Fibre-matrix adhesion in glass-fibre reinforced polyamide-6 silicate nanocomposites

A three-phase composite material is studied to investigate interfacial bonding between the fibres and the matrix. The main reinforcing phase consists of continuous E-glass fibres, whereas the polyamide-6 based matrix is a nanocomposite reinforced with platelets of exfoliated layered silicate. Two different types of nanocomposite were used with different degrees of exfoliation of the silicate layers: one with non-modified silicate and one with an organically modified silicate. The fibre-matrix interfacial bonding properties of these fibre-reinforced nanocomposites were studied by means of the single fibre fragmentation test (SFFT). This test provides the critical fibre aspect ratio (critical fibre length/fibre diameter, Lc/D) and this parameter is used to compare the interfacial bonding for different systems. The following parameters and their influence on interfacial bonding are studied: fibre surface treatment, type of clay filler, quantity of clay filler, and moisture content. Mechanical properties of the matrix materials such as stiffness and yield behaviour are studied to find out how they could influence the test results. The SFFT results for the various nanocomposite matrix materials are compared with various models that describe the critical aspect ratio as a function of the mechanical properties. We conclude that the failure mechanism is by interfacial de-bonding and that both the addition of nanoparticles and moisture conditioning has a negative effect on the bonding between the matrix and the glass fibres.