| Research Abstract |
In this research, the effort is made on developing a constitutive model for particle/fiber dispersed composites such as MMC, when either of the composition undergoes nonlinear deformations. In the first year the mixing law was established, and the theory was expanded toward the application in the wide area of the material situation. The objectives of the research was set to : (I) analyze meso-local nonlinear phenomena occurring around the particle such as plastics and damage by FEM ; (II) further extend the particle dispersed composite theory to the nonlinear regime such as plasticity or damage. Moreover, derive a thermal expansion law and a thermal conduction law for the composite ; (III) conduct a uniaxial tension test of the composite material to examine the developed constitutive model ; and (IV) derive a constitutive law for the fiber reinforced composite material, where the orientation of fiber plays an important role on the characteristics of the composite.
Along the objectives s
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tated above, the research was conducted and yielded the following results :
(1) In the present effort, basic theories of with regard to the mixing law, that is the Self-consistent Compliance Method (SCC), and a Localized Rigidity Method (LRM) for the nonlinear constitutive law have been developed. Especially, the development of the latter made, for the first time in this field, the nonlinear constitutive law for the particle dispersed composite possible with an excellent accuracy of the model.
(2) The aspect ratio of the particle in the model was set to be large number in order to model a fiber inclusion in the composite. Since the characteristics of a whisker dispersed composite is sensitive for the fiber orientation, the effect of the fiber orientation is properly accounted in the model.
(3) In addition to the developed constitutive law, a thermal conduction law and a thermal expansion law were also developed based on the SCC model, in the present effort.
(4) To check the accuracy of the theoretical model above, meso-mechanics analyses by a finite element method were performed. Excellent correlations between the models and the analyses were obtained
(5) In order of showing a practical reliability of the developed models, a tensile test of a commercial fiber dispersed composite material with Nylon 66 as the matrix and carbon fiber as the inclusion was conducted. The same material was used to test the thermal conductivity and the thermal expansion characteristics for various volume fractions of the inclusion.
Very good correlations were obtained also between the model and the experiments in all the cases, where the fiber orientation distribution gives a sensitive effect on the composite characteristics.
(6) The works from the present research effort were published in the JSME journal and several proceedings of international conferences, and presented in a number of domestic as well as international conferences. Still several more publications are under way. Less
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