Investigation On Meso-mechanics Modeling Of Composite Toughening

In the paper, a composite mechanical model, soft phase is enclosed in hard phase (Hard-/soft-phase structure is called "bimodal" structure), was built. Simulation was carried on the model. Toughening effect was researched about the contribution of matrix phase and toughening phase whose volume percent, scale and material are changeable, so, matrix phase mechanical property can be optimized. Uniaxial compression and tensile test simulation and computation were performed. In order to check the accuracy of the model, computation data was compared with experiment data. The work made as follows:(1)This material with "bimodal " structure was viewed as a kind of composite and the idea of hard-/soft-phase composite toughening was put forward.(2)Discovering the toughening mechanism of composite with crisp matrix and searching the optic microstructure combination are principal motive of researching composite structure.(3)By reviewing experimental results and TEM images made by other researchers, a micro-mechanical model of hard-/soft-phase composite toughening was built by several defined steps including building unit cell, confirming basic hypothesis, boundary conditions, and terminating conditions.(4)The static tensile test of unit cells was simulated by finite element method. The theoretical results were compared with the practically experimental results and the rationality and feasibility of the micro-mechanical model was checked. And more, the performance diversity of this hard-/soft-phase composite was studied that was influenced by scale, volume percentage and shape of toughening phase. Simulation result as follows:(l)The mechanical property change of toughening phase and matrix phase: Toughening phases reveal evident strain strengthening. Matrix phase's plasticity is improved as toughening phase's softening.(2)Mechanical property's matching of two phases: when toughening phase's elastic modulus and poison's ration is closer to matrix phase, matrix phase's toughening effect is better; On the contrary, strong stress concentration between two phases can easily lead to interfaces' mechanical property deteriorism.(3)The influence of toughening phase's scale on composite mechanical property: For the same micro-grain, toughening phase's scale plays a great role in matrix phase's mechanical property. For example, when scale is above 10um, toughening effect gets better of the counterpart below 10um.(4)The influence on toughening effect of toughening phase's volume percent: When toughening phase's volume percent is low, toughening effect is poor. By comparison with toughening phase's scale, toughening phase's volume percent has more influence than grain's scale in toughening effect.(5)The influence on toughening effect of toughening phase's shape (the paper made a study to ratio of length , width and height of cube): Toughening phase's shape has little influence on composite mechanical property for symmetrical cube.(6)Lastly, the model which soft phase is enclosed in hard phase (called "bimodal" structure) is correct by comparison simulation result with experiment result.