"DuPont des Matériaux" Award 2010 - Aude Hauert

"For a new stochastic damage mechanics model, built on the basis of careful experimentation coupled with advanced micromechanical analysis, that predicts the mechanical properties and engineering potential of novel infiltrated ceramic particle reinforced metals for energy-efficient structural applications. "

Damage propagation and fracture in highly reinforced particulate metal matrix composites.

The present work contributes to understand damage evolution and fracture behaviour of two-phase materials that combine brittle particles with a ductile matrix. We focus on model composites roughly half-ceramic/half-metal produced in-house by infiltrating ceramic powder beds with liquid aluminium. Like many other materials, these composites exhibit two modes of tensile failure; either by tensile instability, or alternatively break prematurely, in a brittle fashion.
The physics of fracture in these two-phase materials is explored by testing samples of varying size and geometry. Furthermore, a micromechanical model is established that links damage build-up and composite fracture, accounting for two extreme modes of load sharing (similarly to models for continuous-fibre reinforced composites). This model predicts the tensile curve and the strength of particulate composites that undergo damage in the form of statistical particle fracture. It captures the transition from failure by tensile instability to brittle failure that occurs with an increase in matrix strength or with a decrease in particle strength. Strength predicted under the assumption of local load sharing is in good agreement with experiment. The local load redistribution upon particle fracture and avalanche-like growth of damage can thus explain the premature brittle failure observed in some composites.