This paper provides an overview of the different types of fiber optic sensors (FOS) that can be used with composite materials and also their compatibility with and suitability for embedding inside a composite material. An overview of the different types of FOS used for strain/temperature sensing in composite materials is presented. Recent trends, and future challenges for FOS technology for condition monitoring in smart composite materials are also discussed. This comprehensive review provides essential information for the smart materials industry in selecting of appropriate types of FOS in accordance with end-user requirements.

/pdf/overview-of-fiber-optic-sensor-technologies-for-strain-4gcv7kkbp2.pdf

Overview of Fiber Optic Sensor Technologies for Strain/Temperature Sensing Applications in Composite Materials

The skin is the largest organ of the body, having a complex multi-layered structure and guards the underlying muscles, bones, ligaments, and internal organs. It serves as the first line of defence to any external stimuli, hence it is the most vulnerable to injury and warrants the need for rapid and reliable regeneration methods. Tissue engineered skin substitutes help overcome the limitations of traditional skin treatment methods, in terms of technology, time, and cost. While there is commendable progress in the treating of superficial wounds and injuries with skin substitutes, treatment of full-thickness injuries, especially with third or fourth degree burns, still looks murkier. Engineering multi-layer skin architecture, conforming to the native skin structure is a tougher goal to achieve with the current tissue engineering methods, if not impossible, restoring all the functions of the native skin. The testing of drugs and cosmetics is another area, where engineered skins are very much needed, with bans being imposed on product testing on animals. Given this greater need, 3D bioprinting is a promising technology that can achieve rapid and reliable production of biomimetic cellular skin substitutes, satisfying both clinical and industrial needs. This paper reviews all aspects related to the 3D bioprinting of skin, right from imaging the injury site, 3D model creation, biomaterials that are used and their suitability, types of cells and their functions, actual bioprinting technologies, along with the challenges and future prospects.

https://iopscience.iop.org/article/10.1088/1758-5090/8/3/032001/pdf

3D bioprinting of skin: a state-of-the-art review on modelling, materials, and processes

http://roboticslab.uc3m.es/roboticslab/sites/default/files/montero2015past-preprint.pdf

Past, present and future of robotic tunnel inspection

Composite materials/structures are advancing in product efficiency, cost-effectiveness and the development of superior specific properties. There are increasing demands in their applications to loa...

/pdf/non-destructive-testing-and-evaluation-of-composite-25jy7cttmq.pdf

Non-destructive testing and evaluation of composite materials/structures: A state-of-the-art review

Wind energy is one of the fastest growing renewable energy resources. It is distinctly important to increase reliability and availability of wind turbines and further to reduce the wind energy cost. Blades are considered to be one of the most critical components in wind turbine system because they convert Kinetic energy of wind into useable power. Blades are fabricated by carbon fiber reinforced polymer (CFRP) or glass fiber reinforced polymer (GFRP). Flaws and damages are inevitable during either fabrication or lifetime of a composite blade. Thus, non-destructive testing (NDT) and structural health monitoring (SHM) for wind turbine blade (WTB) are required to prevent failures and increase reliability in both manufacturing quality control and in-service inspection. In this work, a fully, in-depth and comprehensive review of NDT techniques for WTB inspection was reported based on an orderly and concise literature survey. Firstly, typical flaw and damage occurring in manufacturing progress and in service of WTB were introduced. Next, the developments of visual, sonic and ultrasonic, optical, electromagnetic, thermal and radiographic NDT for composite WTB inspection were reviewed. Thereafter, strengths and limitations of NDT techniques were concluded through comparison studies. In the end, some research trends in WTB NDT have been predicted, for example in combination with SHM. This work will provide a guide for NDT and SHM of WTB, which plays an important role in wind turbine safety control and wind energy cost savings. In addition, this work can benefit the NDT development in the field of renewable energy, such as solar energy, and energy conservation field, such as building diagnosis.

Progress and trends in nondestructive testing and evaluation for wind turbine composite blade

Optical non-destructive testing (NDT) has gained more and more attention in recent years, mainly because of its non-destructive imaging characteristics with high precision and sensitivity. This paper provides a review of the main optical NDT technologies, including fibre optics, electronic speckle, infrared thermography, endoscopic and terahertz technology. Among them, fibre optics features easy integration and embedding, electronic speckle focuses on whole-field high precision detection, infrared thermography has unique advantages for tests of combined materials, endoscopic technology provides images of the internal surface of the object directly, and terahertz technology opens a new direction of internal NDT because of its excellent penetration capability to most of non-metallic materials. Typical engineering applications of these technologies are illustrated, with a brief introduction of the history and discussion of recent progress.

/pdf/a-review-of-optical-ndt-technologies-7szzyoznru.pdf

A review of optical NDT technologies.

