Optimizing Lattices for Sports: Effects of Vapor Polishing on Energy Absorption and Comfort

This study investigates the effects of chemical vapor polishing (VP) on the mechanical behavior of Face Centered Cubic (FCC) and Kelvin (KE) lattice structures fabricated using Laser Powder Bed Fusion (LPBF) of two different thermoplastic polyurethanes (TPU). These structures are designated for personal protective equipment (PPE) in contact sports. It is known that significant surface roughness inherent to the LPBF process can compromise the mechanical performance of PPE. VP is intended to provide the best post-processing solution to smooth the as-built surface with the objective of improving both the aesthetics and the mechanical properties of printed structures.

Through quasi-static and dynamic testing, this research examines how vapor polishing affects the stiffness and the energy absorption capacity of FCC and KE lattice structures at different pad thicknesses. The study further explores the optimization of lattice geometries by modifying the density and cell size, accounting for the interplay between surface modification and structural integrity. A first attempt in linking static properties to the dynamic response of the printed structures is carried out. Experimental results demonstrate that VP significantly modifies the impact resistance of TPU lattices, without affecting their comfort-related characteristics. These findings have direct implications on the development of safer and more comfortable PPE for high-impact contact sports.