Characterization of elastic constants of anisotropic composites in compression using digital image correlation
TL;DR: In this article, a simple direct technique to determine a broad set of elastic moduli is presented based on compression testing of a prism sample, which is used to measure the full-field deformations that allow the determination of Young's moduli and all six Poisson's ratios for the three orthogonal directions based on a single sample.
About: This article is published in Composite Structures.The article was published on 2018-02-01. It has received 28 citations till now. The article focuses on the topics: Digital image correlation & Elastic modulus.
Citations
More filters
TL;DR: In this article, the fracture phenomenon in plain concrete and in concrete reinforced with both recycled steel fibers and industrial steel fibers (ISF) was investigated using the wedge splitting test (WST), which enables stable crack propagation for quasi-brittle materials.
113 citations
TL;DR: In this article, the authors present recent advances in non-destructive testing and evaluation (NDT&E) and in-situ structural health monitoring (SHM) techniques for damage detection in fiber-reinforced polymer (FRP) composites.
Abstract: The application of fiber-reinforced polymer (FRP) composites is continuously increasing due to their superior mechanical properties and the associated weight advantage. However, they are susceptible to more complex types of damage, and advanced damage characterization systems are required to prevent catastrophic failures. Various non-destructive testing and evaluation (NDT&E) and in-situ structural health monitoring (SHM) techniques have been applied for damage detection in FRP composites. These techniques have been continuously developed to achieve reliable inspections, especially for safety-critical applications such as the aerospace industry. This review presents recent advances in NDT&E techniques and SHM techniques, particularly for damage diagnosis in FRP composites. For selecting the most suitable NDT technique based on specific criteria, the analytical hierarchy process is applied as a decision-making tool to evaluate and rank the NDT techniques. The size of the specimen is found to be the most important criterion that significantly affects technique selection. Finally, the importance of developing in-situ SHM systems is outlined, and different in-situ SHM systems are then reviewed and discussed. This review provides progress of the recent damage characterization techniques and enables researchers to devise selection criteria to select the most appropriate technique for their own work.
38 citations
TL;DR: In this paper, a quasi-static elasticity imaging (QSEI) based approach was proposed for determining inhomogeneous orthotropic elastic properties using distributed displacement measurements obtained from digital image correlation (DIC).
Abstract: The ability to accurately determine elastic properties of orthotropic materials is important in the design and health assessment of composite structures. Direct methods using strain gauges and extensometers for estimating orthotropic properties have become popular in recent years. In cases where strains are highly localized, the material properties are inhomogeneous, or the material has localized damage, the use of these measurement schemes often provides insufficient information. To address this, we propose an inverse method, based on quasi-static elasticity imaging (QSEI) for determining inhomogeneous orthotropic elastic properties using distributed displacement measurements obtained from digital image correlation (DIC). The QSEI-based approach is first tested with simulated noisy displacement data considering in-plane deformations of plate geometries undergoing stretching and bending. Following this, experimental DIC measurements are applied to test the feasibility of the QSEI-based approach. Elastic properties of uni-directional CFRP beams with and without localized damage are estimated using the proposed approach. Results demonstrate the feasibility of the proposed inverse approach.
20 citations
TL;DR: In this paper, a numerical simulation algorithm was proposed to investigate fully the overall elastic properties of composite samples, and the authors used Monte Carlo simulations to predict the overall modulus and Poisson's ratio.
20 citations
References
More filters
TL;DR: In this paper, the limits of optical strain measurement system under different environmental conditions were investigated, and the technique was applied to the characterization of polypropylene (PP) and PP composites (PP-C) in the pre- and post-yield regimes.
151 citations
TL;DR: In this article, a simulator able to numerically simulate an experimental test, which involves digital image correlation (DIC) on white light speckles, is presented, where synthetic images are generated and then analyzed by DIC.
