Perforated Composite Joints Using Cold-Sprayed Tapered Fasteners
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Solution Overview
Problem
Conventional joining methods for structural joints in aircraft, particularly those involving metallic and composite materials, face challenges such as strength reductions, increased weight, quality assurance issues, and complexity in handling complex three-dimensional structures, due to the need for drilling and fastener installation, which are not effectively addressed by existing methods like Friction Stir Welding (FSW) when dealing with composite materials.
Innovation Solution
The method involves aligning a structural member with a metallic substrate featuring shaped or tapered cavities, where a metallic material is cold-sprayed to form an in-situ shaped fastener, which is then bonded to the substrate using friction stir welding, eliminating the need for drilling and enhancing load-carrying capacity, while protective inserts and masking layers prevent erosion and surface damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional fastening methods with drilling holes are used to join metallic and composite structures, then the structures can be connected, but the strength is significantly reduced and localized stresses are produced requiring additional reinforcement
Solution Approach 1:
The invention extracts and eliminates the need for separate fasteners by depositing bonding material directly into cavities within the structural members, forming integrated bonding features that combine the functions of traditional fasteners and bonding surfaces into a single monolithic structure
Solution Approach 2:
The invention merges the functions of mechanical fastening and material bonding by depositing bonding material that forms integrated bonding features within cavities, combining what were previously separate fastener and substrate functions into a unified structure
2Ease of manufacture
If drilling holes and installing fasteners is performed to join structural members, then the members can be attached, but significant setup time is required
Solution Approach 1:
The invention performs preliminary action by pre-forming cavities within structural members before the joining process, allowing bonding material to be deposited directly into these pre-prepared spaces, eliminating the need for on-site drilling and fastener installation
Solution Approach 2:
The invention replaces the mechanical drilling and fastener installation system with a material deposition system that deposits bonding material directly into cavities, substituting complex mechanical operations with a more streamlined deposition process
3Ease of operation
If holes are drilled in metallic members for fastening, then fasteners can be installed, but localized stresses and mechanical loads are produced requiring structural reinforcement
Solution Approach 1:
The invention extracts and eliminates the source of localized stresses by removing the need for holes and traditional fasteners, replacing them with distributed bonding material deposited into cavities that creates more uniform stress distribution
Solution Approach 2:
The invention changes the physical state and distribution of the joining material from discrete fasteners creating concentrated loads to distributed bonding material in cavities that spreads mechanical loads more evenly across the joint interface
4Extent of automation
If Friction Stir Welding is used to join metal panels, then robustness and automation are achieved, but it cannot effectively join composite materials or complex three-dimensional structures
Solution Approach 1:
The invention creates a universal joining process that can bond both metallic and composite materials through material deposition, making the process adaptable to multiple material types and complex geometries where traditional FSW is limited
Solution Approach 2:
The invention changes the fundamental mechanism from mechanical mixing (FSW) to material deposition, allowing the process to accommodate composite materials and complex three-dimensional geometries that cannot be effectively joined by friction stir welding
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 approach reduces setup time and costs, minimizes quality assurance issues, and improves mechanical strength by eliminating localized stresses, enabling efficient joining of composite and metallic materials without additional fasteners, thus reducing weight and improving fatigue life.
Implementation Method 1
A metallic or other like material suited to cold spraying technology is deposited into the tapered cavity to form a shaped or tapered fastener bonded to the metallic substrate
Implementation Method 2
Friction Stir Welding (FSW) is a newer joining method... The rotation of tool 24 heats up and plasticizes the materials that the tool is in contact with
Implementation Method 3
The rotation of tool 24 heats up and plasticizes the materials that the tool is in contact with. As tool 24 moves along the joint line 32, material from the front of the tool is swept around this plasticized annulus to the rear
Data Source
AI summary
Embodiments in the present invention provide a system and method of joining structural members. This method involves aligning the first structural member to a metallic substrate when the first structural member has at least one tapered hole or cavity. A metallic or other like material suitable to cold spraying technology is deposited into the tapered cavity to form a shaped or tapered fastener bonded to the metallic substrate. The shape of the fastener secures the first structural member to the metallic substrate. Additionally, a protective insert may be placed within the shaped or tapered cavity to protect the first structural member during hoe cold spraying deposition when the first structural member is a composite material or other like material susceptible to erosion during the cold spraying technique. After the material has been deposited using cold spray techniques this material may be further solidified and bonded to the metallic substrate using a technique such as friction stir welding in order to increase the load carrying capacity of the in-situ shaped fastener.