UC Irvine

The Effect of Manufacturing Defects on Compressive Strength of Polymeric Lattices Fabricated via Fused Deposition Modeling

By

Bianca Lis Rossi Dias Endo

Master of Science in Mechanical and Aerospace Engineering

University of California, Irvine, 2017

Professor Lorenzo Valdevit, Chair

Additive manufacturing is an emerging fabrication technology that has been incorporated into diverse industry segments, from aerospace to biomedical engineering. One of its key strengths is the ability to easily fabricate architected materials (e.g., lattices) with virtually any topology and over a wide range of dimensions. As the smallest dimension in the unit cell approaches the resolution of the equipment, though, significant defects get introduced, which have the potential to strongly affect the mechanical and functional properties of the architected material. Here, the effect of manufacturing defects on the compressive strength of solid lattices produced by Fused Deposition Modeling (FDM) in polycarbonate is studied. The choice of this printing technology was dictated by the commercial penetration of FDM printers in most industrial sectors and the ready availability of FDM machines; polycarbonate was chosen as it is one of the most commonly used structural polymers for FDM.

A state-of-the-art commercially available 3D printer was used to fabricate a large batch of lattice samples, varying topology, bar diameter and aspect ratio. All samples were CT scanned to quantify external and internal defects, and subsequently mechanically tested in compression. Finite elements models were built for the CT-derived lattices and the results compared with the lattice compression experiments. Once the numerical models were validated, the defect sensitivity of these lattices was quantified by comparing the FE strength predictions for nominally perfect and CT-derived lattices. This defect sensitivity was correlated to geometrical dimensions, failure mechanism and lattice topology.