Dynamic response of sandwich structures to impulsive loads

This article considers the dynamic response of sandwich structures to various pulses. During the early phase, waves propagating through the thickness of the sandwich can cause damage to the core. Once the overall bending deformation is established, a different type of response is observed. The challenge in the analysis is to capture both the early phase and the long term response. It is shown that, because of the kinematic assumptions made in their development, plate and shell theories cannot adequately capture the early phase of the response. Here the dynamic behavior of sandwich structures is investigated in details. Two- and three-dimensional finite element models are used to assess the applicability of beam, plate, and shell theories, and determine the response to various pulses. For beams and plates, only a few modes contribute to the overall response but for shells, curvature effects can cause many modes to participate. It is shown that shell theories predict the overall response adequately and that for the early phase of the deformation the method of characteristics and a simple model suitable for design calculations is developed. Previous investigators have considered examples in which the duration of the loading was large compared to the period of the first mode. In practical applications, the reverse is likely to occur and then a different type of response is observed. In that the response depends on the pressure impulse.