Composite Aircraft Control Cables With Twist-Free Carbon Fiber Tow
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Solution Overview
Problem
High-altitude aircraft and airships require control and stabilizing cables that can withstand extreme thermal conditions without significant length changes, while also being lightweight and providing consistent strength, and existing carbon fiber cables suffer from twists that reduce tensile strength and increase length variation.
Innovation Solution
The fabrication method involves consolidating carbon fiber prepreg tow using high-temperature shrink tubing and applying tension during curing to eliminate twists, resulting in a stronger, more consistent carbon fiber control cable, and optionally adding a conductive layer for lightning protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional steel wire rope is used for control cables, then the cables can be easily manufactured and installed, but the cables become overly tight at high altitudes due to thermal contraction
Solution Approach 1:
The patent changes the material parameter from steel wire rope to carbon fiber reinforced polymer (CFRP), which has a negative coefficient of thermal expansion. This parameter change allows the cable to expand slightly in cold temperatures rather than contract, eliminating the problem of excessive tightness at high altitudes while maintaining manufacturability through automated fiber placement techniques.
Solution Approach 2:
The patent employs composite materials by combining carbon fiber reinforcement with polymer matrix, creating a CFRP control cable that exhibits superior thermal stability compared to traditional steel wire rope. The composite structure provides both the necessary mechanical strength and the desired negative thermal expansion characteristic.
2Reliability
If carbon fiber cables are used to reduce thermal expansion effects, then the cables maintain optimal length at high altitudes, but the cables exhibit twists that reduce tensile strength and increase strength variation
Solution Approach 1:
The patent applies preliminary action by pre-tensioning the carbon fiber cables during the manufacturing process and applying heat treatment before final installation. This preliminary action eliminates twists and sets the cable in its optimal configuration, ensuring maximum tensile strength and consistent performance throughout the service life of the aircraft.
Solution Approach 2:
The patent changes the physical state parameter of the carbon fiber cable by applying controlled heat treatment and tensioning during manufacturing. This parameter change transforms the cable from a twisted, variable-strength state to a straight, high-strength configuration that maintains consistent tensile properties.
3Reliability
If carbon fiber cables are used for high altitude flight, then the cables have lower thermal expansion, but the manufacturing process becomes more complex requiring special equipment
Solution Approach 1:
The patent achieves universality by developing a manufacturing process that can produce carbon fiber control cables with standardized configurations for different aircraft applications. The automated fiber placement equipment and pre-tensioning apparatus are designed to accommodate various cable lengths and specifications, reducing the need for custom tooling and simplifying the overall manufacturing complexity.
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 method significantly increases the ultimate tensile strength of the cables and reduces length variation, achieving over twice the strength of prior art cables while maintaining consistent performance across parts.
Implementation Method 1
consolidating carbon fiber prepreg tow using high-temperature shrink tubing
Implementation Method 2
carbon fiber has a slightly negative coefficient of expansion allowing the cables to be adjusted optimally on the ground and not become overly tight during high altitude flight
Data Source
Figure 1
Figure 2A~2C
Figure 2D~2E
AI summary
Control and stabilizing cables and tendons for high altitude aircraft and airships having lightweight, high strength and low CTE are disclosed, along with a method and machine for fabrication of same. The cable is comprised of a fiber prepreg tow encased in a polymer sleeve with one bobbin at each end to facilitate connections. Consolidating the fiber prepreg tow along the length of the cable using high temperature shrink tubing, such as polyvinylidene fluoride (PVDF), allows for eliminating the twisting of the fiber prepreg tow, thus reducing the number of wraps around the bobbins. Eliminating the twists in the fiber prepreg tow also reduces the length of fiber needed, and therefore the overall change in length of the control cable with temperature variations is reduced. Additional cable strength can be achieved by adding and holding significant tension on the fiber prepreg tow by applying weight during the curing process.