Application of Digital Image Correlation to composite reinforcements testing
TL;DR: In this paper, a full-field contactless optical method for measuring displacements in experimental testing, based on the correlation of the digital images taken during test execution, is used for the characterization of composite reinforcements.
About: This article is published in Composite Structures.The article was published on 2017-01-15. It has received 144 citations till now. The article focuses on the topics: Digital image correlation.
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TL;DR: In this paper, the authors present the results of an extensive experimental program on different combinations of basalt fibre textiles and inorganic matrices organized by RILEM TC 250-CSM (Composites for the Sustainable strengthening of Masonry) involving ten European laboratories.
Abstract: An increasing interest and application is nowadays found for composite systems in construction and rehabilitation industry. The consensus on fibre reinforced composite systems was mainly based on high tensile strength, light weight, relative ease of installation, and resistance to corrosion. However, some drawbacks related to the epoxy (hence, organic) matrices of Fiber-Reinforced Polymers (FRP) have been solved by inorganic ones yielding to novel fibre reinforced composites. In these materials the composite action is mainly achieved through mechanical interlock between the matrix (e.g. a cement- or a lime-based mortar or a geopolymer with the option of chopped fibres and/or low-content polymer addition) and the mesh-like fibrous structure (a textile) that allows the mortar to protrude through the grid's openings. Aiming at the investigation of the mechanical properties and the development of testing procedures for this new family of materials (termed herein as Fabric-Reinforced Cementitious Matrix (FRCM)) the present paper presents the results of an extensive experimental program on different combinations of basalt fibre textiles and inorganic matrices organized by RILEM TC 250-CSM (Composites for the Sustainable strengthening of Masonry) involving ten European laboratories. The tests involve more than 100 specimens: half are tensile tests and the other half are bond tests carried out on prisms made of clay bricks, on three different basalt-based FRCM configurations comprising readily available commercial systems provided by different producers. The scope of this work is aimed not only at presenting a comparative performance assessment of different Basalt FRCM systems, but also at providing meaningful criteria to reliably design and analyse retrofit applications. The relevant round robin test program provides valuable data generated during the experimental activity and statistical analysis thereof; then, based on the various testing approaches employed, the advantages/drawbacks of certain testing factors are summarized and critically assessed, reflecting the experience of involved institutions. It is believed that this represents a crucial step in improving knowledge on innovative retrofit applications and developing standard test methods.
161 citations
TL;DR: In this paper, a Round Robin Test initiative was organized by the Rilem TC 250-CSM (Composites for the Sustainable strengthening of Masonry) to investigate the tensile and bond behavior of mortar-based composites with basalt, carbon, glass, polyparaphenylene benzobisoxazole (PBO), aramid and steel textiles.
Abstract: Mortar-based reinforcements are an innovative solution for retrofitting existing structures that combine effectiveness, compatibility, and sustainability. Despite the recent spreading of field applications, there is still insufficient knowledge on their fundamental mechanical properties, and a regulatory gap for experimental procedures and design criteria. A Round Robin Test initiative was organized by the Rilem TC 250-CSM (Composites for the Sustainable strengthening of Masonry) to investigate the tensile and bond behaviour of mortar-based composites with basalt, carbon, glass, polyparaphenylene benzobisoxazole (PBO), aramid and steel textiles. This paper presents the tests carried out on Steel Reinforced Grout (SRG) systems, comprising three textile and four mortar types, supplied by three producers. Ten laboratories from Italy, Poland and Portugal were involved for a total of 150 tests, including direct tensile tests on textiles and composites, and single-lap bond tests on masonry substrate. The influence of the layout of the textile, the mechanical properties of the mortar matrix, the manufacturing and curing conditions, as well as the testing setup and instrumentation, is discussed to contribute to the optimization of the reinforcement systems and to the development of recommendations for laboratory testing. Finally, results are combined to derive engineering parameters for qualification and design purposes.
146 citations
TL;DR: In this article, the main features of the tensile and bond behavior of textile reinforced mortar (TRM) composites are described, and recommendations for performing direct tensile tests and shear bond tests are proposed, based on the outcomes of a Round Robin Test organized by the Rilem TC 250-CSM (Composites for the Sustainable strengthening of Masonry) and Assocompositi (Italian Industry Association for Composite Materials), carried out on 26 TRM systems (made of basalt, carbon, steel, glass, PBO and aramid textiles
Abstract: Textile Reinforced Mortar (TRM) composites, also named Fabric Reinforced Cementitious Matrix (FRCM), comprise high strength textiles embedded into inorganic matrices, and have been recently developed for the repair and rehabilitation of structures. Their effectiveness and compatibility with the substrate fostered the industrial development of a wide number of strengthening systems, which have been applied to masonry and reinforced concrete structures. Nevertheless, an improved knowledge still needs to be gained on their mechanical properties (tensile and bond behaviour) and on the effect they have on the structural performance of reinforced members. Furthermore, except for the US, no standards are available for testing, qualification and design. In this paper, the main features of the tensile and bond behaviour of TRM composites are described. Recommendations for performing direct tensile tests and shear bond tests are proposed, based on the outcomes of a Round Robin Test organized by the Rilem TC 250-CSM (Composites for the Sustainable strengthening of Masonry) and Assocompositi (Italian Industry Association for Composite Materials), carried out on 26 TRM systems (made of basalt, carbon, steel, glass, PBO and aramid textiles, with cement, lime or geopolymer mortar matrices), and involving 19 European research institutions and 11 industrial partners.
123 citations
TL;DR: In this paper, the fracture toughness during Mode I loading of concretes containing the 0, 20% and 30% addition of class F fly ash (FA), was investigated. And the results of the research show the usefulness of the Digital Image Correlation (DIC) method in experiments of that type.
