Distributed Optical Fiber Residual Strain Detection for Composite Impact Damage
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Solution Overview
Problem
Existing methods for detecting damage in composite materials due to low-velocity impact are inefficient, as they require real-time monitoring and are prone to errors from sensor malfunctions, and cannot effectively detect small damages that may affect the material's long-term safety and reliability.
Innovation Solution
A system using distributed optical fibers that measure residual strain by calculating the Brillouin frequency shift before and after impact, allowing for the detection of damage position and level without continuous power supply and real-time operation, utilizing a detector with optical fiber detection lines, transmission lines, and connection lines to calculate residual strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If real-time monitoring using conventional sensors (piezoelectric, optical fiber Bragg grating) is implemented, then damage detection capability is improved, but device complexity and cost increase due to continuous power supply requirements and sensor malfunction risks
Solution Approach 1:
The patent extracts the power consumption requirement from the detection system by using passive optical fiber sensors that do not require continuous power supply. The optical fiber itself serves as the sensing element, eliminating the need for active electronic sensors and their power requirements, thus simplifying the overall system while maintaining damage detection capability.
Solution Approach 2:
The patent replaces electronic sensing systems with optical sensing based on Brillouin scattering. This substitution eliminates the need for electronic components that require power, reducing device complexity while providing distributed sensing capability along the entire optical fiber length for detecting impact damage in composite structures.
2Loss of time
If conventional sensors are used for impact detection, then real-time detection during impact is improved, but reliability decreases due to sensor malfunction and inability to detect elastic recovery
Solution Approach 1:
The patent performs preliminary measurement of the optical fiber's baseline state before impact, then compares post-impact measurements against this baseline. This allows detection of residual strain after the composite structure has fully recovered elastically, ensuring detection occurs even if real-time monitoring during impact is missed or the sensor malfunctions at the critical moment.
Solution Approach 2:
The system uses feedback by continuously monitoring the optical fiber's strain state and comparing it against the pre-impact baseline. Any deviation from the baseline indicates damage, providing reliable detection that is independent of whether the impact moment was captured, thus improving reliability against sensor failure timing issues.
3Device complexity
If distributed optical fiber sensing is implemented, then detection cost and complexity are reduced by removing continuous power supply, but measurement precision must be maintained for residual strain detection
Solution Approach 1:
The patent employs Brillouin optical time domain analysis (BOTDA) to measure residual strain in the optical fiber. This optical measurement technique provides high precision strain detection by measuring the frequency shift of backscattered light, maintaining measurement precision while eliminating the need for complex powered sensor systems.
Solution Approach 2:
The optical fiber serves multiple functions: it acts as both the structural reinforcement element in the composite and the sensing element for damage detection. This multi-functionality reduces overall system complexity by eliminating separate sensor systems while maintaining high measurement precision through the fiber's inherent sensing capabilities.
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
Effectively and economically detects low-velocity impact damage in composite materials, improving long-term safety and reliability by enabling post-impact damage detection and reducing errors from sensor failures.
Implementation Method 1
calculating the position and level of the damage due to the impact on the composite material structure by measuring a residual strain of the detection line
Data Source
AI summary
An apparatus and method for detecting composite material damage due to impact by using distributed optical fiber are disclosed. In the apparatus and method for detecting composite material damage due to impact by using distributed optical fiber, the position and level of damage occurring in a composite material due to low-velocity impact can be effectively and economically detected by measuring the residual strain of optical fiber distributed on the surface of the composite material or inside the composite material. In the apparatus and method for detecting composite material damage due to impact by using distributed optical fiber, there is no need to always operate a sensor in real time, so that detection errors due to temporary failures, malfunctions, etc. of the sensor, as well as a problem of constantly supplying power to the sensor, can be essentially removed.