Composite Fiber Braid with Embedded Optical Sensors for Strain Control
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Solution Overview
Problem
Spacecraft structures, such as RF antenna reflectors, face challenges in accommodating launch loads, temperature variations, and radiation exposure while meeting stringent mass and cost objectives, and existing composite structures struggle with measuring load-induced structural strain and maintaining precise alignment due to intricate lattice structures.
Innovation Solution
The use of composite fiber braid arrangements with high resistivity metal wires and optical fibers embedded in a polymer resin, where the resin is cured by heating the metal wire, and optical fibers sense strain to actively control temperature and alignment, allowing for real-time correction of distortions and misalignments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If composite structures are used for spacecraft, then mass and cost objectives are met, but measurement of load-induced structural strain becomes difficult due to intricate lattice structures
Solution Approach 1:
The patent replaces traditional mechanical strain measurement methods with optical fiber sensing. Optical fibers are embedded within the composite structural members to directly sense strain, eliminating the need for external mechanical gauges that would be difficult to install and read on intricate lattice structures. This substitution enables accurate strain measurement while maintaining the lightweight composite structure.
Solution Approach 2:
The patent embeds optical fibers and metal wires inside the composite fiber braid structures. The sensors are nested within the structural members themselves, allowing simultaneous structural function and sensing capability. This nesting approach integrates measurement functionality into the structure without adding external complexity or weight.
2Strength
If composite fiber braid arrangements are used, then bending stiffness increases significantly after curing, but the structure requires complex curing processes
Solution Approach 1:
The patent incorporates high resistivity metal wires within the composite fiber braid that can be heated by applying electrical potential. This self-heating capability allows the structure to cure itself without requiring external heating equipment or complex curing cycles. The metal wires act as internal heaters that distribute heat uniformly through the resin, simplifying the curing process while achieving the required bending stiffness.
Solution Approach 2:
The patent uses high resistivity metal wires as intermediaries to transfer electrical energy into thermal energy for curing the polymer resin. The metal wires serve as a mediator between the electrical power source and the resin, enabling controlled heating and curing without direct thermal contact from external sources.
3Measurement precision
If optical fibers are embedded in polymer resin, then real-time strain sensing is enabled, but the optical fibers may be damaged during the curing process
Solution Approach 1:
The patent embeds optical fibers within the polymer resin matrix, using the resin itself as a protective intermediary. The cured resin encapsulates and protects the optical fibers from mechanical damage, thermal stress, and environmental factors while allowing the fibers to sense strain effectively. This integration provides both protection and functional coupling.
Solution Approach 2:
The patent carefully selects and applies polymer resin that provides cushioning and protection to the optical fibers before and during the curing process. The resin acts as a protective layer that absorbs stress and prevents damage to the delicate optical fibers while maintaining their sensing capability throughout the curing and operational phases.
4Manufacturing precision
If active temperature control is implemented using metal wires, then alignment precision is maintained, but energy consumption increases
Solution Approach 1:
The patent implements a feedback control system where optical fibers sense strain and temperature, and the control system adjusts current through the metal wires accordingly. This closed-loop feedback ensures that energy is consumed only when and where needed to maintain precise alignment, rather than continuous energy consumption. The system responds dynamically to actual structural conditions.
Solution Approach 2:
The patent applies temperature control locally through embedded metal wires in specific structural members rather than heating the entire structure uniformly. This localized approach concentrates energy only in regions requiring alignment adjustment, significantly reducing overall energy consumption while maintaining precision where needed.
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 results in significantly increased bending stiffness and precise alignment control, enabling structures with superior strength-to-mass ratios and low thermal expansion, effectively addressing the challenges of structural integrity and alignment in space environments.
Implementation Method 1
heating the high resistivity metal wire by applying an electrical potential across a length of the wire
Implementation Method 2
Each optical fiber is configured to sense strain at locations along the length of a respective structural member resulting from thermal and/or dynamic loads
Implementation Method 3
The polymer resin encloses a tow formed from an untwisted bundle of graphite fibers
Implementation Method 4
an outer jacket comprised of relatively dry, non-resin-impregnated, graphite or aramid fibers... a coefficient of friction of the outer jacket may be substantially lower than a coefficient of friction of the bundle of graphite fibers
Data Source
AI summary
A composite fiber braid arrangement includes at least one fiber optic sensor embedded in a polymer resin. The polymer resin encloses a tow formed from an untwisted bundle of graphite fibers, and the untwisted bundle, together with the polymer resin, is enclosed by an outer jacket comprised of relatively dry, non-resin-impregnated, graphite fibers. Techniques for controlling alignment of an assembly of structural members, each structural member including such a fiber braid arrangement are also disclosed.