IMPACT TESTING ON COMPOSITES LAMINATES AND SANDWICH PANELS

The purpose of this work was the evaluation of the behavior of fiber-r einforced composites and sandwich panels for aeronautical applications under impact. Experimental tests were performed on several specimen c onfigurations, based on different quasi-isotropic lay-up and materials such CFRP, CFRTP and a syntactic foam as the core of sandwich panels. Considering the high specific mechanics characteristics of such a foa m and its cocurability with the facesheet material, symmetric and non- symmetric sandwich configurations have been tested. The study has poin ted out the advantages for aeronautic constructions of different mater ials and the influence of the core position along the panel thickness. The impact tests were performed with a falling weight machine, which allowed the most important dynamic and kinetic parameters, such as the contact force, impactor velocity and displacement and perforation ene rgy to be measured. Delamination areas of each specimen were also meas ured using N.D.I. reflection ultrasonic techniques. In order to determ ine the residual strength, Compression After Impact tests were perform ed on specimens that have an indentation of approximately 0.3-0.4 mm. A numerical simulation was performed using a transient dynamic Finite Element Analysis. The main goal of this analysis was to define the con trolling factors for high velocity impact simulation, such as the incr ease of geometric non-linearity and the delamination effects. Moreover , the delamination areas and positions were determined taking in accou nt the different boundary conditions. The study have pointed out the b ehavior of thermoset, thermoplastic and unsymmetric sandwich panels.