Carbon-Based Nanomaterials Thin Film Deposited on a Flexible Substrate for Strain Sensing Application.

Hybrid nanomaterial film consisting of multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelet (GNP) were deposited on a highly flexible polyimide (PI) substrate using spray gun. The hybridization between 2-D GNP and 1-D MWCNT reduces stacking among the nanomaterials and produces a thin film with a porous structure. Carbon-based nanomaterials of MWCNT and GNP with high electrical conductivity can be employed to detect the deformation and damage for structural health monitoring.

Real-Time Temperature Monitoring under Thermal Cycling Loading with Optical Fiber Sensor.

A fiber optic sensing system consisting of a fiber Bragg grating (FBG) sensor, optical circulator, optical band pass filter and photodetector is developed to monitor the real-time temperature response of a structure under a dynamic thermal loading. The FBG sensor is surface-bonded on a test specimen and integrated with an optical band pass filter. As a broadband light source transmits into a FBG sensor, a specific wavelength is reflected and transmitted into an optical band pass filter.

Vibration Excitation and Suppression of a Composite Laminate Plate Using Piezoelectric Actuators.

Piezoelectric (PZT) actuators bonded on a structure can be used to generate deformation and excite vibration for the shape control and vibration suppression, respectively. This article proposes a theoretical model for predicting vibrational response of a composite laminate plate with PZT actuators. The bending moment induced by the PZT actuator was obtained and applied on the composite laminate plate.

Mode II Fracture Analysis of GNP/Epoxy Nanocomposite Film on a Substrate.

Epoxy resin with excellent mechanical properties, chemical stability, and corrosion resistance has been widely used in automotive and aerospace industries. A thin film of epoxy deposited on a substrate has great application in adhesive bonding and protective coating. However, the intrinsic brittleness of epoxy with a relatively low fracture toughness limits its applications.

Mode I Fracture Toughness of Graphene Reinforced Nanocomposite Film on Al Substrate.

Nanocomposites were prepared by adding graphene nanoplatelets (GNP) into epoxy with a variety of loadings. The thickness of GNPs used in this study was in a range of 1 nm to 10 nm. Nanocomposite film was deposited on the aluminum (Al) substrate via a spinning coating process.

Fiber Bragg Grating Pressure Sensor Integrated with Epoxy Diaphragm.

A fiber Bragg grating (FBG) sensor integrated with an epoxy diaphragm was developed for the measurement of pressure and water level. The bending strain of a circular diaphragm induced by uniform pressure was transferred to the FBG sensor. The response of the FBG sensor to the pressure was observed in terms of the Bragg wavelength shift which is linearly proportional to the strain.

Sensing Performance and Mechanical Properties of Buckypaper Impregnated with Epoxy Resin.

Buckypaper consisting of a carbon nanotube (CNT) sheet has a great potential for sensing and structural applications due to the exceptional piezoresistive and mechanical properties of CNTs. In this work, buckypaper was impregnated with the epoxy resin to improve the fragility and handling capability. The mechanical properties of the buckypaper/epoxy composite were determined by the tensile and nanoindentation tests.

Simultaneous Measurement of Temperature and Mechanical Strain Using a Fiber Bragg Grating Sensor.

Based on the shift of the Bragg wavelength, fiber Bragg grating (FBG) sensors have been employed to measure a variety of physical parameters such as stress, strain, displacement, temperature, vibration and pressure. In this work, a simple and easy way to be implemented FBG sensing methodology was proposed to measure the temperature and strain simultaneously. Half of the FBG was bonded on the host structure, while the other half of the FBG was left free.

Deformation of Composite Laminates Induced by Surface Bonded and Embedded Piezoelectric Actuators.

In this work, piezoelectric (PZT) actuators were surface bonded on or embedded in a composite laminate and subjected to an electric voltage across the thickness, resulting in a bending effect on the composite laminate. An analytical expression of the deflection of a simply supported cross-ply composite laminate induced by distributed piezoelectric actuators was derived on the basis of classical plate theory and composite mechanics. The theoretical solution can be used to predict the deformation of the composite laminate.

Strain and Temperature Sensitivities Along with Mechanical Properties of CNT Buckypaper Sensors.

In this work, buckypaper composed of multi-walled carbon nanotubes (MWCNT) was prepared through a vacuum filtration process. The effect of MWCNT aspect ratio on the buckypaper performance was investigated. The freestanding and highly flexible buckypaper can be used as a sensor to attach on a complex surface monitoring the strain and temperature at the critical area.

Mode II Interfacial Fracture Toughness of Multi-Walled Carbon Nanotubes Reinforced Nanocomposite Film on Aluminum Substrate.

In this investigation, various loadings of multi-walled carbon nanotubes (MWCNTs) ranging from 0.3-1.0 wt % were incorporated into the epoxy to fabricate the nanocomposites.

Vibration monitoring based on flexible multi-walled carbon nanotube/polydimethylsiloxane film sensor and the application on motion signal acquisition.

Flexible sensors at small scales have potential applications in many fields. Until now, the research on high-performance vibration sensors based on soft materials with high sensitivity and precision, fast response and high stability are still in its infancy. In this work, a flexible, wearable and high precision film sensor based on multi-walled carbon nanotube (MWCNT) was prepared via a vacuum filtration process and then encapsulated within polydimethylsiloxane (PDMS).

Interfacial Stress Analysis of Adhesively Bonded Lap Joint.

The use of adhesively bonded joints in place of traditional joining techniques such as bolted or rivet joints is becoming greatly popular in recent years. Interfacial stress in the adhesive is critical to the strength of adhesively bonded joints. It is necessary to predict the interfacial stresses accurately to ensure the safety of joints.

