Curable Composite Bushing for Aircraft Joint Eccentricity Gaps
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Solution Overview
Problem
The assembly of aircraft structures is hindered by the need for precise machining of solid bushings to correct eccentricities and gaps between fasteners and holes, leading to increased costs, potential damage, and inefficiencies in the manufacturing process, as well as the requirement for redundant fasteners to ensure load transfer, which results in heavier and more costly structures.
Innovation Solution
A curable composite bushing made from a matrix material pre-impregnated with reinforcement fibers, oriented circumferentially and featuring corrugations for compressibility, is used to fill gaps between fasteners and holes, preventing radial displacement and allowing for standardization across multiple dimensions without machining, along with a tool for compacting and curing the bushing in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solid bushings are machined to correct eccentricity and gaps between fasteners and holes, then manufacturing precision is improved, but assembly time increases and productivity decreases
Solution Approach 1:
The bushing material transitions from solid rigid material to curable composite material that changes state from liquid/paste to solid during installation. This parameter change allows the material to flow into and fill irregularities in the hole, then harden to provide precise alignment, eliminating the need for pre-machined bushings and reducing assembly time while maintaining manufacturing precision
Solution Approach 2:
The curable composite bushing acts as an intermediary between the fastener and the hole. It fills the gap and accommodates eccentricity, providing a reliable connection while eliminating the need for precise pre-machining of either the hole or the fastener, thus improving both precision and productivity
2Reliability
If solid bushings are used to ensure correct fit of fasteners, then reliability is improved, but the risk of damage to composite components increases
Solution Approach 1:
The material state change from liquid/paste to solid during installation allows the bushing to conform to the hole geometry without requiring forceful insertion. This eliminates the risk of damaging composite components while ensuring reliable fastener seating, as the material adapts to the hole shape rather than forcing a rigid fit
Solution Approach 2:
The use of curable composite bushing material provides both the flowability needed for damage-free installation and the final solid structure needed for reliable fastener seating. The composite nature allows tailoring of properties to balance reliability and harm prevention
3Reliability
If redundant fasteners are installed to compensate for incorrect seating, then reliability is improved, but structural weight increases
Solution Approach 1:
By changing the material state and installation process, the bushing ensures correct fastener seating on first attempt, eliminating the need for redundant fasteners. This maintains reliability while reducing structural weight, as the single properly-seated fastener can carry the full design load
4Adaptability or versatility
If various sizes of solid bushings are stored for different hole dimensions, then adaptability is improved, but storage space and asset management complexity increase
Solution Approach 1:
The curable composite material allows a single bushing product to adapt to multiple hole dimensions through controlled material flow and curing. The material can be injected in appropriate quantities and allows the bushing to conform to different hole sizes, eliminating the need for multiple pre-machined bushing sizes and simplifying storage and management while maintaining adaptability
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 solution reduces assembly time and costs, minimizes damage to components, and allows for lighter structural designs with fewer parts, as the curable composite bushing ensures optimal load transfer and seating of fasteners, while being easier to store and install than traditional solid bushings.
Implementation Method 1
a self-curing or externally cured composite bushing material is placed in the gap between the outer diameter of the attachment fastener and the attachment hole
Implementation Method 2
the curable composite bushing material is compressed into the gap between the outer diameter of the attachment fastener and the attachment hole such that the bushing substantially conforms to the dimensions of the gap
Data Source
AI summary
An aircraft structural joint comprising a first structural component provided with an attachment hole that is configured to receive an corresponding attachment fastener provided by a second structural component; a curable composite bush compressed and cured between an outer diameter of the attachment fastener and the attachment hole when the first component is mounted to the second component, wherein the curable composite bush, when cured, prevents radial displacement of the attachment fastener within the attachment hole.