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This paper deals with low velocity and medium velocity impacts on thin carbon/epoxy hybrid laminates made of unidirectional plies and woven fabric layers. Drop weight and gas gun impact tests were performed to compare the damage mechanisms of thin hybrid laminates with those of woven laminates of equivalent stiffness and mass. The results show that hybrid laminates present a better impact behaviour in terms of post impact damage extent. These tests were then modeled using a semi-continuous approach. The numerical results well correlate the experiments.

RésuméLe présent article propose une étude de l'impact de structures similaires à des tronçons de pales d'hélicoptère. Ces structures composites complexes, fabriquées au laboratoire sont impactées par une bille en acier de 125 g à des vitesses d'impact variant de 30 à 130 m/s. Les essais sont enregistrés par une caméra rapide qui permet une acquisition de 120000 images/seconde. Cela a permis de mettre en évidence la cinématique de l'impact et de définir la chronologie des différents mécanismes d'endommagements. Un travail de modélisation est aussi présenté. Différentes stratégies de modélisation EF, à l'échelle macroscopique, permettent ainsi de modéliser ces phénomènes avec des densités de maillage qui ne sont pas pénalisantes lors d'un calcul sur une structure réelle. AbstractThis article presents a study of damage in structures similar to sections of helicopter blades subjected to an impact. These complex composite structures manufactured in the laboratory were impacted by a steel ball of 125 g at impact speeds ranging from 30 to 130 m / s. The tests are recorded by a camera that allows acquisitions of 120,000 fps. This permitted to highlight the kinematics of the impact and to define the sequence of damage's mechanisms. An FE model is also presented. It allows modeling the experimentally observed damage. The mesh density is low and can be used for a calculation on a real structure Mots Clés : IMPACT, COMPOSITE, PALES, MEF

This article deals with the development of a finite element model for the prediction of low velocity impact damage within unidirectional composite laminates. This model is based on analysis of the impact damage observed experimentally. The modelling scale is that of the bundle of fibers of the unidirectional ply. These bundles are represented with 1D rod elements. The matrix is modeled with 2D damageable shell elements. The laminate is the built using cohesive elements. The strategy is validated by a comparison with low velocity drop weight impact tests. Several experimental parameters are varied : the materials (T700/M21 and HTA7/913), the thickness (1.44mm and 2.4mm), the stacking sequence and the impact velocity (2m.s −1 and 3m.s −1). The calculated load-displacement curves and the damage extent correlate well with experimental results.

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