J-testing of polymers via the load separation criterion based ESIS TC4 procedure: Effect of the specimen size

Size-Induced Constraint Effects on Crack Initiation and Propagation Parameters in Ductile Polymers

“…Furthermore, the applied procedure for the calculation of established crack initiation (J bl , J 0.2 and J ini ) and crack growth parameters (crack resistance curve, J–R curve) are given. These values are also used to validate the results of J I,lim , calculated via the TC4 LS method from prior work [ 7 ].…”

“…After the aforementioned examination of the constraint in different specimen sizes, it was possible to further investigate and validate the determined fracture parameters. This knowledge may be used to interpret the results of the previous study [ 7 ], where the so-called pseudo initiation parameter J I,lim , based on the TC4 LS method [ 8 ], displayed dependence with an increasing specimen size. Furthermore, to not only validate these results with the examination of the level of constraint, but also to check for possible inherent flaws in the new testing procedure, established crack initiation and propagation values are also included in the study.…”

“…This crack advancement value was originally chosen since it was large enough to experimentally characterize real crack growth and small enough to be close to real initiation. The parameter J 0.2 is widely accepted and used for the characterization of crack initiation in polymers [ 7 , 11 , 14 , 25 , 26 , 27 ]. The second initiation parameter used in this study is J bl , defined as the intersection of the blunting line with the J–R curve power law fit [ 13 ], where the blunting line is defined as follows: where σ y is the yield stress of the investigated material.…”

“…Based on these results, it appears that it is not yet possible to determine a clear set of rules regarding constraint and corresponding fracture parameters of polymers under the conditions of EPFM. Subsequently, the current work aims towards a deeper understanding of aforementioned results obtained in [ 7 ] with regard to the influence of constraint and specimen sizes.…”

“…Che et al [ 6 ] proved the size-independent crack initiation behavior of polyvinyl chloride above a threshold thickness value of 10 mm, while some differences in crack growth were still visible. Previous research [ 7 ], dealing with the determination of the elastic plastic fracture behavior of up-scaled specimen sizes (increasing specimen size with identical geometrical ratios of width, thickness and initial crack lengths) of acrylonitrile butadiene styrene (ABS), showed strong size dependence of the determined fracture initiation parameters, while the first results indicated a size-independent crack growth behavior. Based on these results, it appears that it is not yet possible to determine a clear set of rules regarding constraint and corresponding fracture parameters of polymers under the conditions of EPFM.…”