Erosion behavior of a large number of gas-turbine grade ceramic matrix composites (CMCs) was assessed using fine to medium grain garnet erodents at velocities of 200 and 300 m/s at ambient temperature. The CMCs used in the current work were comprised of nine different SiC/SiCs, one SiC/C, one C/SiC, one SiC/MAS, and one oxide/oxide. Erosion damage was quantified with respect to erosion rate and the damage morphology was assessed via scanning electron microscopy (SEM) and optical microscopy in conjunction with three-dimensional (3D) image mapping. The CMCs response to erosion appeared to be very complicated due to their architectural complexity, multiple material constituents, and presence of pores. Effects of architecture, material constituents, density, matrix hardness, and elastic modulus of the CMCs were taken into account and correlated to overall erosion behavior. The erosion of monolithic ceramics such as silicon carbide and silicon nitrides was also examined to gain a better understanding of the governing damage mechanisms for the CMC material systems used in this work.

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Foreign object damage (FOD) behavior of an N720/alumina oxide/oxide ceramic matrix composite (CMC) was characterized at ambient temperature by using spherical projectiles impacted at velocities ranging from 100 to 350 m/s. The CMC targets were subject to ballistic impact at a normal incidence angle while being loaded under different levels of tensile loading in order to simulate conditions of rotating aeroengine airfoils. The impact damage of frontal and back surfaces was assessed with respect to impact velocity and load factor. Subsequent postimpact residual strength was also estimated to determine quantitatively the severity of impact damage. Impact force was predicted based on the principles of energy conservation.

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The structural and magnetic properties of the TbPt1−xCux orthorhombic compounds are studied in two series of samples: prepared ‘as quenched’ and after an annealing treatment. An extended analysis of the influence of the annealing in the microstructure of the samples was performed by x-ray, neutron diffraction and scanning electron microscopy. This analysis allows us to understand the modifications in the magnetic properties of both series, as a consequence of the sample homogenization process. Changes from ferromagnetism to antiferromagnetism with increasing Cu concentration are found in both series despite the ionic distance invariance. x = 0.3 is the composition limit between both behaviours. This study strongly supports the importance of the conduction band state rather than ionic distances in the magnetic behaviour of these rare earth–d compounds.