CFRP Push-Pull Rod with Conical Adapter and Elastomeric Layer
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Solution Overview
Problem
Aircraft draw-pull bars made from traditional metallic materials are too heavy, while CFRP single-wall tubular bodies, although lighter, fail to meet industry requirements for damage resistance and load transfer under external impact, especially in compressive loads.
Innovation Solution
A multi-layer CFRP tubular body construction with an outer CFRP tube for tensile loads and an inner CFRP tube for compressive loads, separated by an elastomeric layer, connected to metallic adapters with conical surfaces to absorb momentum and pressure, and protected with a glass fibre layer to prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If single-wall CFRP tubular bodies are used, then weight is reduced, but damage resistance and load transfer capability under external impact deteriorate
Solution Approach 1:
The single-wall CFRP tubular body is divided into multiple concentric CFRP tubes (at least two layers) with different wall thicknesses. The inner tube has greater wall thickness than the outer tube, creating a segmented structure where each layer contributes to overall damage resistance. This segmentation allows the structure to maintain light weight while providing progressive damage tolerance through multiple structural barriers.
Solution Approach 2:
The patent employs composite material construction by combining multiple CFRP tubes with potentially different material compositions and structural characteristics. The inner and outer tubes can have different fiber orientations, resin systems, or manufacturing processes, creating a composite structure that leverages the strengths of each material layer to enhance both weight efficiency and impact resistance.
2Weight of moving object
If single-wall CFRP tubular bodies are used, then weight is reduced, but load transfer capability in compression under external damage deteriorates
Solution Approach 1:
The segmented multi-layer CFRP tube structure provides distinct functional zones for load transfer. The inner tube with greater wall thickness serves as the primary load-bearing element for compressive forces, while the outer tube provides additional structural support and damage containment. This segmentation ensures that compressive load transfer capability is maintained even when the outer tube sustains external damage.
Solution Approach 2:
Different regions of the tubular structure are assigned different wall thicknesses and material properties optimized for their specific functions. The inner tube has greater wall thickness localized to where compressive load transfer is most critical, while the outer tube has reduced wall thickness to minimize weight. This local quality differentiation optimizes the structure for its primary function of compressive load transfer while maintaining overall light weight.
3Reliability
If over-sized single-wall CFRP tubular bodies are used, then damage resistance is improved, but weight increases
Solution Approach 1:
Instead of increasing the size of a single wall tube, the patent segments the structure into multiple concentric tubes with optimized individual wall thicknesses. This segmentation allows each layer to contribute to damage resistance proportionally, achieving the required reliability without the excessive weight penalty of an oversized single-wall construction. The cumulative effect of multiple thinner layers provides equivalent or superior damage resistance at reduced weight.
Solution Approach 2:
The composite construction of multiple CFRP tubes with potentially different material properties allows for optimized weight-resistance trade-offs. Each layer can be tailored with specific fiber types, resin systems, or manufacturing processes to maximize damage resistance per unit weight, achieving superior overall performance compared to a homogeneous over-sized single-wall tube.
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 maintains load transfer capabilities in both tension and compression while reducing weight and enhancing resistance to external damage, ensuring stability and performance even after impact.
Implementation Method 1
the inner and outer CFRP tubular bodies (1) and (2) being separated from each other by a thin elastomeric layer (3)
Implementation Method 2
The conical surfaces between the metallic end (4) and the outer CFRP tubular body (1) absorb the momentum arising from the tension
Data Source
AI summary
A draw-pull bar is described which consists of at least one adapter with a metallic tubular end and of an inner and outer tubular body out of carbon-fiber-reinforced plastic (CFRP). It is characterized thus that the outer CFRP tubular body conically wraps the metallic end of the adapter from the outside in a form-fit manner while the inner CFRP tubular body is form-fit connected with the metallic ends of the adapter. An elastomeric layer is tapered in the contact area between the inner tubular body and the outer tubular body in such a way that both tubular bodies are separated on the one side, but are arranged against each other in a protected and damped manner on the other side.