An analytical and experimental investigation of sandwich composites subjected to low-velocity impact

Abstract

This study involves an experimental and analytical investigation of low-velocity impact phenomenon in sandwich composite structures. The analytical solution of a three-dimensional finite-geometry multi-layer specially orthotropic panel subjected to static and transient transverse loading cases is presented. The governing equations of the static and dynamic formulations are derived from Reissner's functional and solved by enforcing the continuity of traction and displacement components between adjacent layers. For the dynamic loading case, the governing equations are solved by applying Fourier or Laplace transformation in time. Additionally, the static solution is extended to solve the contact problem between the sandwich laminate and a rigid sphere. An iterative method is employed to determine the sphere's unknown contact area and pressure distribution. A failure criterion is then applied to the sandwich laminate's stress and strain field to predict impact damage. The analytical accuracy of the present study is verified through comparisons with finite element models, other analyses, and through experimentation. Low-velocity impact tests were conducted to characterize the type and extent of the damage observed in a variety of sandwich configurations with graphite/epoxy face sheets and foam or honeycomb cores. Correlation of the residual indentation and cross-sectional views of the impacted specimens provides a criterion for the extent of damage. Quasi-static indentation tests are also performed and show excellent agreement when compared with the analytical predictions. Finally, piezoelectric polyvinylidene fluoride (PVF2) film sensors are found to be effective in detecting low-velocity impact.