Academia.eduAcademia.edu

Figure 1 – uploaded by Tamás Barany

See full PDFdownloadDownload figure
integral around the crack tip and plastic deformation at the crac integral can be considered as the d energy between two identical b k tip. Practical ifference of the have slightly different crack lengths. The critica the J-integral (J,) is accompanied by full crack tip blunt- ing prior to crack growth. J, is usually deduced J resistance (Jr) curve when ado thus considers also the y, the J- potential odies under load which value of from the pting the multi ple spec- imen technique. This approach works well for polymers provided they are not too ductil e. T he CTOD criterion is linked to the crack opening prior to its advance. However, this is seldom followed for polymers tion problems. Instead of that usual displacement (COD) is determined. 1 due to instrumenta- y the crack opening [he EWF approach is gaining acceptance to determine the toughness response of highly ductile polymers. The greatest advantage of EWF over the J-integral is that a clear distinction between sur- face (essential part) and volume-related (non-essential part) works is made. For a detailed description of the various fracture mechanical methods, testing standards, their applicability for polymer and polymer composites, the interested reader is addressed to valuable books (e.g. [233]): Contents 1. Introduction

Table 1 integral around the crack tip and plastic deformation at the crac integral can be considered as the d energy between two identical b k tip. Practical ifference of the have slightly different crack lengths. The critica the J-integral (J,) is accompanied by full crack tip blunt- ing prior to crack growth. J, is usually deduced J resistance (Jr) curve when ado thus considers also the y, the J- potential odies under load which value of from the pting the multi ple spec- imen technique. This approach works well for polymers provided they are not too ductil e. T he CTOD criterion is linked to the crack opening prior to its advance. However, this is seldom followed for polymers tion problems. Instead of that usual displacement (COD) is determined. 1 due to instrumenta- y the crack opening [he EWF approach is gaining acceptance to determine the toughness response of highly ductile polymers. The greatest advantage of EWF over the J-integral is that a clear distinction between sur- face (essential part) and volume-related (non-essential part) works is made. For a detailed description of the various fracture mechanical methods, testing standards, their applicability for polymer and polymer composites, the interested reader is addressed to valuable books (e.g. [233]): Contents 1. Introduction

Related Figures (25)

