This study investigates the use of imperfect Kinematic Uniform Boundary Conditions (KUBC) in experimental setups to measure the effective stiffness of architectured materials. To this aim, a numerical model simulates various experimental configurations: the number of grips applying the discretised KUBC, their compliance and clearance, etc. Simulations are conducted on bulk, periodic, and quasi-periodic specimens to understand the interactions between the grips and the mesostructures. The paper compares results from this Experimental KUBC (E-KUBC) to classical numerical KUBC to assess accuracy. Errors from E-KUBC are typically within 2–5%, but can significantly rise for some specimen design choices. The study identifies design guidelines to mitigate these errors, including adding notches to lower the stiffness of the specimen boundary and avoiding matching the specimen pattern with machine one. Quasi-periodic structures tend to be less sensitive to these issues. Overall, E-KUBC setups can yield accurate stiffness measurements if carefully implemented.

Two kinds of behaviour are commonly distinguished among porous architectured materials: stretching-dominated and bending-dominated ones. One or the other is favoured depending on the mechanical application. This property has been widely studied for random foams and periodic lattices, but has not yet been considered for quasi-periodic ones. Generally speaking, few studies have investigated their mechanical behaviour, and when this has been done, the impact of the elementary pattern shape has not been considered. In this paper we propose a classification of quasi-periodic structures depending on their dominance type by performing numerical simulations on mesoscopic models, and analysing the proportions of the strain energy stored in stretching and bending. As a result, three different dominance behaviours can be distinguished: completely stretching or bending dominated and varying dominance. Belonging to one or the other category depends mainly on the elementary pattern shape, and thus so does the overall mechanical behaviour.

This paper is a review on distributed optic fiber sensing for structural health monitoring applications, with a deeper focus on technologies relying on the Rayleigh backscattering phenomenon. It addresses the basic physical principles which are involved, the implementation and instrumentation of the measurement techniques, as well as recent practical applications, current performance, and remaining challenges. Being written at an elementary level and integrating relevant theoretical and technical details, we hope the document can be useful for researchers and engineers looking for an up-to-date overview on a field which currently undergoes significant development and increasing attractiveness, in particular for damage tracking in complex mechanical structures.

With the increasing use of composite materials and the emergence of 3D printing technologies in advanced industrial sectors, the architected materials seem to be one of the main answers to reduce the mass and to increase the performance of structures. As a matter of fact, for such materials, the mesoscopic arrangement of matter gives specific macroscopic properties highly interesting for such structures. If those

In order to characterize the mechanical behavior of a reinforced concrete beam–column joint, an experiment is designed whereby different histories of increasing cyclic loads are applied, and the structure deformation (as well as the morphology of apparent surface cracks) is studied using multi-view correlation. The complex three-dimensional geometry and the slender nature of the beam and column call for numerous digital cameras were positioned around the specimen. Assessing the feasibility of image acquisition and estimating a priori uncertainties on multi-view correlation became a true challenge. It is shown that the recourse to photo-realistic rendering software provides the needed tools to perform this experiment design optimization.

The dataset presents a synthesis of an experimental benchmark performed in the context of the French national research network GDR FATACRACK . A sample has been designed to produce mixed-mode crack propagation and variation of small scale yielding conditions. Two geometries and two maximum load levels are defined for the two tested materials: a stainless steel and an aluminum alloy. Around ten participants performed experiments using their usual instrumentation. Among the eight possible parameter sets, three are selected for which detailed results are presented. A satisfying overall agreement is obtained. But, some discrepancies are evidenced due either to limitations of the instrumentation or simply because from one lab to the other the applied load is not exactly the same. The results obtained by all the participants as well as the description of their testing setups and measurement tools are collected in this dataset. It includes crack path, stress intensity factor range and crack growth rate measurement for the selected configurations.

