Composite Window Phase-Change Mounting for Thermal Shock
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-temperature windows used in electro-optical/infra-red (EO/IR) sensors for hypersonic applications often fail due to thermal shock caused by improper mechanical fixturing, with existing solutions like coefficient of thermal expansion matching materials and slip gaskets being inadequate for large temperature variations.
Innovation Solution
The window is mounted in metals with low melting points, allowing it to float within a volume of molten metal during thermal shock, with a phase-change filler material providing a zero-stress seal and EMI protection, and optionally supported by a thin frame to minimize thermal shock effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the window is rigidly mounted in the frame, then mechanical support is provided, but thermal stress accumulates during temperature variations causing premature failure
Solution Approach 1:
The mounting material undergoes a phase change from solid to liquid at a predetermined temperature, fundamentally changing its mechanical properties from rigid to fluid. This allows the system to transition from a stress-constraining state to a stress-relieving state during thermal shock events, resolving the contradiction between mechanical support and thermal shock resistance.
Solution Approach 2:
The mounting material's physical state dynamically changes in response to temperature conditions. At operating temperatures, it remains solid providing structural support; during thermal shock, it melts to liquid allowing the window to float freely, thus adapting the mounting characteristics to match the operational requirements at different temperature states.
2Stress or pressure
If coefficient of thermal expansion matching material is used, then stress is minimized at lower temperatures, but it fails when ambient temperature varies from 30°C to 1000°C
Solution Approach 1:
The mounting material utilizes a phase transition (melting) at a predetermined temperature to fundamentally change its behavior. This phase change allows the system to handle extreme temperature variations beyond what CTE matching alone could achieve, providing adaptability across the full temperature range from 30°C to 1000°C by switching between solid (low stress) and liquid (zero stress) states.
3Stress or pressure
If slip gaskets are used to minimize framing stress, then thermal expansion is accommodated, but EMI protection and electrical ground are compromised
Solution Approach 1:
The mounting material performs multiple functions simultaneously: it provides mechanical support, accommodates thermal expansion, and maintains EMI protection through electrical conductivity. The liquid state of the mounting material continues to provide electrical ground and EMI shielding while allowing stress-free mounting, thus achieving universal functionality that single-purpose solutions cannot provide.
4Strength
If brazing is used to secure the window, then strong mechanical bonding is achieved, but thermal stress concentration occurs at the bond interface
Solution Approach 1:
The invention extracts the window from the rigid bonded structure, allowing it to float independently in the liquid mounting material. This eliminates the bonded interface entirely, removing the source of stress concentration while still maintaining secure mechanical positioning through the fluid's buoyancy and surface tension forces.
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 solution effectively prevents stress failure and maintains EMI protection by allowing the window to float during thermal shocks, reducing thermal shock effects and supporting active cooling, while maintaining electrical connectivity.
Implementation Method 1
a phase-change filler material sealing an outer edge of the window, and coupling the window to a frame around the window. The filler material in a solid state rigidly holds the window in place. During thermal shock the filler material melts and allows the window to float within the frame guides.
Implementation Method 2
During thermal shock the filler material melts and allows the window to float within the frame guides
Implementation Method 3
High surface tension in the fluid gasket prevents air, environmental fluids, or coolant from penetrating the seal
Implementation Method 4
making the window thin, which lowers window surface temperature by placing the coolant (thermally) closer to the thermal heat source
Data Source
AI summary
A window installation includes a phase-change filler material sealing an outer edge of the window, and coupling the window to a frame around the window. The filler material in a solid state rigidly holds the window in place. When the filler material is in a liquid state it allows the window to float in its coupling to the frame. There may be supports within the rigid material that contact the window, but allow the window to expand or contract by sliding along the supports. The installation may be useful in situations where the window is subjected to thermal shocks, or other sorts of heating. The installation may be used for a sensor window, and may be part of a hypersonic vehicle.