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Provided for non-commercial research and education use. Not for reproduction, distribution or commercial use.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Provided for non-commercial research and education use. Not for reproduction, distribution or commercial use.
Fig.1. Schematic diagram showing the fracture zones (a) (IFPZ: inner frac- ture process zone, OPDZ: outer process dissipation zone) and (b) the data reduction method of the EWF.
Fig.1. Schematic diagram showing the fracture zones (a) (IFPZ: inner frac- ture process zone, OPDZ: outer process dissipation zone) and (b) the data reduction method of the EWF.
Fig. 2. Energy partitioning, schematically illustrated according to (a) the initiation and (b, c) yielding concepts. Note: in case b) the ligament yielding is instantaneous, whereas in case c) it is time-dependent.
Fig. 2. Energy partitioning, schematically illustrated according to (a) the initiation and (b, c) yielding concepts. Note: in case b) the ligament yielding is instantaneous, whereas in case c) it is time-dependent.
Fig. 3. Unstable cracking after full ligament yielding in a DEN-T specimen from low molecular weight PEN [25] Copyright 2000, with permission from Elsevier.
Fig. 3. Unstable cracking after full ligament yielding in a DEN-T specimen from low molecular weight PEN [25] Copyright 2000, with permission from Elsevier.
Fig. 5. (a) Light microscopic pictures (back illumination) showing the outer plastic zone and (b) the strain hardening of the ligament caused by the injection moulding induced skin-core structure. Note: the latter was oriented along the loading direction [28] Copyright 1999, with permission from John Wiley and Sons. This crack deflection can be considered as caused by the Cook-Gordon mechanism, well explained in Ref. [29]. Note that its onset is favored by an inherent anisotropic (super)molecular structure of the tested material. Such structure deve ops in uniaxial oriented films, in injection molded parts showing prominent skin-shear-core struc- ture (cf. Fig. 5 aligned in the posites, MFC) a , composites with various reinforcements loading direction (e.g. microfibrillar com- nd the like. It should be noted that in neat polymers this behavior appears exclusively in semicrys- talline polymers (mostly those with a high molecular weights), which are prone for deformation (strain)-induced changes in morphology, including alterations in the crys- talline superstructure (orientation and defolding of the The EWF method became very popular for the assess- ment of the plane stress fracture toughness of thin polymer sheets. In spite of that fact that the EWF has some prereq- uisites as noted in the preceding, the relevant criteria often seem to be flexible enough. The test conditions (loading rate, gauge length, temperature etc.) are selected freely by the researchers. In order to make the EWF results comparable the testing conditions should be fixed, i.e.,
Fig. 5. (a) Light microscopic pictures (back illumination) showing the outer plastic zone and (b) the strain hardening of the ligament caused by the injection moulding induced skin-core structure. Note: the latter was oriented along the loading direction [28] Copyright 1999, with permission from John Wiley and Sons. This crack deflection can be considered as caused by the Cook-Gordon mechanism, well explained in Ref. [29]. Note that its onset is favored by an inherent anisotropic (super)molecular structure of the tested material. Such structure deve ops in uniaxial oriented films, in injection molded parts showing prominent skin-shear-core struc- ture (cf. Fig. 5 aligned in the posites, MFC) a , composites with various reinforcements loading direction (e.g. microfibrillar com- nd the like. It should be noted that in neat polymers this behavior appears exclusively in semicrys- talline polymers (mostly those with a high molecular weights), which are prone for deformation (strain)-induced changes in morphology, including alterations in the crys- talline superstructure (orientation and defolding of the The EWF method became very popular for the assess- ment of the plane stress fracture toughness of thin polymer sheets. In spite of that fact that the EWF has some prereq- uisites as noted in the preceding, the relevant criteria often seem to be flexible enough. The test conditions (loading rate, gauge length, temperature etc.) are selected freely by the researchers. In order to make the EWF results comparable the testing conditions should be fixed, i.e.,
Fig. 4. (a) Data reduction of the EWF tests performed on amorphous PEN of low molecular mass and (b) the related primary load—displacement (F-x) curves measured on DEN-T specimens [25], Copyright 2000, with permission from Elsevier.
Fig. 4. (a) Data reduction of the EWF tests performed on amorphous PEN of low molecular mass and (b) the related primary load—displacement (F-x) curves measured on DEN-T specimens [25], Copyright 2000, with permission from Elsevier.
T. Bardny et al. / Progress in Polymer Science 35 (2010) 1257-1287
T. Bardny et al. / Progress in Polymer Science 35 (2010) 1257-1287
EWF results on polycondensation polymers under static loading. Table 2
EWF results on polycondensation polymers under static loading. Table 2
Table 2 (Continued)
Table 2 (Continued)
EWF results on natural polymers (biopolymers) under static loading.
EWF results on natural polymers (biopolymers) under static loading.
EWF results on crosslinked polymers under static loading.
EWF results on crosslinked polymers under static loading.
