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A new approach to correlate slow crack growth of HDPE nanocomposites with fracture toughness

The slow crack growth (SCG) behavior of high density polyethylene (HDPE) blends has been conventionally approached by using applied stresses with respect to the failure time. In this paper, the failure behavior of a nonlinear elastic-plastic material such as HDPE is defined by the time-independent plane-strain fracture toughness that is commonly determined by short-term experimental tests. We established the correlation between the time-dependent SCG and the time-independent fracture toughness employing the elastic-plastic fracture mechanics (EPFM). SCG of HDPE blends was evaluated by the notched constant ligament stress (NCLS) test while the plane-strain fracture toughness was estimated by the essential work of fracture (EWF) test using the energy partitioning method. These two different time-domain fracture behaviors can be integrated by a power law relationship under the plane-strain condition. Subsequently, the SCG behavior of various HDPE blends including pristine/recycled HDPE and nanoclay composites was explained in terms of the plane-strain fracture toughness.