Oluschinski at 13:27, 12 December 2025

2025-12-12T13:27:48Z

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	==General information==		==General information==

	The failure of [[Plastic ~~Components~~\|components]] made of [[Plastics\|plastics]] and [[Composite Materials Testing\|composite materials]] (see: [[Fracture Behaviour of Plastics Components\|fracture behaviour of plastics components]]) is promoted by a number of factors known as brittle fracture promoting factors. In addition to an increased strain rate (see: [[Strain Rate Basics\|strain rate – basics]]), low temperatures and/or [[Multiaxial Stress State\|multiaxial stress states]], including [[Tensile Test Residual Stresses Orientations\|residual stresses]], are of crucial importance. The formation of [[Fracture Types\|brittle fracture]] is particularly promoted by stress concentrations at corners, [[Notch\|notches]] or [[Crack\|cracks]], so that the [[Deformation\|deformation]] behaviour under [[Impact Loading Plastics\|impact]] [[Stress\|stress]] on notched test [[Specimen\|specimens]] with varying temperatures must be considered as the critical stress.		The failure of [[Plastic Component\|components]] made of [[Plastics\|plastics]] and [[Composite Materials Testing\|composite materials]] (see: [[Fracture Behaviour of Plastics Components\|fracture behaviour of plastics components]]) is promoted by a number of factors known as brittle fracture promoting factors. In addition to an increased strain rate (see: [[Strain Rate Basics\|strain rate – basics]]), low temperatures and/or [[Multiaxial Stress State\|multiaxial stress states]], including [[Tensile Test Residual Stresses Orientations\|residual stresses]], are of crucial importance. The formation of [[Fracture Types\|brittle fracture]] is particularly promoted by stress concentrations at corners, [[Notch\|notches]] or [[Crack\|cracks]], so that the [[Deformation\|deformation]] behaviour under [[Impact Loading Plastics\|impact]] [[Stress\|stress]] on notched test [[Specimen\|specimens]] with varying temperatures must be considered as the critical stress.

	==Influence of internal condition==		==Influence of internal condition==

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{{Language_sel|LANG=ger|ARTIKEL=Sprödbruchfördernde Faktoren}}
{{PSM_Infobox}}
<span style="font-size:1.2em;font-weight:bold;">Brittle fracture promoting factors</span>
__FORCETOC__

==General information==

The failure of [[Plastic Components|components]] made of [[Plastics|plastics]] and [[Composite Materials Testing|composite materials]] (see: [[Fracture Behaviour of Plastics Components|fracture behaviour of plastics components]]) is promoted by a number of factors known as brittle fracture promoting factors. In addition to an increased strain rate (see: [[Strain Rate Basics|strain rate – basics]]), low temperatures and/or [[Multiaxial Stress State|multiaxial stress states]], including [[Tensile Test Residual Stresses Orientations|residual stresses]], are of crucial importance. The formation of [[Fracture Types|brittle fracture]] is particularly promoted by stress concentrations at corners, [[Notch|notches]] or [[Crack|cracks]], so that the [[Deformation|deformation]] behaviour under [[Impact Loading Plastics|impact]] [[Stress|stress]] on notched test [[Specimen|specimens]] with varying temperatures must be considered as the critical stress.

==Influence of internal condition==

When investigating the deformation behaviour under impact loading, it is not possible to derive generally valid statements about the behaviour of plastics under this stress, even as a funkctino of temperature, using just a few characteristic [[Material Value|values]]. Particularly in the case of [[Thermoplastic Material|thermoplastics]], test [[Specimen|specimens]], [[Moulding Compound|moulded parts]] and semi-finished products manufactured from a material differ in their processing-related internal states:

* [[Tensile Test Residual Stresses Orientations|Orientations]]
* [[Tensile Test Residual Stresses Orientations|Residual stresses]]
* [[Microscopic Structure|Morphology]]
* [[Crystallinity|Degree of crystallinity]] and
* [[Spherulitic Structure|Spherulite size]].

