In this study, a micromechanics model has been proposed for predicting the effects of particle size and aggregation on elastic properties of nanocomposites, and the interphase between the particle and matrix is also taken into account. Inherent characteristics of nanoparticle, such as small size and high surface area ratio, make nanoparticle in a state of unstable energy and easy to agglomerate in matrix. The analytical expressions for the effective elastic modulus of nanocomposites are derived, which can consider the effect of particle agglomeration. The dispersion state or degree of agglomeration of nanoparticle and the thickness and stiffness of interphase are known to have a significant influence on nanocomposites. The results show that the increase of particle radius and agglomeration volume fractions reduces the elastic stiffness of nanocomposites. Moreover, the composite reinforcement can be improved by increases of interphase thickness and stiffness.
In this paper, the effective properties of particle-reinforced composites with a weakened interphase are investigated. The particle and interphase are regarded as an equivalent-inclusion, and the interphase zone around the particle is modeled as a linear elastic spring layer. A modified micro-mechanics model is proposed to obtain the effective elastic modulus. Moreover, a statistical debonding criterion is proposed to characterize the varying probability of the evolution of interphase debonding. Numerical examples are considered to illustrate the effect of imperfect interphases on the effective properties of particle-reinforced composites. It is found that the effective elastic properties obtained in the present work are in a good agreement with the existing data from the literatures.
The microstructure evolution of a ferrite/bainite dual-phase steel during uniaxial tension was observed in-situ technology. The effects of tensile rates on microstructure, mechanical properties and fracture mechanism were studied. The result shows that stress concentration is easy to form cracks at the interfaces between ferrite and bainite. The sample exhibits high uniform elongation and strength at low-strain rate, which is attributed to the effective interaction between dislocations. The microstructure undergoes orderly and continuous high hardening rate under ‘harmonious’ conditions. Dislocations are rapidly entangled at high-strain rate and dislocation cells forms. The increased strength of the ferrite brings a reduction in its ability to coordinate more plastic deformation, which eventually leads to local plastic instability and early fracture.
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