Terahertz metamaterial absorbers are important functional devices for liquid analyte detection. In contrast to general metamaterial absorbers with single-layer metasurfaces that possess only one resonant mode, a triple-band terahertz metamaterial absorber formed by a single layer of symmetrically arrayed snowflake-shaped resonators was proposed in this study. The simulation results showed that the absorption of the metamaterial absorber reached 97.43% at 0.550 THz, 79.22% at 1.249 THz, and 99.02% at 1.867 THz with narrow resonant peaks. The resonant frequencies were sensitive to the refractive index of the surrounding medium at a fixed analyte thickness, which would play an important role in the performance of the sensor for detecting changes in the surrounding refractive index. The maximum value of the refractive index sensitivity was 137.70 GHz/RIU, 306.25 GHz/RIU, and 473.86 GHz/RIU, with a figure of merit (FoM) of 3.14, 2.33, and 6.46, respectively, for refractive index values ranging from 1.0 to 2.2 under three resonant modes. It is worth noting that most of the liquid samples showed a refractive index ranging from 1.0 to 2.0. Furthermore, the identification of peanut oil, carbon disulfide, and turpentine was considered to verify that the proposed terahertz sensor could be used for high-sensitivity liquid detection and has broad development prospects in the field of detecting and sensing.

/pdf/sensing-performance-of-triple-band-terahertz-metamaterial-1i2h3fys.pdf

Sensing Performance of Triple-Band Terahertz Metamaterial Absorber Based on Snowflake-Shaped Resonators

In order to determine the properties of thin films with the required performance and reliability, a sensing system for
dynamic monitoring is proposed to measure the thickness of thin films. The system is based on the principle of
white-light interference, and is combination of spectrum analysis and optical fiber techniques. When two reflected lights
interfere within white-light coherent length range, relationship of between interference intensity and the wavelength of
incident light is achieved according to the equation of interference light's intensity. According to different thickness of
film, the relevant method is selected to calculate the thickness of thin film. So the interference can be analyzed in
spectral domain. The scheme of the system is set up including white-light source, multi-mode optical fiber, beam splitter,
spectrometer. With the help of optical fiber, the interference pattern is captured by spectrometer. When thickness of thin
film is varying, spectra curve will shift. The original spectra curve is processed in the computer. In order to determine
accurate extreme points, many methods of curve processing are used to decrease the noise. The spectra curve is
smoothed by signal processing method called empirical mode decomposition (EMD). This method is suitable for
non-linear and non-stationary data processing. The experimental data is contrast to the calibrated value. The results
show that the relative error of this method is lower 1%. This method has advantages over other measuring methods, such
as higher accuracy, low-cost instrument, extensive measurement range, simple structure and non-destructive.

A sensing system for monitoring the thickness of thin films by spectrum analysis of white-light interference

It briefly introduces the international development status of the high resolution for air-to-ground remote sensing satellite.
High resolution for the air-to-ground observation is also the civil and martial pursuing target. Because of the rising cost
along with the large-diameter telescope, the weight, cubage will also become large. Nowadays, how to get high
resolution with light weight, small cubage launch and large diameter is one of the important research directions in many
countries. We raise a method of large field-of-view and high resolution optical synthesis telescope which can solve this
problem. It is a co-phased segment mirrors which synthetic aperture diameter is about 1 m. Four 50cm diameter segment
mirrors can fulfill the requirement. It is folded during its launch and is spread after it reaches to its working spot. In this
way, it can reach the requirement of low launch weight, small launch cubage and can get high resolution observation.
This method contains the key technologies of real-time UV coverage, optics design optimization, co-phase measurement
and adjustment, micro-displacement sensor technology, the optics design and structure design. We explore the
technology which can fulfill field-of-view of 1.86° and the resolution of 0.4m. We will discuss the UV-coverage method
which includes the aperture arrangement, the relationship between the aperture number and the synthetic aperture
diameter. There are much more detail calculation and analysis to it. Something is discussed about its structure design and
optics design in the paper.

The key technologies research on the large field-of-view and high resolution optical synthesis telescope

The principle of the inductance displacement sensor on optical aperture synthesis telescope is given with a measure- ment of mutual inductance to deduce the axial distance. It illustrates an effective modelling and calculation method based on Partial Element Equivalent Circuit (PEEC). PEEC is the method to calculate mutual inductances between coils utilizing partial parameter concept. Simulation for the change of mutual inductances is done which is prepared for the next step work.

Yongkai Zhu

Papers

A review of optical NDT technologies.

Sensing Performance of Triple-Band Terahertz Metamaterial Absorber Based on Snowflake-Shaped Resonators

A sensing system for monitoring the thickness of thin films by spectrum analysis of white-light interference

The key technologies research on the large field-of-view and high resolution optical synthesis telescope

A study of inductance displacement sensor on optical aperture synthesistelescope