Oluschinski: Created page with "{{Language_sel|LANG=ger|ARTIKEL=ENF-Prüfkörper}} {{PSM_Infobox}} ENF specimen FORCETOC ==General== The Anglo-Saxon abbreviation ENF stands for "End-Notched Flexure". The ENF test specimen is used to determine the interlaminar fracture toughness of mode II loading. A critical energy release rate in plane strain is determined as a fracture mechanical parameter...."

2025-12-01T10:23:14Z

Created page with "{{Language_sel|LANG=ger|ARTIKEL=ENF-Prüfkörper}} {{PSM_Infobox}} ENF specimen __FORCETOC__ ==General== The Anglo-Saxon abbreviation ENF stands for "End-Notched Flexure". The ENF test specimen is used to determine the interlaminar fracture toughness of mode II loading. A critical energy release rate in plane strain is determined as a fracture mechanical parameter...."

New page

{{Language_sel|LANG=ger|ARTIKEL=ENF-Prüfkörper}}
{{PSM_Infobox}}
ENF specimen
__FORCETOC__

==General==

The Anglo-Saxon abbreviation ENF stands for "End-Notched Flexure".

The ENF test specimen is used to determine the interlaminar fracture toughness of mode II loading. A critical [[Energy Release Rate|energy release rate]] in plane strain is determined as a fracture mechanical [[Material Parameter | parameter]]. Shear loading without much friction between the surfaces of a crack is assumed. Shear stresses and strains before the crack tip (see also [[Crack Tip Opening Displacement Concept (CTOD) | crack opening]]) can have an influence on the calculation of the [[Energy Release Rate|energy release rate]].

==Test specimen shape==

[[file:ENF-specimen_1.jpg|500px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px" |Schematic illustration of ENF specimen
|}

==Determination equation==

To calculate the energy release rate ''G''IIc for EDZ, the following equation applies

{|
|-
|width="20px"|
|width="500px" | <math>G_{IIc} = \frac{9 \cdot F^2 \cdot a^2 \cdot C_b}{2 \cdot W \left (2 \cdot L^3 + 3 \cdot a^3 \right) } \left [ \frac{J}{m^2} \right ] </math>
|}

width:
{|
|-
|''a''
|width="15px" |
|crack length
|-
|''F''
|
|failure force (Fmax)
|-
|''C''b
|
|compliance of the test specimen
|-
|''W''
|
|specimen width
|-
|''L''
|
|distance between pressure fin and support
|}

As a conservative estimate of the compliance, the simple beam theory is sufficient in many cases; the test is carried out with a three-point bending device (see [[Bend Test|bend test]]) and a defined initial crack of 25 mm.

[[file:enf_jis.jpg|400px]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px" |ENF specimen in unloaded and loaded states according to JIS K 7086
|}

The compliance can be determined experimentally or calculated according to

{|
|-
|width="20px"|
|width="500px" | <math>C = \frac{2 \cdot L^3+3 \cdot a^3}{8 \cdot E \cdot f \cdot d^3}</math>
|}

width:
{|
|-
|''E''
|width="15px" |
|flexural modulus in axial direction
|-
|''d''
|
|half of elastic beam height
|-
|''f''
|
|deflection
|-
|''L''
|
|half of [[Support Distance|support distance]]
|}

By substituting these equations, one obtains a calculated energy release rate

{|
|-
|width="20px"|
|width="500px" | <math>G_{IIc} = \frac{9 \cdot F^2 \cdot a^2}{16 \cdot W \cdot f \cdot d^3 \cdot E}</math>
|}

A comprehensive compilation of suitable test specimens for [[Fracture Mechanical Testing|fracture mechanics testing]] on [[Plastics|plastics]] and composites is contained in [[Specimen for Fracture Mechanics Tests | test specimens for fracture mechanics tests]].

==Test system for performing of ENF tests==

The test set-up shown in '''Fig. 3''' was implemented at [[Polymer Service GmbH Merseburg | Polymer Service GmbH Merseburg]] to carry out fracture mechanics tests under Mode II loading on ENF specimens. The left partial image shows the installation of an ENF specimen in a universal testing machine Z 050 from [https://www.zwick.de/ Zwick Roell GmbH & Co. KG] in unloaded condition. The right partial image shows a loaded condition with crack propagation in the test specimen.

[[file:enf_pruefanordnung.jpg|650px]]
{|
|- valign="top"
|width="50px"|'''Bild 3''':
|width="600px" |Test system for carrying out fracture mechanics tests on ENF specimens from the company [https://www.polymerservice-merseburg.de/ Polymer Service GmbH Merseburg]
|}

==See also==

* [[Specimen for Fracture Mechanics Tests | Specimen for fracture mechanics tests]]
* [[Bend Test|Bend test]]

'''References'''

{|
|-valign="top"
|<li>
|Carlsson, L. A., Pipes, R. B.: Hochleistungsverbundwerkstoffe, B. G. Teubner, Stuttgart (1989) (ISBN 978-3-519-03250-2; e-Book ISBN 978-3-322-96703-9)
|-valign="top"
|<li>
|Valisetly, R. R., Chamis, C. C.: ASTM STP 972 (1988) 41–72 (Composite Materials. Testing and Design / Eighth Conference)
|-valign="top"
|<li>
|Russel, A. J., Street, K. N.: Moisture and Temperature Effects on the Mixed Mode Delamination. Fracture of Unidirectional Graphite / Epoxy. Delamination and Deponding of Materials, ASTM STP 876 (1985) 349
|-valign="top"
|<li>
|Hodgkinson, J. M. (Ed.): Mechanical Testing of Advanced Fibre Composites, Woodhead Publishing, Cambridge (2000) (ISBN 978-1-8557-3891-1)
|-valign="top"
|<li>
|Altstädt, V.: Testing of Composite Materials. In: [[Grellmann,_Wolfgang|Grellmann, W.]], [[Seidler,_Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser Munich (2022) 3rd Edition, pp. 549–550 (ISBN 978-1-56990-806-8; see [[AMK-Büchersammlung|AMK-Library]] under A 22)

'''Standards'''

* ASTM D 7905/D 7905M (2019): Standard Test Method for Determination of the Mode II Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites
* JIS K 7086 (1993): Testing Methods for Interlaminar Fracture Toughness of Carbon Fiber Reinforced Plastics (JIS – Japan Industrial Standards)

[[Category:Bend Test]]
[[Category:Fracture Mechanics]]
[[Category:Specimen]]

ENF-Specimen - Revision history