Instrumented puncture tests were performed on high-density polyethylene (HDPE) sheets using a flat-ended indenter and a clamped specimen holder. By correlating in situ morphology with puncture force–displacement curves, a consistent set of characteristic displacements was identified for a range of samples with different thicknesses. DC marks the critical displacement where a bending-to-stretching transition, accompanied by stress concentration, drawing of the crown wall, and the onset of microfibrillation, sets in. DD corresponds to the displacement where the maximum force within the fibrillation-dominated regime is reached. A puncture step-cycle test protocol separated recoverable and residual displacements, quantitatively validating the inferred elastoplastic sequence. Based on an energy partition at DC, the critical energy (UC), total absorbed energy (Utotal), and plastic dissipation energy (UP) were determined, and a puncture-specific ductile ratio (D.R.p) was proposed to quantify ductile energy dissipation. Under the present experimental conditions, systematic variations in puncture rate (2–800 mm/min) and specimen thickness (0.47–2.63 mm) reveal two critical thresholds: a transition from quasi-static to rate-dominated response at approximately 80 mm/min and a plate-like to film-like mechanism boundary at approximately 1.2 mm. These results establish a physical framework for mechanistic interpretation and ductility quantification in the puncture behavior of polymers.
Zang et al. (Mon,) studied this question.