Oluschinski at 06:38, 15 December 2025

2025-12-15T06:38:04Z

← Older revision		Revision as of 08:38, 15 December 2025
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	* plastic deformation and matrix failure		* plastic deformation and matrix failure

	[[file:~~faserverbund~~.jpg\|300px]]		[[file:Fibre_Composite-2.jpg\|300px]]

	==Fracture behaviour, particle filled thermoplastics==		==Fracture behaviour, particle filled thermoplastics==
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	* fibril fracture		* fibril fracture

	[[file:~~teilchenverbunde~~.jpg\|300px]]		[[file:Fibre_Composite-3.jpg\|300px]]

	==See also==		==See also==

Oluschinski: Created page with "{{Language_sel|LANG=ger|ARTIKEL=Bruchverhalten}} {{PSM_Infobox}} Fracture behaviour, plastics FORCETOC ==General information== Depending on the type and stress conditions, polymer materials (see also: plastics) exhibit very different behaviour at break. Some semi-crystalline polymers such as polyamide (abbreviation: PA), polyethylene (..."

2025-12-02T08:24:40Z

Created page with "{{Language_sel|LANG=ger|ARTIKEL=Bruchverhalten}} {{PSM_Infobox}} Fracture behaviour, plastics __FORCETOC__ ==General information== Depending on the type and stress conditions, polymer materials (see also: plastics) exhibit very different behaviour at break. Some semi-crystalline polymers such as polyamide (abbreviation: PA), polyethylene (..."

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{{Language_sel|LANG=ger|ARTIKEL=Bruchverhalten}}
{{PSM_Infobox}}
Fracture behaviour, plastics
__FORCETOC__

==General information==

Depending on the type and [[Stress | stress]] conditions, polymer materials (see also: [[Plastics | plastics]]) exhibit very different behaviour at break.

Some semi-crystalline polymers such as polyamide ([[Plastics – Symbols and Abbreviated Terms |abbreviation]]: PA), polyethylene ([[Plastics – Symbols and Abbreviated Terms |abbreviation]]: PE) and polypropylene ([[Plastics – Symbols and Abbreviated Terms |abbreviation]]: PP) can be cold-drawn up to an elongation ratio of ''λ'' = 20, whereby a stable necking moves along the test [[Specimen | specimen]].

Many amorphous plastics (e.g. polystyrene ([[Plastics – Symbols and Abbreviated Terms |abbreviation]]: PS)) or polymethyl methacrylate ([[Plastics – Symbols and Abbreviated Terms |abbreviation]]: PMMA) are brittle under [[Tensile Test | tensile stress]], but deform plastically under [[Compression Test| compressive stress]] or pure shear stress. Epoxy resins ([[Plastics – Symbols and Abbreviated Terms |abbreviation]]: EP) also exhibit a high degree of [[Ductility Plastics| ductility]] in compression. Typical examples of ductile and tough fracture behaviour include PP, PE and PA.

==Typical mechanisms of plastic deformation==

'''Plastic deformation''' occurs in two forms in ductile polymers:

* '''Shear yielding''', i.e. the formation of shear stress flow zones, which causes a strong change in shape without a change in volume. Many semi-crystalline polymers show shear deformation under tensile stress, room temperature (RT) and testing in air ('''Fig.''').

* '''Crazing''' (normal stress flow zone formation), i.e. the formation of cavities (see also: [[Micromechanics & Nanomechanics | micromechanics & nanomechanics]]) This process causes a strong change in density and occurs in blends and practically all glassy polymers. Individual isolated crazes are often found at low stresses ('''Fig.''').

[[file:bruchverhalten_kunststoffe.png|600px]]
{|
|- valign="top"
|width="50px"|'''Fig.''':
|width="600px" |Schematic representation of deformation phenomena in amorphous plastics
(a) Craze (see: [[Micromechanics & Nanomechanics | micromechanics & nanomechanics]]) 
(b) Sher band
|}

The occurrence of one or both mechanisms depends on the following conditions:

* Structure of macromolecules
* Degree of [[Crystallinity|crystallisation]] and spherulite size
* Degree of deformation
* Presence of a second phase and test conditions
* Temperature
* Deformation rate
* Triaxial stress rate
* Ambient conditions

==Fracture behaviour, short fibre composites==

The use and application limits of short-fibre-reinforced composites are also determined by the need to determine the expected composite properties as precisely as possible in advance. The variety of influencing factors means that a comprehensive theory of the mechanics of polymer composites will not be possible in the future either. It therefore seems most appropriate to describe empirically determined laws using application-orientated, target-oriented models in mathematically simple forms.

