Sound Isolation Analysis And Optimization Of Carbon Fiber Composite Materials

Safety, energy conservation and environmental protection have become the main theme of the current automotive industry, and lightweight design proves to be the mainstream trend for modern automotive design.Carbon fiber reinforced polymer (CFRP), as a a newly emerging composite material, has become one important lightweight substitute due to its outstanding mechanical and chemical properties. The strength-to-weight ratio of CFRP is much larger than that of steel. Moreover, with other exceptional properties such as heat resistance, anti-friction and anti-corrosion, CFRP turns out to be ideal for the manufacture of car bodies. Compared with traditional materials, however, CFRP has its own weaknesses. It is more likely to produce vibration and sound radiation due to its smaller density. What’s more, the orthotropic property of CFRP makes it more difficult for the investigation of its dynamic behaviors compared with its isotropic counterparts.For the sake of exploring the sound isolation property of laminated CFRP panel, and finding the way to optimize its sound transmission loss value in low and medium frequency range, this paper investigated and discussed the dynamic properties of CFRP in the following several aspects.Firstly, the sound isolation mechanism of thin infinite isotropic panels and the basic structure and mechanical properties of fiber reinforced laminated panels were introduced, with an elaboration of its naming method and expression of bending stiffness. Based on these, a sound isolation model of infinite laminated composite material panels was established and validated.Secondly, the frequency-based sound isolation characteristics of panel structures were briefly introduced. Then, on the basis of mechanics of composites, the expression and maximization method of the first-order natural frequency of simply-supported anti-symmetric CFRP panel were theoretically deduced and numerically validated, based on which the optimization method of the low-frequency sound isolation capacity of simply-supported anti-symmetric CFRP panels was acquired. Also, the sound transmission loss values in the low-frequency range of panels made of steel, aluminum and CFRP under the condition of either identical thickness or bending stiffness were compared respectively. Thirdly, the conception of simulated annealing (SA) algorithm as well as the sound radiation theory of panel structure was introduced, on the basis of which a SA algorithm that can optimize the medium-frequency sound isolation ability of simply-supported anti-symmetric CFRP panel was programmed. Then, the sound transmission loss values in the medium-frequency range of panels made of steel, aluminum and CFRP under the condition of either identical thickness or bending stiffness were compared respectively, as in the previous chapter.Finally, in the light of the frequency-based characteristics of environmental noise a car is exposed to, a strategy was put forward that CFRP panels with optimum medium-frequency sound isolation ability are most suitable for the manufacture of car bodies. As has been justified numerically, the strategy is beneficial for both the improvement of sound isolation capacity of the car body and practical design and manufacture.