Staggered Composite-to-Metal Joint for Load Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing composite structures face challenges in creating a cost-effective, lightweight, and durable composite-to-metal joint that minimizes residual stresses and avoids chemical reactions between metal fittings and carbon fiber reinforced composites, while also addressing issues of eccentricity and weight increase due to local thickness changes around fasteners.
Innovation Solution
A hybrid composite structure with a fiber-reinforced resin composite-to-metal joint using staggered metal sheets interleafed with composite plies, forming multiple bond lines and reducing the length of the transition section to minimize residual stresses, and employing a metal laminate for improved load transfer and reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the local thickness of the composite structure is increased to withstand fastener loads, then the joint strength is improved, but the weight of the structure increases
Solution Approach 1:
The structure is segmented into composite regions and metal laminate regions, with the metal laminate strategically placed only in the fastener joint area where high strength is required. This segmentation allows the structure to have high joint strength without increasing the weight of the entire structure, as metal sheets are substituted for composite plies only in the transition section and fastener region.
Solution Approach 2:
The metal laminate is applied locally in the transition section and fastener joint area rather than throughout the entire structure. This local quality approach provides enhanced strength and stiffness exactly where the fastener loads are transmitted, while maintaining the lightweight composite construction in other areas, thus improving joint strength without proportionally increasing overall weight.
2Strength
If the local thickness of the composite structure is increased around fasteners, then the joint strength is improved, but the eccentricity of the load path increases
Solution Approach 1:
The structure is divided into composite plies and metal laminate sections with a defined transition zone. This segmentation creates a gradual thickness transition rather than an abrupt change, which helps align the load path more directly through the fastener, reducing eccentricity while maintaining joint strength.
Solution Approach 2:
The transition from composite to metal laminate is achieved in the thickness dimension through a transition section where the number of plies changes gradually. This dimensional approach to transitioning material properties helps create a more direct load path through the fastener joint, reducing bending moments and eccentricity.
3Strength
If metal fittings are used to connect composite structures, then the joint strength and durability are improved, but the manufacturing cost increases
Solution Approach 1:
The invention uses a hybrid composite structure combining composite plies and metal laminate in a single integrated construction. This approach achieves the strength and durability of metal fittings while avoiding the high costs associated with forming complex metal shapes, as the metal laminate is applied in a more straightforward manner during the composite layup process.
Solution Approach 2:
The metal laminate and composite plies are merged into a single hybrid structure with a transition section, eliminating the need for separate metal fittings that would require additional manufacturing steps. This combined approach achieves comparable joint strength while simplifying the manufacturing process and reducing costs associated with forming and attaching complex metal components.
4Strength
If a long transition section is used between composite and metal portions, then the load transfer is improved, but the residual stresses in the joint increase
Solution Approach 1:
The invention optimizes the transition section parameters, specifically the number of composite plies and metal laminate layers, to achieve an optimal balance between load transfer and residual stress. By carefully selecting the ply schedule and transition section length, the design achieves adequate load transfer while minimizing the CTE mismatch effects that cause residual stresses during thermal cycling.
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 improved joint robustness, reduced weight, enhanced safety, and manufacturing cost savings, while maintaining the strength and durability of metal structures and the weight and fatigue characteristics of composite resin laminates, with reduced residual stresses and minimized need for machined end-fittings.
Implementation Method 1
An adhesive placed between the metal sheets binds and unitizes the sheets into a nearly solid metal fitting
Implementation Method 2
The staggered transition results in an interleaving between the composite plies and the metal sheets and creates multiple bond lines that may reduce the occurrence and/or propagation of cracks or disbonds in the joint
Implementation Method 3
A shorter bond length resulting from use of the disclosed joint may minimizes residual (or cured in) stresses due to CTE (coefficient of thermal expansion) mismatch between the metallic and composite materials forming the joint
Data Source
AI summary
A composite structure comprises stacked sets of laminated fiber reinforced resin plies and metal sheets. Edges of the resin plies and metal sheets are interleaved to form a composite-to-metal joint connecting the resin plies with the metal sheets.