Nonlinear behaviour and homogenization of metaplates

Large deflections in thin plates introduce a nonlinear membrane-flexural coupling which significantly modifies the plate behaviour under transversal and in-plane loadings. This effect is often important when considering metamaterial plates with periodically distributed heterogeneities or holes. In this work, we employ the asymptotic homogenization technique to study the effective nonlinear behaviour of periodic Föppl-von Kármán plates in the static regime. Then, we validate the method by simulating the nonlinear response of the perforated plate (backplate) which is present in a micro-electro-mechanical microphone to limit the displacements of the vibrating membrane

Homogenization of Thermal Properties in Metaplates

Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of such metamaterials also causes, in general, a thermal-induced deflection. The prediction of the equivalent thermal properties is important to design the metamaterial suitable for a specific application. Under the hypothesis of small thickness with respect to the global in-plane dimensions, we make use of asymptotic homogenization to describe the thermoelastic behaviour of these metamaterials as that of an equivalent homogenous plate. The method provides explicit expressions for the effective thermal properties, which allow for a cost-effective prediction of the thermoelastic response of these metaplates

The effect of external sulfate attack on concrete, mortar and cement paste

Abstract. The present work reports the results of an experimental campaign started two years ago and still ongoing, aimed to assess the behavior of different cementitious materials subject to external sulfate attack. To this purpose prismatic specimens of cement paste and specimens of mortar and concrete produced with the same Portland cement, were immersed in demineralized water and in different solutions containing 5% and 10% sodium sulfates. The expansion was monitored in time by direct length measurements and the degradation of the stiffness was indirectly obtained through non-destructive ultrasound wave propagation tests. XRD tests and SEM observations evidenced the presence of secondary gypsum in the outer part of the specimens were sulfates penetrated. An increase of the material porosity was also measured in this region

Two-phase damage modeling of concrete affected by alkali–silica reaction under variable temperature and humidity conditions

AbstractIn the present work the concrete affected by alkali–silica reaction (ASR) is represented as a two-phase material made of a solid skeleton and a wet expanding gel, which exerts a pressure capable of severely damaging the concrete surrounding the reactive sites. Both the effects of temperature and humidity conditions on the kinetic of the chemical reaction and on the final value of the consequent expansion are included in the proposed model. The mechanical degradation induced by the ASR is described by a phenomenological isotropic damage model. The constitutive model, implemented in a finite element code, is used for the analyses of structures made of reactive concrete in the presence of temperature and moisture gradients. Firstly the temperature and humidity fields are obtained through uncoupled heat and moisture transport analyses and then the chemo-mechanical analysis is performed starting from the values of temperature and humidity preliminary calculated

Wave Polarization Control in Anisotropic Locally Resonant Materials

Elastic wave propagation in solids can be controlled and manipulated by properly designed metamaterials. In particular, polarization conversion can be obtained by using anisotropic materials. In this paper, we propose a three-component locally resonant material with non-symmetrically coated inclusions, and we study the effect of the anisotropic equivalent mass on band gap formation and the polarization conversion of elastic waves. The equivalent frequency-dependent mass tensor is obtained through the two-scale homogenization approach. The study of the eigenvalues of the mass tensor enables to predict band gaps and polarization bands, as well as identifying a priori the effect of different geometric and material parameters, thus opening the way to metamaterial optimization

Assembly and disassembly – The module as a compositional element for a ‘new’ sustainability – The Spanish case

This paper investigates the concept of module based on Argan’s proposed dual definition of module-measure and module-object, reflecting on architectural design by ‘elements’ from a circular economy perspective. This reflection is conducted by selecting case studies on prefabricated architecture within the Iberian context, comparing contemporary projects with selected works by 20th-century Masters, following a reverse process. These works are offered as emblematic, in a logic of interaction and ‘synthesis’ between technology and design in relation to the contemporary global challenges of sustainability and energy transition. The investigation into new ways of understanding and designing architecture introduces the method of Design for Disassembly and extends the reflection on the reuse of buildings to the individual elements they are composed of.   Article info Received: 15/09/2023; Revised: 19/10/2023; Accepted: 26/10/202