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{{Language_sel|LANG=ger|ARTIKEL=Kurzfaserverstärkte Verbundwerkstoffe}}
{{PSM_Infobox}}
Short-fibre reinforced plastics
__FORCETOC__

==General==

Short-fibre reinforced [[Thermoplastic Material|thermoplastics]] are a group of materials whose properties close the gap between unreinforced and long-fibre reinforced polymeric materials. A key aspect of the use of this group of materials is their processability in injection moulding.

During the injection moulding process, a specific [[Fibre Orientation|fibre orientation]]—which depends on the material and filler—is created within the [[Plastic Component|component]] or [[Specimen|test specimen]]. Both the degree of orientation and the distribution of the fibres depend on the flow conditions in the melt, the geometry of the [[Moulding Compound|moulded part]] – for example, in the case of [[Specimen|test specimens]], particularly the thickness B – and on fibre-specific parameters such as fibre length and fibre volume content [1–3].

==Models for describing fibre orientation==

Various models exist in the literature that describe the formation of regions with different orientations [3–6]; in the simplest case, a three-layer model, as shown schematically in '''Fig. 1''', can be assumed (see also: [[Glass Fibre Orientation|glass fibre orientation]]).

[[File:SF reinforced Plastics Fig-1.jpg|600px]]
{|
|- valign="top"
|width="50px"|'''Fig. 1''':
|width="600px" |Schematic illustration of the formation of the orientation profile in short-fibre reinforced thermoplastics [1]
|}

In addition, there are interactions between the individual parameters. For example, as the fibre volume content increases, the average fibre length – and thus the aspect ratio – decreases, whilst at the same time the resulting fibre length distribution becomes narrower [1].

The key objective in the development of [[Fibre-reinforced Plastics|fibre-reinforced plastics]] is, in particular, to increase [[Stiffness|stiffness]], [[Strength|strength]] and dimensional stability. However, an increase in stiffness and strength is often accompanied by a decrease in [[Toughness|toughness]]. For this reason, knowledge of the material’s resistance to crack initiation (see: [[Crack Initiation|crack initiation]]) and [[Crack Propagation|crack propagation]] is of ongoing interest for the optimal utilisation of the composite’s properties.

In [7], it is shown that in glass-fibre reinforced polypropylene ([[Plastics – Symbols and Abbreviated Terms|abbreviation: PP]]) materials, depending on the adhesion conditions (see: [[Fibre–Matrix Adhesion|fibre–matrix adhesion]]), non-negligible proportions of stable crack growth can occur, which manifest themselves in the load–deflection diagram as elastic-plastic material behaviour and in the occurrence of [[Crack Propagation Energy|crack propagation energies]]. Elasto-plastic material behaviour also occurs in laminates [8, 9].

==Deformation behaviour of short-fibre reinforced PA6 and PA66 materials==

The following '''Fig. 2''' illustrates, using the matrix materials PA6 and PA66 as examples, as well as a PA6/GF composite with ''φ''v = 0.12 and a PA66/CF composite with ''φ''v = 0.11, the typical load–deflection behaviour recorded in the [[Instrumented Charpy Impact Test|instrumented Charpy impact test]] (ICIT) at a test speed of ''v''H = 0.8 m/s. The materials exhibit elastic-plastic behaviour followed by unstable [[Crack Propagation|crack propagation]].

[[File:SF reinforced Plastics Fig-2.jpg|600px]]
{|
|- valign="top"
|width="50px"|'''Fig. 2''':
|width="600px" |Load–deflection diagram from the instrumented Charpy impact test on PA and PA short-fibre composites
|}

The [[Deformation#Plastic deformation|plastic part]] to the overall deformation process is small, which suggests a low proportion of stable crack growth. Only in the PA6/GF composites do [[Crack Propagation Energy|crack propagation energies]] ''A''R occur after the maximum load has been reached; these indicate a reduction in the crack propagation velocity within the material. The change in crack propagation velocity in these materials is a consequence of the interactions between the [[Crack|crack]] and the fibres.

==See also==

* [[Fibre-reinforced Plastics|Fibre-reinforced plastics]]
* [[Composite Materials Testing|Composite materials testing]]
* [[Layer Silicate-reinforced Plastics|Layer silicate-reinforced plastics]]
* [[Particle-filled Thermoplastics|Particle-filled thermoplastics]]
* [[Glass Fibre Orientation|Glass fibre orientation]]

==References==

{|
|-valign="top"
|[1]
|[[Seidler,_Sabine|Seidler, S.]]: Anwendung des Risswiderstandskonzeptes zur Ermittlung strukturbezogener bruchmechanischer Werkstoffkenngrößen bei dynamischer Beanspruchung. Fortschritt-Berichte VDI-Series 18, No. 231, VDI Publishing, Düsseldorf (1998) p. 71ff; see [[AMK-Library]] under B 2-1)
|-valign="top"
|[2]
|[https://de.wikipedia.org/wiki/Klaus_Friedrich_(Werkstoffwissenschaftler) Friedrich, K.]: Proc. Toughness Fracture and Fatigue of Polymers and Composites. “How to Improve the Toughness of Polymers and Composites”. Yamagata, 11.10.1990, 201
|-valign="top"
|[3]
|Friedrich, K.: Microstructural efficiency and fracture toughness of short fiber/thermoplastic matrix composites. Composites Science and Technology 22 (1985) 43–74; https://doi.org/10.1016/0266-3538(85)90090-9
|-valign="top"
|[4]
|Hegler, R. P.: Faserorientierung beim Verarbeiten kurzfaserverstärkter Thermoplaste. Kunststoffe 74 (1984) 5
|-valign="top"
|[5]
|Kaliske, G., Erber, M., Meyer, F.: Grundsätzliches zur Problematik der Maßänderungen bei glasfaserverstärkten Thermoplasten vom Kurzfasertyp. Plaste und Kautschuk 25 (1978) 647
|-valign="top"
|[6]
|McNally, D.: Short fiber orientation and its effects on the properties of thermoplastic composite materials. Polymer-Plastics Technology and Engineering 8 (1977) 101–154; [https://doi.org/10.1080/03602557708545033 https://doi.org/10.1080/03602557708545033]
|-valign="top"
|[7]
|[https://www.researchgate.net/profile/Sabine-Seidler Seidler, S.], [[Grellmann,_Wolfgang|Grellmann, W.]]: Zähigkeit von teilchengefüllten und kurzfaserverstärkten Polymerwerkstoffen. Fortschritt-Berichte VDI-Series 18, No. 92, VDI Publishing, Düsseldorf (1991), (ISBN 3-18-149218-3; see [[AMK-Library]] under A 4)
|-valign="top"
|[8]
|Karger-Kocsis, J., Czigany, T.: Fracture behaviour of glass-fibre mat-reinforced structural nylon RIM composites studied by microscopic and acoustic emission techniques. Journal of Materials Science 28 (1993) 2438–2448; [https://doi.org/10.1007/BF01151677 https://doi.org/10.1007/BF01151677]
|-valign="top"
|[9]
|Tschegg, E. K., Humer, K., Weber, H. W.: Fracture tests in mode I on fibre reinforced plastics. Journal of Materials Science 28 (1993) 2471–2480; [https://doi.org/10.1007/BF01151682 https://doi.org/10.1007/BF01151682]
|}

[[Category:Plastics]]

Short-fibre Reinforced Plastics - Revision history