1,721,134 research outputs found
Modeling micro-cracking and failure in short fiber-reinforced composites
Full text linkComposites made of reinforcing short fibers embedded into brittle matrices, like, e.g., fiber-reinforced concretes, exhibit enhanced strength and ductility properties. Their failure process induced by tensile loadings involves hardening and softening stages as a result of matrix multiple micro-cracking, due to stress bridging of fibers across matrix micro-cracks, and strain localization phenomena. In the present paper, a variational model is proposed for the description of the intriguing failure mechanisms observed in short fibre-reinforced composites subjected to tensile loadings. The key modeling idea is to schematize the composite as a mixture of two phases, a brittle phase, representative of the matrix, and a ductile phase, accounting for the fibers reinforcement, which are coupled by elastic bonds. Different modeling levels of increasing complexity are proposed, ranging from a simplified one-dimensional analytical model to a three-dimensional variational model. Within the variational formulation, specific damage and plastic energies are assigned to the two phases, incorporating non-local gradient terms, and governing equations and evolution laws for the internal variables, as yield inequalities, consistency conditions and normality rules, are deduced from minimum principles. Parameters calibration is discussed as well as the importance of three internal lengths incorporated into the model. Moreover, the variational structure of the problem allow for a straightforward finite element implementation based on an incremental energy minimization algorithm and several aspects of the response are highlighted by means of numerical examples
A phase-field variational approach to model the fracture mechanisms of fabric-reinforced cementitious matrices
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Theoretical prediction of the crack paths in the damaged masonry of the French Panthéon
No full textFlexure waves in electroelastic plates
No full textThe near-cutoff propagation of free waves of flexure in a transversely isotropic, linearly electroelastic plate is studied, in two cases: for the simplest kinematics, when both the mechanical displacement and the electric potential are taken linear in the thickness variable; and for the entriched, third-order kinematics. The dispersion curves are four in the second case, only two in the first. By a comparison with the first four dispersion curves obtained by solving the corresponding three-dimensional problem, it is shown that perhaps the most definite advantage of adopting an enriched kinematics is a better approximation of the low-cutoff curves. (C) 2002 Elsevier Science B.V All rights reserved
Arabic Grammar and Qurʾānic Scholarship in 2nd/8th Century's Basra: A Comparative Analysis of the Qurʾānic Material Found in the Kitāb Sībawayhi and in al-ʾAḫfaš al-ʾAwsaṭ's Maʿānī al-Qurʾān
No full textApprendimento in condizioni di post-coma grave: da una diagnosi di stato vegetativo ad una possibile di minima coscienza.
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