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Finite element stress and strain analysis in composites with embedded optical fiber sensors
No full textAdvanced finite element (FE) techniques are used to analyse mechanical stress and strain concentrations in and around an optical fibre (OF) embedded in composite laminates. The models represent many features observed in real materials with embedded OFS. Three general laminate constructions were analysed with the OF at the mid-plane and near the laminate surface. Models represent test coupons used to measure effects of embedded OF on laminate strength in tension and flexure; applied loads and boundary conditions reflect these tests. Failure analysis is performed
Factors affecting the embedding of optical fibre sensors in advanced composite structures
No full textComposite materials offer tremendous benefits for engineering applications and arc now specified for use in several safety critical studies. However, despite extensive materials research and development, they do have a number of areas where their behaviour is still not fully understood. This is particularly so with the more complex mechanical parameters in larger structures. Current structural design attempts to allow for these unknowns by overdesigning, extensive testing and frequent inspection. Embedded optical fibre sensors offer the potential to monitor many of these parameters, and are additionally of a similar physical and mechanical nature to the reinforcement fibre used in advanced composites
Fibre optic Bragg grating sensor measurements in composite materials
No full textDespite the many advantages of composite materials, limited data on their inservice performance continues to restrict their application in aircraft structures. Networks of strain sensing elements offer the potential to perform continuous structure health monitoring, as well as gathering information on structure operating conditions. This paper describes some preliminary findings of an ongoing research programme, which aims to implement embedded optical fibre sensing systems. It is envisaged that these systems will be used for health monitoring of composite aircraft components
Finite element analysis of embedded optical fibre sensors
No full textMicromechanical Finite Element (FE) analysis was used to model stress and strain fields in and around embedded optical fibres EOF'S) in flexural test coupons of carbon fibre composite. The coupons were used in studies of EOF effects on macroscopic laminate properties. The FE method allows complex material inhomogeneities, laminate boundaries and load conditions to be modelled
Electronic tracking system for multiplexed fibre grating sensors
No full textWe demonstrate for the first time an electronic lock-in system using an acousto-optic tunable filter (AOTF) to track the wavelength of a fibre Bragg grating. The system has an output frequency proportional to the grating wavelength. Initial results show microstrain resolution at data acquisition rates of 10 Hz
New OTDR technique for monitoring the range of reflective markers
No full textA novel OTDR technique to accurately monitor the optical path length to multiple reflective markers is described. The method can monitor changes in optical path length of 40 ppm in a 1 sec measurement time and is suitable for multiplexed optical-fibre strain sensing over gauge lengths of several metres
Progress on grating interrogation schemes using a tunable filter
Get PDFWe discuss theoretically and experimentally a wavelength interrogation system for Bragg gratings using an acousto-optic tunable filter (AOTF). The measured resolution of 0.5µm in 5 Hz bandwidth agrees well with the theoretical analysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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