Mechanical behavior of bio-aggregates based buildings materials

Damage assessment studies in CFRP composite laminate with cut-out subjected to in-plane shear loading

Digital image correlation analysis of interfacial debonding properties and fracture behavior in concrete

ABSTRACTSurface deformation study of a polymer film during plastic film blowing (PFB) extrusion process though is considered essential, is difficult to execute as the process is fast and continuous. Digital image correlation (DIC) is an optical technique that is non-destructive, highly accurate and designed to measure deformations from micro to macro scale. DIC can be proposed as a reliable tool to understand the relationship of polymer structure-processing-properties. In this literature, digital image correlation, its basic principle of operation and reliability guided DIC for continuous large deformation are comprehensively explored. Versatility of DIC, and the conditions that affect the measurement algorithm as well as preceding use of DIC in polymer processes are reviewed. The implementation and potential use of DIC in PFB are described.This review was submitted as part of the 2019 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged.

Optical methods are becoming commonplace in investigations of the physical and mechanical behavior of biological tissues. Digital image correlation (DIC) is a versatile optical method that shows tremendous promise for applications involving biological tissues and biomaterials. We present the fundamentals of DIC with an emphasis on the application to biological materials. An approach for surface preparation is described that facilitates its application to hydrated substrates. Three examples are presented that highlight the use of DIC for biomedical research. The first example describes the use of DIC to study the mechanical behavior of arterial tissues up to 40% elongation. The second example describes an evaluation of the mechanical properties of bovine hoof horn in the dehydrated and fully hydrated states. Uniaxial tension experiments are performed to determine the elastic modulus (E) and Poisson's ratio (nu) of both the arterial and dermal tissues. Spatial variations in the mechanical properties are evident from the full-field characterization of both tissues. Finally, an application of DIC to study the evolution of loosening in cemented total hip replacements is described. The noncontact analysis enables measurement of the relative displacement between the bone/bone cement and bone cement/prosthesis interfaces. Based on the elementary optical arrangement, the simple surface preparation, and the ability to acquire displacement/strain measurements over a large range of deformation, DIC should serve as a valuable tool for biomedical research. Further developments will enable the use of DIC for in vivo applications.

In building materials, the incorporation of plant aggregates into mineral matrix is an eco-friendly promising solution as these biobased building materials can answer to the new requirements for thermal and hydric performances. Nevertheless, plant aggregates can have deleterious effects on the hardening mechanisms of mineral binders. The aim of this study is to evaluate the incidence of the water-soluble compounds contained into bioaggregates on the hardening process of three mineral binders (CEMI 52.5 cement, metakaolin-based pozzolanic binder, limebased commercial binder). Two vegetal by-products were selected (lavender straw and sunflower depithed stalk) because of their large availability in France. Distilled lavender straw is the by-product of the steam distillation process applied to lavender plant. Sunflower bark aggregates were obtained from the fractionation of the entire stalk (i.e. bark plus pith). The chemical composition of the two bioaggregates was first studied by the ADF-NDF method of Van Soest and Wine. The cellulose, hemicellulose and lignin contents were thus determined. In addition, the water-soluble components were estimated by measuring the mass loss of the bioaggregates after 1 h in boiling water. Large differences were highlighted concerning the content in water-soluble compounds between the two plant aggregates. Model pastes were then elaborated with a solution obtained by soaking lavender or sunflower powder in demineralized water for 48 h and then filtering. The properties of the pastes were compared with those of neat pastes of the three mineral binders. The setting time (followed by isothermal calorimetry), the hardening mechanisms (followed by X-ray diffraction and thermogravimetric analysis) and the mechanical performance of the different binders were clearly and variously influenced by the lavender and the sunflower extractives at early ages. The level of the impact on the cementitious and pozzolanic binders can be correlated with the content in water-soluble compounds. Concerning the lime-based binder, it was less impacted by the water-soluble species.

