Composite Structural Member Fitting and Shaft Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The integration of metallic and resin-based components in composite structural members for aircraft construction faces challenges such as residual stresses, stress concentrations, and reduced adhesive strength, leading to potential de-bonding and failure at joints.
Innovation Solution
A composite structural member design featuring a fitting with a recessed portion and a tubular shaft that mechanically interferes, with a reinforcing member and sleeve to prevent relative movement and de-bonding, and the use of adhesive to enhance bonding between components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If adhesive bonding is used to join metal and resin parts, then the composite structural member can be assembled into an integrated part, but residual stresses and thermal expansion mismatches can cause de-bonding and joint failure
Solution Approach 1:
The coupling region is divided into multiple functional zones: a first region with the resin-based shaft, a second region with the metal fitting, and a third intermediate region containing the reinforcing member. This segmentation allows each region to be optimized for its specific material properties and loading conditions, preventing stress concentration at material interfaces.
Solution Approach 2:
A reinforcing member composed of fiber-reinforced resin material is embedded in the intermediate region of the coupling region. This composite material provides enhanced mechanical strength and stiffness to bridge the metal and resin parts, distributing stresses and preventing de-bonding caused by thermal expansion mismatches.
2Strength
If metal and resin parts are fastened together, then an integrated composite component is achieved, but stress concentrations occur at fastening areas leading to failure
Solution Approach 1:
The coupling region exhibits spatially varying properties: the intermediate region has increased fiber reinforcement concentration and may include voids or cavities to accommodate thermal expansion. This local quality enhancement specifically addresses stress concentration zones without compromising the overall structural integrity.
Solution Approach 2:
The reinforcing member is pre-positioned in the intermediate region before final assembly, creating a stress-distributing framework that cushions against concentrated loads and thermal stresses before they can cause failure at the metal-resin interface.
3Reliability
If adhesive strength is increased to prevent de-bonding, then bond integrity improves, but the adhesive itself becomes a weaker link compared to component parts
Solution Approach 1:
The reinforcing member acts as an intermediary element between the metal fitting and resin shaft, providing a mechanical bridge that transfers loads without relying solely on adhesive bonding. This mediator approach allows the use of adhesives optimized for bonding performance rather than structural load-bearing.
Data Source
AI summary
Composite structural members are provided including a fitting and a tubular shaft. The fitting has a coupling region defining at least one recessed portion bounded by one or more non-recessed portions. The recessed portion may extend circumferentially around the fitting to form a neck. The tubular shaft has a mating region and defines a lumen in which the fitting is disposed. The mating region of the shaft mates with the coupling region of the fitting to create interference between the shaft and fitting. Adhesive may be disposed between the mating region of the fitting and the coupling region of the shaft. The mating region of the shaft may be partially and proximately surrounded by a reinforcing member, and a sleeve may be coupled substantially concentrically to the shaft for discouraging separation of the reinforcing member and the mating region of the shaft. In some cases, adhesive is disposed between the reinforcing member and sleeve.