Executive Summary : | Sandwich structures constitute very important structural components in many engineering applications, specifically where weight saving is an important design requirement, such as in the aerospace, naval, and automobile industries. Sandwich is typically a structural configuration consisting of two skins separated by a lightweight core. As a consequence of the skins being separated by a distance, the bending rigidity of the sandwich structure becomes much higher than the conventional monolithic panel. It can be noted that most of the conventional core materials in sandwich structures have positive Poisson's ratios. On the contrary, auxetic cores exhibit the property of negative Poisson's ratio (NPR). In fact, these auxetic core structures can transform the design of the cores in the sandwich panel due to their enormous capability of energy absorption. Unlike conventional materials, auxetic materials contract orthogonally due to the NPR property when subjected to a compressive force which results in the densification of material near the application of the load. Thereby, these structures have the capacity to withstand more loads and have higher energy absorption capacity. In this regard, the basic idea of the present research proposal is to study the behavior of composite sandwich plate structures by considering the core body as an auxetic material. The main focus of the project would be the performance improvement of the auxetic-based sandwich under impact loads. The underwater impact behavior of the sandwich structures will be also studied as it is important in the field of marine engineering. To the authors' best knowledge, no work has been presented in the literature which considers the application of auxetic-based sandwich plates subjected to underwater impact loads. Note that the shape of the auxetic core has an enormous influence on the performance of the sandwich structures. To arrive at the best design of the auxetic core, we plan to implement a machine learning (ML) based optimization strategy. In the first step, parametric models of the cores will be developed. For each of these parametric models, the performance analysis of the sandwich structure will be carried out numerically using finite element (FE) analysis. These FE-simulated data will be used for the ML-based optimization study. Different innovative designs of auxetic cores will be considered which can be fabricated using 3D printing technologies. Finally, experimental studies will be performed to validate the efficacy of the adopted optimization strategy. Therefore, the novelty of the present proposal lies in the implementation of an ML-based optimization strategy in determining the optimal design of the auxetic core for maximizing the impact behavior of the sandwich structures and subsequent experimental validation of the optimal configurations by developing suitable verification experiments. |