View source for 4 End-Notched Flexure Specimen

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<span style="font-size:1.2em;font-weight:bold;">4 ENF-specimen or also Four End-Notched Flexure (4 ENF) specimen</span>
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==Diagram of the experimental setup==

A modification of the [[ENF-Specimen|ENF-test]] is the ‘'''4''' '''E'''nd-'''N'''otched '''F'''lexure’ (4 ENF) test, which uses the test setup of the [[Bend Test#The four-point bending test method| four-point bending test]] [1] (see '''Figure''').

[[File:4_ENF-Specimen_Fig.jpg|450px]]
{| 
|- valign="top"
|width="50px"|'''Fig.''': 
|width="600px" |Schematic presentation of the test setup for the 4 ENF bending test [3]
|}

The delamination front lies within the range of constant bending moment where no shear stresses occur; this reduces friction effects between the upper and lower [[Crack|crack]] surface. To determine the [[Energy Release Rate|energy release rate]], the [[Specimen Compliance|compliance]] (see also: [[Bend Test Compliance|bend test compliance]]) is plotted as a function of the delamination length (crack length) and the increase in this curve is determined [2].

==Equation of determination==

If the deflection is too great, correction functions must be determined. The [[Energy Release Rate|energy release]] rate ''G''<sub>IIc</sub> is calculated using the equation

{|
|-
|width="20px"|
|width="500px" | <math>G_{IIc}=\frac{F^2 \cdot \Delta C}{2 \cdot W \cdot \Delta a}</math>
|}
with:
{|
|-
|''F''
|width="15px" | 
|force
|-
|''W''
|
|specimen width
|-
|<math>\Delta</math>C/<math>\Delta</math>a
|
|
increase in the dependence of compliance on crack length
|}

An extensive summary of suitable test specimens for [[Fracture Mechanical Testing|fracture mechanics investigations]] on [[Plastics|plastics]] and [[Composite Materials Testing|composite materials]] is included in [[Specimen for Fracture Mechanics Tests|fracture mechanics test specimens]].

==See also==

* [[Specimen for Fracture Mechanics Tests|Specimen for fracture mechanics tests]]
* [[ENF-Specimen|ENF-specimen]]
* [[Fracture Modes|Fracture modes]]
* [[Composite Materials Testing|Composite materials testing]]
* [[CLS-Specimen|CLS-specimen]]

==References==

{|
|-valign="top"
|[1]
|[[Bierögel, Christian|Bierögel, C.]]: Quasi-static Test Methods. In: [[Grellmann, Wolfgang|Grellmann, W.]], [[Seidler, Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, pp. 133–143 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see [[AMK-Library]] under A 22)
|-valign="top"
|[2]
|[[Altstädt,_Volker|Altstädt, V.]]: Testing of Composite Materials. In: [https://de.wikipedia.org/wiki/Wolfgang_Grellmann Grellmann, W.], Seidler, S. (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, pp. 550/551 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see [[AMK-Library]] under A 22)
|-valign="top"
|[3]
|Robinson, P., Hodgkinson, J. M.: Interlaminar Fracture Toughness. In: Hodgkinson, J. M (Ed.): Mechanical Testing in Advanced Fibre Composites. Woodhead Publishing, Cambridge (2000) (ISBN 1-85573-312-9) [https://doi.org/10.1533/9781855738911.170 https://doi.org/10.1533/9781855738911.170]
|}

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