Short fiber reinforced polypropylene usually used for the manufacturing of automotive exterior parts such as bumpers and hatch due to its low density allowing high fiber content filling and low water absorption. For such use, glass fiber reinforced polypropylene (PPGF40) must exhibit great structural durability especially against fatigue and thermal fatigue loading. The investigation of the fatigue properties and the damage mechanisms of this class of material is therefore necessary in order to propose models and criterion capable to predict the mechanical response of structures.