Ceramic Filament Radome Structure With Graded Dielectric Layers
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Solution Overview
Problem
The fabrication of ceramic broadband radomes for hypersonic missiles is hindered by the fragile nature of ceramic materials, coefficient of thermal expansion (CTE) mismatch between layers, and difficulty in grading the dielectric constant due to structural breakup during firing.
Innovation Solution
The method involves constructing multiple ceramic layers by winding continuous ceramic filaments, where the dielectric properties are defined by inter-filament spacing and filament count, allowing for flexible selection of oxide or non-oxide ceramic fibers and using a single resin for infiltration to avoid CTE mismatch and enhance structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple ceramic layers are constructed using traditional molding or slip casting methods, then the radome structure can be formed, but the fragile nature of ceramic material makes it difficult to shape and sinter for bigger pieces without defects
Solution Approach 1:
The radome is divided into multiple discrete ceramic layers that are constructed separately and then assembled. Each layer can be independently formed and sintered, reducing the risk of defects in large monolithic pieces. The layers are joined using a resin-based bonding system that accommodates the fragile nature of individual ceramic layers while building up the overall structural integrity of the complete radome assembly.
Solution Approach 2:
The ceramic layers are pre-formed and pre-sintered as separate units before final assembly into the complete radome structure. This preliminary fabrication allows each layer to be optimized and cured independently, ensuring structural stability before the layers are combined. The resin infiltration and firing process then bonds these pre-prepared layers together, avoiding the need to handle and shape large fragile ceramic pieces in a single operation.
2Adaptability or versatility
If multiple ceramic layers with different dielectric properties are stacked to achieve broadband characteristics, then the dielectric constant can be graded, but the CTE mismatch between layers leads to micro cracks and delamination during firing
Solution Approach 1:
A resin-based bonding system serves as an intermediary material between the ceramic layers with different coefficients of thermal expansion. The resin layer absorbs and accommodates the differential expansion and contraction stresses that occur during firing and thermal cycling, preventing direct stress transmission between the ceramic layers that would cause micro cracks and delamination. This intermediary bonding layer enables the assembly of multi-layer structures with graded dielectric properties while maintaining structural reliability.
3Adaptability or versatility
If traditional molding techniques are used to fabricate ceramic radomes, then the structure can be formed, but it is difficult to grade the dielectric constant by porosity due to the breakup of the structure along the pore chain
Solution Approach 1:
The dielectric constant is graded by locally varying the porosity characteristics within each ceramic layer through controlled infiltration of ceramic suspensions with different solid loadings. Each layer can be tailored with specific porosity levels and pore distributions to achieve the desired dielectric properties at different radial positions. This local control of quality parameters allows for precise dielectric constant grading without causing structural breakup, as the porosity is distributed uniformly throughout each layer rather than forming continuous pore chains that could lead to structural failure.
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
This approach enables the creation of RF-transparent structures with graded dielectric properties, improving toughness and reducing the risk of catastrophic failure, while simplifying the machining process and ensuring homogenous composition across layers.
Implementation Method 1
the structure is removed from the winding surface (e.g. mandrel), infiltrated with resin in a separate set up
Implementation Method 2
The inorganic resin is either polysilicone or polysilozane, which is converted to silica or silicon nitride after pyrolysis, respectively
Implementation Method 3
The inorganic resin is either polysilicone or polysilozane, which is converted to silica or silicon nitride after pyrolysis, respectively
Data Source
AI summary
A method for constructing a plurality of ceramic layers by winding continuous ceramic filaments to prepare RF-transparent structures is provided. Dielectric properties of each layer of the plurality of ceramic layers are characterized by an inter-filament spacing, a filament count and thickness. Once the plurality of ceramic layers are constructed, a structure is removed from a winding surface, wherein the winding surface is a mandrel, infiltrated with a resin in a separate set up and fired.