A study on fracture behavior of particle reinforced metal matrix composites by using acoustic emission source characterization

A one directional acoustic emission (AE) source characterization has been used during a three point bending fracture toughness test on 6061 aluminum matrix composites with Al2O3 particle reinforcements of 5 and 10 μm sizes, in order to evaluate the dynamic process of micro-fracture in these materials. Different acoustic emission sources are characterized and, as a result, two types of AE events are distinguished. It is observed that at very low strain levels void nucleation is the main source for acoustic emission. At higher levels, the micro pop-in of primary voids and their eventual coalescence results in a different type of acoustic emission. In fine particle reinforced materials, when the amplitude of AE events in void nucleation at fine particles is not high enough to be detected, the main source of AE events is only the void coalescence. By increasing the particle size, the number of detectable events during void nucleation is increased.