One promising approach to increase mechanical properties as well as fatigue life of composite laminates is thus a modification of the matrix with carbon nanoparticles such as few layer graphene. In order to understand the mechanisms of crack initiation in neat as well as nanoparticle modified matrix in the small volume between the fibres, size effects of the material should be concerned.
Brittle materials like epoxy matrix systems show a size effect due to a statistical defect distribution that results in increasing strength with decreasing volume. This size effect is investigated for unmodified and carbon-nanoparticle modified epoxy matrix. Nanoparticles are dispersed in the matrix with a three roll mill. Unmodified and modified matrix fibres are manufactured and tested in single fibre tension tests. With scanning electron microscopy (SEM) the influence of the nanoparticles with regard to failure initiation is evaluated.
The influence of graphene nanoparticle modification on crack initiation and crack propagation in carbon fibre reinforced plastics (CFRP) is investigated using cross-ply laminates [0°/90°2]s in cyclic tests (f = 6 Hz). For determining the effect in the different layers, the matrix either in the 0°-layers or in the 90°-layers is modified. Unmodified laminates are tested for comparison. Interrupted tests are performed in order to analyse the crack development via ex-situ x-ray measurements.
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