Oluschinski: Created page with "{{Language_sel|LANG=ger|ARTIKEL=CLS-Prüfkörper}} {{PSM_Infobox}} CTS-specimen The Anglo-Saxon abbreviation CLS stands for ‘Crack-Lap Shear’. FORCETOC ==General information== The CLS-specimen was originally designed for investigating shear-dominated failure in adhesive joints (see also: [[Adhesive Joints – Determination of Characteristic Values|adhesive joints – determination of characteristic values]..."

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Created page with "{{Language_sel|LANG=ger|ARTIKEL=CLS-Prüfkörper}} {{PSM_Infobox}} CTS-specimen The Anglo-Saxon abbreviation CLS stands for ‘Crack-Lap Shear’. __FORCETOC__ ==General information== The CLS-specimen was originally designed for investigating shear-dominated failure in adhesive joints (see also: [[Adhesive Joints – Determination of Characteristic Values|adhesive joints – determination of characteristic values]..."

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{{Language_sel|LANG=ger|ARTIKEL=CLS-Prüfkörper}}
{{PSM_Infobox}}
CTS-specimen

The Anglo-Saxon abbreviation CLS stands for ‘Crack-Lap Shear’.
__FORCETOC__

==General information==

The CLS-specimen was originally designed for investigating shear-dominated failure in adhesive joints (see also: [[Adhesive Joints – Determination of Characteristic Values|adhesive joints – determination of characteristic values]]).

==Test specimen shape [1, 2]==

''Specimen shape''

[[File:CLS-Specimen-1.jpg|500px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px" |Crack-Lap Shear (CLS) specimen
|}

This test specimen shape with a ‘free shear layer’ was introduced in the literature by Wilkins [1] and Valisetty [2] (see '''Fig. 1'''). The CLS test specimen does not have a pure [[Fracture Modes|mode II]] load at the [[Crack|crack tip]]. The unbalanced configuration of the CLS test specimen results in a normal stress (mode I). As a result, this test specimen is referred to as a mixed-mode test specimen.

A geometrically non-linear finite element analysis by Law and Wilkins [3] showed that the mode II component varies with the load. However, the change in the Mode II component is small compared to the expected fluctuations in the critical force. For a typical carbon fibre/epoxy resin system with a layered structure, for example, the [[Mixed-Mode Crack Propagation|mode II]] component is approximately 70 %.

==Equation for determining the energy release rate==

[[Altstädt, Volker|Altstädt]] describes a CLS-specimen in [4] in which only the clamping position is subjected to stress ('''Fig. 2''').

[[File:CLS-Specimen-2.jpg|450px]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px" |CLS-specimen according to ESIS TC 4
|}

Since there is no Mode II stress alone at the [[Crack|crack tip]], this is a [[Crack Opening Modes|mixed-mode]] stress. In order to obtain a natural initial crack (see also: [[Initial Crack Length|initial crack length]]), the crack is first opened and extended to a certain length. The [[Crosshead Speed|crosshead speed]] is preferably 0.5 mm/min, whereby only the clamped position is stressed; the free shear lag is not stressed. Between loading and unloading, the crack length is recorded to determine the compliance. Based on a strength analysis, the [[Tensile Test Compliance|compliance]] ''C'' and the [[Energy Release Rate|energy release rate]] ''G'' can be determined for the plane strain state:

{|
|-
|width="20px"|
|width="500px" | <math>C=\frac{L}{B \cdot E \cdot d_1}+\frac{a \left(d_1-d_2\right)}{B \cdot E \cdot d_1 \cdot d_2}</math>
|}

{|
|-
|width="20px"|
|width="500px" | <math>G_{I/IIc}=\frac{F^2 \cdot \left(d_1-d_2\right)}{2 \cdot B^2 \cdot E \cdot d_1 \cdot d_2}</math>
|}

with
{|
|-
|''a''
|width="15px" |
|[[Initial Crack Length|initial crack length]]
|-
|''d''1
|
|thickness of the clamping layer
|-
|''d''2
|
|thickness of the free shear layer
|}

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|test specimens for fracture mechanics tests]].

==See also==

* [[Crack Opening Modes|Crack opening modes]]
* [[Crack]]
* [[Adhesive Joints – Determination of Characteristic Values|Adhesive joints – Determination of characteristic values]]
* [[Specimen for Fracture Mechanics Tests|Specimen for fracture mechanics tests]]
* [[Fracture Mechanics|Fracture mechanics]]

==References==

{|
|-valign="top"
|[1]
|Wilkins, D. J., Eisenmann, R. A., Camin, R. A., Margolis, W. S., Benson, R. A.: ASTM STP 775 (1982), Short Fiber Reinforced Composite Materials
|-valign="top"
|[2]
|Valisetty, R. R., Chamis, C. C.: ASTM STP 972 (1988) 41–72, Composite Materials: Testing and Design. Editor: Whitcomb, J. D. (ISBN 0-8031-0980-6; ISBN 978-0-8031-0980-3)
|-valign="top"
|[3]
|Law G. E., Wilkinson, D. J.: Delamination Failure Criteria for Composite Structures, Final Report NAV-GD-0053 (Mai 15, 1984)
|-valign="top"
|[4]
|[[Altstädt, Volker|Altstädt, V.]]: Testing of Composite Materials. In: [[Grellmann, Wolfgang|Grellmann, W.]], [[Seidler, Sabine|Seidler, S.]] (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, p. 553 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see [[AMK-Library]] under A 22)
|}

[[Category:Fracture Mechanics]]
[[Category:Specimen]]

CLS-Specimen - Revision history