Metal-matrix composites combine the properties of metals with those of ceramic fibres. Pistons of highly stressed Diesel engines are reinforced in their bottom zones by the implantation of a preform of fibres.Investigations concentrate on the nondestructive detection of inclusions and defects of fibre distribution.Due to the very small dimensions of the defects test methods capable of responding sensitively to such small defect dimensions have to be applied.Good prerequisites to solve the task of defect detection are provided in first line by ultrasonic inspection within the high-frequency range in connection with scanning methods. Natural defects up to a size of 120 pm could be detected by ultrasonics. With artificial test defects, the limit was reached at 100 pm.Eddy-current inspection, another test procedure, was applied for the detection of fibreless zones, as there exist differences of conductivity between fibreless and fibre-reinforced zones. The use of scanning methods with special probes allows to depict fibreless zones up to a size of 100 pm on the specimen surface.

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