Experimental and numerical studies of curved structures under impact loading

Abstract

There are lots of leading edge shapes that we can observe on the aircrafts nowadays. Each design has its own effects on the structural strength and aerodynamic point of view. Both structural and aerodynamic points of view are important in order to achieve design optimization. The comprehension of impact on a curved panel such as wing leading edge by rigid projectile with different parameters of structure such as the curvature radius and the thickness of panel is interesting and important to be established for the design of curved panel subjected to impact loading. The leading edge model is to have improvement in energy absorption capability which transfers lesser reaction forces to the supporting structures. This research focuses on one bay of leading edge impacted by rigid sphere projectile. Experimentally, three different shapes of aluminum and carbon-fiber-epoxy-specimen which are flat plate, semicircular and semi ellipse having different thickness were prepared and impacted by rigid sphere projectile. Experimental results show the trend of specific energy absorption capability of structures in function of the radius, thickness of panel and stacking sequences (for carbon-fiber-epoxy specimens). For each different specimen, observed that the specimens with the highest thicknesses have the highest value of energy absorption because for specimen having the higher thicknesses, more energy is required to deform the specimen .The specific energy absorption also increases with the thickness. Besides that, curvature radius also has effect in amount of absorbed energy by the specimens. Specimens having higher radius of curvature require higher energy in order to deform them. From experimental observation, shows that the failure of structure subjected to impact loading can be distinguished in two types of failure; the projectile went through the structure and large displacement of curved panel. The two failure criteria are used later on to determine the energy absorption capability using Finite Element Analysis. In this research simulation results for both metallic (Aluminum) specimens and composite (carbon-fiber-epoxy) specimens were successfully validated by the experimental results. Thus, LS-DYNA is suitable to be used as a simulation tool in designing the leading edge of wing with the best radius curvature, stacking sequences and thickness of wing edge panel to absorb a specific magnitude of impact energy.