Fabrication, characterization, and dynamic behavior of polyester/TiO2 nanocomposites

By Victor M.F. Evora and Arun Shukla

Materials Science and Engineering, A 361 (2003) 358-366

Purpose of Study

Use experimental techniques to study the effect of nanosized particles on the bulk mechanical properties of nanocomposites.

Methods

Polyester resins were used as the matrix material and were loaded with TiO2 nanoparticles. The nanocomposite was fabricated using a casting process which included mechanical mixing, deaeration  and ultrasonication. Ultrasonification was employed to produce nanocomposites with uniform distribution of nanofibers which was verified by using TEM. Mechanical properties including tension, compression, quasi-static fracture toughness (3-point bending test) and dynamic fracture toughness (split Hopkinson pressure bar) were measured. Scanning electron microscopy is used to characterize the fracture surfaces.

Key Findings

1. It is observed that agglomeration of nanoparticles leads to significant decrease in quasi-static fracture toughness. There is a slight decrease in properties beyond a volume percentage of 1 % (nanofillers)which is attributed to clustering of nanoparticles. This is different from previous researchers who show a consistent increase in fracture properties with increase in volume percent of nanofillers.
2. Fracture toughening mechanisms are identified to be crack pinning and crack trapping using SEM photography. Thumbnail type markings and out-of-plane flakings exist in nanocomposites (in contrast with neat polyester where they are absent) which indicate the requirement of greater energy to form fracture surfaces.
3. The dynamic fracture toughness is observed to be higher than its quasi-static counterpart for all volume fractions. This was attributed to the rate dependency of the material.
4. Only moderate changes were observed in case of quasi-static mechanical properties like compression and tension. This is due to the weak interfacial bonding between the matrix and filler.