Abstract Lightweight structural cores were first used in aircraft in the 1940s to reduce weight and increase payload and flight distance. This article focuses on the three primary types of lightweight structural cores: honeycomb, balsa, and foam. In many applications, lightweight structural cores are used in sandwich panels. The article also presents an overview of various techniques available for modeling sandwich structures, providing the basic concept of a sandwich panel, where the facings carry the bending loads, and the honeycomb core carries the shear loads.