| Fiber reinforced epoxy matrix composites have many merits,such as high specific stiffness,high specific strength,corrosion and fatigue resistance as well as property designable.Recently,environmental protection receives more and more concern,therefore natural fiber composites has become a focus of people's attention.The moduli and strengths of natural fibers are usually much lower than that of synthetic fibers(carbon fibers,glass fibers).Hybrid composites which made of natural fibers and synthetic fibers is a solution to achieve a balance between performance and environmental protection.At present,natural fiber/synthetic fiber hybrid composites have been applied in some industrial fields,such as automobile manufacturing,construction and so on.However,its wet diffusion properties and the moisture absorption effect on its modulus and strength still need thoroughly understood in the application in practical engineering.In this paper,the hygroscopicity,modulus and strength of flax/glass fiber hybrid composites are studied.The main contents of this paper are as follows:(1)Based on the general mass diffusion model,the Fick and non-Fick phenomena of moisture diffusion in hybrid composites and the moisture diffusion model of two-phase symmetrical laminates are studied.The micro-model of moisture diffusion coefficient of unidirectional composites and the average moisture diffusion coefficient model of two-phase symmetrical laminates are also studied.(2)The dynamic viscoelastic model of hybrid composites is established.Firstly,the three-element model is used to simulate the dynamic viscoelasticity of resin matrix and flax fibers.Then,based on the viscoelastic-elastic correspondence principle,the micro-mechanical model of single-type fiber composites and hybrid composites is established.(3)The residual strength model of hybrid composites after hygroscopic aging is established,and the fracture morphology of hybrid composites before and after hygroscopic aging is observed. |
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