EWF results on polyurethane under static loading.
EWF results on polyurethane under static loading.
EWF results on polymer blends under static loading. Table 6
EWF results on polymer blends under static loading. Table 6
Table 6 (Continued )
Table 6 (Continued )
EWF results on polymer micro- and macrocomposites under static loading.
EWF results on polymer micro- and macrocomposites under static loading.
EWF results on nanostructured, nanoreinforced systems under static loading.
EWF results on nanostructured, nanoreinforced systems under static loading.
T. Barany et al. / Progress in Polymer Science 35 (2010) 1257-1287
T. Barany et al. / Progress in Polymer Science 35 (2010) 1257-1287
Fig. 6. (a) Schematic diagram showing the fracture zones on the trousers specimen and (b) evaluation of out-of-plane EWF results (trousers) of PET [94]. Picture b: Copyright 2005, with permission from Springer Science + Business Media. into account the work needed for bending and unbending of the specimen to determine the specific tearing essen- tial work of fracture parameter (wre) [7]. However, since this contribution is negligible with ductile polymer films because of their low stiffness, so this approach cannot be used directly for them. Wong et al. published a two-zone model for polymeric materials [258]. According to this con- cept, the tearing fracture process in ductile polymers can be divided into two parts. In the initial zone (Zone A), the crack starts and the height h of the outer plastic zone increases continuously with the torn ligament length. At the end of Zone A, in Zone B, the height of plastic zone adopts a constant value hg during further crack propa- gation in a “saturation” region, see Fig. 6a. Fig. 7 shows that in this trousers tearing test a well developed plas- tic zone appears in the preferred amorphous copolyesters. In Zone A:
Fig. 6. (a) Schematic diagram showing the fracture zones on the trousers specimen and (b) evaluation of out-of-plane EWF results (trousers) of PET [94]. Picture b: Copyright 2005, with permission from Springer Science + Business Media. into account the work needed for bending and unbending of the specimen to determine the specific tearing essen- tial work of fracture parameter (wre) [7]. However, since this contribution is negligible with ductile polymer films because of their low stiffness, so this approach cannot be used directly for them. Wong et al. published a two-zone model for polymeric materials [258]. According to this con- cept, the tearing fracture process in ductile polymers can be divided into two parts. In the initial zone (Zone A), the crack starts and the height h of the outer plastic zone increases continuously with the torn ligament length. At the end of Zone A, in Zone B, the height of plastic zone adopts a constant value hg during further crack propa- gation in a “saturation” region, see Fig. 6a. Fig. 7 shows that in this trousers tearing test a well developed plas- tic zone appears in the preferred amorphous copolyesters. In Zone A:
Fig. 7. Cross polarized image of the plastic deformation along the tea path within zone B for an amorphous copolyester.
Fig. 7. Cross polarized image of the plastic deformation along the tea path within zone B for an amorphous copolyester.
Fig. 8. Correlation between in-plane and out-of-plane EWF results [94]. Copyright 2005, with permission from Springer Science + Business Media. I We based on the results achieved on ABS [254] and HDPE [255], respectively. The authors of this review are con- vinced that mode II tests have to be done on amorphous copolyesters in order to get a clearer picture on this issue.
Fig. 8. Correlation between in-plane and out-of-plane EWF results [94]. Copyright 2005, with permission from Springer Science + Business Media. I We based on the results achieved on ABS [254] and HDPE [255], respectively. The authors of this review are con- vinced that mode II tests have to be done on amorphous copolyesters in order to get a clearer picture on this issue.
EWF results on polymer composites under dynamic loading.
EWF results on polymer composites under dynamic loading.
Fig.9. Effect of the ligament length on the stress state in DEN-T specimens schematically.
Fig.9. Effect of the ligament length on the stress state in DEN-T specimens schematically.
Fig. 10. DEN-T specimen of an amorphous PEN before (upside) and after (downside) heat treatment [25]. Copyright 2000, with permission from Elsevier.
Fig. 10. DEN-T specimen of an amorphous PEN before (upside) and after (downside) heat treatment [25]. Copyright 2000, with permission from Elsevier.
Fig. 11. Yielding-related essential work of fracture vs. square root of the mean molecular weight between entanglements [272,273]. Copyright 2002 with permission from Wiley-VCH Verlag GmbH & Co. KGaA. T. Bardny et al. / Progress in Polymer Science 35 (2010) 1257-1287
Fig. 11. Yielding-related essential work of fracture vs. square root of the mean molecular weight between entanglements [272,273]. Copyright 2002 with permission from Wiley-VCH Verlag GmbH & Co. KGaA. T. Bardny et al. / Progress in Polymer Science 35 (2010) 1257-1287
Fig. 12. Predicted change of toughness as a function of crystallinity [11,273]. Copyright 2002 with permission from Wiley-VCH Verlag GmbH & Co. KGaA.
Fig. 12. Predicted change of toughness as a function of crystallinity [11,273]. Copyright 2002 with permission from Wiley-VCH Verlag GmbH & Co. KGaA.
Related topics:
EngineeringPolymer BlendsFracture MechanicRelational dataPolymer BlendG
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved