Oluschinski: Created page with "{{Language_sel|LANG=ger|ARTIKEL=Mehrfachbruch UD-Tapes}} {{PSM_Infobox}} Multiple fracture UD tapes FORCETOC ==Multiple Fracture UD Tapes== The phenomenon of multiple fracture of a test specimen under stress in a tensile test is observed in fibre-reinforced plastics, e.g. in unidirectional (UD) continuous-fibre-reinforced plastics (CFRPs), known as UD tapes [1]. Due to t..."

2026-09-04T08:54:14Z

Created page with "{{Language_sel|LANG=ger|ARTIKEL=Mehrfachbruch UD-Tapes}} {{PSM_Infobox}} Multiple fracture UD tapes __FORCETOC__ ==Multiple Fracture UD Tapes== The phenomenon of multiple fracture of a test specimen under stress in a tensile test is observed in fibre-reinforced plastics, e.g. in unidirectional (UD) continuous-fibre-reinforced plastics (CFRPs), known as UD tapes [1]. Due to t..."

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{{Language_sel|LANG=ger|ARTIKEL=Mehrfachbruch UD-Tapes}}
{{PSM_Infobox}}
Multiple fracture UD tapes
__FORCETOC__

==Multiple Fracture UD Tapes==

The phenomenon of multiple fracture of a [[Specimen|test specimen]] under [[Stress|stress]] in a [[Tensile Test|tensile test]] is observed in fibre-reinforced plastics, e.g. in unidirectional (UD) continuous-fibre-reinforced plastics (CFRPs), known as UD tapes [1]. Due to the unidirectional continuous reinforcement, UD tapes can meet very high [[Strength|strength]] and [[Stiffness|stiffness requirements]] in the fibre direction. By applying the UD tapes along the load paths or in the direction of loading, these advantages can be fully exploited, either directly as tape or, following the consolidation of several layers, as a laminate, whereby the [[Fibre Orientation|fibre orientation]] of the layers can be individually adapted to the [[Plastic Component|component]] (see also: [[Glass Fibre Orientation|glass fibre orientation]]). Due to their advantages in processing and in applications within lightweight structures or as replacements for metallic components, UD tapes with a [[Thermoplastic Material|thermoplastic matrix]] are becoming increasingly important [2, 3].

For the production of laminates from UD tapes, the layering of the tape at precise angles, a constant thickness and uniform, defect-free compression are particularly important. If deviations occur during this process, the effects on the nature of the [[Deformation|deformation]] and [[Fracture Behaviour|fracture behaviour]] – and in particular on [[Component Failure|failure due to fracture]] – are significant. The properties of a single ply determine the properties of the composite as a whole. For this reason, the selection of meaningful test methods for [[Polymer Testing|polymer testing]] and [[Polymer Diagnostic|diagnostics]], which can characterise the properties of thin FRP plies, is of essential importance (see also: [[Composite Materials Testing|composite materials testing]]).

Despite the fact that pure tensile stress is generally the exception in practice, the [[Tensile Test|tensile test]] is often the preferred method for characterising properties from a testing methodology perspective.

==Multiple fractures in single-layer UD tapes PA/eGF and PPeGF, and in the multi-layer UD tape PET/CReF/PET==

The occurrence of multiple fractures is illustrated using the example of two single-layer UD tapes with a matrix of polyamide 6 ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: PA6) and polypropylene ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: PP), respectively, reinforced with continuous glass fibres (designated PA/eGF and PP/eGF, respectively). Furthermore, a multi-layer UD tape consisting of a matrix of polyethylene terephthalate ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: PET) and a continuous fibre made of regenerated cellulose (CReF) was characterised. This tape is three-layered (PET/CReF/PET). The single-layer tapes have a thickness of approx. 300 µm and 500 µm for PET/CReF/PET, respectively. The [[Tensile Test|tensile test]] was carried out in accordance with ISO 527-4 [4], with the continuous fibres aligned unidirectionally in the direction of loading, analogous to the intended use of the UD tapes in the component. The [[Material Value|characteristic values]] determined were the [[Elastic Modulus|modulus of elasticity]] ''E''t, the stress at the first peak ''σ''B1 (i.e. at the first fibre break) and the maximum stress ''σ''M.

The PA/eGF and PP/eGF UD tapes exhibit typical splice formation and strand-by-strand fracture under tensile stress. This is illustrated in '''Figs. 1a)''' and '''b)'''.

[[File:Mehrfachbruch_UD-Tapes-1.JPG|550px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px"|Splitting and strand-by-strand fracture of the test specimens under tensile stress in PA/eGF (a) and PP/eGF (b), and fracture of PET/CReF/PET in the lower region (c)
|}

The individual fibre strands of the UD tapes break in short intervals. This leads to multiple fractures, which can also be seen in the [[Tensile Test True Stress–Strain Diagram|stress–strain diagrams]] (see '''Fig. 2''' and '''Fig. 3'''). Despite the fractures, the tapes are still able to absorb further load. It is only when a critical load condition is exceeded in the separated strands that complete failure (see: [[Fracture|fracture]]) of the [[Specimen|test specimen]] occurs. PET/CReF/PET exhibits a completely different failure behaviour. Following a [[Fracture Types|brittle fracture]] of the PET layers, the fibres still retain some residual strength and continue to adhere to the edge of the [[Fracture Process Zone|fracture zone]] within the matrix. This can be observed during the test. This allows the tape to absorb further work until [[Fracture|total fracture]] of the test specimen occurs. Thus, both the single-layer UD tapes PA/eGF and PP/eGF, as well as PET/CReF/PET, exhibit a complex fracture process under tensile stress.

