Towards the Design of Metamaterials with Enhanced Damage Sensitivity: Second Gradient Porous Materials

Abstract

Numerous computational and conceptual difficulties are often encountered when conceiving techniques which are effective in detecting damage intensity, localization, and onset. Actually, also when the semi-inverse or the material characterization problems (which are commonly formulated in this context) can be recognized to be well posed, the numerical and computational obstacles which need to be overcome can render useless the conceived methodology. In the present paper we propose to change the paradigm used up to now when addressing the problem of damage assessment in engineering materials. In fact, we propose to conceive a metamaterial the properties of which make more expedite and effective the detection of cracks onset and damage evolution via the study of reflection and transmission of waves. More particularly, porous materials with underlying heterogeneous micro-structure may magnify the effects of reflection and transmission of waves at damaged sites depending on the considered boundary conditions. Materials of this type would make easier the structural health monitoring via nondestructive evaluation of local damage and would permit to detect incipient structural failure in a more efficient way. By analyzing the characteristic patterns of the reflection and transmission properties of surfaces where damage is concentrated, we show that, in the considered metamaterials, slow incident waves can be used to detect the onset and evolution of first gradient macroscopic damage ( e ), while fast incident waves can be used to reveal loss of contact at the microscopic level, i.e. to detect the onset of second gradient macroscopic damage ( r ).

Constitutive models for strongly curved beams in the frame of isogeometric analysis

“…), such as those presented in [37] for historic masonry arches, where only de Saint-Venant's model has been considered until now; buckling problems following the way traced into [38][39][40][41] and the papers cited therein. dynamic analysis of curved beams in the framework of isogeometric analysis, as an extension of the works [42] and [11]; extension to mixed-hybrid methods [43][44][45] which provide more accurate stress description also in the case of layered structures [46]; mathematical model improvement, for example using a suitable damage parameter [47][48][49][50] taking into account that in some cases it leads to non-unique and non-stable solutions, see [51][52][53]. Alternatively, there is the method proposed in [54,55], where a two-dimensional model for an interfacial zone is introduced and this could be used to describe concentrated damages.…”

Designing a light fabric metamaterial being highly macroscopically tough under directional extension: first experimental evidence

“…The reader is warned: no attempt is made here to model damage and failure phenomena. This challenge has to be confronted, following the ideas presented in [68][69][70] suitably adapted to the context of second-gradient materials as done in [43,60,64]. Another consideration is needed here: In the present work, we do not try to derive the used continuum model by means of a homogenization procedure.…”

Surface waves at the interface between an inviscid fluid and a dipolar gradient solid

“…Several works on the subject can be found in the recent literature, see e.g. dell'Isola et al [5], Gourgiotis et al [6], Madeo et al [7] and Rosi et al [8]. This revival can be partially explained by the fact that the recent advances in meta-material synthesis and conception allow to produce artefacts that have the actual behaviour of a generalized continuum.…”