Comparison of two fiber-optical temperature measurement systems in magnetic fields up to 9.4 Tesla.

PURPOSE Precise temperature measurements in the magnetic field are indispensable for MR safety studies and for temperature calibration during MR-guided thermotherapy. In this work, the interference of two commonly used fiber-optical temperature measurement systems with the static magnetic field B0 was determined. METHODS Two fiber-optical temperature measurement systems, a GaAs-semiconductor and a phosphorescent phosphor ceramic, were compared for temperature measurements in B0 . The probes and a glass thermometer for reference were placed in an MR-compatible tube phantom within a water bath. Temperature measurements were carried out at three different MR systems covering static magnetic fields up to B0  = 9.4T, and water temperatures were changed between 25°C and 65°C. RESULTS The GaAs-probe significantly underestimated absolute temperatures by an amount related to the square of B0 . A maximum difference of ΔT = -4.6°C was seen at 9.4T. No systematic temperature difference was found with the phosphor ceramic probe. For both systems, the measurements were not dependent on the orientation of the sensor to B0 . CONCLUSION Temperature measurements with the phosphor ceramic probe are immune to magnetic fields up to 9.4T, whereas the GaAs-probes either require a recalibration inside the MR system or a correction based on the square of B0 . Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.

Intraply fracture of fiber-reinforced composites: microscopic mechanisms and modeling

The fracture behavior parallel to the fibers of an E-glass/epoxy unidirectional laminate was studied by means of three-point tests on notched beams. Selected tests were carried out within a scanning electron microscope to ascertain the damage and fracture micromechanisms upon loading. The mechanical behavior of the notched beam was simulated within the framework of the embedded cell model, in which the actual composite microstructure was resolved in front of the notch tip. In addition, matrix and interface properties were independently measured in situ using a nanoindentor. The numerical simulations very accurately predicted the macroscopic response of the composite as well as the damage development and crack growth in front of the notch tip, demonstrating the ability of the embedded cell approach to simulate the fracture behavior of heterogeneous materials. Finally, this methodology was exploited to ascertain the influence of matrix and interface properties on the intraply toughness.

Tuning the properties of carbon fiber-reinforced poly (phenylene sulphide) laminates via incorporation of inorganic fullerene-like WS2 nanoparticles

Novel carbon fiber (CF)-reinforced poly(phenylene sulphide) (PPS) laminates incorporating inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles were prepared via melt-blending and hot-press processing. The influence of the IF-WS2 on the morphology, thermal, mechanical and tribological properties of PPS/CF composites was investigated. Efficient nanoparticle dispersion within the matrix was attained without using surfactants. A progressive rise in thermal stability was found with increasing IF-WS2 loading, as revealed by thermogravimetric analysis. The addition of low nanoparticle contents retarded the crystallization of the matrix, whereas concentrations equal or higher than 1.0 wt% increased both the crystallization temperature and degree of crystallinity compared to those of PPS/CF. Mechanical tests indicated that with only 1.0 wt% IF-WS2 the flexural modulus and strength of PPS/CF improved by 17 and 14%, respectively, without loss in toughness, ascribed to a synergistic effect between the two fillers. A significant enhancement in the storage modulus and glass transition temperature was also observed. Moreover, the wear rate and coefficient of friction strongly decreased, attributed to the lubricant role of the IF-WS2 combined with their reinforcing effect. These inorganic nanoparticles show great potential to improve the mechanical and tribological properties of conventional thermoplastic/CF composites for structural applications.

Packaging and testing of fiber Bragg gratings for use as strain sensor for rock specimens

This paper reports a packaging and calibration procedure for surface mounting of fiber Bragg grating (FBG) sensors to measure strain in rocks. The packaging of FBG sensors is performed with glass fiber and polyester resin, and then subjected to tensile loads in order to obtain strength and deformability parameters, necessaries to assess the mechanical performance of the sensor packaging. For a specific package, an optimal curing condition has been found, showing good repeatability and adaptability for non-planar surfaces, such as occurs in rock engineering. The successfully packaged sensors and electrical strain gages were attached to standard rock specimens of gabbro. Longitudinal and transversal strains under compression loads were measured with both techniques, showing that response of FBG sensors is linear and reliable. An analytical model is used to characterize the influences of rock substrate and FBG packaging in strain transmission. As a result, we obtained a sensor packaging for non-planar and complex natural material under acceptable sensitivity suitable for very small strains as occurs in hard rocks.

