Delaminations buckling and growth phenomena in stiffened composite panels under compression. Part II: a numerical study

Abstract

A numerical study has been carried out on stiffened composite panels under compression, focusing on the delamination-related phenomena. A robust numerical finite elements model has been introduced to simulate the compression behavior of the panel, including the delamination buckling and growth, and to provide reasonable predictions of the strain measurements in the delaminated area. The robustness of the novel approach, which adopts an improved (mesh and time step independent) virtual crack closure technique for the simulation of the delamination propagation, has been demonstrated by comparisons with standard commercial FEM (Finite Element Method) codes results and experimental data. Indeed, the numerical results, in terms of strains and delamination size as a function of the applied load, have been compared to experimental strain gauges readings, embedded optical fibers measurements, and thermography images of the delamination taken at different load steps. Actually, the performed numerical activity contributed to improve the knowledge on delamination-related phenomena in stiffened composite panels, focusing on delamination growth initiation and delamination growth stability, by providing reasonable justifications and interpretations of experimental strain measurements and thermography images.

Cross-Influence between Intra-Laminar Damages and Fibre Bridging at the Skin–Stringer Interface in Stiffened Composite Panels under Compression

“…Using the Ansys Parametric Design Languages (APDL), a new numerical methodology has been implemented in the Ansys ® Finite Element Model (FEM) simulation software. SMXB is described in detail in [12,13]. It is the result of an improved combination of the Virtual Crack Closure Technique (VCCT) and the Fail release (FR) method.…”

“…It is the result of an improved combination of the Virtual Crack Closure Technique (VCCT) and the Fail release (FR) method. In particular, the proposed methodology is able to overcome the main limitations of the standard VCCT-FR approaches [12] in terms of dependence on mesh and load-step size. The potential area of interest with the delamination growth is simulated by means of contact elements and fail-release conditions, which can be deactivated where the propagation criterion is fulfilled.…”

“…Tabiei and Zhang [11] describe and compare the advantages and the drawbacks of the VCCT and the CZM. In [12], the weaknesses in terms of mesh and time-step size dependence of the classical VCCT-based approaches are described. A robust numerical tool for the assessment of inter-laminar damages in composite structures, also based on the VCCT, but able to overcome mesh and time step dependence issues, has been proposed.…”

On the use of global–local kinematic coupling approaches for delamination growth simulation in stiffened composite panels

“…Nevertheless, in the models with a more refined local mesh (LMD2), a slightly faster delamination grow is appreciated. The mesh dependency of the VCCT technique is a well-known trouble, which may be solved by tuning the mesh parameters with respect to an experimental DCB test, or applying mesh and time step independent approaches [22][23][24][25][26] which is not the scope of the investigated application.…”

Numerical Analysis of the Influences of Geometrical Deviation on Delamination in Composite Laminates around the Countersunk Hole

“…Finite element method (FEM) is widely employed to predict the mechanical behavior of composite structures with delamination by means of the virtual crack closure technique (VCCT) [2][3][4][5] and cohesive zone model (CZM) [6][7][8]. The VCCT is based on the assumption of the energy release rate, an initial defect or crack length, and complex mesh moving technique, while CZM can predict both the onset and the non-self-similar propagation of delamination.…”