E.V. González

Size Effect Law and Critical Distance Theories to Predict the Nominal Strength of Quasibrittle Structures

The design of structures with a nonuniform stress field is of great industrial interest. The ability of the size effect law and critical distance theories to predict the nominal strength of notched and open hole specimens is analyzed in the present paper. The results obtained with these methods are compared with the solution of the problem computed, taking into account the material cohesive law. A conclusion of this paper is that the role of the critical fracture energy in determining the structural strength is negligible, except in large cracked structures. For unnotched structures of any size and for small cracked structures, the key parameter is the initial part of the softening cohesive law. This allows us to define design charts that relate the structural strength to a specimen size normalized with respect to a material characteristic length.

Comment to the paper ‘Analysis of Progressive Matrix Cracking in Composite Laminates II. First Ply Failure’ by George J Dvorak and Norman Laws:

Dvorak and Laws published in Ref. 1 a paper that addresses transverse cracking of composite laminates for small crack densities. An accurate cracking criterion is obtained by means of linear elastic fracture mechanics. The equations developed in the paper are used by many researchers – this is shown by the 75 citations in the last 25 years. More significantly, the 44% of the citations occurred in the last decade. Furthermore, to the authors’ knowledge, the expressions developed are implemented in design codes used by the aerospace and aeronautical companies. The determination of the elastic energy stored in the ply requires the computation of its compliance, denoted as ij in Ref. 1. Equation 3 in the commented paper is written as:

Specimen geometry and specimen size dependence of the \({\mathcal {R}}\)-curve and the size effect law from a cohesive model point of view

An analytic model has been developed for a Compact Tension specimen subjected to a controlled displacement and corresponding load within a cohesive model framework. The model is able to capture the material response while the Fracture Process Zone is being developed, obtaining the evolution of multiple variables such as the crack opening and the cohesive stresses, for an arbitrary Cohesive Law shape. The crack growth prediction based on the R\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

Low-velocity impact damage on dispersed stacking sequence laminates. Part II: Numerical simulations

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Effects of ply clustering in laminated composite plates under low-velocity impact loading

\end{document}-curve and the nominal strength prediction based on Bažant’s Size Effect Law have been implemented using the output variables available from the proposed analytic model. The minimum specimen size has been found in order to properly apply R\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

Damage resistance and damage tolerance of dispersed CFRP laminates: Effect of ply clustering

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