Embedded Optical Fiber Structural Monitoring in Composite Aircraft
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Solution Overview
Problem
Composite aircraft structures, particularly those made of carbon fiber resin composites, can experience invisible delamination damage due to layer separation, which is difficult to detect under stress and can lead to delayed identification and potential failure, as they return to original shape when stress is removed, and the use of optical fibers for data transmission is hindered by the need for protection against damage.
Innovation Solution
Embedding optical fibers within the composite structure to detect delamination by analyzing changes in light propagation and bit error rates, where the fibers can switch to steady unmodulated light to monitor damage growth and estimate failure time through spectral analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical fibers are embedded in composite structure for protection, then fiber damage risk is reduced, but device complexity increases
Solution Approach 1:
The patent combines the optical fiber with the composite structure by embedding the fiber directly into the composite material layers. This merging approach provides physical protection to the fiber through the composite structure itself, eliminating the need for separate protective conduits while reducing overall system complexity.
Solution Approach 2:
The composite structure serves dual functions: it provides structural integrity for the aircraft and simultaneously protects the embedded optical fiber from damage. This multi-functionality resolves the contradiction by making the protective function inherent to the structure rather than requiring additional dedicated protective elements.
2Weight of moving object
If optical fibers are used for data transmission, then weight is reduced, but fiber vulnerability to damage increases
Solution Approach 1:
The optical fiber is merged with the composite structure through embedding, where the fiber becomes an integral part of the composite material layers. This provides mechanical protection to the fragile fiber while maintaining the weight advantages of using optical instead of electrical cables.
Solution Approach 2:
The composite structure acts as a protective cushion around the optical fiber before any damage can occur. The embedding process places the fiber within the protective matrix of the composite material, providing beforehand protection against mechanical damage, bending, and environmental factors.
3Reliability
If delamination damage occurs in composite structure, then structural integrity is reduced, but visual detection becomes difficult
Solution Approach 1:
The optical fiber serves as an intermediary sensor that detects delamination damage indirectly through changes in light transmission. When delamination occurs, it affects the fiber's optical properties, allowing the fiber to mediate between the structural damage and the detection system, making invisible damage detectable.
Solution Approach 2:
The patent replaces traditional mechanical visual inspection methods with optical detection. Instead of relying on visual examination of the composite surface, the system uses optical fiber sensors to detect structural changes through light transmission variations, substituting mechanical inspection with optical sensing.
4Difficulty of detecting and measuring
If optical fiber monitoring is implemented, then damage detection capability is improved, but system complexity increases
Solution Approach 1:
The embedded optical fiber serves multiple functions: it provides structural reinforcement as part of the composite material and simultaneously acts as a sensor for damage detection. This multi-functionality reduces system complexity by eliminating separate sensing elements while improving damage detection capability.
Solution Approach 2:
The optical fiber monitors the structural health of the composite by detecting changes in its own optical properties when subjected to delamination or other damage. The fiber essentially monitors itself and the surrounding structure, providing self-service damage detection without requiring external sensing systems.
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
Enables early detection of delamination and prediction of structural failure in composite aircraft structures, allowing for timely intervention and minimizing weight addition by using optical fibers for both data transmission and damage assessment, reducing the risk of fiber damage and ensuring continuous data communication.
Implementation Method 1
the fiber could crack and separate causing light passing through the fiber to be modulated by the damaged area separating and recovering
Implementation Method 2
optical fibers for carrying data and other messages. Optical fibers are very light and delicate requiring some form of conduit to protect them from being damaged
Data Source
Figure 1~2
AI summary
A method for detecting defects in a composite structure, such as in an aircraft structure, that includes sending an optical signal down an optical fiber embedded in the composite structure and analyzing the optical signal at a detector. If it is determined that the optical signal is turning on and off or an increase in the bit error rate is occurring at the detector, the composite structure may be delaminating or the composite structure may be somehow damaged. If it is determined that the composite structure is damaged, the optical signal can be sent down a different optical fiber that may not be at a location where the composite structure is damaged, and a continuous beam of light can be sent down the optical fiber that is at the damaged part of the composite structure to determine whether the damage is increasing.