To predict and optimize the mechanical properties of new class of advanced composites, real engineering situations and appropriate assumptions should be considered. Moreover, a profound understanding of the relationship between real microstructure of composites and their mechanical properties is necessary. This study is concerned with the debonding damage and particle distribution effects of reinforcements on overall mechanical properties of particulate reinforced light weight metal matrix composites. A micromechanical model is developed to take into account debonding of reinforcements, particle size and the elastoplasticity by means of incremental damage theory. Reinforcement/matrix interfacial debonding phenomena is characterized by a cohesive zone model implemented in finite element method. The results show that the assumption of fully bonded particles in composites under loading is incomplete and the influence of cohesive energy at interface is considerable. In the case of a lower cohesive energy value, there are potential sites for debonding and the stress-strain relation of damaged composite deviates from that of the perfect composite at a lower stress level.Mechanical properties of particulate reinforced composites are highly dependent on the real microstructure of the composite and spatial distribution of reinforcement particles. A new micromechanical model based on defining clustering parameters is presented to take account of effects of the randomness of the particles. For composite with clustering defect, the clustered regions would start yielding at a higher macroscopic stress during uniaxial tension. The finite element simulation based on the real morphology shows that the plastic flow on the matrix inside the cluster is inhibited. Due to the plastic flow constraint, there is a great tendency towards debonding and crack initiation around the perimeter of a cluster. Experimental findings show that there is a strong relationship between damage formation and the local volume fraction of reinforcements. Moreover, effects of microstructure and particle clustering on fatigue properties and crack initiation and propagation of novel amorphous particles reinforced Mg-composites are investigated. The experimental results show that the crack growth in particulate reinforced composites is a highly localized phenomenon influenced primarily by the distribution and microstructure of particles near the vicinity of the crack tip. The rate of the crack growth through the clustered region was significantly higher than through the matrix or through a region of well-dispersed particles. It is shown that composites with more uniform particle distribution possess a superior fatigue resistance and fatigue limit.
|Julkaisun otsikon käännös||Mechanical modeling of particulate reinforced metal matrix composites|
|Tila||Julkaistu - 2016|
|OKM-julkaisutyyppi||G5 Tohtorinväitöskirja (artikkeli)|