Mostapha Tarfaoui

Mechanical behavior of carbon nanotubes-based polymer composites under impact tests:

This study was focused on the effect of carbon nanotubes on the impact resistance and damage evolution in laminate carbon nanotubes/epoxy composites under an impact loading. The composite panels were made from carbon fibers and carbon nanotubes randomly distributed into epoxy resin. The amount of carbon nanotubes dispersion was varied up to 4% by weight. Taylor impact tests were carried out to obtain the impact response of specimens with dimensions of 70×70×4u2009mm3. A projectile manufactured from a high strength and hardened steel with a diameter of 20u2009mm and 1.5u2009kg of mass was launched by a compressed gas gun within the velocity of 3u2009m/s, 7u2009m/s and 12u2009m/s. For the experimental test, three velocity levels were used: 3u2009m/s for the elastic deformation, 7u2009m/s for the penetration of the impactor and 12u2009m/s for the perforation of panels. Deformation histories and damage modes in specimens were recorded during the impact test using a high-speed camera. Processing of carbon nanotubes dispersed in laminates, testing, damage, and key findings is reported. It is observed that the impact resistance of laminates reinforced with a random distribution of carbon nanotubes increases up to 15.6% at high-strain rate compared with that of 0% of carbon nanotubes. It is also observed that the resistance to damage initiation and evolution increases with the addition of carbon nanotubes concentration.

Thermomechanical behavior of adhesively bonded joints under out-of-plane dynamic compression loading at high strain rate

In this study, a new experimental approach in which the deformation, the damage kinetic, and the temperature are measured simultaneously during a high strain rate on adhesively bonded composite joints. Especially, our goal is to quantify the amount heat dissipation during impact and to identify the mechanisms that induce this dissipation. Out of plane dynamic compression tests were conducted on assembled specimens over a range of strain rate from 372u2009s−1 to 1030u2009s−1 using the Split hopkinson Pressure Bars technique. The specimen surface temperatures were monitored using an infrared camera. The increase in the strain rate has a dramatic effect on the stress–strain behavior producing a significant heat dissipation in the material. The infrared monitoring provides the spatial distribution of temperature that increase near the adhesive/adherent interfaces of the specimen. The observed temperature increase profiles clearly show that the stress concentration appears in the adhesive area and provide valuable information regarding the damage mechanisms and their role in the heat dissipation during dynamic loading conditions. The dependence of these results on strain rate indicates that there exists a correlation between the thermo-mechanical behavior and the strain rate effect, which might be useful when developping damage models taking into account the energy balance for adhesively bonded joints under impact loading conditions.