View source for Fibre–Matrix Adhesion

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<span style="font-size:1.2em;font-weight:bold;">Fibre–Matrix Adhesion</span>
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==Fibre–Matrix Adhesion==

The influence of the fibre–matrix [[Phase Boundary Surface|interface]] is considered significant for [[Strength|strength]] and [[Toughness|toughness]] properties. Compared to fully bonded fibres, which allow force transfer during mechanical [[Stress|stress]], the increase in [[Toughness|toughness]] and [[Tensile Strength|strength]] achievable with non-bonded or only partially bonded fibres is low. With little or no adhesion, less energy is required to detach the fibre and force transfer is not possible due to the absence of interaction at the fibre–matrix interface. Furthermore, with sufficient filler content, the boundary layer leads to local [[Ductility Plastics|ductility]] in the adjacent matrix and thus to a reduction in stress concentrations (see: [[Fracture Mechanics|fracture mechanics]]) [1].

==Verification of adhesion==

[[Scanning Electron Microscopy|Scanning electron microscope]] images (SEM images) enable a qualitative assessment of the adhesion of the fibres in the [[Polymer|polymer]] matrix. Figure 1 shows the fracture surface topography (see also: [[Fracture Types#Microscopic fracture features|fracture types]] for [[Plastics|plastics]]) of polypropylene-glass fibre ([[Plastics – Symbols and Abbreviated Terms|abbreviation]]: PP/GF) composites with different adhesion conditions [2].

[[File:fa_ma_bild1.jpg]] 
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|width="50px"|'''Fig. 1''': 
|width="600px" |Fracture surface images for evaluating the [[Fracture Behaviour|fracture behaviour]] of a PP/GF composite with missing (a) and good interfacial adhesion (b); I – fibres not covered by matrix material, II – [[Hole Formation Plastics|hole formation]] due to pulled-out fibres, III – fibre imprint, IV – fibre bonded to the matrix, and V – locally plastically deformed matrix area [2]
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'''Subfigure 1a''' shows that the fibres are not covered with matrix material (I) and that no [[Deformation#Plastic deformation|plastic deformation]] can be observed in the area of the fibres and holes (II and III) depending on the matrix properties and the [[Deformation Velocity|deformation velocity]]. '''Subfigure 1b''', on the other hand, shows a [[Fracture Surface|fracture surface]] with good interfacial adhesion. Damage initiation (see also: [[Failure Analysis – Basics|failure analysis – basics]])  is characterised by the breaking of bonds at the fibre boundary layer (IV), preferably at the fibre ends, and leads to pull-out or fibre fracture with very little matrix deformation in a brittle matrix. In a ductile matrix, the processes of ‘[[Fibre-reinforced Plastics Fracture Model|debonding]]’ and ‘[[Fracture Behaviour#Fracture behaviour, short fibre composites|pull-out]]’ can occur through local plastic flow processes (V), with void formation as the dominant damage mechanisms [1, 3]. Comparable [[Electron Microscopy|electron microscope]] images can be found in [1, 4–6].

'''Figure 2''' shows the fibre–matrix adhesion of a polyamide 66/glass fibre composite material as a function of location on the [[Fracture Surface|fracture surface]].

[[File:Fibre-Matrix_Adhesion_Fig-2.jpg|650px]]
{| 
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|width="50px"|'''Fig. 2''': 
|width="600px" |Fracture surface images of polyamide 66/glass fibre composites for investigating fibre–matrix adhesion as a function of location on the [[Fracture Surface|fracture surface]] perpendicular to the surface (a) and at an acute angle to the [[Surface|surface]] (b) [2]
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==Preparation of fracture surfaces==

If the [[Fracture Surface|fracture surface]] is prepared to check the bonding of the fibres to the matrix, attention must be paid to the location of the specimen. For example, if a [[Crack|crack]] propagates in a [[Fibre-reinforced Plastics|fibre-reinforced plastic]], leading to a brittle fracture, brittle material failure (see also: [[Brittle Fracture Promoting Factors|brittle fracture promoting factors]]) is more likely to occur, especially in thick-walled components. If the crack does not run perpendicular to the surface, i.e. if the direction of crack propagation changes due to geometric features, for example, and runs at an acute angle to the outside near the surface, a peel fracture occurs. Here, the crack propagation speed is reduced, the [[Deformation#Plastic deformation|plastic deformation]] capacity of the matrix material increases as a result of the transition to a [[Plane Stress and Strain State|plane stress state]], and the fibres are no longer completely separated from the matrix in this area; the material appears to have better fibre--matrix adhesion in this area.

==See also==

* [[Fracture Types|Fracture types]]
* [[Fibre-reinforced Plastics Fracture Model|Fibre-reinforced plastics fracture model]]
* [[Fracture Process Zone|Fracture process zone]]
* [[Fibre Agglomeration|Fibre agglomeration]]
* [[Fibre Orientation|Fibre orientation]]

==References==

{|
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|[1]
|[[Michler,_Goerg_Hannes|Michler, G. H.]]: Kunststoff-Mikromechanik – Morphologie, Deformations- und Bruchmechanismen. Carl Hanser, Munich Vienna (1992), (ISBN 3-446-17068-5; see [[AMK-Library]] under F 4) 
|-valign="top"
|[2]
|Kotter, I.; Langer, B.; [[Bierögel,_Christian|Bierögel, C.]]; [[Grellmann,_Wolfgang|Grellmann, W.]]: Technische Kunststoffdiagnostik – Schadensanalyse an Kunststoffbauteilen. In: Pohl, W. (Eds:): Konstruktion, Qualitätssicherung und Schadensanalyse. Conference „Werkstoffprüfung 2007“, November 29–30, 2007, Neu-Ulm, Proceedings, pp. 273–278 (ISBN 978-3-514-00753-6; see [[AMK-Library]] under M 14) 
|-valign="top"
|[3]
|[https://de.wikipedia.org/wiki/Klaus_Friedrich_(Werkstoffwissenschaftler) Friedrich, K.]: Fractographic analysis of polymer composites. In: Friedrich, K. (Eds.), Application of Fracture Mechanics to Composite Materials. Elsevier Science Publishers B. V., Amsterdam (1989) 425–487 (e-Book: ISBN 978-0-4445-9721-2) 
|-valign="top"
|[4]
|Michler, G. H.: Electron Microscopy of Polymers. Springer, Berlin Heidelberg (2008) (ISBN 978-3-540-36350-7; see [[AMK-Library]] under F 1) 
|-valign="top"
|[5]
|Michler, G. H., Balta-Calleja, F. J.: Nano- and Micromechanics of Polymers – Structure Modification and Improvement of Properties. Carl Hanser, Munich (2012) (ISBN 3-446-42767-8; see [[AMK-Library]] under F 13) 
|-valign="top"
|[6]
|Sommer, G. S.: Mikromechanische Untersuchungen zur Faser-Matrix-Haftung in Faser-Kunststoff-Verbunden: Einfluss von Härtungsdauer, Feuchtigkeit und Prüfparametern. Technische Universität Dresden, Fakultät Maschinenwesen (2018) (see [[AMK-Library]] under C 43)
|}

[[Category:Morphology and Micromechanics]]
[[Category:Damage Analysis_Component Failure]]