Cryogenic Tank With Heat-Bonded Resin Layer
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Solution Overview
Problem
Conventional cryogenic liquid tanks made of composite materials face fuel leaks due to micro cracks caused by thermal expansion differences between the epoxy resin and reinforcing fibers, and similar issues arise with liquid crystal polymer film-based tanks due to adhesive layer cracks from temperature changes.
Innovation Solution
A tank design featuring a pressure-resistant inner shell and outer shell both made of fiber-reinforced resin composites, with a heat-bonded thermoplastic airtight resin layer on the inner surface, eliminating the need for an adhesive layer and preventing cracks at cryogenic temperatures, while allowing the outer shell to be molded below the melting point of the airtight resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a composite material is used for the tank to reduce weight, then weight is reduced, but micro cracks occur in the epoxy resin due to thermal expansion differences between the epoxy and reinforcing fiber at cryogenic temperatures
Solution Approach 1:
The patent introduces a liquid crystal polymer layer as an intermediary between the composite material tank and the cryogenic liquid. This layer has thermal expansion properties that bridge the gap between the epoxy resin and the cryogenic liquid, preventing micro crack formation while allowing the lightweight composite structure to be used.
Solution Approach 2:
The patent changes the thermal expansion parameter matching by inserting a liquid crystal polymer layer with intermediate thermal expansion characteristics. This layer's expansion coefficient is between that of the epoxy resin and the cryogenic liquid, eliminating the thermal stress mismatch that causes cracking.
2Reliability
If liquid crystal polymer films are bonded with adhesive to form an airtight layer, then airtightness is improved, but cracks are generated in the adhesive layer due to thermal expansion differences between the composite material and adhesive during temperature changes
Solution Approach 1:
The liquid crystal polymer layer serves as a mediator between the composite tank and the adhesive, absorbing thermal expansion differences and preventing stress concentration in the adhesive layer during cryogenic temperature cycles.
Solution Approach 2:
The patent modifies the thermal expansion parameter profile by introducing the liquid crystal polymer layer, which has expansion characteristics that match better with both the composite material and the adhesive, thereby maintaining adhesive layer integrity through temperature variations.
3Manufacturing precision
If the inner shell can withstand high temperatures above the melting point of the airtight resin, then the airtight resin layer can be heat-bonded without deforming the inner shell, but the outer shell must be molded at temperatures below the melting point of the airtight resin
Solution Approach 1:
The patent divides the tank into two separate shells with different material properties: the inner shell made of high-temperature resistant composite material for heat-bonding the airtight resin, and the outer shell made of lower-temperature moldable composite material for ease of manufacturing. This segmentation allows each shell to be optimized for its specific manufacturing requirements.
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 design ensures airtightness and durability without crack generation, maintaining structural integrity and reducing weight by using fiber-reinforced resin composites for both shells, and an additional airtight resin layer enhances overall airtightness by preventing cryogenic liquid contact with adhesives.
Implementation Method 1
the inner shell is comprised of a fiber-reinforced resin composite which can withstand temperatures above the melting point of the airtight resin layer
Implementation Method 2
upon contact with a cryogenic liquid, has many micro cracks in the epoxy resin due to the difference in thermal expansion between the epoxy and the reinforcing fiber
Data Source
AI summary
The present invention relates to a tank for holding a cryogenic liquid. According to the present invention, there is provided a light and durable tank which is airtight even at cryogenic temperatures without generating cracks. The tank includes: a pressure-resistant layer having an inner shell and an outer shell; and an airtight resin layer on an inner surface of the inner shell, wherein the inner shell is comprised of a fiber-reinforced resin composite which can withstand temperatures above the melting point of the airtight resin layer, and the outer shell is comprised of another fiber-reinforced resin composite which can be cured at a temperature below the melting point of the airtight resin layer.