Study Of Mechanical And Acoustic Properties Of Composite Materials With Polygonal Inclusions

Nowadays,composite material has become one of the four materials,and more attention has been paid by scholars because of its excellent comprehensive properties and wide application prospects.Especially the designability of material performance,to attract a large number of scholars have conducted a lot of research.Based on the finite element method(FEM),the mechanical and acoustic properties of the composite materials are studied.The main contents of this paper are as follows:In the first chapter,the development and application of composite materials are summarized.And the research status of mechanical and acoustic properties of composites are introduced.In the second chapter,a computational micromechanics model of oriented hexagonal fibers in periodic unidirectional composite materials is established for the determination of effective orthotropic elastic properties of the composite.And then the theory and calculation model of phononic crystals are introduced.In the third chapter,the mechanical properties of the composite materials are studied.Firstly,the influence of the he orientation of hexagonal fibers was studied when E=10,and the fiber volume ratio of 10% and 50% were compared with each other.Then when the effect of E=100 was studies as E=10.Finally,the random distribution of hexagonal fibers is studied.The results show that the simple distribution of the hexagonal fiber can represent the perfect isotropy of the composite for the small fiber volume fraction,i.e.10%,regardless of the oriented angle and the elastic modulus of the hexagonal fiber;While,when the fiber volume fraction increases to 50%,the apparent orthotropic behavior of the composite is observed and becomes stronger with larger elastic modulus of the fiber;More importantly,the results of each mechanical property are symmetrical with respect to those for the 30 oriented angle.For the composite with randomly distributed fibers,it shows stronger orthotropy for both the unified oriented angle and the random oriented angle,compared to the simple fiber distribution.Both the simple fiber distribution and random distribute,the equivalent elastic modulus and shear modulus increase and Poisson’s ratio decrease with the elastic modulus increase of the fiber.Moreover,the change of number of fibers within the cell,including both the hexagonal fibers and the circular fibers,also has significant effect on the effective elastic properties of the composite.In the fourth chapter,the acoustic properties of polygonal inclusion composites are discussed.The band structure of the phononic crystal included by the hole and solid scatterer were calculated respectively.The main models are as follows: two kinds of scatterers with different volume ratio(10% and 30%),the combined scatters and single scatter,the distance of combined scatterers.The results show that there is no complete band gap for the single polygon hole scatterer,There exists a complete band gap when the volume ratio is 30%,and The band gap of hexagonal is wider than that of circle.For the single polygon solid scatterer exists complete band gap in two volume ratio,with the increase of the volume ratio the band gap wider.For the combined hole scatterer,the frequency of band gap and the band gap width increase with the increase of the distance.The combined solid is contrary to the result of hole.In the fifth chapter,the work done in this paper is summarized and the future work is prospected.