Carbon Nanotube/Graphene Nanoplatelet Hybrid Film as a Flexible Multifunctional Sensor.

A flexible hybrid film consisting of graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWCNTs) was prepared and employed as a multifunctional sensor to monitor temperature and liquid leakage, based on the piezoresistive effect. The influences of the GNP content on the mechanical, thermal, and sensing properties were investigated. Experimental results showed that both the hardness and Young's modulus of the hybrid film were decreased with an increasing GNP content, while the thermal conductivity exhibited in an opposite trend.

Synthesis and Characterization of Multi-Walled Carbon Nanotube/Graphene Nanoplatelet Hybrid Film for Flexible Strain Sensors.

Graphene nanoplatelet (GNP) and multi-walled carbon nanotube (MWCNT) hybrid films were prepared with the aid of surfactant Triton X-100 and sonication through a vacuum filtration process. The influence of GNP content ranging from 0 to 50 wt.% on the mechanical and electrical properties was investigated using the tensile test and Hall effect measurement, respectively.

Stress analysis of sandwich composite beam induced by piezoelectric layer.

Introduction: Smart structures equipped with piezoelectric devices to sense and actuate the structure could be used in many engineering applications. To explore the smart structure further and apply it to more complex structures, some problems are critical to be concerned. Among them, delamination due to the high stress is an important issue since its serious effect on the strength and stiffness of the composite structure.

Load transfer of nanocomposite film on aluminum substrate.

Introduction: Nanocomposite films have attracted much attention in recent years. Depending on the composition of the film and fabrication method, a large range of applications has been employed for nanocomposite films.

Method: In this study, nanocomposite films reinforced with multi-walled carbon nanotubes (MWCNTs) were deposited on the aluminum substrate through hot press processing.

Fracture Analysis of MWCNT/Epoxy Nanocomposite Film Deposited on Aluminum Substrate.

Multi-walled carbon nanotube (MWCNT) reinforced epoxy films were deposited on an aluminum substrate by a hot-pressing process. Three-point bending tests were performed to determine the Young's modulus of MWCNT reinforced nanocomposite films. Compared to the neat epoxy film, nanocomposite film with 1 wt % of MWCNT exhibits an increase of 21% in the Young's modulus.

Dynamic mechanical analysis of carbon nanotube-reinforced nanocomposites.

Background: To predict the mechanical properties of multiwalled carbon nanotube (MWCNT)-reinforced polymers, it is necessary to understand the role of the nanotube-polymer interface with regard to load transfer and the formation of the interphase region. The main objective of this study was to explore and attempt to clarify the reinforcement mechanisms of MWCNTs in epoxy matrix.

Methods: Nanocomposites were fabricated by adding different amounts of MWCNTs to epoxy resin.

Fabrication and Characterization of Indium Tin Oxide Films.

Background: Transparent conducting oxide (TCO) films are of particular interest in the field of optoelectronics, due to the requirement for transparent electrodes in applications such as organic light-emitting diodes, solar cells and so on. The aim of this study was to obtain a better understanding of the effects of preparation temperature on indium tin oxide (ITO) films, to improve their performance for optoelectronic applications.

Methods: ITO films were deposited on glass substrate at different temperatures, using direct current (DC) magnetron sputtering.

Non-destructive evaluation of depth of surface cracks using ultrasonic frequency analysis.

Ultrasonic is one of the most common uses of a non-destructive evaluation method for crack detection and characterization. The effectiveness of the acoustic-ultrasound Structural Health Monitoring (SHM) technique for the determination of the depth of the surface crack was presented. A method for ultrasonic sizing of surface cracks combined with the time domain and frequency spectrum was adopted.

Dynamic Behavior of Nanocomposites Reinforced with Multi-Walled Carbon Nanotubes (MWCNTs).

The influence of multi-walled carbon nanotubes (MWCNT) on the structural dynamic behavior of MWCNT/epoxy nanocomposites was investigated. Two different types of MWCNTs, pristine MWCNT and functionalized MWCNT, were used in this study. Carboxylic acid-functionalized MWCNTs (MWCNT-COOH) were obtained by oxidation pristine MWCNTs via sonication in sulfuric-nitric acid and characterized by Fourier transform infrared spectroscopy (FTIR).

Vibration analysis of composite laminate plate excited by piezoelectric actuators.

Piezoelectric materials can be used as actuators for the active vibration control of smart structural systems. In this work, piezoelectric patches are surface bonded to a composite laminate plate and used as vibration actuators. A static analysis based on the piezoelectricity and elasticity is conducted to evaluate the loads induced by the piezoelectric actuators to the host structure.

Fabrication and characterization of the composites reinforced with multi-walled carbon nanotubes.

Carbon nanotubes with superior mechanical, electrical and thermal properties have received intensive attention in recent years. In this study, multi-walled carbon nanotubes (MWCNT) were infused into a liquid epoxy, and the solution was sonicated for three hours to separate the aggregation of the MWCNTs and achieve good dispersion. The trapped air was removed from the mixture using a high vacuum.

Thermal strain analysis of optic fiber sensors.

An optical fiber sensor surface bonded onto a host structure and subjected to a temperature change is analytically studied in this work. The analysis is developed in order to assess the thermal behavior of an optical fiber sensor designed for measuring the strain in the host structure. For a surface bonded optical fiber sensor, the measuring sensitivity is strongly dependent on the bonding characteristics which include the protective coating, adhesive layer and the bonding length.