Experimental and numerical studies of impact behaviour of GRP reinforced composite sandwich materials

Abstract

The main focus of this study is on two parts: a testing part and a numerical simulation part. Three different tests are performed: four point bending testing, static deflection and drop weight impact tests.

The four point bending test is a fast and simple test where a simply supported sandwich beam is loaded at two points. Such tests allow material properties in the facings and core to be found along with the ultimate stresses in the materials. In the static deflection test, a sandwich plate lying on a quadratic frame is loaded at the centre, and corresponding centre deflections and the applied loads are logged. The data retrieved from this test are then compared with numerical, static loading simulations. In the drop weight tests, sandwich plates are impacted with a projectile. The acceleration of the projectile is logged during the impact. These data provide important plate response characteristics during impact. To provide strain information during the tests, all test specimens are equipped with strain gauges on the facings.

The static deflection test is simulated with both an analytical model and a finite element model using the ANSYS program. Various ANSYS elements have been used, and their restrictions when modelling sandwiches have been investigated. Good agreement between test and simulations have been found. Also, ANSYS has a shell element which uses the same assumptions as in the analytical model. Simulations with these two models show the very same centre deflection.

The drop weight impact is simulated with the AUTODYN program. From the acceleration data found in the test, kinetic energy of and deflection due to the projectile were calculated and are compared with the simulations. The AUTODYN software manages to simulate the impacts very accurately.