Search Results (16)

The large-scale deployment of aerospace composite structures has become a defining trend in modern aeronautics; however, hidden damage is difficult to detect over the full life cycle with conventional non-destructive inspection. This creates an urgent demand for on-line, high-fidelity structural health monitoring (SHM) technology. Optical-fiber sensors—featuring minimal mass, micron-scale diameter, immunity to electromagnetic interference and the ability to be co-cured into composite laminates for distributed measurement—are widely regarded as the key enabling technology. This paper presents a comprehensive review of recent advances and engineering applications of optical fiber sensing. Emphasis is placed on its engineering applications covering wing strain mapping, landing-gear load tracking, fuselage deformation localization, and cure-process monitoring and low-velocity impact damage identification of composite materials. Emerging intelligent assessment methodologies are examined. Finally, the development trends of optical fiber sensing technology are prospected, offering a reference framework for future theoretical innovation and engineering deployment of aerospace composite SHM technology. Full article

The article deals with the evaluation of dimensional deformations of a building element manufactured additively from a cement mixture. The study follows up on previous research within the 3DStar project and expands the methodology for monitoring deformations over time. The aim is to contribute to the development of more accurate simulation models for predicting the behaviour of printed structures, especially in the early stages after printing. For the analysis, an experimental ‘L’-shaped element was designed and printed, whose deformations were monitored using repeated 3D scanning and dimensional changes were evaluated for up to 93 days. The results show that the most significant deformations occur in the first hours after printing due to gravitational loading and mixture curing, while later changes are mainly due to shrinkage. The element’s geometry and the walls’ thickness also play a role. The analysis confirms the effectiveness of the ‘Caliper’ measurement method and outlines the potential for future use of photogrammetry as a method for online deformation monitoring. The data obtained will be used to optimise printing parameters and calibrate material parameters in the developed simulation software for non-linear numerical simulations in additive manufacturing using cement mixtures. Full article

Chronic viral infections and virus-induced cancers have been actively studied for decades, with many significant advancements in basic science, disease cure, treatment, and prevention. Yet, today, these infections and pathologies remain major contributors to morbidity and mortality worldwide. The international online conference “VIRCAN2024: Chronic viral infections and cancer, openings for Vaccines and Cure” aimed to address the remaining issues, present the research carried out in this broad field, and prognose directions for its development. The conference covered oncogenicity mechanisms and new approaches in the development of treatments and vaccines. VIRCAN2024 was held on the platform of Riga Stradins University, Riga, Latvia. The conference was supported by the Latvian Science Council grant “Human papillomavirus genome associated correlates of disease progression and treatment response for cervical neoplasms and cancer”, and the scientific journal Vaccines (MDPI). This report summarizes the lectures and presentations given at the conference. Full article

Monitoring the curing process is crucial for guiding and optimizing the curing procedures of composite material repair patches. Traditional embedded online monitoring methods are limited in their ability to track the curing process of these patches. This paper presents a composite material curing monitoring platform designed using dielectric methods. It integrates temperature control, pressure control, dielectric signal acquisition, control and display modules, and is specifically tailored for bag molding curing of repair patches. The platform measures the ionic viscosity of T300 2019B composites, analyzes the curing index, and correlates it with DSC-cured degree tests. The results indicate that the multiple ionic viscosity curves obtained from monitoring exhibit consistent trends, with correlation coefficients between curves exceeding 0.96. The changes in curing index align with the changes in curing degree, demonstrating that the platform can reliably and accurately monitor the ionic viscosity of repair patches. This platform enables effective monitoring of the ionic viscosity during the curing process of composite material repair patches. Full article

The temperature and strain fields monitoring during the preparation process of buoyancy materials, as well as the health status after molding, are important for mastering the mechanical properties of buoyancy materials and ensuring the safety of operators and equipment. This paper proposes a short and high-density femtosecond fiber Bragg grating (fs-FBG) array based on different temperature coefficients fibers. By optimizing the parameters of femtosecond laser point-by-point writing technology, high-performance fs-FBG arrays with millimeter level gating length and millimeter level spatial resolution were prepared on two types of fibers. These were successfully embedded in buoyancy materials to achieve in-situ online monitoring of the curing process and after molding. The experimental results show that the fs-FBG array sensor has good anti-chirp performance and achieves online monitoring of millimeter-level spatial resolution. Intelligent buoyancy materials can provide real-time feedback on the health status of equipment in harsh underwater environments. The system can achieve temperature monitoring with an accuracy of 0.56 °C and deformation monitoring with sub-millimeter accuracy; the error is in the order of micrometers, which is of great significance in the field of deep-sea exploration. Full article

