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Wave propagation and free vibration of FG graphene platelets sandwich curved beam with auxetic core resting on viscoelastic foundation via DQM

Al Mukahal F. H. H., Sobhy Mohammed

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e12, 2022

EN

A novel shear and normal deformations theory is presented in this article to illustrate the wave propagation and free vibration of three-layer sandwich curved beams subjected to elevated temperature and moisture environments and resting on viscoelastic foundation. The upper and lower layers are made of metal matrix reinforced with functionally graded (FG) graphene platelets (GPLs). While, the core layer is made of auxetic honeycomb structures. For the layers to be more bonded, the matrix of the face layers and the auxetic layer are both made of aluminum material. The volume fraction of GPLs is varied through the thickness of the face layers according to a layer-wise rule. The modified Halpin–Tsai model is used to describe the effective material properties of the face layers. Four types of GPLs distribution are considered in the present analysis. The differential quadrature method (DQM) is employed to discretize the equations of motion and then converted to a system of algebraic equations. This system can be solved to obtain the natural frequencies of the sandwich curved beams. Whereas, the wave dispersion relations are determined by solving the motion equations analytically. Convergence and comparison examples are presented to adjust and validate the present solution. In addition, comprehensive parametric studies are performed to investigate the effects of the weight fraction of GPLs, temperature, moisture concentrations, core thickness, boundary conditions, and viscoelastic foundation stiffness on the natural frequency, wave frequency and phase velocity of the honeycomb sandwich curved beams.

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Mechanical and hygrothermal performance of fly-ash and seashells concrete: in situ experimental study and smart hygrothermal modeling for Normandy climate conditions

Bouasria Manal, Benzaama Mohammed-Hichem, Pralong Valéry, El Mendili Yasmin

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e100, 1--22

EN

The aim of this study is to investigate the effect of partial substitution of cement by a smart mixture of waste materials, fly ash and Crepidula shells. The cement is replaced by fly ash and Crepidula accordingly in the range of 5, 10 and 15% by weight. This study focuses on three steps: (i) find the best formulation in terms of compression and hygrothermal behavior, (ii) build a prototype and follow the hygrothermal behavior with sensors, (III) data collection and development of a neural network model to predict the hygrothermal behavior of the prototype. The results showed that for a fly ash-Crepidula incorporation rate up to 10%, the mechanical properties are higher than the control mortar. Furthermore, the cement substitution by fly ash and Crepidula improves the thermal conductivity of concrete. With the cement replacement of 30%, a prototype was built to monitor the hygrothermal behavior. The data collected from the wireless sensors placed in the prototype are used to train and validate the artificial neural network model. The model used in this study is conducted with eight inputs and two outputs data. The investigation of the condensation risk and the mould growth shows that the chosen concrete mixture can avoid the condensation phenomenon. Indeed, the smart fly ash-Crepidula mixture provides high silica, aluminate, and calcium contents, which react with water originating from humid ambient air to form additional hydrates as a result of pozzolanic reaction and lead to a continuous strengths enhancement.

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Buforowanie wilgoci przez innowacyjne przegrody wewnętrzne

Kaczorek D., Pietruszka B.

Materiały Budowlane

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2017

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nr 8

35--37

PL

W artykule przedstawiono wyniki z badań dotyczących tzw. buforowania wilgoci MBV (z ang. Moisture Buffer Value) przez przegrody, w których zastosowano higroskopijne biomateriały, powstałe na bazie surowców odnawialnych. Wszystkie z przebadanych konstrukcji ściennych, przy zmiennym obciążeniu wilgocią (50 – 80%), wykazały się „dobrą” klasą buforowania wilgoci w odniesieniu do skali zaproponowanej przez Rode [11]. Przedstawione wyniki potwierdzają, że na potencjał buforowania wilgoci przez poszczególne przegrody wpływ mają zastosowane w nich materiały, w szczególności skład surowcowy.

EN

In this paper, the results of Moisture Buffering Test (MBV) of the internal walls with a range of different internal and external layers, made from renewable, hygroscopic row-materials were presented. All of the investigated wall assemblies, with varying moisture loads in the range (50 – 80%), showed “good” moisture buffering value in relation to the buffer class proposed by Rode [11]. The presented results confirmed that the moisture buffer potential of the assemblies is influenced by used materials especially theirs material composition and structure.