In general, it can be said that higher orientation in amorphous plastics leads to higher impact strength (see: [[Toughness|toughness]]). In semi-crystalline plastics, high orientations can reduce the deformation reserves and thus lead to a reduced [[Material Value|characteristic value]] level.

Furthermore, as the temperature decreases, the molecular mobility freezes, resulting in increasing ambrittlement.

==Selected testing method==

The following methods, which are also listed in this encyclopaedia, are hoghly relevant in practice for investigating the effects of factors that promote brittle fracture:

* [Impact Test|Impact tests]] according to [[Charpy Testing|Charpy]], [[Impact Test#Izod impact test|Izod]] and [[Impact Test#Dynstat impact test|Dynstat]]
* [[Instrumented Charpy Impact Test|Instrumented Charpy impact test (ICIT)]]
* Conventional [[Tensile Impact Test|Tensile impact test]]
* [[Notched Tensile Impact Test|Conventional]] and [[Instrumented Tensile Impact Test (ITIT)|Instrumented tensile impact test (ITIT)]]
* [[Instrumented Puncture Impact Test|Instrumented puncture impact test]]

There are also different technical variants and test specimen shapes for these tests.

==Factors influencing fracture behaviour==

'''Fig. 1''' below shows the factors influencing the [[Fracture Behaviour of Plastics Components|fracture behaviour of plastics components]], categorised according to [[Stress|stress]], geometry, material and environment.

[[file:Brittle_Fractur_Factors.jpg|500px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px" |Factors influencing the fracture behaviour of plastic components
|}

When analysing the mechanical properties and evaluating the deformation and [[Fracture Behaviour|fracture behaviour]] of [[Plastic Component|plastic components]], it is necessary to combine microscopic and macroscopic aspects in order to contribute decisively to the understanding of [[Deformation|deformation]] and fracture mechanisms.

==See also==

* [[Failure Analysis – Basics|Failure analysis]]
* [[Failure Analysis Plastics Products, VDI Guideline 3822|Failure analysis plastics products, VDI Guideline 3822]]
* [[Fibre-reinforced Plastics Fracture Model|Fibre-reinforced plastics fracture model]]
* [[Crack Toughness|Crack toughness]]
* [[Slow Crack Growth|Slow crack growth]]
* [[Vibration Fracture|Vibration fracture]]

'''References'''

* [[Blumenauer, Horst|Blumenauer, H.]], Pusch, G.: Technische Bruchmechanik. Deutscher Verlag für Grundstoffindustrie, Leipzig Stuttgart (2003), 3rd Edition (ISBN 3-342-00659-5; see [[AMK-Büchersammlung|AMK-Library]] under E 29-3)
* Anderson, T. L.: Fracture Mechanics; Fundamental and Applications. CRC Press, Boca Raton (2005) (ISBN 978-0849342608; see [[AMK-Büchersammlung|AMK-Library]] under E 8-2); https://doi.org/10.1201/9781315370293
* [[Grellmann, Wolfgang|Grellmann, W.]], [[Seidler, Sabine|Seidler, S.]]: Mechanical and Thermomechanical Properties of Polymers. Landolt-Börnstein. Volume Band VIII/6A3, Springer, Berlin (2014), (ISBN 978-3-642-55165-9; see [[AMK-Büchersammlung|AMK-Library]] under A 16)
* Krüger, L., Trubitz, P., Hentschel, S.: Bruchmechanisches Verhalten unter quasistatischer und dynamischer Beanspruchung. In: Biermann, H., Krüger, L.: Moderne Methoden der Werkstoffprüfung. Wiley-VCH Publishing, Weinheim (2014) pp. 1–52; ISBN 978-3-527-33413-1 (see [[AMK-Büchersammlung|AMK-Library]] under M 35)

[[category:Instrumented Impact Test]]
[[category: Damage Analysis Component Failure]]

Brittle Fracture Promoting Factors - Revision history

Oluschinski at 13:27, 12 December 2025