Experimental data about mechanical behaviour during compression tests for various matted fibres

A specific experimental device has been set up to test compressive mechanical behaviour of an assembly of fibres. Simple compression, as well as cyclic loading experiments and relaxation tests were performed. The experimental set up also allows to record the evolution of the mat fibre electrical resistance while testing. Experimental results are presented for a variety of fibrous materials. Despite the very different nature of each of these individual fibres, it appears that the mats exhibit a very similar mechanical behaviour. This common behaviour has been observed during monotonic single compression tests, as well as during cyclic or relaxation experiments. These experimental results are discussed in terms of different parameters such as the intrinsic mechanical properties of individual fibres and moreover the tangle intrinsic parameters (effect of fibre length, effect of geometrical position of fibres in the sample, fibre surface modifications. . .). The influence of the contact points between fibres is discussed in regard of the electric resistivity measurement

Rafting microstructure during creep of the MC2 nickel-based superalloy at very high temperature

Directional coarsening of the single-crystalline nickel-based superalloy MC2 has been investigated by means of tensile creep tests at 1100 ◦C. Two specific specimen geometries were designed in order to generate a variety of stress and strain states. Different coarsening microstructures are observed: N- and P-type classical rafting but also coarsening oriented 45◦ away from the load axis. The comparison of microstructure maps with the local mechanical state evaluated by finite element calculations shows that the 45◦ directional coarsening appears in case of very high cumulated strain values (above 10%), independent of the stress sign. Transmission electron microscopy investigations showthat the dislocation microstructure is similar in both N-type and 45◦ coarsened areas

High-temperature oxidation kinetics of NiAl single crystal and oxide spallation as a function of crystallographic orientation

Isothermal and cyclic high-temperature oxidation of NiAl single crystal samples are presented. Oxidations have been carried out at 900, 1050, 1100 and 1150 ◦C on (1 0 0) and (1 1 0) oriented surface. Continuous thermogravimetry in cyclic conditions allows isothermal oxidation kinetics and spalling at each cycle to be followed. Oxidation kinetics are compared between (1 0 0) surface and (1 1 0) surface. (1 0 0) oriented surfaces appeared to oxidize slightly faster than (1 1 0) oriented surfaces. Experimental results of cyclic oxidation are compared to simulated results using a previously published statistical model. Spalling increases when the average oxide scale thickness increases with the number of cycles. Longer tests are necessary to study this evolution during the ’steady-state’ but no critical oxide thickness was found