Magnetostrictive properties of epoxy resins modified with Terfenol-D particles for detection of internal stress in CFRP. Part 1: Materials and processes

Magnetostrictive particles like Terfenol-D are investigated with respect to their ability to detect internal stress, generated in carbon fibre-reinforced polymers (CFRP) in a non-destructive way. The results are presented in two parts. The first part elucidates the ideas for the preparation of dispersions based on these particles with high density in epoxy resins. There is particular focus on the effects of particle size and concentration. Different particle sizes in a range of 0–300 μm are selected by special separation techniques. The particle size distribution is controlled in dry state by laser diffraction method. Changing of the chemical composition, particularly by the oxidation of particles, is analysed by EDX. Use of a magnetic field is identified as a suitable means for the stabilisation of these high-weighted particle fractions dispersed in epoxy resins. The particle size distribution, as well as the alignment of particles, in the cured epoxy resins is investigated by SEM and light microscopy. The second part of the study covers the magnetostrictive properties of the modified epoxy resins which are quantified by the detection of internal stress in CFRP.