Core materials can be added in between layers of cloth in a laminate to form a sandwich structure with increased stiffness over the original laminate while only marginally increasing the weight. Core materials increase the stiffness of a laminate by placing more material farther away from the neutral plane in the laminate allowing the material to more efficiently support loads and resist deflection. This is similar to how an I-beam is stiffer than a section of flat plate of the same width and weight. The core material acts like the shear web in an I-beam while the composite skin on each side of the core acts like the flanges of an I-beam. Core materials must have sufficient shear strength and compressive strength to be suitable for use in aerospace composite sandwich structures. In general, the higher the core density, the stronger it will be both in shear and compression.