Cryogenic Bonded Joints Using Flexible Composite Softening Strips
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Solution Overview
Problem
Current bonded joints in spacecraft and launch vehicles using cryogenic propellants face challenges with materials becoming too stiff at low temperatures and having incompatible thermal expansion coefficients, leading to reduced strength and potential joint failure.
Innovation Solution
A method and apparatus using a three-dimensional preform with a plastic matrix impregnated to form a softening strip, capable of remaining flexible at cryogenic temperatures, which is bonded between structures to enhance joint strength and compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional materials are used for softening strips, then the joint structure is simple, but the materials become too stiff at cryogenic temperatures and have incompatible thermal expansion coefficients
Solution Approach 1:
The patent uses a composite material consisting of a three-dimensional preform (made of fibers such as glass, carbon, or aramid) impregnated with a plastic matrix (such as polyurethane, polyester, or epoxy). This composite structure maintains flexibility at cryogenic temperatures while providing the necessary mechanical strength, resolving the contradiction between strength and temperature adaptability.
Solution Approach 2:
The patent changes the physical and chemical parameters of the softening strip material by selecting specific plastic matrices with low glass transition temperatures and appropriate coefficients of thermal expansion. This allows the material to remain flexible and compatible with other joint components across a wide temperature range, including cryogenic conditions.
2Strength
If a three-dimensional preform with plastic matrix is used to form a softening strip, then flexibility at cryogenic temperatures is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The three-dimensional preform is manufactured and prepared in advance before being impregnated with the plastic matrix. This preliminary action allows for optimized fiber architecture and easier subsequent impregnation, reducing the overall manufacturing complexity despite the multi-step process.
Solution Approach 2:
The patent replaces traditional mechanical joining methods with chemical bonding through the plastic matrix that impregnates the preform. This substitution creates a more integrated structure that is easier to manufacture as a single component rather than assembling multiple parts.
3Ease of manufacture
If simple lap joints are used, then the manufacturing process is simple, but the joints cannot withstand loading that exceeds their strength
Solution Approach 1:
The softening strip uses a composite material with a three-dimensional preform and plastic matrix that provides superior mechanical properties compared to simple lap joints. The composite structure distributes stresses more effectively and increases joint reliability while maintaining reasonable manufacturing complexity.
Solution Approach 2:
The softening strip is placed locally at the joint region where it is needed to reinforce the connection. This localized application of enhanced material properties improves joint reliability without requiring the entire structure to be manufactured with the same complexity.
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 solution provides increased strength and flexibility of bonded joints at cryogenic temperatures, preventing joint failure due to thermal stresses and maintaining structural integrity under shear forces.
Implementation Method 1
A plastic matrix may be impregnated in the three-dimensional preform to form a softening strip
Implementation Method 2
The softening strip may be bonded to the first structure and to the second structure to form the joint
Data Source
AI summary
A method and apparatus for strong bonded wide joints for cryogenic applications. In one advantageous embodiment, an apparatus may comprise a three-dimensional preform and a plastic matrix. The plastic matrix may be impregnated in the three-dimensional preform to form a softening strip that may be capable of remaining flexible at a temperature at which a gas may have a liquid form.