Digital Image Correlation became one of the dominant optical full-field techniques used in experimental mechanics. It does not require sophisticated equipment to evaluate the full displacement vector field of the specimen under test with great accuracy. In this paper, we would like to put the reader's attention to the DIC technique as a solution that may identify the genuine character of the load applied to the object under test. Our experience with testing wind turbine blades using DIC proves that possibility. Full Text: PDF References E.M.C Jones, M.A. Iadicola, "A good practises guide for digital image correlation" International Digital Image Correlation Society, (2018), CrossRef B. Pan, "Digital image correlation for surface deformation measurement: historical developments, recent advances and future goals", Meas. Sci. Technol. 29, 082001 (2018), CrossRef B. Pan, L.P. Yu, Q.B. Zhang, "Review of single-camera stereo-digital image correlation techniques for full-field 3D shape and deformation measurement", Sci. China Technol. Sci. 61, 2 (2018), CrossRef S. Sharma, N. Iniyan Thiruselvam, S.J. Subramanian, G.S. Kumar, "Computation of strains from stereo digital image correlation using principal component analysis", Meas. Sci. Technol. 32, 105201 (2021), CrossRef IEC 61400-5:2020 Wind energy generation systems - Part 5: Wind turbine, DirectLink IEC 61400-23:2014 Wind turbines - Part 23: Full-scale structural testing of rotor blades, DirectLink

Determination of Strain Field on the Superior Surface of Excised Larynx Vocal Folds Using DIC

The energy and environmental transition in the building sector requires the development and use of low-impact materials. Despite the growing interest in bio-based and earth-based building materials, their widespread adoption is still limited due to a lack of hindsight, as their study is relatively recent. This study aims to contribute to the development of these materials by providing an extensive overview of key contributors (authors, countries, journals) in these fields. Then, the keywords of the corresponding publications were analyzed to reveal the main topics covered to date. First, a broad scale is presented, followed by a focus on sub-categories, specifically raw materials for bio-based building materials and implementation techniques for earth-based ones. Finally, a comparative analysis, with the themes covered by composite construction materials as a whole, completes the study. Using statistical analysis coupled with bibliometric network visualization software, this study provides clear, quantifiable, and objective insights into current trends. Furthermore, it facilitates the identification of new, promising research perspectives and highlights the importance of interdisciplinary collaboration. Physics, modeling, durability and microstructure studies emerge as relevant levers for advancing the future development of these eco-friendly building materials.

<p>As reinforced concrete structures reach the end of their design lives, technology for improving accuracy and efficiency of inspections and structural health monitoring rapidly progresses. Concrete cracking and reinforcement strains are two relevant parameters in assessing damage and safety of these structures. The use of Digital Image Correlation (DIC) systems and distributed Fibre Optic Sensors (FOS) to evaluate these parameters are two of the technologies that have been gaining momentum due to their advantages over other approaches. This study presents an experimental investigation of crack propagation of a reinforced concrete beam specimen through FOS and DIC. The FOS were positioned inside a groove carved in the rebar and in the concrete immediately outside the bar for comparison. The results showed a significant difference between both positions, with more reliable data coming from inside the bar. The addition of the DIC crack propagation images to the FOS analysis complemented the results, and good visual correlation was identified between both methods. This study is part of a broader research program, which aims at applying DIC and FOS for structural health monitoring of a real scale bridge structure.</p>

Background The hole-drilling method, widely used to evaluate near-surface residual stresses, typically relies on strain gauge rosettes to measure surface deformations resulting from stress relaxation. However, this approach has several limitations, including a small number of discrete measurement points, the need for careful surface preparation, and sensitivity to misalignment between the rosette and the drilled hole. Objective To address these issues, the use of Digital Image Correlation (DIC), a full-field optical measurement technique, was investigated as a replacement for the strain gauge rosette within the hole-drilling method. Methods DIC was employed to measure strain and displacement fields around drilled holes in steel specimens subjected to various load levels, aiming to identify the minimum stress that could be accurately resolved. Several adjustments were made to both the hardware configuration and data processing procedures within the DIC setup to improve the accuracy of measured deformation. Results Accurate stress evaluation was achieved even at low stress levels, on the order of a few MPa, despite the relatively small strain magnitudes compared to the noise level. Conclusions The results obtained demonstrate that integrating DIC with the hole-drilling method offers a promising and effective alternative to traditional strain gauge-based residual stress measurement.

