Entire Life Time Monitoring of Filament Wound Composite Cylinders Using Bragg Grating Sensors: II. Process Monitoring

Abstract

This article is the second of a series of three papers concerning monitoring of filament wound cylinders using Bragg gratings. In this second part, the tooling presented in Part I is used to embed gratings and thermocouples in filament wound glass reinforced epoxy composite cylinders during fabrication. Bragg grating strain was obtained from wavelength and temperature response, by a calibration technique described here. Results from tests on five cylinders show the Bragg grating's capability to monitor strain evolution during fabrication, and the capacity to detect several phenomena occurring during cure is established, in addition to quantifying the initial material condition of the cylinder before it enters service.

Field Deployable Fiber Bragg Grating Strain Patch for Long-Term Stable Health Monitoring Applications

“…The effects observed here cannot therefore clearly be separated into temperature load and mechanical forces acting at the sensor. For a description of the curing process, and for the use of these sensors for cure monitoring, it is necessary to develop a specially adapted sensor system based on fundamental work in literature [5][6][7]. Additionally, interferences on spectral phenomena have to be investigated, e.g.…”

Entire Life Time Monitoring of Filament Wound Composite Cylinders Using Bragg Grating Sensors: III. In-Service External Pressure Loading

“…2), [20]. The instrumented specimen used for pressure testing here was cylinder 37 (see Part II [8]), which has one rhomboid pattern in the circumferential direction. The Bragg gratings are located at mid-length of the cylinder, between the first and second reinforcement layers near the inner surface.…”

“…If such applications are to become more widespread, particularly for the offshore oil industry, it is essential to be able to monitor the material condition during manufacturing and then throughout the service life. Two previous papers in this series [7,8] have shown how a filament wound composite cylinder can be instrumented with Bragg gratings, which enable its condition during and after manufacture to be evaluated. In the present paper one of those cylinders, which was previously monitored during fabrication, is subjected to increasingly high external pressure cycles up to failure, in order to demonstrate how monitoring can be performed in service.…”

“…In recent years optical fiber based sensors, such as Bragg gratings, have been increasingly used for in situ strain and temperature monitoring, references can be found in the previous papers [7,8]. One example developed specifically for underwater applications was described by Brower [10], who presented a "smart pipe system" composed of a "smart layer" (composite material) with embedded Bragg gratings, placed between the pipe outer skin and the thermal insulation layer, this system allows pipe monitoring during service.…”

Multi-instrumentation monitoring for the curing process of a composite structure

“…The nature of their constitutive layers allows the possibility to implement in-core instrumentation for monitoring since the manufacturing process until their final application. Numerous studies have proven the value added of composites in-core instrumentation to follow through-the-thickness properties [1][2][3]. However, composites in-core instrumentation still reveals worries which retard its plenty application.…”