Size effects governing damage resistance of architected PMMA

Abstract

This study investigates the effect of feature size, volume fraction, and sample size on the damage resistance of an architected brittle Poly(methylmethacrylate) (PMMA) polymer. Holes with varying diameters and number of layers were micro-machined in samples of different sizes in PMMA throughout the beam and tested under bending in the presence of a pre-crack. The initiation and total work of fracture (WOF) are determined for different feature sizes of holes. In the case of a single hole feature ahead of the crack tip, overall fracture resistance increased with increasing diameter of the hole, while no effect was seen on the initiation fracture resistance. This was reflected as increased damage resistance in the fully architected specimen with increasing diameter of holes as well as with increasing number of layers of the features (and hence their volume fraction). However, an increase in sample size led to catastrophic failure and a decrease in damage resistance. These effects are quantifiably explained in terms of crack driving force calculations done through finite element modelling.