Localized Temperature Variations in Laser-Irradiated Composites with Embedded Fiber Bragg Grating Sensors

The mechanical properties of parallel bamboo strand lumber beams could be improved by aramid fiber reinforced polymer (AFRP). So far, no investigation has been conducted on the strengthening of engineering bamboo beams using AFRP. In order to study the efficiency of AFRP reinforcement on parallel bamboo strand lumber beams, 13 beams had been tested and analyzed. Strain gauges and Laser Displacement Sensors were used for the tests. By sensing the strain and deformation data for the specimens under the applied loads, the results showed that AFRP can effectively improve the flexural mechanical properties of parallel bamboo strand lumber beams. However, this reinforcement cannot increase the deflection of bamboo beams indefinitely. When the cloth ratio was 0.48, the deflection of the specimens reached its maximum. With the increase of cloth ratio, the stiffness of parallel bamboo strand lumber beams was increasing. When the cloth ratio reached 0.72%, compared with the un-reinforced specimen, the stiffness increased by 15%. Therefore, it can be inferred that bonding AFRP on the considered specimens can increase the stiffness of parallel bamboo strand lumber beams. The ductility of the specimen can be effectively enhanced by adopting the AFRP provision.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

AFRP Influence on Parallel Bamboo Strand Lumber Beams

Zhang

Corbi

et al. 2018

“…Optical fiber sensors based on Raman scattering [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ], Brillouin [ 16 , 17 ], and fiber Bragg grating [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ] are three common ways to realize multipoint measurement. Rusen Yan et al [ 9 ] reported a temperature-dependent Raman sensor, and the temperature sensitivities are −0.011 cm −1 /K and −0.013 cm −1 /K for different modes in the range from 100 K to 320 K, respectively.…”

Section: Introductionmentioning

confidence: 99%

High Temperature High Sensitivity Multipoint Sensing System Based on Three Cascade Mach–Zehnder Interferometers

Zhao

Lin

Yao

et al. 2018

A temperature multipoint sensing system based on three cascade Mach–Zehnder interferometers (MZIs) is introduced. The MZIs with different lengths are fabricated based on waist-enlarged fiber bitapers. The fast Fourier transformation is applied to the overlapping transmission spectrum and the corresponding interference spectra can be obtained via the cascaded frequency spectrum based on the inverse Fourier transformation. By analyzing the drift of interference spectra, the temperature response sensitivities of 0.063 nm/°C, 0.071 nm/°C, and 0.059 nm/°C in different furnaces can be detected from room temperature up to 1000 °C, and the temperature response at different regions can be measured through the sensitivity matrix equation. These results demonstrate feasibility of multipoint measurement, which also support that the temperature sensing system provides new solution to the MZI cascade problem.

“…Composites present new and interesting challenges for non-destructive evaluation and inspection (NDE/NDI), given their inhomogeneity, anisotropy, opacity, complex chemical structure, and degradation behavior. With the increasing amount of composite structure in service, there is increased demand for development of NDE/NDI techniques and sensor technology to deal with the unique requirements these structures present [ 1 , 2 , 3 , 4 ].…”

Section: Introductionmentioning

confidence: 99%

“…Thermocouples based on the Seebeck effect must be wired to a data recording device to provide the needed time–temperature data, which is not always possible in aerospace applications; thermocouples also only provide temperature data within a few microns of the bimetallic weld, and must be wired in an array to cover wide areas [ 21 ]. Temperature sensors based on fiber Bragg gratings show promise but must also be used as an array, with wiring requirements and wide-area application limitations similar to thermocouple arrays [ 3 ]. Commercially available thermal exposure labels, markers, and paints based on the melting point of a calibrated wax layer can only record the maximum temperature experienced by a surface without any time information [ 22 ].…”

Section: Introductionmentioning

confidence: 99%

Thermochromic Polymer Film Sensors for Detection of Incipient Thermal Damage in Carbon Fiber–Epoxy Composites

Toivola

Jang

Baker

et al. 2018

Carbon fiber–epoxy composites have become prevalent in the aerospace industry where mechanical properties and light weight are at a premium. The significant non-destructive evaluation challenges of composites require new solutions, especially in detecting early-stage, or incipient, thermal damage. The initial stages of thermal damage are chemical rather than physical, and can cause significant reduction in mechanical properties well before physical damage becomes detectable in ultrasonic testing. Thermochromic fluorescent probe molecules have the potential to sense incipient thermal damage more accurately than traditional inspection methods. We have designed a molecule which transitions from a colorless, non-fluorescent state to a colorful, highly fluorescent state when exposed to temperature–time combinations that can cause damage in composites. Moreover, this molecule can be dispersed in a polymer film and attached to composite parts as a removable sensor. This work presents an evaluation of the sensor performance of this thermochromic film in comparison to ultrasonic C-scan as a method to detect incipient thermal damage in one of the most widely used carbon fiber–epoxy composite systems. Composite samples exposed to varying thermal exposures were used to evaluate the fluorescent thermal sensor films, and the results are compared to the results of ultrasonic imaging and short-beam shear tests for interlaminar shear strength.