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The process of repair of structures by using bonded composite patch is an effective and economical method to increase the service life of damaged structures. In this study, the finite element method is used to analyze the behavior of a crack repaired by a circular patch by computing the stress intensity factor (SIF) at the crack tip with and without the disbond. The obtained results show that the boron/epoxy 0° fiber perpendicular to the crack, considerably influences the reduction of the SIF with regard to the boron/epoxy 0° fiber oriented in the parallel direction to the crack. Moreover, the increase of the disbond area amplifies the SIF of the repaired crack and the rate of this increase strongly depends on the disbond area. When the disbond is significant between the patch and the plate, it reduces the repair effectiveness and the crack growth under loading becomes important. The disbond growth results in patch separation.

To study the behavior of composite materials to erosive wear, we have carried out bench tests simulating the erosive wear according to ASTM D 673 standard. The principle consists in impacting composite specimens by an abrasive water jet containing sand particles, taking into account several parameters affecting the erosive wear. The first material consisting of thermoplastic matrix reinforced with E-glass fiber and the second with 8H Satin carbon fiber where as the thermoset matrix material was reinforced with 2/2 Twill glass fiber. Influential parameters such as composite hardness, abrasive particle size, speed, and impact angle were taken into account. During the experimental study, only the most influential parameters have been taken into account such as: hardness of the composite materials, abrasive size, abrasive particle speed, and angle of impact. Applying Design of experiment (DOE) strategy with experimental planning, a mathematical model was obtained describing the wear of these materials as a function of the most influential parameters led to the following results: Wear is maximum when the angle of incidence of the jet is normal to the specimen surfaces; wear is minimum when the angle of incidence of the jet is (α = 30°); mass loss is proportional to abrasive particle size and speed and inversely proportional to composite hardness.

This article addresses the experimental characterization of the abrasive wear of two woven fabric carbon fiber and glass fiber composite materials, taking into account the effect of moisture absorption. The composite materials were tested to three level loadings and two sliding speeds. The abrasive used was dry sand of size 0.6 mm, and the time of wear testing was 10 min. In order to study the effects of moisture on wear behavior, another series of samples was introduced into the tank of water during a period of 40 days at ambient temperature. The planning design experimentation approach was applied to obtain a mathematical model taking into account the influencing parameters on the wear behavior of the composites. The wear results have shown that for a higher turn speed and a load, the loss of matter increases. In the case of samples exposed to water absorption, the wear rate increases more than the dry samples. The micrographs of the surface of the samples tested were taken in order to characterize the wear mechanism.