For validating physics based analytical models predicting spallation life of environmental barrier coating (EBC) on fiber reinforced ceramic matrix composites, the fracture strength of EBC and kinetics of crack growth in EBC layers need to be experimentally determined under engine operating conditions. In this study, a multi layered barium strontium aluminum silicate (BSAS) based EBC-coated, melt infiltrated silicon carbide fiber reinforced silicon carbide matrix composite (MI SiC/SiC) specimen was tensile tested at room temperature. Multiple tests were performed on a single specimen with increasing predetermined stress levels until final failure. During loading, the damage occurring in the EBC was monitored by digital image correlation (DIC). After unloading from the predetermined stress levels, the specimen was examined by optical microscopy and computed tomography (CT). Results indicate both optical microscopy and CT could not resolve the primary or secondary cracks developed during tensile loading until failure. On the other hand, DIC did show formation of a primary crack at ~ 50% of the ultimate tensile strength and this crack grew with increasing stress and eventually led to final failure of the specimen. Although some secondary cracks were seen in the DIC strain plots prior to final failure, the existence of these cracks were not confirmed by other methods. By using a higher resolution camera, it is possible to improve the capability of DIC in resolving secondary cracks and damage in coated specimen tested at room temperature, but use of DIC at high temperature requires significant development. Based on the current data, it appears that both optical microscopy and CT do not offer any hope for detecting crack initiation or determining crack growth in EBC coated CMC tested at room or high temperatures after the specimen has been unloaded. Other methods such as, thermography and optical/SEM of the polished cross section of EBC coated CMC specimens stressed to predetermined levels and cycled to certain time at a given stress need to be explored.

This paper introduces a new test configuration for the determination of panel shear properties in structural sizes. This original test configuration has been successfully applied to calculate the shear properties of beech plywood. A numerical model has been developed to evaluate the influence of such a novel setup in comparison to the common standard. The research includes the mechanical characterization of a total of 36 samples using Digital Image Correlation (DIC) to measure the in plane displacements. The use of DIC has been proven to be efficient to measure the shear properties and also acts as a tool to ensure that the solicitation was adequate during the test. Finally, the results highlight the interest to actually perform the proposed test instead of using the alternative density-based equivalencies provided by the standards.

Digital image correlation (DIC) techniques were used to evaluate strain distributions along tensile gage lengths immediately after yielding of a medium manganese steel (7 wt% Mn) in samples cold rolled in the range of 1–6 pct. With an increase in cold work, DIC confirmed that the yielding behavior transitioned from nucleation and propagation of a single localized deformation zone (Lüders band) to uniform deformation, that is, no evidence of strain localization. At intermediate amounts of cold work, a unique yielding behavior was evident where the initially-low positive strain hardening rate increased with tensile strain until conventional strain hardening (i.e., decrease in strain hardening rate with strain). The intermediate yielding behavior was associated with the development of multiple non‑propagating regions of strain localization, an observation not previously evident without the use of DIC.

Impact testing of polymeric foam using Hopkinson bars and digital image analysis

An analysis technique to assess the viability of digital image correlation (DIC) in tracking the full‐field strains across the surface of hanging historic tapestries is presented. Measurement uncertainty related to the use of the inherent tapestry image in tracking displacements is investigated through use of “synthetic” deformation fields. The latter are generated by mapping the details of a given tapestry image into finite element analyses. The combination of self‐weight loading, material non‐linearity, and image specific heterogeneity (related to slit stitching, damage, and patch‐restorations) serve to generate a bespoke deformation field complex enough to assess the reliability of DIC measurements. Accuracy is evaluated by comparing measured results with the original known deformations. The technique demonstrates that the optimum imaging settings and the choice of subset size for DIC analysis are strongly influenced by the tapestry image and the goal of the measurement, they are found using a compromise between conflicting objectives: minimising measurement error while maximising resolution.