Inorganic Nanoparticle-Modified Poly(Phenylene Sulphide)/ Carbon Fiber Laminates: Thermomechanical Behaviour

Carbon fiber (CF)-reinforced high-temperature thermoplastics such as poly(phenylene sulphide) (PPS) are widely used in structural composites for aerospace and automotive applications. The porosity of CF-reinforced polymers is a very important topic for practical applications since there is a direct correlation between void content and mechanical properties. In this study, inorganic fullerene-like tungsten disulphide (IF-WS2) lubricant nanoparticles were used to manufacture PPS/IF-WS2/CF laminates via melt-blending and hot-press processing, and the effect of IF-WS2 loading on the quality, thermal and mechanical behaviour of the hybrid composites was investigated. The addition of IF-WS2 improved fiber impregnation, resulting in lower degree of porosity and increased delamination resistance, compression and flexural properties; their reinforcement effect was greater at temperatures above the glass transition (Tg). IF-WS2 contents higher than 0.5 wt % increased Tg and the heat deflection temperature while reduced the coefficient of thermal expansion. The multiscale laminates exhibited higher ignition point and notably reduced peak heat release rate compared to PPS/CF. The coexistence of micro- and nano-scale fillers resulted in synergistic effects that enhanced the stiffness, strength, thermal conductivity and flame retardancy of the matrix. The results presented herein demonstrate that the IF-WS2 are very promising nanofillers to improve the thermomechanical properties of conventional thermoplastic/CF composites.

Impact Behavior of Hybrid Glass/Carbon Epoxy Composites

The high velocity impact performance in hybrid woven carbon and S2 and E glass fabric laminates manufactured by resin transfer molding (RTM) was studied. Specimens with different thicknesses and glass-fiber content were tested against 5.5 mm spherical projectiles with impact velocities ranging from 300 to 700 m/s to obtain the ballistic limit. The resulting deformation and fracture micromechanisms were studied. Several impacts were performed on the same specimens to identify the multihit behavior of such laminates. The results of the fracture analysis, in conjunction with those of the impact tests, were used to describe the role played by glass-fiber hybridization on the fracture micromechanisms and on the overall laminate performance under high velocity impact.

Nanoarchitectures Based on Layered Titanosilicates Supported on Glass Fibers: Application to Hydrogen Storage

This work reports on the synthesis of nanosheets of layered titanosilicate JDF-L1 supported on commercial E-type glass fibers with the aim of developing novel nanoarchitectures useful as robust and easy to handle hydrogen adsorbents. The preparation of those materials is carried out by hydrothermal reaction from the corresponding gel precursor in the presence of the glass support. Because of the basic character of the synthesis media, silica from the silicate-based glass fibers can be involved in the reaction, cementing its associated titanosilicate and giving rise to strong linkages on the support with the result of very stable heterostructures. The nanoarchitectures built up by this approach promote the growth and disposition of the titanosilicate nanosheets as a house-of-cards radially distributed around the fiber axis. Such an open arrangement represents suitable geometry for potential uses in adsorption and catalytic applications where the active surface has to be available. The content of the titanosilicate crystalline phase in the system represents about 12 wt %, and this percentage of the adsorbent fraction can achieve, at 298 K and 20 MPa, 0.14 wt % hydrogen adsorption with respect to the total mass of the system. Following postsynthesis treatments, small amounts of Pd (<0.1 wt %) have been incorporated into the resulting nanoarchitectures in order to improve their hydrogen adsorption capacity. In this way, Pd-layered titanosilicate supported on glass fibers has been tested as a hydrogen adsorbent at diverse pressures and temperatures, giving rise to values around 0.46 wt % at 298 K and 20 MPa. A mechanism of hydrogen spillover involving the titanosilicate framework and the Pd nanoparticules has been proposed to explain the high increase in the hydrogen uptake capacity after the incorporation of Pd into the nanoarchitecture.

Preparation of water samples for asbestos fiber counting by electron microscopy /

Prepared by Ontario Research Foundation, under contract no. 68-03-2389.

In-fiber polymer–glass hybrid waveguide Bragg grating

A 1.2 µm (height) × 125 µm (depth) × 500 µm (length) microslot along a fiber Bragg grating was engraved across the optical fiber by femtosecond laser patterning and chemical etching. By filling epoxy in the slot and subsequent UV curing, a hybrid waveguide grating structure with a polymer core and glass cladding was fabricated. The obtained device is highly thermally responsive with linear coefficient of 211 pm/°C.

