Fibre-matrix coupling

Fibre matrix coupling in aligned fibre composite (a) coupling for tensile stress parallel to axis 1 and (b) coupling for tensile stress parallel to axis 2. 

The three most important aspects to be characterized in fibre reinforced compounds are fibre aspect ratio, 1/d, fibre orientation and fibre-matrix adhesion, (1/d). An experimental difficulty in studying the processing-structure-properties relationships in these materials is the strongly coupled interrelations of interfaces and processing on the microstructure. 

The quality of the fibre-matrix interface is significant for the application of natural fibres as reinforcement fibres for plastics. Physical and chemical methods can be used to optimise this interface. These modification methods have a different efficiency for the adhesion between matrix and fibre. Accordingly, one has to modify the surface of the fibres or the chemical structure of the plastic or use coupling agents. 

The effect of surface treatment of the cellulose-pulp fibres with various coupling agents to enhance the fibre-matrix interaction was reported in several studies [34-40]. Coutts and Campbell [35] and Blankenhorn et al. [36-38] evaluated a... 

The high performances of HPGF are due to a better coupling of fibre and matrix, and the properties are near those of the LFRT grades with some advantages ... 

The sensitivity of o-Ps to small holes and defects in the material renders PALS a potentially interesting technique for studying composites. If the adhesion between the filler/fibres and the matrix is poor, small voids or defects may be present at the interface which may be detected by the positrons. On the other hand, if the coupling between the constituents in the composite is good, there may be an... 

The addition of MAPP at around 1-2% ensures perfect coverage of the wood fibres by polypropylene or polyethylene. The micrographs in Figure 5.25 clearly show the lack of adhesion between the fibres (in dark colour) and the PP matrix (in light colour). The mechanical properties are increased by at least 30% when a coupling agent is used. 

Figure 4.3 Influence of bend-twist coupling on buckling load of a laminate, (a) Variation of buckling load factor with fibre angle 6 for a laminates with varying bend-twist coupling, (b) Selected D-matrix terms for [—61—61+01+6]s laminate.

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