Elastomeric Shape Memory Composites With Tunable Filament Porosity
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Solution Overview
Problem
Stochastic elastomeric foams exhibit unpredictable mechanical performance due to high local stress concentrations, leading to material failure, and existing 3D printing methods struggle to create self-standing structures with graded porosity and shape memory behavior.
Innovation Solution
A method involving the extrusion of a mixture containing a first ink with a matrix material and second ink with unexpanded gas-filled microballoons, followed by heating under negative pressure to expand the microballoons, creating hierarchical porosity and shape memory properties in 3D printed structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If stochastic elastomeric foams are used to create porous structures, then manufacturing simplicity is maintained, but mechanical performance becomes unpredictable due to high local stress concentrations
Solution Approach 1:
The patent segments the porous structure into two distinct levels: macro-scale stochastic porosity created by traditional foam expansion, and micro-scale ordered porosity created by embedded microballoons. This hierarchical segmentation allows the macro structure to maintain manufacturing simplicity while the micro structure provides predictable stress distribution and mechanical performance.
Solution Approach 2:
The patent embeds microballoon-containing inks within the elastomeric foam matrix, creating a nested structure where micro-scale ordered porosity (microballoons) is contained within the macro-scale stochastic foam structure. This nesting enables both manufacturing approaches to coexist, with the microballoons providing predictable mechanical behavior within the otherwise simple foam matrix.
2Reliability
If traditional 3D printing methods are used to create ordered porous structures, then mechanical performance predictability is improved, but the ability to create self-standing structures with graded porosity is limited
Solution Approach 1:
The patent applies local quality by varying the concentration and distribution of microballoon-containing inks at different locations within the foam matrix. This enables spatially graded porosity where microballoon density can be adjusted locally to create regions with different mechanical properties, combining ordered micro-structure with macro-scale manufacturing simplicity.
Solution Approach 2:
The patent creates a composite material system combining elastomeric foam matrix with embedded microballoon structures. This composite approach integrates the benefits of stochastic foam (manufacturing ease) with ordered microballoon structures (predictable mechanics and graded porosity capability), achieving both reliability and adaptability.
3Manufacturing precision
If microballoons are expanded after extrusion to create intra-filament porosity, then porosity control and shape memory behavior are achieved, but additional processing steps are required
Solution Approach 1:
The patent incorporates unexpanded microballoons into the ink formulation before extrusion, preparing the structure in advance for subsequent expansion. This preliminary action embeds the porosity-generating elements during the extrusion process itself, so that the expansion step later activates pre-positioned microballoons rather than requiring complex real-time porosity control mechanisms.
Solution Approach 2:
The patent utilizes the phase transition of microballoons from unexpanded to expanded state after extrusion. This phase change enables controlled porosity generation and shape memory behavior through a simple thermal or pressure stimulus, achieving high manufacturing precision through a relatively simple additional processing step based on fundamental material phase behavior.
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 method enables the formation of 3D printed structures with predictable, reproducible, and architecturally complex porosity, achieving high porosity and shape memory behavior, including full recovery upon reheating.
Implementation Method 1
heating the extruded filaments of the formed structure under a negative pressure system for expanding the unexpanded gas-filled microballoons
Implementation Method 2
heating the extruded filaments of the formed structure under a negative pressure system for expanding the unexpanded gas-filled microballoons
Implementation Method 3
curing the matrix material of the extruded filaments to at least a pre-defined extent
Data Source
AI summary
A method includes extruding a mixture through a nozzle to form a structure of extruded filaments arranged in a pre-defined arrangement. The mixture includes a first ink and a second ink with each of the inks having a matrix material and a filler. The second ink includes a plurality of unexpanded gas-filled microballoons. In addition, the method includes heating the extruded filaments of the formed structure under a negative pressure system for expanding the unexpanded gas-filled microballoons to achieve intra-filament porosity and curing the matrix material of the extruded filaments to at least a pre-defined extent. A ratio of the first ink to the second ink in the mixture extruded through the nozzle is pre-defined and/or controlled.