what this sentences exactly mean?
(a) localised plastic shear-band yielding around the particles and
(b) cavitation of the particles followed by plastic void growth of the epoxy polymer
Hi,
It means following,
(a) Your S-CSR particles and Epoxy has an interface. When you apply stress through different modes, like any composite, matrix will transfer load to the filler through matrix-filler interface. When you applied stress to a composite, both matrix and filler go through deformation (depends on how strong the interface is, if the interface is stronger and the filler is a tougher material (in your case), the matrix will go through deformation hence plastic deformation of matrix material around a tough filler)
(b) This phenomenon is observed as an addition to (a). When your filler can not yield (higher toughness compare to matrix), the matrix material will fail at the interface (hence the void will be generated). This will be followed by domino effect of stress concentration at multiple matrix-filler interface. You will ultimately have multiple failure in the matrix phase at the interface.
Dear all,
the mechanism of toughning is based on a dumping process in which the diepersed phase acts as both stress concentrator and absorber via a molecular mobility (motion) mechanism. Good stress transmission between the continuous and the dispersed phase is crucial for coherent response between them to a given form of stress. Regards
The crack propargation is stopped at the rubber particles which should have a low glass transition temperature. Crucial for this mechanism is a coupling of rubber particles to matrix. In this case the core of the rubber particles is a silicone rubber with a glass transition temperature of -100°C. As shell some glycidyl methacrylate is radically grafted on the silicone core of the S-CSR particles so that the shell is epoxy functional. This epoxy functinal shell co-reacts with the epoxyde resin during preparation so that there is a coupling at the interface by chemical bonds.
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