Application of essential work of fracture concept to toughness characterization of high‐density polyethylene

Abstract

Deformation and fracture toughness of high-density polyethylene (HDPE) in plane-stress tension was studied using the concept of essential work of fracture (EWF). Strain range for necking was determined from uniaxial tensile test, and was used to explain the deformation transition for 2-staged crack growth in doubleedge-notched tensile test. Through work-partitioning, EWF values for HDPE were determined for each stage of the crack growth. Appropriateness of these EWF values to represent the material toughness is discussed. The study concludes that the EWF values for ductile polymers like HDPE may not be constant, but vary with the deformation behaviour involved in the crack growth process. FIG. 8. Variation of D n /D f (~) and D y /D f (^) of DENT specimens in (a) the rolling direction and (b) the transverse direction. FIG. 7. Plots of ligament length reduction versus time from two DENT tests with L 0 ¼ 30 mm.

Fracture development and deformation behavior of zeolite-filled high density polyethylene annealed composites in the plane stress fracture

“…Previous studies evaluating the EWF of polyethylene such as HDPE [6,11,12] have neglected the process of neck developing in analyzing the energy needed during the fracture. In contrast to those studies, Jar and co-workers [13,14] have observed neck formation during fracture process and reported that in plane stress fracture of DENT specimen, the neck was initiated along the ligament part, it spread to adjacent areas which had been deformed at an early step of the test.…”

“…It can be elucidated as follows. Strain increment (dε) in the plastic zone can be obtained from the relationship as follows [14,28,29]:…”

“…In situ measurement of crack tip angle in the DENT specimen test were rationalized by a though that the relationship between the crack angle (θ), elongation of the specimen (δ), and ligament length (ℓ), as shown in Fig. 7c can be expressed by the mathematical equation as follow [14]:…”

“…As an assumption, the strain of DENT tested in the direction of ligament length was ignored [14,25]. During the test, the crack growth and deformation process were recorded using SONY HDR-CX405 Handycam.…”

Toughness of high-density polyethylene in shear fracture

“…Several test methods have been designed based on the concept, to separate the energy consumed in the fracture process zone (FPZ) from the other forms of energy consumption during the crack growth, including that for the global plastic deformation in ductile fracture (Kwon and Jar 2006a). Currently, double-edge-notched tensile test (DENT test) is the most popular method based on the EWF concept, and has been successfully used to quantify toughness for ductile fracture in mode I, commonly known as specific essential work of fracture (w I e ).…”