96 citations
TL;DR: In this paper, the authors proposed a thorough experimental analysis of basalt textile reinforced mortar, and four series of tensile tests were carried out on specimens characterised by three different basalt reinforced ratio and two different kinds of mortar (usual gauged mortar and thixotropic mortar with additives).
Abstract: The use of textile reinforced mortar (TRM) composites is considered a suitable solution to strengthen historical masonry structures. Specifically, TRM composites are characterised by a textile embedded in a mortar matrix. In the present work, we propose a thorough experimental analysis of basalt textile reinforced mortar. Four series of tensile tests were carried out on specimens characterised by three different basalt textile reinforcing ratio and two different kinds of mortar (usual gauged mortar and thixotropic mortar with additives). The use of digital image correlation facilitated detailed description of the displacement fields and the crack pattern during the tests. The comparison between the results of each series allowed us to evaluate the influence of the different parameters on the behaviour of the analysed TRM and to obtain useful information regarding the strengthening design.
94 citations
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TL;DR: In this article, a review of the 2D digital image correlation (2D DIC) technique for displacement field measurement and strain field estimation is presented, and detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided.
Abstract: As a practical and effective tool for quantitative in-plane deformation measurement of a planar object surface, two-dimensional digital image correlation (2D DIC) is now widely accepted and commonly used in the field of experimental mechanics. It directly provides full-field displacements to sub-pixel accuracy and full-field strains by comparing the digital images of a test object surface acquired before and after deformation. In this review, methodologies of the 2D DIC technique for displacement field measurement and strain field estimation are systematically reviewed and discussed. Detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided. Measures for achieving high accuracy deformation measurement using the 2D DIC technique are also recommended. Since microscale and nanoscale deformation measurement can easily be realized by combining the 2D DIC technique with high-spatial-resolution microscopes, the 2D DIC technique should find more applications in broad areas.
2,530 citations
Book•
26 Mar 2009TL;DR: In this paper, a comprehensive overview of image correlation for shape, motion and deformation measurements is provided. But, the authors do not discuss the effect of out-of-plane motion on 2D measurements.
Abstract: Image Correlation for Shape, Motion and Deformation Measurements provides a comprehensive overview of data extraction through image analysis. Readers will find and in-depth look into various single- and multi-camera models (2D-DIC and 3D-DIC), two- and three-dimensional computer vision, and volumetric digital image correlation (VDIC). Fundamentals of accurate image matching are described, along with presentations of both new methods for quantitative error estimates in correlation-based motion measurements, and the effect of out-of-plane motion on 2D measurements. Thorough appendices offer descriptions of continuum mechanics formulations, methods for local surface strain estimation and non-linear optimization, as well as terminology in statistics and probability. With equal treatment of computer vision fundamentals and techniques for practical applications, this volume is both a reference for academic and industry-based researchers and engineers, as well as a valuable companion text for appropriate vision-based educational offerings.
2,454 citations
TL;DR: In this paper, the surface displacement components in laser speckle metrology were measured using a digital image scanner interfaced to a computer. Butt et al. used a boundary integral equation method to calculate surface traction in the contour.
Abstract: Digital imaging techniques are utilized as a measure of surface displacement components in laser speckle metrology. An image scanner which is interfaced to a computer records and stores in memory the laser speckle patterns of an object in a reference and deformed configuration. Subsets of the deformed images are numerically correlated with the references as a measure of surface displacements. Discrete values are determined around a closed contour for plane problems which then become input into a boundary integral equation method in order to calculate surface traction in the contour. Stresses are then calculated within this boundary. The solution procedure is illustrated by a numerical example of a case of uniform tension.
1,617 citations
TL;DR: Ncorr is an open-source subset-based 2D DIC package that amalgamates modern DIC algorithms proposed in the literature with additional enhancements and several applications of Ncorr that both validate it and showcase its capabilities are discussed.
Abstract: Digital Image Correlation (DIC) is an important and widely used non-contact technique for measuring material deformation. Considerable progress has been made in recent decades in both developing new experimental DIC techniques and in enhancing the performance of the relevant computational algorithms. Despite this progress, there is a distinct lack of a freely available, high-quality, flexible DIC software. This paper documents a new DIC software package Ncorr that is meant to fill that crucial gap. Ncorr is an open-source subset-based 2D DIC package that amalgamates modern DIC algorithms proposed in the literature with additional enhancements. Several applications of Ncorr that both validate it and showcase its capabilities are discussed.
1,184 citations
TL;DR: A theoretical model of the displacement measurement accuracy of DIC can be accurately predicted based on the variance of image noise and Sum of Square of Subset Intensity Gradients (SSSIG), which leads to a simple criterion for choosing an optimal subset size for the DIC analysis.
Abstract: Digital Image Correlation (DIC) has been established as a flexible and effective technique to measure the displacements on specimen surface by matching the reference subsets in the undeformed image with the target subsets in the deformed image. With the existing DIC techniques, the user must rely on experience and intuition to manually define the size of the reference subset, which is found to be critical to the accuracy of measured displacements. In this paper, the problem of subset size selection in the DIC technique is investigated. Based on the Sum of Squared Differences (SSD) correlation criterion as well as the assumption that the gray intensity gradients of image noise are much lower than that of speckle image, a theoretical model of the displacement measurement accuracy of DIC is derived. The theoretical model indicates that the displacement measurement accuracy of DIC can be accurately predicted based on the variance of image noise and Sum of Square of Subset Intensity Gradients (SSSIG). The model further leads to a simple criterion for choosing a proper subset size for the DIC analysis. Numerical experiments have been performed to validate the proposed concepts, and the calculated results show good agreements with the theoretical predictions.
486 citations