Archive Toulouse Archive Ouverte ( OATAO )

Even if the mechanical performances of composite materials give new perspectives for the aircraft and space design, the variability of their behavior, linked to the presence of initial microscopic defects or led in service, constitute however a still important brake in their development. As regards particularly the response to fatigue loads or ageing, the behavior of these materials is affected by several sources of uncertainties, notably on the nature of the physical mechanisms of degradation, which are translated by a strong dispersion in life time. In aerospace industry, low energy impact phenomenon is not well known concerning composite materials and composite structures. Many manufacturers use important safety factors to design structures. The aim of this work is to define the most predominant parameters which permit a good response of damage using experiences plans. The differences of these parameters by using Resin Transfer Molding (RTM) or Liquid Resin Infusion (LRI) process than prepreg one is also studied in this work. Introduction Nowadays, in aerospace industry, composite materials are used but their behavior is not well known. During their life in aerostructure, these materials are subjected to many different loads as maintainability impacts, hail, birds, and others. These loads can be classified according to their energies or strain speed, as shown on figure 1 and 2. Under dynamics loads or medium loads, the structure is affected and many damages are visible. In this case, this structure is automatically replaced. In case of quasi-static loads, the surface of the structure is few affected but damage can occur in it. The detailed inspection (DET) and General Visual Inspection (GVI) inspection do not reveal systematically these defects. One of the main problems is to know how the structure responds on impact in terms of damage produced inside and residual strength after impact. The knowledge of the entire phenomenon which acts in this response is a good way to control it. First, we have to define these phenomena and all the parameters linked to them. Then, we have to understand how they act to choose the best configuration. To understand all the effects, we have to make experiments using a special test apparatus. For the low energy impacts, a drop weight machine is used, and for upper energies, a gas gun is used. Furthermore, we decided to know how the sample, impacted or not impacted, behave under fatigue loads. The aim is to understand how the damage will initiate for no impacted samples and how it will propagate for others.