Emilio Vitale

Analysis of fatigue delamination growth in carboresin specimens with central hole

Abstract The paper illustrates the damage evolution observed in carboresin specimens with a central hole subjected to cyclic tensile loading. Damage monitoring was conducted via a purpose-designed automatic Ultrasonic (US) scanning apparatus, whose responses were qualified by means of micrographical observations. Observed delamination onset and growth are discussed with reference to the results of three-dimensional finite element analyses. In particular, a model simulating the presence of delaminations and their partial closure through non-linear contact calculations is employed in order to evaluate the distribution of the energy release rates along the delamination boundaries. The results indicate that the observed evolution of delamination may be explained by numerical models, provided that closure effects are taken into account.

Evaluation of the elastic stress distribution ahead of a crack by weight functions

Abstract A method is illustrated for the evaluation of the stress distribution ahead of a crack under Mode I loading. The method is based on the knowledge of the weight function, whose general properties are employed to derive an integral equation. The solution of this integral equation, having the stress distribution as the unknown function, is reached through a numerical technique. Comparison with theoretical solutions shows that the proposed method allows an accurate reproduction of the stress distribution for every distance from the crack tip. The possibilities offered by the use of the method in combination with local fracture criteria are discussed.

Effect of Stacking Sequence on the Fatigue Delamination Growth in Carboresin Specimens with Central Hole

This paper illustrates the general organization and the preliminary results of a comprehensive research program, aimed at the characterization of fatigue delamination growth in laminated carboresin composites. The study included two types of test, conducted to determine both the basic material properties (under single fracture mode conditions) and the behavior of a simple structural component, i.e. a laminated plate specimen with a central hole. Results obtained in the two types of test are presented and discussed, with reference to the problem of predicting the behavior of actual laminated components on the basis of the results of commonly employed laboratory tests.