Shear response of pyramidal lattice sandwich cores with tailored I-beam struts

This research paper investigates the shear response of pyramidal lattice (PL) sandwich cores, where square-shaped strut cross-sections are geometrically modified into I-beam-like configurations. These PL sandwich cores are 3D printed via Digital Light Processing (DLP), and their shear performance is experimentally and numerically evaluated for various I-beam-like strut cross-sections. The measurements reveal that PL structures with I-beam struts outperform conventional square-beam structures in terms of shear modulus (+ 13%), shear strength (+ 11%) and gravimetric energy (+ 24%). These improvements are attributed to the larger bending stiffness of the I-beam struts, enhancing their capacity to resist shear loads. A numerical parametric study further examines how various architectural parameters of the tailored PL structure affect the shear performance, showing significant enhancements in shear modulus (6-23%), shear strength (3-16%), and gravimetric energy (8-25%) compared to square-strut PL structures of equal weight. Additionally, a simple analytical model is developed to estimate the strength enhancements, demonstrating a reasonable agreement with the numerical predictions and measurements. Notably, a reduction of the internal strut angle to 30° is found to enhance the shear strength of the PL structure in both shearing directions, making this arrangement an excellent choice for sandwich designs where core shear failure is a limiting factor.