Composite-Aluminum Joint Using Titanium Expansion Strap
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Solution Overview
Problem
In aircraft gas turbine engine propulsion systems, the difference in coefficients of thermal expansion between aluminum and composite materials leads to significant loads at fastener locations, potentially damaging composite components, necessitating reinforcement that increases weight and cost.
Innovation Solution
A joint configuration using a titanium expansion strap with a coefficient of thermal expansion between that of aluminum and composite materials, reducing bearing loads on the composite components by distributing stress through additional fasteners, thereby minimizing the need for additional reinforcement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum and composite materials are fastened together directly, then the joint can be simple and lightweight, but the differing coefficients of thermal expansion cause significant loads at fastener locations that may damage the composite components
Solution Approach 1:
A titanium expansion strap is introduced as an intermediary component between the aluminum component and the composite component. The titanium strap has a coefficient of thermal expansion that is greater than the composite material but less than aluminum, serving as a stress-absorbing intermediary that reduces bearing loads on the composite component while maintaining joint integrity under thermal cycling conditions
2Strength
If composite components are sufficiently reinforced against thermal expansion loads, then the components can withstand the stresses, but this reinforcement usually means more weight and cost
Solution Approach 1:
The titanium expansion strap acts as a stress-absorbing intermediary that reduces bearing loads on the composite component, allowing the composite component to be designed with less reinforcement and therefore less weight while still maintaining sufficient strength to withstand operational thermal expansion loads
3Strength
If composite components are sufficiently reinforced against thermal expansion loads, then the components can withstand the stresses, but this reinforcement usually means higher cost
Solution Approach 1:
The titanium expansion strap serves as a stress-absorbing intermediary that reduces the bearing loads on the composite component, enabling the composite component to be manufactured with less reinforcement and therefore lower cost while still maintaining the required strength to withstand thermal expansion stresses
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 titanium expansion strap effectively reduces stress on composite components, allowing them to withstand high temperatures without excessive reinforcement, thereby reducing weight and cost penalties.
Implementation Method 1
The third coefficient of thermal expansion may be greater than the second coefficient of thermal expansion. The second component may be configured to decrease a bearing load on the first component.
Data Source
AI summary
A composite component may be coupled to an aluminum component with a plurality of fasteners. An expansion strap may be located between the composite component and the aluminum component. The expansion strap may have a coefficient of thermal expansion which is greater than the coefficient of thermal expansion of the composite component, and less than the coefficient of thermal expansion of the aluminum component. A first set of fasteners may be inserted through the composite component, the expansion strap, and the aluminum component. A second set of fasteners may be inserted through the composite component and the expansion strap. The expansion strap may decrease stress in the composite component at the fastener locations.