Abstract: The use of experimental tests that involve full-field measurements to characterize mechanical material properties is becoming more widespread within the engineering community. In particular digital image correlation (DIC) on white light speckles is one of the most used tools, thanks to the relatively low cost of the equipment and the availability of dedicated software. Nonetheless the impact of measurement errors on the identified parameters is still not completely understood. To this purpose, in this paper, a simulator able to numerically simulate an experimental test, which involves DIC is presented. The chosen test is the Unnotched Iosipescu test used to identify the orthotropic elastic parameters of composites. Synthetic images are generated and then analysed by DIC. Eventually the obtained strain maps are used to identify the elastic parameters with the Virtual Fields Method (VFM). The numerical errors propagating through the simulation procedure are carefully characterized. Besides, the simulator is used to compare the performances of DIC and the grid method in the identification process with the VFM. Finally, the influence of DIC settings on the identification error is studied as a function of the camera digital noise level, in order to find the best testing configuration.
96 citations
TL;DR: In this paper, the authors applied digital image correlation (DIC) to analyze the deformation mechanisms under transverse compression in a fiber-reinforced composite and found that DIC of low-magnification micrographs was able to capture the long range fluctuations in strain due to the presence of matrixrich and fiber-rich zones, responsible for the onset of damage.
Abstract: Digital image correlation (DIC) is applied to analyzing the deformation mechanisms under transverse compression in a fiber-reinforced composite. To this end, compression tests in a direction perpendicular to the fibers were carried out inside a scanning electron microscope and secondary electron images obtained at different magnifications during the test. Optimum DIC parameters to resolve the displacement and strain field were computed from numerical simulations of a model composite and they were applied to micrographs obtained at different magnifications (250×, 2000×, and 6000×). It is shown that DIC of low-magnification micrographs was able to capture the long range fluctuations in strain due to the presence of matrix-rich and fiber-rich zones, responsible for the onset of damage. At higher magnification, the strain fields obtained with DIC qualitatively reproduce the non-homogeneous deformation pattern due to the presence of stiff fibers dispersed in a compliant matrix and provide accurate results of the average composite strain. However, comparison with finite element simulations revealed that DIC was not able to accurately capture the average strain in each phase.
95 citations
TL;DR: In this article, a case study of a SiC/SiC composite comprising 2-D woven fiber is presented, where the results of mechanical tests on aluminum alloy specimens in various geometric configurations are provided for selecting DIC test parameters to maximize the extent of correlation and to minimize errors in displacements and strains.
Abstract: Digital image correlation (DIC) is assessed as a tool for measuring strains with high spatial resolution in woven-fiber ceramic matrix composites. Using results of mechanical tests on aluminum alloy specimens in various geometric configurations, guidelines are provided for selecting DIC test parameters to maximize the extent of correlation and to minimize errors in displacements and strains. The latter error is shown to be exacerbated by the presence of strain gradients. In a case study, the resulting guidelines are applied to the measurement of strain fields in a SiC/SiC composite comprising 2-D woven fiber. Sub-fiber tow resolution of strain and low strain error are achieved. The fiber weave architecture is seen to exert a significant influence over strain heterogeneity within the composite. Moreover, strain concentrations at tow crossovers lead to the formation of macroscopic cracks in adjacent longitudinal tows. Such cracks initially grow stably, subject to increasing app lied stress, but ultimately lead to composite rupture. Once cracking is evident, the composite response is couched in terms of displacements, since the computed strains lack physical meaning in the vicinity of cracks. DIC is used to identify the locations of these cracks (via displacement discontinuities) and to measure the crack opening displacement profiles as a function of applied stress.
85 citations
TL;DR: In this paper, the meso-scale analysis of textile composite deformation and failure is performed using a digital image correlation technique, and the surface strain measurement is used for: (1) experimental investigation, which includes study of strain distribution at various stages of deformation, plasticity detection, damage initiation; (2) numerical validation of the correspondent finite element (FE) models.
73 citations