There are numerous attempts in the literature to describe the toughness behaviour of fibre-reinforced composites using models [2, 3]. An essential basic assumption in these models is often a brittle material behaviour (see: [[Fracture Types | fracture types]]). Based on this, the toughness behaviour was modelled using theoretical concepts, whereby interaction parameters could often not be taken into account. In general, however, the failure process of short fibre-reinforced plastics is characterised by the occurrence of energy-dissipative processes, whereby the mechanisms shown in the figure occur:

* crack runs around fibre
* pull-out
* debonding
* plastic deformation and matrix failure

[[file:faserverbund.jpg|300px]]

==Fracture behaviour, particle filled thermoplastics==

The model by Bohse [4, 5] shows one possibility for modelling the fracture work that is performed in particle-filled [[Thermoplastic Material | thermoplastics]] with unstable [[Crack Propagation | crack propagation]] and elastic-plastic material behaviour.

In analogy to the model concepts of Friedrich and Lauke [6] for short fibre composites, the following work components occur:

* matrix/particle detachment
* non-linear viscoelastic matrix deformation
* plastic dformation of matrix fibrils
* fibril fracture

[[file:teilchenverbunde.jpg|300px]]

==See also==

* [[Fracture Mechanics | Fracture mechanics]]
* [[Fracture Behaviour of Plastics Components | Fracture behaviour components]]
* [[Fracture Types | Fracture types]]
* [[Micromechanics & Nanomechanics]]
* [[Plastics]]

'''References'''

{|
|-valign="top"
|[1]
|[[Michler,_Goerg_Hannes|Michler, G. H.]]: Kunststoff-Mikromechanik – Morphologie, Deformation und Bruchmechanismen von polymeren Werkstoffen. Carl Hanser Munich Vienna (1992) ISBN 3-446-170685 (see [[AMK-Büchersammlung | AMK-Library]] under F 4)
|-valign="top"
|[2]
|Friedrich, K. (Ed.): Application of Fracture Mechanics to Composite Materials. Elsevier (Composite Materials Science Volume 6), Amsterdam New York (1989), e-Book ISBN 978-0-4445-9721-2
|-valign="top"
|[3]
|Sanadi, A. R., Prasad, S. V. and Rohatgi, P. K.: Sunhemp Fiber-reinforced Polyester. 1. Analysis of Tensile and Impact Properties. J. Material Science 21 (1986)12, 4299–4304; https://doi.org/10.1007/BF01106545
|-valign="top"
|[4]
|[[Grellmann,_Wolfgang|Grellmann, W.]], Bohse, J., [[Seidler,_Sabine|Seidler, S.]]: Bruchmechanische Analyse des Zähigkeitsverhaltens von teilchengefüllten Thermoplasten. Materialwissenschaft und Werkstofftechnik 21 (1990) 9, S. 359–364; https://doi.org/10.1002/MAWE.19900210910
|-valign="top"
|[5]
|Bohse, J., [https://www.researchgate.net/profile/Wolfgang-Grellmann Grellmann, W.], Seidler, S.: Micromechanical Interpretation of Fracture Toughness of Particulate-filled Thermoplastics. J. Material Science 26 (1991) 24, 6715–6721; https://doi.org/10.1007/BF00553697
|-valign="top"
|[6]
|Lauke, B., Friedrich, K.: Fracture Toughness Modelling of Fibre Reinforced Composites by Crack Resistance Curves. Adv. Compos. Mater. 26 (1991) 261–275; https://doi.org/10.1016/0266-3538(86)90055-2
|}

[[Category:Damage Analysis_Component Failure]]

Fracture Behaviour - Revision history

Oluschinski at 06:38, 15 December 2025