Indentation Fracture Mechanics for Toughness Assessment of PMMA/SiO 2 Nanocomposites

Based on the results from agglomerate‐free PMMA nanocomposites with 10 and 20 wt.‐% spherical SiO 2 nanoparticles, it has been shown that indentation fracture mechanics is a straightforward, powerful, cost‐effective and time‐effective tool for analyzing the fracture resistance of novel polymer materials, such as brittle nanostructured polymer‐ceramic hybrids. In contrast to pure PMMA, the R‐curve effect, i.e., the enhancement in crack resistance as a function of crack size, was not observed in the nanocomposites investigated. Fracture toughness was found to depend on the SiO 2 nanoparticle content, and the maximum value was observed at 10 wt.‐%. A significant reduction in fracture toughness occurred at 20 wt.‐% SiO 2 nanoparticles, which is associated with a percolation of the bound layers (interfacial layers) around the SiO 2 particles. From DSC data, the thickness of the interfacial polymer layer was estimated to be about 9 nm. Hardness, elastic modulus and fracture toughness of PMMA/SiO 2 composites as a function of nanoparticle fraction. magnified image Hardness, elastic modulus and fracture toughness of PMMA/SiO 2 composites as a function of nanoparticle fraction.