Microstructures made in optical fiber with femtosecond laser

Different types of microstructures including microchannels and microslots were made in optical fibers using femtosecond laser inscription and chemical etching. Integrated with UV-inscribed fiber Bragg gratings, these microstructures have miniature, robustness and high sensitivity features and have been used to implement novel devices for various sensing applications. The fiber microchannels were used to detect the refractive index change of liquid presenting sensitivities up to 7.4 nm/refractive index unit (RIU) and 166.7 dB/RIU based on wavelength and power detection, respectively. A microslot-in-fiber based liquid core waveguide as a refractometer has been proposed and the device was used to measure refractive index, and a sensitivity up to 945 nm/RIU (10-6/pm) was obtained. By filling epoxy in the microslot and subsequent UV light curing, a hybrid waveguide grating structure with polymer core and glass cladding was fabricated. The obtained device was highly thermal responsive, demonstrating a linear coefficient of 211 pm/°C.

High-power diode-pumped fiber laser operating at 3 μm

A high-power diode-cladding-pumped Ho-doped fluoride glass fiber laser operating in cascade mode is demonstrated. The 5|6 -> 5|7 and 5|7 -> 5|8 laser transitions produced 0:77W at a measured slope efficiency of 12.4% and 0:24Wat a measured slope efficiency of 5.2%, respectively. Using a long fiber length, which forced a large threshold for the 5|7 -> 5|8 transition, a wavelength of 3:002 µm was measured at maximum output power, making this system the first watt-level fiber laser operating in the mid-IR.

Numerical modeling of holmium-doped fluoride fiber lasers

We combine all the known experimental demonstrations and spectroscopic parameters into a numerical model of the Ho3+ -doped fluoride glass fiber laser system. Core-pumped and cladding-pumped arrangements were simulated for all the population-bottlenecking mitigation schemes that have been tested, and good agreement between the model and the previously reported experimental results was achieved in most but not in all cases. In a similar way to Er3+ -doped fluoride glass fiber lasers, we found that the best match with measurements required scaled-down rate parameters for the energy transfer processes that operate in moderate to highly concentrated systems. The model isolated the dominant processes affecting the performance of each of the bottlenecking mitigation schemes and pump arrangements. It was established that pump excited-state absorption is the main factor affecting the performance of the core-pumped demonstrations of the laser, while energy transfer between rare earth ions is the main factor controlling the performance in cladding-pumped systems.

High-power diode-pumped fiber laser operating at 3 μm

A high-power diode-cladding-pumped Ho-doped fluoride glass fiber laser operating in cascade mode is demonstrated. The 5|6 -> 5|7 and 5|7 -> 5|8 laser transitions produced 0:77W at a measured slope efficiency of 12.4% and 0:24Wat a measured slope efficiency of 5.2%, respectively. Using a long fiber length, which forced a large threshold for the 5|7 -> 5|8 transition, a wavelength of 3:002 µm was measured at maximum output power, making this system the first watt-level fiber laser operating in the mid-IR.

In-fiber polymer–glass hybrid waveguide Bragg grating

A 1.2 µm (height) × 125 µm (depth) × 500 µm (length) microslot along a fiber Bragg grating was engraved across the optical fiber by femtosecond laser patterning and chemical etching. By filling epoxy in the slot and subsequent UV curing, a hybrid waveguide grating structure with a polymer core and glass cladding was fabricated. The obtained device is highly thermally responsive with linear coefficient of 211 pm/°C.

Microstructures made in optical fiber with femtosecond laser

Different types of microstructures including microchannels and microslots were made in optical fibers using femtosecond laser inscription and chemical etching. Integrated with UV-inscribed fiber Bragg gratings, these microstructures have miniature, robustness and high sensitivity features and have been used to implement novel devices for various sensing applications. The fiber microchannels were used to detect the refractive index change of liquid presenting sensitivities up to 7.4 nm/refractive index unit (RIU) and 166.7 dB/RIU based on wavelength and power detection, respectively. A microslot-in-fiber based liquid core waveguide as a refractometer has been proposed and the device was used to measure refractive index, and a sensitivity up to 945 nm/RIU (10-6/pm) was obtained. By filling epoxy in the microslot and subsequent UV light curing, a hybrid waveguide grating structure with polymer core and glass cladding was fabricated. The obtained device was highly thermal responsive, demonstrating a linear coefficient of 211 pm/°C.