7.1 SEM characterization of flexible strain sensor wires

All the filaments were uniformly coated; however, after large magnification, it appeared that some filaments exhibited cracks or gaps. Another phenomenon observed during the SEM characterization was that the silver coating was made of Nanotechnology and Development of Strain Sensor for Damage Detection DOI: http://dx.doi.org/10.5772/intechopen.82871

#### Figure 6.

molds were used for the preparation of samples and glass fiber fabric was used as reinforcement. The glass fabric was cut into segments and placed into a mold and a sensor (nylon yarn coated with silver) was inserted between the plies of fiberglass. Then, resin mixed with hardener with a ratio of 1:4 was poured into the mold. Once the molds were filled, one could no longer see the fiberglass layers, the samples were completely transparent. Now, one could view all of the sensors easily. After

A cured composite sample with integrated sensor was tested using an Instron test machine and the oscilloscope was connected to sensor lids. Uniaxial tensile testing machine and oscilloscope were used simultaneously to correlate the

mechanical behavior of the composite specimen with the electrical response of the strain sensor wire. Three experimental tests were performed to confirm the reproducibility of the results. In addition, electrodes were attached at both ends of the specimen to provide better connection. Then, the specimen was placed in the tensile machine and test was performed, Figure 5. As a result, the stress-strain behavior of

composite specimen with resistance profile of the sensor was obtained.

that, samples were left to cure for 48 hours at room temperature.

6. Experimental test of composite with sensor wire

Advances in Structural Health Monitoring

7. Results and discussion

Figure 5.

102

7.1 SEM characterization of flexible strain sensor wires

All the filaments were uniformly coated; however, after large magnification, it

appeared that some filaments exhibited cracks or gaps. Another phenomenon observed during the SEM characterization was that the silver coating was made of

Composite sample mounted on test frame for mechanical test. Sensor lids are connected to the oscilloscope.

SEM characterization of the Ag thin film-coated untwisted yarn: (a) shows the uniform coating with some minute discontinuities and defects in the coating and (b) confirms that the Ag thin film coating on the nylon surface consisted of deposition of nanoparticles of silver.

nanoparticle grains, or aggregates less than one micro-meter in size, Figure 6. SEM characterization of the coated untwisted yarn showed uniform coating with some minute discontinuities and defects and also confirmed that the Ag thin film coating consisted of deposition of nanoparticles of silver. Regardless of the imperfections in the Ag film coating in some filaments, it did not seem to affect the electrical conductivity.