'''Table 1''' summarises the [[Material Value|characteristic values]] determined by the [[Tensile Test|tensile test]]. The [[Elastic Modulus|modulus of elasticity]] ''E''t is a measure of the [[Stiffness|stiffness]] of the test specimens under tensile stress and is comparatively high for the UD tapes, due to the uniaxial orientation of the continuous fibres. The stress at the first strand break σB1 is significantly higher for the two UD tapes, PA/eGF and PP/eGF, than the comparable [[Tensile Strength|tensile strength]] ''σ''M of PET/CReF/PET.

[[File:Mehrfachbruch_UD-Tapes-2.JPG|550px]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px"|Stress–strain diagram for 5 test specimens each (1–5) for the UD tapes made from the materials PA/eGF and (b) PP/eGF
|}

[[File:Mehrfachbruch_UD-Tapes-3.JPG|275px]]
{|
|- valign="top"
|width="50px"|'''Fig. 3''':
|width="600px"|Stress–strain diagrams for 5 test specimens (1–5) for the UD tape PET/CReF/PET
|}

{|
|- valign="top"
|width="70px"|'''Table 1''':
|width="415px"|Characteristic values from the tensile test: [[Elastic Modulus|modulus of elasticity]] ''E''t, stress at the first strand break ''σ''B1 and [[Tensile Strength|tensile strength]] ''σ''M
|}
{| border="1px" style="border-collapse:collapse"
!! style="width:160px; background:#DCDCDC"|UD-Tape
!! style="width:80px; background:#DCDCDC"|Et (GPA)
!! style="width:80px; background:#DCDCDC"|σB1 (MPa)
!! style="width:80px; background:#DCDCDC"|σM (MPa)
!! style="width:80px; background:#DCDCDC"|σB (MPa)
|-
|style="text-align:left"|PA/eGF
|style="text-align:center"|23.0 ± 1.7
|style="text-align:center"|550 ± 81
|style="text-align:center"|-
|style="text-align:center"|408 ± 75
|-
|style="text-align:left"|PP/eGF
|style="text-align:center"|24.0 ± 1.4
|style="text-align:center"|416 ± 67
|style="text-align:center"|-
|style="text-align:center"|258 ± 86
|-
|style="text-align:left"|PET/CReF/PET
|style="text-align:center"|6.1 ± 0.5
|style="text-align:center"|-
|style="text-align:center"|114 ± 9
|style="text-align:center"|26 ± 6
|}

The fracture behaviour of UD tapes in [[Tensile Test|tensile tests]] is highly complex. The [[Material Value|characteristic values]] determined allow for the differentiation of UD tapes and the characterisation of the material. For a more detailed description of the fracture behaviour of UD tapes, the application of fracture mechanics methods to evaluate [[Crack Initiation|crack initiation]] and [[Crack Propagation|crack propagation]] represents a promising approach for the further development of the concepts used to date (see: [[Fracture Mechanical Testing|fracture mechanical testing]]).

==See also==

* [[Composite Materials Testing|Composite materials testing]]
* [[Fibre Orientation|Fibre orientation]]
* [[Glass Fibre Orientation|Glass fibre orientation]]
* [[Plastography]]
* [[Stiffness]]

==References==

{|
|-valign="top"
|[1]
|Monami, A., Langer, B., [[Grellmann, Wolfgang|Grellmann, W.]]: Modern Methods of Polymer Testing for Material Development and Testing of Components. Werkstoffprüfung 2016, Fortschritte in der Werkstoffprüfung für Forschung und Praxis December 1 and 2, (2016) Neu-Ulm, Proceedings pp. 219–224 (ISBN 978-3-514-00830-4; see [[AMK-Library]] under G 61)
|-valign="top"
|[2]
|Haanappel, S. P., Akkerman, R.: Shear characterisation of uni-directional fibre reinforced thermoplastic melts by means of torsion. Composites Part A: Applied Science and Manufacturing 56 (2014) 8−26; [https://doi.org/10.1016/j.compositesa.2013.09.007 https://doi.org/10.1016/j.compositesa.2013.09.007]
|-valign="top"
|[3]
|Gao, S.-L., Kim, J.-K.: Cooling rate influences in carbon fibre/PEEK composites. Part II: Interlaminar fracture toughness. Composites Part A: Applied Science and Manufacturing 32 (2001) 763−774; [https://doi.org/10.1016/S1359-835X(00)00188-3 https://doi.org/10.1016/S1359-835X(00)00188-3]
|-valign="top"
|[4]
|ISO 527-4 (2021-12): Plastics – Determination of Tensile Properties – Part 4: Test Conditions for Isotropic and Orthotropic Fibre-reinforced Plastic Compounds (see also the version with amended test conditions in ISO 527-4 (2023-03))
|}

[[Category:Fracture Mechanics]]

Multiple Fracture UD Tapes - Revision history