Freeform Extrusion Fabrication of Advanced Ceramic Components with Embedded Sapphire Optical Fiber Sensors

Abstract

Traditionally, sensors to be integrated into a structural component are attached to or mounted on the component after the component has been fabricated. This tends to result in unsecured sensor attachment and/or serious offset between the sensor reading and the actual status of the structure, leading to performance degradation of the host structure. This paper describes a novel extrusion-based additive manufacturing process that has been developed to enable embedment of sensors in ceramic components during the part fabrication. In this process, an aqueous paste of ceramic particles with a very low amount of binder content ( < 1 vol%) is extruded through a moving nozzle to build the part layer-by-layer. In the case of sensor embedment, the fabrication process is halted after a certain number of layers have been deposited. The sensors are placed in their predetermined locations, and the remaining layers are deposited until the part fabrication is completed. Because the sensors are embedded during the fabrication process, they are fully integrated with the part and the aforementioned problems of traditional sensor embedment can be eliminated. The sensors used in this study were made of sapphire optical fibers of 125 and 250 micro-meters diameter and can withstand temperatures up to 1600 °C. After the parts were built, two different drying processes (freeze drying and humid drying) were investigated to dry the parts. The dried parts were then sintered to achieve near theoretical density. Scanning electron microscopy was used to observe the embedded sensors and to detect any possible flaws in the part or embedded sensor. Attenuation of the sensors was measured in near-infrared region (1500-1600 nm wavelength) with a tunable laser source. Raman spectroscopy was performed on the samples to measure the residual stresses caused by shrinkage of the part and its slippage on the fibers during sintering and mismatch between the coefficients of thermal expansion of the fiber and host material. Standard test methods were employed to examine the effect of embedded fibers on the strength and hardness of the parts. The result indicated that the sapphire fiber sensors with diameters smaller than 250 micrometers are able to endure the freeform extrusion fabrication process and also the post-processing without compromising the part properties.

Meeting Name

ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2016 (2016: Sep. 28-30, Stowe, VT)

Department(s)

Mechanical and Aerospace Engineering

Second Department

Materials Science and Engineering

Third Department

Electrical and Computer Engineering

Research Center/Lab(s)

Intelligent Systems Center

Keywords and Phrases

Adaptive optics; Ceramic materials; Chemical sensors; Drying; Extrusion; Fabrication; Fiber optic sensors; Fibers; Infrared devices; Intelligent materials; Intelligent systems; Optical fibers; Sapphire; Scanning electron microscopy; Sintering; Structural health monitoring; Thermal expansion; Additive manufacturing process; Coefficients of thermal expansions; Near infrared region; Performance degradation; Sapphire fiber sensors; Standard test method; Structural component; Tunable laser sources; Optical fiber fabrication

International Standard Book Number (ISBN)

978-0-7918-5048-0

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2016 American Society of Mechanical Engineers (ASME), All rights reserved.

Publication Date

30 Sep 2016

Link to Full Text

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