Monitoring of molding processes is one of the most challenging future tasks in polymer processing. In this work, the in situ monitoring of the curing behavior of highly filled EMCs (silica filler content ranging from 73 to 83 wt%) and the effect of filler load on curing kinetics are investigated. Kinetic modelling using the Friedman approach was applied using real-time process data obtained from in situ DEA measurements, and these online kinetic models were compared with curing analysis data obtained from offline DSC measurements. For an autocatalytic fast-reacting material to be processed above the glass transition temperature T_g and for an autocatalytic slow-reacting material to be processed below T_g, time–temperature–transformation (TTT) diagrams were generated to investigate the reaction behavior regarding T_g progression. Incorporating a material containing a lower silica filler content of 10 wt% enabled analysis of the effects of filler content on sensor sensitivity and curing kinetics. Lower silica particle content (and a larger fraction of organic resin, respectively) favored reaction kinetics, resulting in a faster reaction towards T_g1. Kinetic analysis using DEA and DSC facilitated the development of highly accurate prediction models using the Friedman model-free approach. Lower silica particle content resulted in enhanced sensitivity of the analytical method, leading, in turn, to more precise prediction models for the degree of cure. Full article

Background: Dermal fillers for soft tissue for the treatment of face sagging, volume loss, and wrinkles have become popular among patients of all ages and ethnicities, and their use is becoming increasingly widespread. Aim: the goal of this study was to evaluate the effectiveness and safety of a micro-pulsed, 1444 nm Nd:YAG laser on dermal filler complications, in particular on granuloma management. Methods: A subcutaneous, 1444 nm Nd:YAG laser was used on five female patients (range age 52–68 years) with hyaluronic filler granulomas located on the face (two on the cheek area and three on the lips); three patients had self-injected the filler, buying it online. Before and after the therapy, the patients received a skin ultrasound to determine the form and location of the granulomas and to determine if there had been a full or partial resolution. During this study, all possible adverse effects at the treatment site were monitored. The 5-point Global Aesthetic Improvement Scale (GAIS) (0 point—no change; 1 point—25%, mild improvement; 2 points—50%, moderate improvement; 3 points—75%, good improvement; 4 points—100%, excellent improvement) was recorded at a 3-month follow-up. Results: good results were obtained in the treatment of filler granulomas with the intralesional 1444 nm laser, even if just a single treatment was performed (one intervention was effective for curing granulomas up to 5 mm in diameter). Three patients were satisfied with excellent improvement, and two patients experienced good improvement. The results are functional and aesthetically satisfying, as shown by photographic assessment. At the last follow-up, the granuloma had reduced or completely disappeared in all cases, and no infections, burns, scarring or fibrosis, episodes of severe bleeding, or other serious adverse effects had been reported. All subjects tolerated the post-treatment period well. Conclusions: Our findings showed that granuloma treatment with an intralesional 1444 nm Nd:YAG laser is a minimally invasive, easy, fast, efficient, and low-risk procedure. Full article

This paper presents a numerical framework for modelling and simulating convection–diffusion–reaction flows in liquid composite moulding (LCM). The model is developed in ANSYS Fluent with customised user-defined-functions (UDFs), user-defined-scalar (UDS), and user-defined memory (UDM) codes to incorporate the cure kinetics and rheological characteristics of thermoset resin impregnation. The simulations were performed adopting volume-of-fluid (VOF)—a multiphase flow solution—based on finite volume method (FVM). The developed numerical approach solves Darcy’s law, heat transfer, and chemical reactions in LCM process simultaneously. Thereby, the solution scheme shows its ability to provide information on flow-front, viscosity development, degree of cure, and rate of reaction at once unlike existing literature that commonly focuses on impregnation stage and cure stage in isolation. Furthermore, it allows online monitoring, controlled boundary conditions, and injection techniques (for design of manufacturing) during the mould filling and curing stages. To examine the validity of the model, a comparative analysis was carried out for a simple geometry, in that the numerical results indicate good agreement—3.4% difference in the degree of cure compared with previous research findings. Full article

Hydrogels are ideal candidates for the sustained local administration of antimicrobial drugs because they have customizable physicochemical properties that allow drug release kinetics to be controlled and potentially address the issue of systemic side effects. Consequently, the purpose of this study was to use 266 nm-pulsed laser beams to photo-crosslink gelatin methacryloyl hydrogels using Irgacure 2959 as a photo-initiator to reduce the curing time and to have an online method to monitor the process, such as laser-induced fluorescence. Additionally, irradiated chlorpromazine was loaded into the hydrogels to obtain a drug delivery system with antimicrobial activity. These hydrogels were investigated by UV–Vis and FTIR absorption spectroscopy, scanning electron microscopy, and laser-induced fluorescence spectroscopy and their structural and morphological characteristics, swelling behavior, and drug release profile were obtained. As a result the morphology, swelling behavior, and drug release profile were influenced by both the energy of the laser beam and the exposure time. The optimal hydrogel was obtained after 1 min of laser irradiation for Irgacure 2959 at 0.05% w/v concentration and gelatin methacryloyl at 10% w/v concentration. The hydrogels loaded with irradiated chlorpromazine show significant antimicrobial activity against Staphylococcus aureus and MRSA bacteria and a non-cytotoxic effect against L929 fibroblast cell lines. Full article

