Summary This paper presents the experimental results of strain measurements made by the fiber Bragg grating sensors embedded into polymer composite materials (PCMs). A series of performed experiments are described to demonstrate the capability of fiber optic sensors to measure strains in the case of their pronounced gradient distribution within the material, under compression and tension, at cyclic variation of strains with time and at different temperatures. A measuring technique is presented, and the results of strain measurements during the process of preparation of PCM including measurements of residual process‐induced strains are discussed.The results of strain measurements made by fiber optic strain sensors (FOSS) are compared with the results of numerical modeling based on the finite element method and independent measurement data obtained with the use of a digital optical system Vic‐3D and other experimental devices. The comparison made shows good agreement between the results obtained by the experimental methods and numerical simulation.The results of numerical computations demonstrate that the embedment of optical fibers in a PCM introduces perturbations in the strain distribution pattern in the vicinity of optical fibers but practically does not cause changes in the value of the strain tensor component measured by the FOSS. The conclusions about applicability range of FOSS embedded into PCM were made based upon the numerical simulation. The interrelation model between Bragg wavelength peak shift and the strain of the optical fiber in the fiber Bragg grating area for the sensor that is not affected by the environment is proposed.
The problem of propagation of an acoustic surface Rayleigh wave in an infinite half-space is considered within the framework of the asymmetric theory of elasticity (Cosserat medium). It is assumed that material deformation is described not only by the displacement vector but also by an independent rotation vector. A global analytical solution of the problem in displacements is obtained. A comparative analysis of the solution obtained and the corresponding solution for the classical elastic medium is performed. Macroparameters characterizing the difference of the stress-strain state from that predicted by the classical theory of elasticity are introduced.Introduction. The model of the medium whose deformation is described not only by the displacement vector u but also by a kinematically independent rotation vector ω, which are functions of coordinates and time, has riveted attention of researchers for a long time. This theory was called the moment or asymmetric theory of elasticity. The deformation behavior of elastic bodies in this theory has some specific features, namely, the elastic body, beginning from a certain characteristic scale and (or) at high gradients of stresses or strains, can acquire a stress-strain state significantly different from that predicted by the classical (symmetric) theory of elasticity.In the theory of the Cosserat medium [1, 2], the vector ω characterizes small turns of particles, and the tensors of stressesσ and moment stressesμ are asymmetric. The dynamic behavior of an elastic isotropic medium with no allowance given to temperature effects is characterized by eight constants: two Lamé constants, four elastic constants characterizing the microstructure, density, and a parameter responsible for the measure of inertia of the medium during its rotation (density of the moment of inertia).In many publications, the analysis of the moment behavior of the material is considered within the framework of a simplified medium called the medium with constrained rotation or the Cosserat pseudomedium [3]. Simplification is reached by using the dependence ω = (1/2) rot u, which, in particular, allows one to reduce the number of physical parameters from eight to five. Because of the drawbacks considered in detail in [1], however, the Cosserat pseudomedium model will not be further used in the present work.A large amount of exact analytical solutions have been obtained within the framework of the asymmetric theory of elasticity (especially in the case of constrained rotation). In many papers, these solutions are analyzed and compared with the corresponding solutions of the classical theory of elasticity. In such a comparison, new physical constants determining the contribution of the moment components are normally chosen from the range of their energetically admissible values. This is caused by the lack of information on material constants with a microstructure, which is one of the main factors preventing the development of models of asymmetric media.There are several papers where the physical constant...
In this paper, we proposed an approach to study the strain response of polymer film samples under various temperature effects and note their corresponding effects. The advantages of the developed approach are determined by the fact that thin films of material are used as samples where it is possible to generate a sufficiently uniform temperature field in a wide range of temperature change rates. A dynamic mechanical analyzer was used for the experimental implementation of the above approach for two UV-curable polymers and one type of epoxy resin. Experimental results have shown that the thermal expansion coefficients for these polymers depend significantly not only on the temperature but also on its change rate. The strain response of the polymer to heating and cooling, with the same absolute values of the rate of temperature change, differs significantly, and this dissimilarity becomes stronger with its increasing. The results of thermomechanical experiments for massive samples on traditional dilatometer are shown to compare with the results for film samples. The discovered dependences of the temperature expansion coefficient on the temperature and its change rate can be used for mathematical modeling of thermomechanical processes arising during the operation of products made of polymers.
The presence of process-induced strains induced by various manufacturing and operational factors is one of the characteristics of polymer composite materials (PCM). Conventional methods of registration and evaluation of process-induced strains can be laborious, time-consuming and demanding in terms of technical applications. The employment of embedded fibre-optic strain sensors (FOSS) offers a real prospect of measuring residual strains. This paper demonstrates the potential for using embedded FOSS for recording technological strains in a PCM plate. The PCM plate is manufactured from prepreg, using the direct compression-moulding method. In this method, the prepared reinforcing package is placed inside a mould, heated, and then exposed to compaction pressure. The examined technology can be used for positioning FOSS between the layers of the composite material. Fibre-optic sensors, interacting with the material of the examined object, make it possible to register the evolution of the strain process during all stages of polymer-composite formation. FOSS data were recorded with interrogator ASTRO X 327. The obtained data were processed using specially developed algorithms.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.