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.
The thermal power plants are globally criticized for generating large amount of solid wastes often with a potential environmental impact. The main objective of this study is characterized the CCRs (Coal Combustion Residues) produced by the thermal power plant in the East region of Morocco (Jerada city). On other hand, in order to use this CCRs (fly ash and bottom ash) effectively, it is necessary to study the raw material of which they are trained in all their aspects and to check their behavior in the various employment possibilities. For this purpose, mechanical compressive test on 10x10x10 cm 3 of mortar specimens and chemical test of X-ray on CCRs are performed. We did work on the use of CCRs as an addition in Portland cement. Firstly, compressive tests and chemical requirements were used to evaluate the pozzolanic activity index according to ASTM C618 which is about 89,75%. Indeed, the results of an experimental plan, on compressive strength of the new by -product (10% CCRs and 90% cement), gave a good response of our plan, it's about 24,20 MPa. Secondly, we have added this new by-product with the clay to produce the fired compressed bricks according to a new experimental plan, where we found that the most response of the compressive strength equal to 3,12 MPa, in which a minimum volume of water of 581 cm 3 and a minimum quantity of clay of 50% (by total mass of 1kg), were used. In order to valorize these residues, our results show a good correlation with the ASTM standard and we can use this by-products in bricks manufacture.
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