The idea of an experimental homogenization device adapted to the case of architectural materials is discussed here. Although more advanced homogenization schemes exist, the case of average-field homogenization by KUBC within the framework of linear elasticity is studied here because of its (relative!) simplicity of adaptation to an experimental setup. The main idea here is to propose a device that is simple to implement, inexpensive but that allows to apply a load as close as possible to a perfect KUBC thanks to the use of pantographs to distribute the displacements on the edges of the specimen. For the purposes of the design and tests-design, a reduced model of the device has been developed.

The design of reliable structures and the estimation of the residual fatigue life of industrial parts containing flaws or cracks rely on our ability to predict the propagation of fatigue cracks. Whereas in industrial component cracks might have a complex path due to geometry and loading, lab experiments used for identifying crack propagation law are often in pure mode I. The paper presents a synthesis of an experimental benchmark performed in the

The following data can be used for benchmarking numerical simulations of crack propagation test on quasi-brittle materials. Two crack propagation tests are proposed here, close to the well-known Nooru-Mohamed tests, but with modern instrumentation so that they provide trustworthy data. They present initiation and propagation. The goal is to compare your simulation results with the measured crack paths and force-displacement curves. The input data consists in specimen geometry, experimentally determined material properties (Young modulus, tensile strength, compressive strength and fracture energy) and the measured boundary conditions.

This second paper presents a series of 4 crack propagation tests with the same experimental protocol as in a companion paper, but with some significant loading modifications. The first difference is that the loading is composed of in-plane rotation in addition to tension and shear translations. The second difference is that the loading is manually changed during the tests, depending on the crack tip location. This leads to tests with several bifurcations, and/or different loading ratios during the same test. One of them leads to mode I+II, and then mode I+III crack propagation. Some tests end with instabilities while others are controlled to be stable up to the complete failure of the specimen. In some cases, crack closure and friction between the crack faces occur.

A series of experiments has been performed to build a benchmark for the numerical modeling of mixed mode crack propagation in concrete. Two tests are selected so that the propagation is almost always stable although the material is quasi-fragile. Moreover the variation of mode mixity enables the study of the reorientation of the crack, as well as more complex phenomena such as branching or link-up. To control stability and mode mixity, the loading is imposed with a 6-axis testing machine while the crack propagation is assessed by full-field measurement. In this paper, a description of the experimental setup is provided as well as numerical simulation results illustrating the sensitivity to boundary conditions and geometry. Links to data needed to perform numerical simulations of these benchmark experiments are given, together with references to publications giving full descriptions of the protocol and experiment results.

An online calibration procedure for x-ray lab-CT is developed using projection-based digital volume correlation. An initial reconstruction of the sample is positioned in the 3D space for every angle so that its projection matches the initial one. This procedure allows a space-time displacement field to be estimated for the scanned sample, which is regularized with (i) rigid body motions in space and (ii) modal time shape functions computed using model reduction techniques (i.e. proper generalized decomposition). The result is an accurate identification of the position of the sample adapted for each angle, which may deviate from the desired perfect rotation required for standard reconstructions. An application of this procedure to a 4D in situ mechanical test is shown. The proposed correction leads to a much improved tomographic reconstruction quality.

Materials with coarse inner architecture being easily made with modern additive or folding processes, the question of their overall behavior rises. Do they behave like classical elastic continua, or do they exhibit additional higher-order effects ? Further, if present are those effects stable with respect to imperfections (geometry, constitutive material, ...) ? In this view, the current work is an experimental investigation for the need, in static, of a higher-order overall description. It comes from noticing that such behaviors are up to now nearly exclusively studied from a theoretical and numerical point of view. In the present study a non-centro-symmetric sample has been manufactured, based on an industrial honeycomb geometry used for aeronautic/aerospace composite materials. The geometrical anisotropy of the elementary cell and the scale separation ratio have been chosen in order to detect non-classical couplings. Samples are obtained by Fused Deposition Modeling (FDM), one of the most widespread 3D printing techniques. Simple experiments based on load controlled tests with full-field kinematic measurement have been performed. A distributed load control reveals that the overall behavior of the architectured material cannot be described within the realm of Cauchy elasticity.