The aim of this work is to control the state of the structure of a composite material after low velocity impact. In fact, the impact damage is one of the most critical flaws that can reduce the intrinsic characteristics of a composite structure drastically. The diagnostic of composite laminates in this case will be very difficult, because during impact several modes of failure appear (matrix carking, delamination and fiber breakage), and it can be often not visible on the surface. For this reason it will be necessary to use the non-destructive techniques (NDT) of control to make sure of the state of the material without damaging it. This paper presents some methods of control to detect and characterize defects appeared after low velocity impact on a hybrid composite plate of epoxy resin reinforced with carbon fiber. The methods used in this work are considered among the most used in the control of composite material. Indeed, each technique has advantages and disadvantages. Therefore, the use of several control techniques ensures the diagnosis, so we talk about the complementarity of techniques. For this reason, the following methodology is followed. First of all, a quick and general control is performed of the whole specimen to designate the damaged area using the infrared technique. After that, the ultrasonic technique (phazed array) is performed in the previously localized area for finer results. Finally, for validating the precision of the results obtained by the ultrasonic technique a metallurgy study is used. The methodology followed in this work will allow us a fast and precise control.

The numerical prediction of composite material damages remains a strong tool that develops day by day. Several numerical models have been developed in the literature for simulating the progressive damage. In this paper the most used low velocity impacts numerical methods available in the literature are reviewed. First the various damage mechanisms of laminated composite materials are described. Then, different damages modelling are presented, from the onset to the final rupture. Finally, some results of the finite element model (FEM) are reported.

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