The need for high performance-to-weight ratio structures coming from the most advanced engineering fields is the main driver of the increasing usage of composite materials for critical applications. In order to design light and safe systems on time to meet the market requirements, accurate and effective analysis tools are necessary. NASA has recently developed LaRC02, a set of first-ply-failure criteria for composites which have been shown to be accurate and physically consistent. The LaRC02 formulation seemed to be particularly well suited for design purposes, due to its optimal trade-off between accuracy, material characterization requirements, computational effort and ease of results interpretation.
This paper presents a step forward in the formulation for incompressible fluid flow analysis using the Finite Element Method (FEM) for naval hydrodynamics problems. The necessary stabilization of convective character and incompressibility restriction are introduced via the finite increment calculus (FIC) technique. A second order implicit monolithic method, based on projection schemes, to solve Navier Stokes equations is also presented. The fluid flow equations are written in an Arbitrary Lagrangian Eulerian way, useful to treat fluid-structure interaction problems, both using the standard ALE approach or the fully Lagrangian one. Finally, some examples of application of this formulation in practical naval problems are presented.
La riduzione a superelemento con il metodo di Craig-Bampton è una procedura utilizzata in vari settori dell’ingegneria, quali l’automobilistico e l’aeronautico, nel contesto di simulazioni in dinamica strutturale su modelli di calcolo particolarmente complessi. Nella prima parte del presente lavoro vengono affrontati gli aspetti teorici legati alla riduzione di Craig-Bampton di un modello ad elementi finiti. Successivamente viene descritto il FEMtools Application Framework, l’ambiente di programmazione avanzata per la gestione e la manipolazione di dati dinamici ottenuti sia tramite analisi FEM che attraverso test sperimentali, qui utilizzato per lo sviluppo dell’algoritmo di Craig-Bampton. La procedura viene applicata al modello ad elementi finiti di un componente automobilistico e viene mostrato il grado di accuratezza fornito dalla tecnica di condensazione implementata. I risultati ottenuti dal modello ridotto vengono quindi correlati e validati con quelli del modello completo.
A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C1 shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin’s criterion, and Christensen’s criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure.
