Failsafe Adhesive Joint with Interlocking Resin Keys
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Solution Overview
Problem
The challenge in joining structural composite parts or composite to non-composite parts using adhesives lies in ensuring uniform adhesive distribution and preventing catastrophic failure modes, particularly in aircraft structures, where mechanical fasteners are often required to mitigate debonding issues, which compromises the advantages of bonded joints.
Innovation Solution
The method involves forming elongated, undulating recesses on the bonding surfaces to create a cavity for adhesive injection, allowing the adhesive to form interlocking resin keys that carry loads in case of bond failure, eliminating the need for mechanical fasteners and enabling failsafe features compatible with composite and metal parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive bonds are used to join structural members, then the advantages of bonded joints are maintained, but the catastrophic failure mode of debonded joints occurs and certification is difficult
Solution Approach 1:
The patent incorporates mechanical interlocking features (recesses and protrusions) into the bonding surfaces before assembly. These features act as a preemptive safety mechanism that provides alternative load paths if the adhesive bond fails, thus cushioning against catastrophic failure while maintaining the benefits of bonded joints.
Solution Approach 2:
The patent creates a composite joint system combining adhesive material with mechanically interlocking geometric features. This hybrid approach integrates the advantages of adhesive bonding with the reliability of mechanical fastening, resulting in a joint that is both easy to manufacture and highly reliable.
2Manufacturing precision
If adhesive is applied to ensure complete coverage, then uniform bond thickness is achieved, but the process time increases and costs increase
Solution Approach 1:
The recesses and protrusions are pre-formed into the structural members before the bonding process. This preliminary action creates self-aligning features that guide adhesive flow and ensure complete coverage without requiring precise manual application, thus maintaining manufacturing precision while reducing process time.
Solution Approach 2:
The bonding surface is segmented into recesses and protrusions, creating discrete zones that control adhesive placement. This segmentation ensures adhesive is confined to specific areas where it is needed, improving distribution uniformity while reducing the total amount of adhesive required and speeding up the process.
3Reliability
If mechanical fasteners are added to bonded joints to prevent debonding, then joint reliability improves, but the advantages of bonded joints are compromised
Solution Approach 1:
The recesses and protrusions serve multiple functions: they provide mechanical interlocking for reliability, guide adhesive flow for uniform distribution, and create self-aligning features for ease of assembly. This multi-functionality eliminates the need for separate mechanical fasteners, maintaining the simplicity of bonded joints while improving reliability.
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 ensures complete adhesive filling and curing verification, reduces manufacturing complexity, and allows for dry assembly and sequential bonding, enhancing the reliability and efficiency of the bonding process without the need for mechanical fasteners, while maintaining structural integrity.
Implementation Method 1
As the adhesive flows through the grooves, it will completely fill the channel
Implementation Method 2
The adhesive typically transfers shear load between the members via an adhesive bond
Data Source
AI summary
A composite member is joined to another composite or noncomposite member, using liquid or paste adhesive resin that cures in the joint. The joint is configured in such a way that the adhesive forms an interlocking key within recesses in the joined members that prevents joint disassembly once the adhesive has cured and hardened. Both of the members are provided with recesses extending along their lengths in the joint. The recesses register with each other to define a cavity and may undulate. The recessed are designed in such a way as to take the full load capability if the joint, even if there is no adhesion to the joined members. Adhesive is injected into the cavity through injection ports spaced periodically along the length of the joint.