Ei dispersed in a second phase with a higher Young's modulus Eh, where the wavy segments change direction at an angle 2θm greater than 0° and less than 90°, formed via additive manufacturing, allowing for either positive or negative Poisson's ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional materials with positive Poisson's ratio are used, then manufacturing simplicity is maintained, but auxetic properties cannot be achieved
Solution Approach 1:
The material is segmented into distinct phases: a soft phase forming wavy segments and a hard phase forming a continuous matrix. This segmentation allows the soft phase to exhibit auxetic behavior through its wavy geometry while the hard phase provides structural support, resolving the contradiction between achieving auxetic properties and maintaining manufacturability.
Solution Approach 2:
The invention uses a composite material system with a soft phase (exhibiting auxetic properties) dispersed in a hard phase matrix. This composite approach enables the material to achieve auxetic behavior through the soft phase's wavy structure while the hard phase provides ease of manufacture and structural integrity, simultaneously satisfying both requirements.
2Adaptability or versatility
If wavy network structures are introduced to achieve auxetic behavior, then auxetic properties are obtained, but structural complexity increases
Solution Approach 1:
The wavy structure is localized to the soft phase segments rather than the entire material structure. The soft phase forms discrete wavy segments dispersed in the hard phase matrix, allowing auxetic behavior to be achieved locally where needed while maintaining overall structural simplicity through the continuous hard phase matrix.
3Strength
If the stiffness ratio Eh/Ei is increased to enhance auxetic properties, then mechanical performance improves, but manufacturing precision requirements increase
Solution Approach 1:
The invention controls the stiffness ratio Eh/Ei as a key parameter to optimize mechanical performance. By selecting materials with appropriate stiffness ratios (Eh>Ei) and controlling the volume fraction and geometry of the wavy segments, the patent achieves enhanced mechanical properties while managing manufacturing precision requirements through parameter optimization rather than extreme precision demands.
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 wavy network structure enhances mechanical properties such as stiffness, strength, and fracture toughness, and can achieve auxetic behavior by optimizing the waviness and stiffness ratio, leading to improved resistance against damage initiation and crack propagation.
Implementation Method 1
the wavy segments are positioned between the first and a second connection location and at about a midpoint between the first and second connection locations the wavy segments change direction and define an angle 2θm wherein the value of θm is greater than zero and less than 90°
Data Source
AI summary
The present invention is directed at materials and methods for their formation having wavy network structures dispersed in a second and relatively harder phase. The materials can be designed to exhibit auxetic properties (e.g. a negative Poisson's ratio) in response to an application of force.