J.-F. Ferrero

Modeling of Impacts on Sandwich Structures

In aeronautics, passenger safety and reliability of structures are essential aspects. Helicopter blades are particularly sensitive to impact solicitations but modeling these phenomena is still difficult and experimental tests often replace the prediction. This study will be focused on the modeling of an impact on the skin of the blade. It is equivalent in a first approach to an impact on a sandwich panel made up with a foam core and a thin composite skin. The objective is to develop a representative model of the damage kinetics adapted to the modeling of the complete structure. Thus, an F.E. explicit model has been developed. It relies on the development of a multiscale approach. Damage is modeled at an intermediate scale (mesoscopic) in order to reproduce the damage kinetics observed at a microscopic scale. Numerical results obtained are correct and reproduce the behavior of the panel for a static test of indentation and low velocity impact test.

Experimental and Numerical Study of Normal and Oblique Impacts on Helicopter Blades

This study is concerned with the understanding, analysis, and prediction of major damage mechanisms in helicopter blade components subjected to a high velocity impact load. Two types of impact are studied: the frontal impact, which corresponds to a normal impact on the leading edge, and the oblique impact on the skin of the lower surface of the blade.

Study of medium velocity impacts on the lower surface of helicopter blades

This chapter deals with the study of medium velocity impacts on the lower surface of helicopter blades. The blades are complex composite structures that can be impacted in flight by external soft or hard objects. Due to the inclination of the blade in flight, impacts generally occur in the lower surface. In that area, the skin is built with two or three layers of carbon/epoxy and glass/epoxy woven composite and stabilized with a polymeric foam. In this chapter a strategy for the modeling of impacts on the lower surface of the blade is presented. A specific finite element that can reproduce the damage chronology observed experimentally is developed. Numerical and experimental results are compared. A good correlation is found.