A combined analytical and computational approach to the structural behavior of composite tubes
In this paper, we touch on the mechanical behavior of casing-infill composite tubes, as potential new lightweight structural elements. The axial and the torsional behavior of composite tubes of circular cross-section, comprising a casing and an infill, is addressed analytically, to develop physical insight into the mechanical interactions between these two components, in the linear range. The influence of the material parameters of the infill, relative to those of the casing, and of geometry – such as the ratio of wall-thickness to diameter of the casing – on the structural stiffness and capacity of the composite are revealed and presented in a novel graphical form. It is shown that significantly improved overall stiffness and capacity at yield can be obtained by bonding a moderately softer, but highly auxetic, infill to the casing, which highlights the need to develop new lightweight auxetic materials, without compromising their stiffness. These predictions are verified in torsion and confirmed in bending by means of suitable computational models based on the finite element method.
Computer-aided measurements of the electrical resistivity fields in concrete mixtures with and without polyethylene terephthalate
Naji Khoury, Yara Maalouf, Sophia Ghanimeh and Gérard-Philippe Zéhil
This study aims at determining the electrical resistivity and mechanical properties of concrete mixes with and without polyethylene terephthalate (PET). 2-D Electrical Resistivity Tomographies (ERTs) were obtained using 14 electrodes spread on the surface of the concrete cylinder. AGI Supersting R1/IP was used for data acquisition and data were processed by an iterative finite element based inversion algorithm with EarthImager 2D. 1D testing was also performed on concrete cylinders with two stainless steel plates located at the ends acting as a source and a receiver. ERTs and 1D results showed that the electrical resistivity of concrete was lower in specimens with PET than in those without PET. After ERT testing, compressive strength tests were conducted on specimens. Findings revealed an increase in the compressive strength up to a PET content of 5% then a decrease up to a PET content of 20%. Findings also showed that the inclusion of PET increased the probability of corrosive action in PET concrete.