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The time difference of arrival (TDOA) method has traditionally proven effective for locating acoustic emission (AE) sources and detecting structural defects. Nevertheless, its applicability is constrained when applied to anisotropic materials, particularly in the context of fiber-reinforced composite structures. In response, this paper introduces a novel COmposite LOcalization using Response Surface (COLORS) algorithm based on a two-step approach for precise AE source localization suitable for laminated composite structures. Leveraging a response surface developed from critical parameters, including AE velocity profiles, attenuation rates, distances, and orientations, the proposed method offers precise AE source predictions. The incorporation of updated velocity data into the algorithm yields superior localization accuracy compared to the conventional TDOA approach relying on the theoretical AE propagation velocity. The mean absolute error (MAE) for COLORS and TDOA were found to be 6.97 mm and 8.69 mm, respectively. Similarly, the root mean square error (RMSE) for COLORS and TODA methods were found to be 9.24 mm and 12.06 mm, respectively, indicating better performance of the COLORS algorithm in the context of source location accuracy. The finding underscores the significance of AE signal attenuation in minimizing AE wave velocity discrepancies and enhancing AE localization precision. The outcome of this investigation represents a substantial advancement in AE localization within laminated composite structures, holding potential implications for improved damage detection and structural health monitoring of composite structures. [ABSTRACT FROM AUTHOR]

Composite manufacturing demands mould tooling to produce dimensionally accurate parts, adding substantial capital costs to their production. Recent developments in advanced manufacturing of fibre-reinforced polymer composite elements have seen the implementation of mould-free technologies that can produce complex shaped parts off a flat tool. This paper presents eccentric fibre prestress as a novel mould-free method for producing curvatures within carbon fibre and glass fibre laminates. Tailoring the flexural rigidity along the primary orientation of the laminate is shown to result in predictable compound curvature profiles with a low average root mean square error of 1.39 across the four geometries tested. An analytical model based on Euler–Bernoulli beam theory is proposed and proven to correlate closely with the experiential laminates. Finally, an inverse design approach based on a genetic algorithm is demonstrated to design an accurate laminate configuration, achieving the top surface of a NACA 4412 aerofoil section with a low root mean square error of 1.98 using the proposed eccentric fibre prestress. [ABSTRACT FROM AUTHOR]

Embedded optical fibre sensors (OFSs) offer the potential to monitor the internal strains at various stages during the manufacturing and service life of fibre-reinforced polymer (FRP) composite structures. Various aspects associated with the embedment of OFSs, such as integration, material compatibility, and sensing performance of the embedded sensor needs to be investigated to develop reliable OFSs based internal sensing platform for composite structures. In this study, Polyimide (PI) and Polyether ether ketone (PEEK) coated optical fibres (OF) were embedded into glass fibre-reinforced polymer (GFRP) composites to evaluate four important aspects associated with the embedment of OFs, which include; i). Structural integrity of the OFs against chemical reactions from vinyl ester resin and its additives through immersion testing, ii). Methods of integrating the OFs into layered glass fibres for the vacuum resin infusion manufacturing process, iii). Sensing performance of the embedded OFs during manufacturing and structural testing (tensile and compressive), and iv). Internal structural integrity of the embedded OFs and the host composite structure using X-Ray micro-computerised tomography technique (μ-CT). The results from the immersion testing and manufacturing process monitoring showed that both PEEK and PI coated OFs can resist the chemical and mechanical stresses caused by resin polymerisation during curing process. The subsequent mechanical testing showed a similar sensing performance by the PI and PEEK coated OFs. Under tensile loads, the OFs monitored the tensile strain distribution up to 7,000 με and compressive strain distribution up to −1,200 με under flexural loading without compromising their optical performance. Finally, the μ-CT scanning results had shown a minimal structural deterioration of the embedded OFs and host composite structure. The outcomes from this detailed experimental investigation on the embedment of OFS in GFRP structures provided useful information towards the integration and performance of optical sensors in composite structures. [ABSTRACT FROM AUTHOR]

The increasing use of sandwich composites for structural applications brings with it a need to establish a reliable inspection and monitoring method to ensure structural integrity and safe operation throughout the service life. Since optical fibre-based photonic sensing technologies are increasingly common for structural health monitoring of composite structures, selection of optical fibre Bragg grating sensors could be one possible choice for this purpose. In this paper, performance characterisation of sandwich composite with embedded silica fibre Bragg grating sensor is reported. Experimental tests were performed on a carbon fibre foam core sandwich composite embedded with a silica fibre Bragg grating sensor to extract the structural health monitoring parameters such as strain and temperature. The current study found that sandwich composite exhibits foam relaxation; however, its impact on strain measurement is negligible. Another important finding from the theoretical and the experimental thermal modelling was that although the constituent components of the sandwich composite have entirely different thermal expansion coefficients, its effect on the embedded fibre sensor can be minimal if the sensors are embedded between the face sheets. These results can initiate further research in this area and can lead to the development of state-of-the art structural health monitoring techniques for sandwich composite structures. [ABSTRACT FROM AUTHOR]

A strain profile measurement technique using a chirped fibre Bragg grating (CFBG) sensor by implementing an integration of differences (IOD) method is reported in this paper. Using the IOD method the spatial distribution of strain along the length of the CFBG is extracted from its power reflectance spectra. As a proof of concept demonstration, the developed technique is applied to measure the polymerisation shrinkage strain profile of a photo-cured polymer dental composite which exhibits a non-uniform strain distribution attributed to the curing lamp characteristics. The result from the CFBG technique is compared with that of an FBG array embedded in the dental composite and is correlated with the degree of conversion of the material which also depends on the curing lamp intensity distribution. This technology will have significant impact and applications in a range of medical, materials and engineering areas where strain or temperature gradient profile measurement is required in smaller scales. [ABSTRACT FROM AUTHOR]

Our environment is subjected to exposure to microwave and radio electromagnetic irradiations because of widespread use of wireless telecommunication services. The electromagnetic radiations like radio waves, microwaves and Infrared rays emitted from the multiple telecom sites also contributing large amounts of environment harming to natural eco systems and causing climate change. A potentially constant exposure has caused an alert in public and governments about the so-called environmental electromagnetic pollution. Assessment of the RF EMF impact on plants is of great importance because plants have an important role in the living world as main primary producers of organic compounds and oxygen. Plants are continuously exposed to various environmental stresses and display a wide spectrum of developmental and biochemical responses contributing to stress adaptation. Their physiological responses can be evoked by a great variety of external stimuli, including mobile phone radiation. The adverse effects of electromagnetic radiation from mobile phones and communication towers on health of human beings are well documented today. However, exact correlation between radiation of communication towers and eco-system, are not yet very well established. In this context, there is need to carry out the scientific investigations to understand the effects of RF radiation on plants. The main objective of this research is to measurement of signal strength and power emitted by the tower and to establish guidelines for limiting EMF exposure that will provide protection against blown adverse effects on ecosystems will be studied using Geo-Informatics techniques in Udupi District, Karnataka State. The advancement in the recent years in the field of Geo-Informatics has enabled us to get the required spatial information of the environment in a better way. [ABSTRACT FROM AUTHOR]