Material as well as process variations in the composites industry are reasons to develop methods for in-line monitoring, which would increase reproducibility of the manufacturing process and the final composite products. Fiber Bragg Gratings (FBGs) have shown to be useful for monitoring liquid-composite molding processes, e.g., in terms of online gel point detection. Existing works however, focus on in-plane strain measurements while out-of-plane residual strain prevails. In order to measure out-of-plane strain, FBG inscribed in highly birefringent fiber (HB FBG) can be used. The purpose of this research is the cure stage detection with (a) FBG inscribed in single mode and (b) FBG inscribed in highly-birefringent side-hole fiber in comparison to the reference gel point detected with an in-mold DC sensor. Results reveal that the curing process is better traceable with HB FBG than with regular FBG. Thus, the use of HB FBG can be a good method for the gel point estimation in the RTM process. Full article

Two-part epoxy adhesives are widely used in a range of industries. Two-part epoxy adhesive is composed of a resin and a hardener. Both materials remain stable in the general environment but curing begins when mixed in the specified mixing ratio. However, it has the disadvantage of requiring a specific mixing device. In addition, if the mixing ratio is different from the specified ratio due to the error of the mixing system, it has a fatal effect on the adhesion performance. The dielectric constant is a characteristic constant of a material. Therefore, it represents the mixing ratio of mixed two-part epoxy adhesives. With the electrical impedance spectroscopy technique, it can be measured indirectly by measuring impedance according to frequency and temperature. In this study, a sensor and embedded device for an online monitoring of its integrity using a regression method among machine learning are developed, which can acquire impedance data with frequency and temperature data according to the change in the mixing ratio of a two-part epoxy adhesive. The experimentally collected data were used as training data for the machine learning algorithm. It was found that the learned machine learning algorithm effectively estimates the mixing ratio of the two-part epoxy with an arbitrary value. Full article

A cure kinetics investigation of a high temperature-resistant phenol novolac cyanate ester toughened with polyether sulfone (CE-PES blend) was undertaken using non-isothermal differential scanning calorimetry. Thin ply carbon fiber prepreg, based on the CE-PES formulation, was fabricated, and plates for further in-situ cure monitoring were manufactured using automated fiber placement. Online monitoring of the curing behavior utilizing Optimold sensors and Online Resin State software from Synthesites was carried out. The estimation of the glass transition temperature and degree of cure allowed us to compare real time data with the calculated parameters of the CE-PES formulation. Alongside a good agreement between the observed online data and predicted model, the excellent performance of the developed sensors at temperatures above 260 °C was also demonstrated. Full article

The increasing demand for low cost consistent quality composite materials, especially of the automotive industry, creates the necessity for fast high quality processes. Pultrusion is one of the processes that can fulfill this demand. While the process is highly automated, manufacturing parameters still have to be chosen manually. The choice of line speed, mould temperature and injection pressure is based on best practice and therefore requires manual optimization that results in cost intensive manufacturing errors and suboptimal machine productivity. This paper presents a possible solution for this problem by providing an on-line cure monitoring approach that allows to overcome this challenge. Resonant Ultrasonic Spectroscopy (RUS) shows a high potential for in-line cure monitoring inside the pultrusion tool. RUS has been adapted for the first time in a pultrusion process. This paper focuses on the successful application of this technique to control the pultrusion process based on the state of cure of the material inside of the tool. As one of the only techniques for in-line cure monitoring which can be used continuously in closed tools despite high abrasion, it provides a new insight into the pultrusion process. Full article

Moisture diffusion in carbon fiber composites changes the mechanical properties of the composite. Therefore, a monitoring method of the actual content of moisture in the composite is important. However, at the moment there are no online methods established. A common method is the measurement of the mass changes due to water uptake. This method is not suitable for online monitoring of a real composite part in service. We demonstrate that miniaturized flexible interdigital sensors are suitable for moisture measurement inside the carbon fiber composite. These sensors are directly integrated inside the composite. It was already demonstrated that these can be successfully used for resin-curing monitoring as a primary application. Here we demonstrate that the same sensors are also suitable for moisture measurement inside the material. In order to do so, we expose samples with and without integrated sensors to hot-wet conditions and measure the dielectric changes with the sensors and the mass gain. The moisture concentration and the measured admittance can be directly correlated to each other. This demonstrates that the sensors can be used for moisture measurement as a secondary application. In addition, it is shown that the sensors have the potential to measure the moisture locally inside the material. Full article

An important factor for maintaining hermeticity of a metal-to-glass sealed electrical penetration assembly (EPA) is the residual stress in the sealing glass, which is generated during the EPA sealing process. A novel method to investigate and optimize the sealing process of EPAs, based on a fiber Bragg grating (FBG) sensor, is proposed in this research. An FBG was well bonded with sealing glass to measure the parameters of the glass during the sealing process. The temperature change during the heating process was able to be measured by Bragg wavelength shift. After the sealing glass solidified and dropped to room temperature, the residual stress was determined and the effect of temperature was minimized because the temperature before and after the sealing process was the same as room temperature. The curing temperature of the sealing glass was evaluated to specifically investigate the solidification process of the EPA. This study provides a basis for online stress and temperature monitoring of EPAs under external loads in nuclear power plants. Full article