Embedded Fiber-Optic Sensor for Composite Welding Temperature Monitoring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In-situ temperature distribution measurement during thermoplastic composite welding is challenging due to limitations of existing sensors, such as thermocouples, which provide pointwise measurements and create mechanical discontinuities, failing to accurately represent spatial temperature gradients essential for quality control and defect detection in processes like induction welding of carbon fiber reinforced polymers (CFRP) composites.
Innovation Solution
A distributed fiber-optic sensor is permanently embedded in the thermoplastic welded structure, capable of lifelong monitoring and inspection, using high-temperature coated small-diameter fibers that withstand welding temperatures and pressures, allowing for simultaneous measurement of temperature fields inside and outside the welding region, and can be adapted for various applications including thermoset composite curing and compression molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermocouples are used for temperature measurement during welding, then temperature data can be obtained, but the measurements are pointwise only and create mechanical discontinuities in the welded structure
Solution Approach 1:
The patent replaces mechanical thermocouples with an optical fiber sensing system that uses light propagation to detect temperature. The optical fiber acts as a distributed sensor along the weld line, eliminating mechanical discontinuities while providing continuous temperature measurement through optical properties that change with temperature.
Solution Approach 2:
The optical fiber is divided into multiple sensing segments along its length, with each segment providing temperature data for a specific location. This segmentation allows distributed temperature measurement across the entire weld zone, transforming a single point measurement into multiple spatially-resolved measurements without requiring multiple discrete thermocouple insertions.
2Loss of information
If traditional sensors are used for monitoring, then some temperature data is obtained, but spatial temperature gradients and interior temperature distribution cannot be accurately measured
Solution Approach 1:
The patent transitions from pointwise temperature measurement to distributed spatial measurement by utilizing the length dimension of the optical fiber. Temperature is measured as a function of position along the fiber, creating a one-dimensional temperature profile that captures spatial gradients and distribution patterns throughout the weld zone.
Solution Approach 2:
The optical fiber serves as an intermediary medium that transfers temperature information from the weld zone to the measurement system. The fiber's optical properties (such as Brillouin scattering or Raman scattering) change in response to temperature, allowing indirect but accurate measurement of the temperature field without direct electrical contact.
3Ease of operation
If surface temperature measurement is used via infrared techniques, then non-contact measurement is achieved, but interior temperature and actual welding zone temperature cannot be determined
Solution Approach 1:
The optical fiber sensor is embedded within the welded structure during the welding process itself, nesting the measurement system inside the workpiece. This allows the sensor to be positioned at the weld interface and interior zones, capturing temperature data from within the material rather than from the surface only.
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 real-time, on-demand process monitoring and diagnosis, improving the quality control of thermoplastic welding by providing accurate spatial temperature distribution data, reducing the risk of defects and enhancing the mechanical strength of welded structures without affecting the material's properties.
Implementation Method 1
a fiber optic sensor comprising an optical fiber having an elongated body portion for being a distributed sensor
Implementation Method 2
an associated optical data acquisition system for being connected to the fiber optic sensor
Data Source
AI summary
An in-situ fiber-optic temperature field measurement is disclosed that can allow process monitoring and diagnosis for thermoplastic composite welding and other applications. A distributed fiber-optic sensor can be permanently embedded in a thermoplastic welded structure when it is welded and left there to perform lifelong monitoring and inspection. The fiber optic sensor can include a dissolvable coating, or a coating matched to the composite material to be welded. Other applications include in-situ fiber-optic temperature field measurement on thermoset composite curing (autoclave), for thermoplastic and thermoset composites during compression molding, and for fiber-optic field measurements on freeze/thaw of large items of public health interest, such as stored or transported foodstuffs.