Mixed-Polygon Truss Lattices for Isotropic NPO Stiffness
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Solution Overview
Problem
Existing lattice materials, particularly those with negative Poisson's ratio (NPO), often exhibit anisotropic mechanical properties and low stiffness, failing to meet the diverse requirements of various engineering applications that prioritize isotropic properties, high stiffness, and high energy absorption capacity.
Innovation Solution
The development of truss structures that form lattice materials by arranging struts to create at least two triangles on each side of a polygon, such as a triangle, quadrilateral, or hexagon, resulting in lattice materials with isotropic or orthotropic mechanical properties and negative Poisson's ratio, enhanced elastic and shear moduli, and the ability to be manufactured in tubular or spherical shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If lattice materials are designed with negative Poisson's ratio (NPO) properties, then energy absorption capacity is improved, but mechanical anisotropy increases and stiffness decreases
Solution Approach 1:
The patent employs asymmetric unit cell geometries (kagome, gyroid, diamond structures) that inherently produce negative Poisson's ratio behavior. These asymmetric arrangements of struts and nodes create the desired NPO effect while the periodic tiling of unit cells ensures macroscopic isotropy through symmetric distribution of asymmetric elements
Solution Approach 2:
The patent systematically varies geometric parameters including strut thickness ratio (α), unit cell size (L), and material density (ρ) to optimize the balance between energy absorption capacity and stiffness. By adjusting these parameters, the material achieves high energy absorption while maintaining adequate mechanical properties and reducing anisotropy
2Strength
If lattice materials are designed with negative Poisson's ratio (NPO) properties, then energy absorption capacity is improved, but stiffness decreases
Solution Approach 1:
The patent creates composite lattice structures combining multiple unit cell types (kagome, gyroid, diamond) with different mechanical characteristics. This composite approach allows the material to achieve high energy absorption capacity through the NPO behavior of individual cells while the combination of different structures provides enhanced overall stiffness and reduced anisotropy
Solution Approach 2:
The patent optimizes strut thickness ratio (α) and unit cell size (L) to balance energy absorption and stiffness. Thicker struts and optimized cell dimensions increase stiffness while the NPO geometry maintains energy absorption capacity, resolving the trade-off between these two properties
3Stability of the object's composition
If complex truss structures are arranged to form lattice materials with isotropic properties, then mechanical isotropy is improved, but device complexity increases
Solution Approach 1:
The patent divides the lattice material into repeating unit cells (kagome, gyroid, diamond structures) that can be independently designed and then periodically tiled to achieve macroscopic isotropy. This segmentation allows complex isotropic behavior to emerge from simple, repeatable modular units, reducing manufacturing complexity while maintaining mechanical isotropy
Solution Approach 2:
The patent designs universal unit cell structures that simultaneously provide multiple functions: negative Poisson's ratio behavior, energy absorption, and contribution to macroscopic isotropy when tiled. This multi-functionality reduces the need for additional specialized components, simplifying the overall structure while achieving isotropic mechanical properties
Data Source
AI summary
Disclosed are lattice materials including a truss structure obtained by arranging struts to form at least two triangles on each side of a polygon (i.e., a triangle, a quadrilateral, or a hexagon), which are used in many engineering fields, especially in materials engineering. The elastic modulus values per unit weight of many of the lattice materials produced from the truss structure are higher than those of the most existing cellular solids with stochastic cell distributions and many existing lattice materials. Using the truss structure disclosed herein, it is possible to produce two-dimensional (planar) lattice materials as well as spherical or tubular lattice structures in the form of a first cylindrical tube or a second cylindrical tube.