Auxetic Void Structures for Combustor Stress Reduction
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Solution Overview
Problem
The challenge in fabricating materials with auxetic properties lies in embedding intricate geometries within a host matrix, which complicates the manufacturing process and limits practical applications, particularly in achieving negative Poisson's Ratio behavior.
Innovation Solution
A void structure with a repeating elongated-aperture pattern, where first and second elongated apertures with perpendicular major axes are arranged in alternating rows and columns, achieving negative Poisson's Ratio behavior without collapsing the material during manufacturing, and applied in gas turbine combustors for thermal, damping, and acoustic functionalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intricate geometries are embedded within a host matrix to achieve auxetic properties, then negative Poisson's Ratio behavior is achieved, but manufacturing complexity increases significantly
Solution Approach 1:
The structure is divided into repeating unit cells, each containing a specific aperture pattern. This segmentation allows the complex auxetic behavior to be achieved through simple, repeatable geometric units rather than intricate continuous geometries, significantly simplifying manufacturing while maintaining the negative Poisson's Ratio effect
Solution Approach 2:
The invention changes the geometric parameters of the apertures (elongated shape, specific aspect ratios, perpendicular orientations) to achieve auxetic behavior. By optimizing these parameters, the patent achieves negative Poisson's Ratio with simpler geometries that are more manufacturable while maintaining the desired mechanical properties
2Ease of manufacture
If conventional cooling holes are used in combustor liners, then manufacturing is simple, but thermal stress reduction and fatigue life are limited
Solution Approach 1:
The patent creates a composite structure by combining the host matrix material with a specific void pattern (elongated apertures arranged in perpendicular orientations). This composite void structure provides both the manufacturing simplicity of conventional holes and the advanced functionality of stress reduction and fatigue life extension through the auxetic effect
Solution Approach 2:
The elongated aperture geometry provides localized stress redistribution at critical regions around each aperture. The perpendicular arrangement of apertures creates different local properties in different directions, optimizing stress management in the high-temperature combustor environment while maintaining overall structural integrity
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 void structure exhibits negative Poisson's Ratio behavior, reducing thermal stresses and increasing stress fatigue life by up to five-fold, while maintaining cooling and damping performance, and can be manufactured using various methods like microfabrication or laser cutting.
Implementation Method 1
The apertures are cooperatively configured to achieve negative Poisson's Ratio behavior under stress or strain, or both
Implementation Method 2
reducing thermal stresses and increasing stress fatigue life by up to five-fold
Data Source
AI summary
Void structures, systems and devices with void structures, and methods of fabricating void structures are disclosed. A void structure is disclosed with a repeating elongated-aperture pattern designed to provide negative Poisson's Ratio behavior under macroscopic stress and strain loading. The pattern can include horizontal and vertical elliptically shaped apertures that are arranged on horizontal and vertical lines in a way that the lines are equally spaced in both dimensions. The centers of each aperture is on a crossing point of two of the lines. The vertical and horizontal elliptically shaped apertures alternate on the vertical and horizontal lines such that any vertical aperture is surrounded by horizontal apertures along the lines (and vice versa), and the next vertical apertures are found on both diagonals. The voids can also act as cooling and/or damping holes and, due to their arrangement, also as stress reduction features.