Melt-mixed PA-6/LDPE-g-MA/nanoclay ternary nanocomposite: Micro-mechanisms from post-yield fracture kinetics and strain field analysis

The post-yield fracture behavior of nanoclay filled polyamide-6 (PA-6)/low density polyethylene-grafted-maleic anhydride (LDPE-g-MA) based ternary nanocomposites revealed a prominent semiductile-to-ductile transition in the deformation mode characterized by the essential work of fracture (EWF) parameters. The fracture parameters in terms of crack-extension (Δa) and crack tip opening displacement (CTOD; δ) were quantified and the crack-toughness aspects have been critically discussed in the realms of CTOD-rate as a measure of blunting efficiency. The crack resistance behavior revealed a three-staged crack extension in combination with a two-stepped crack tip opening displacement (CTOD) phenomena. The CTOD-rate dependent fracture transitions have been qualitatively ascertained. To ascertain the kinetic and dynamics of crack growth micro-mechanisms time-synchronized deformation data prior to failure were acquired and analyzed using digital image correlation technique followed by the integral computation of deformation-stage images using the ARAMIS-GOM software to lead to strain field contours. The strain field so obtained revealed the distinct nature of energy dissipation in the inner-fracture process zone (IFPZ) and outer-plastic deformation zones (OPDZ). Such quantification of the stress wave dissipation modes via strain field analysis demonstrates fundamentally a new approach to understand fracture-mechanics for designing materials objectively aided by convincing visualization.