The use of load separation criterion and normalization method in ductile fracture characterization of thermoplastic polymers

Bernal, Celina Raquel; Montemartini, Pablo E.; Frontini, Patricia María

doi:10.1002/(sici)1099-0488(199608)34:11<1869::aid-polb4>3.0.co;2-n

Cited by 50 publications

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“…Because of the extensive experimental activity and the considerable amount of material required in a multi-specimen procedure, the applicability of single-specimen techniques for the construction of a J R curve of polymers has also been analysed. Among these techniques, the normalization method (Landes and Zhou 1993;Zhou et al 1994;Bernal et al 1995;Bernal et al 1996;Morhain and Velasco 2002) and, more recently, the S pb method (Wainstein et al 2004;Salazar and Rodriguez 2008) have been proven to produce for ductile polymers J R curves in good agreement with those determined by a multi-specimen technique. Both these singlespecimen approaches are theoretically based on the load separation criterion (Ernst et al 1981), whose validity in fracture tests on metals was extensively investigated by Sharobeam and Landes (1991); Sharobeam and Landes (1993).…”

Section: List Of Symbols Asupporting

confidence: 88%

“…The attractive features of this approach are that it does not need any optical system to monitor the specimen during the experiment and that it requires the use of only two specimens. This method was used for the measurement of J Ic in fracture tests on polymers in very few cases (Bernal et al 1995;Bernal et al 1996;Salazar and Rodriguez 2008) and, to the authors' knowledge, no systematic work has been done on the analysis of the effects of the testing conditions (geometry and loading rate) on the applicability of this method.…”

Section: List Of Symbols Amentioning

confidence: 99%

“…The difference between this value and the value of 2 derived by Rice et al (1973) for η pl , and widely adopted in literature, is probably the consequence of the measurement uncertainties intrinsically associated to the quantities involved in the experimental evaluation of the η-factor. A similar difference between the experimental and the theoretical value of η pl has been observed also in other literature works (Sharobeam and Landes 1993;Bernal et al 1996;Baldi and Riccò 2005). According to Eq.…”

Section: Applicability Of the Load Separation Criterion During Fractumentioning

confidence: 99%

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On the applicability of the load separation criterion in determining the fracture resistance (J Ic) of ductile polymers at low and high loading rates

2010

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In this work, the applicability of a procedure based on the load separation criterion in determining the fracture resistance (J Ic ) of a rubber modified polyamide 66 (PA66) was analyzed and discussed. In particular, the effects of the testing conditions, with particular reference to geometry and loading rate, on the applicability of the method were investigated. The tests were performed both at low (from 0.5 to 50 mm/ min) and moderately high (0.6 m/s) loading rates, on single edge notched in bending specimens with different initial crack length to width ratios (a 0 /W ), which ranged between 0.3 and 0.7. Among the various findings it is worthwhile to point out that this analysis revealed that the plastic displacement at the end of the blunting process (at fracture initiation) resulted geometry independent. A clear dependence of such a parameter on the loading rate was observed. Further, it was shown that load separation is maintained beyond the blunting phase, as observed in the experiments carried out at low rate. List of symbolsa Crack length ( mm) a 0 Initial crack length ( mm) A pl Area under the load per unit thickness vs plastic displacement (J/m) b Ligament length ( mm) b 0 Initial ligament length ( mm) B Specimen thickness ( mm) C Specimen elastic compliance ( mm/N) C 0 Initial elastic compliance of the specimen ( mm/N) E Young's modulus ( MPa) f Tabulated function (Williams 1987) G Geometry function H Material deformation function J Fracture resistance (J-integral) ( kJ/m 2 ) J bl J at the blunting line ( kJ/m 2 ) J el Elastic part of J ( kJ/m 2 ) J pl Plastic part of J ( kJ/m 2 ) J Ic J at fracture initiation ( kJ/m 2 ) J I,lim J at the point corresponding to the upper limit of the separable blunting region ( kJ/m 2 ) J 0.2 J at 0.2 mm crack extension ( kJ/m 2 ) m Multiplicative coefficient in blunting line equation P Load (kN) P b Blunt notched specimen load (kN) P N Normalized load ( MPa) P p Sharp notched specimen load (kN) 123 106 F. Baldi et al.

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Section: List Of Symbols Asupporting

confidence: 88%

Section: List Of Symbols Amentioning

confidence: 99%

Section: Applicability Of the Load Separation Criterion During Fractumentioning

confidence: 99%

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On the applicability of the load separation criterion in determining the fracture resistance (J Ic) of ductile polymers at low and high loading rates

2010

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“…As the conditions for the validity of the EWF approach were not fulfilled, it was decided to employ the J ‐integral approach for the present study. This technique has been found to be successful for a wide variety of polymers and toughened polymers blends that exhibited plastic flow at the crack tip, either under quasistatic loading38–40 or impact loading conditions,41, 42 before fracture.…”

Section: Discussionmentioning

confidence: 99%

Fracture toughness of polymers in the ductile‐to‐brittle transition region: Statistical approach and lower bound determination

Cocco

Frontini

Ipiña

2005

J Polym Sci B Polym Phys

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A method available in literature was adapted and proposed for treating scatter and nonlinearity effects in fracture toughness of polymers in the ductile‐to‐brittle transition regime. The materials used were polypropylene homopolymer (PPH) and a polypropylene‐elastomeric polyolefin blend (PPH/POes 20 wt %), at room temperature and at 20‐mm/min test rate. Under such conditions, the fracture toughness presents a large scatter and a mean value can not be used as a design parameter because it leads to toughness overestimation. Then, there is a need to find a threshold of toughness, as a safe characteristic value for design. The toughness was evaluated by using the J‐integral approach. Large sets of specimens, 53 samples per each material, were tested with the purpose to reveal a reliable tendency in fracture behavior. As the toughness was considered nonuniform throughout the material, a weakest link model was assumed, and then results were analyzed statistically by means of a three‐parameter Weibull model (3P‐W). The PPH responded well to this 3P‐W model, whereas some deviations from the original model were observed in the PPH/POes blend. However, lower‐bound toughness values could be determined for both materials by censoring nonvalid data (Δa > 0.1b0). From an engineering point of view, the results are very encouraging, since this methodology allows to obtain a threshold of fracture toughness from a given population, that is suitable to characterize the material fracture toughness at a given temperature and strain rate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3674–3684, 2005

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“…The normalization technique was proposed by Landes and Herrera [30] and has been included in ASTM Standard E1820 for elastic-plastic fracture toughness. Although developed for metals, the normalization technique has been demonstrated to yield equivalent results to multi-specimen methods for a variety of polymers [17,18,[31][32][33][34]. The required data for application of the normalization technique consists of a record of load versus displacement P i Kd i , the initial crack length a 0 , and the final crack length a f .…”

Section: Experimental Methodsmentioning

confidence: 99%

The role of crystalline phase on fracture and microstructure evolution of polytetrafluoroethylene (PTFE)

Brown

Dattelbaum

2005

Polymer

187

107

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The use of load separation criterion and normalization method in ductile fracture characterization of thermoplastic polymers

Cited by 50 publications

References 2 publications

On the applicability of the load separation criterion in determining the fracture resistance (J Ic) of ductile polymers at low and high loading rates

On the applicability of the load separation criterion in determining the fracture resistance (J Ic) of ductile polymers at low and high loading rates

Fracture toughness of polymers in the ductile‐to‐brittle transition region: Statistical approach and lower bound determination

The role of crystalline phase on fracture and microstructure evolution of polytetrafluoroethylene (PTFE)

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