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.

In the present paper, advanced numerical methodologies have been adopted to investigate the influence of impact angle on the crashworthiness behavior of a composite fuselage section. The analyzed fuselage section, made of unidirectional fiber-reinforced material, woven fabric material, and aluminum material, is representative of a regional aircraft fuselage. Two different angles of impact with rigid ground have been investigated and reported: Perpendicularly to the ground and with a pitch angle of 3 degrees with respect to the ground. The adopted numerical models have been preliminarily validated with experimental data from a drop test on a full-scale fuselage section, in terms of deformations and failure location and progression. The correlation between the numerical model and the experimental test has enabled evaluation of the effect of the impact angle on the deformation and damage in the sub-cargo floor area.

Composite laminates are characterized by high mechanical in-plane properties and poor out-of-plane characteristics. This issue becomes even more relevant when dealing with impact phenomena occurring in the transverse direction. In aeronautics, Low Velocity Impacts (LVIs) may occur during the service life of the aircraft. LVI may produce damage inside the laminate, which are not easily detectable and can seriously degrade the mechanical properties of the structure. In this paper, a numerical-experimental investigation is carried out, in order to study the mechanical behavior of rectangular laminated specimens subjected to low velocity impacts. The numerical model that best represents the impact phenomenon has been chosen by numerical–analytical investigations. A user defined material model (VUMAT) has been developed in Abaqus/Explicit environment to simulate the composite intra-laminar damage behavior in solid elements. The analyses results were compared to experimental test data on a laminated specimen, performed according to ASTM D7136 standard, in order to verify the robustness of the adopted numerical model and the influence of modeling parameters on the accuracy of numerical results.