Equivalent Properties And Scale Effect Of The Random Short Spruce Fiber Reinforced Composite

Short plant fiber reinforced composites have been widely used in the automotiveindustry and the construction industry recently due to their good anti-wear properties,high specific strength and stiffness. The equivalent properties are their significantdesigning criteria. In addition to experiment, the numerical method plays an importantrole in predicting the effective property of composites.A simple2D FEM unit cell model of short spruce fiber/polypropylene compositewas set up to predict the equivalent elasto-plastic property by considering both thefiber volume content and the aspect ratio. Among six classic theoretical results, thenumerical prediction showed good agreement with the Wu’s while λ=1.7. The stresstransfer mechanism in the anisotropy spruce fiber was studied and the normalcohesive strength of the interface was predicted initially under the CZM framework.By compiling program with Python, a2D random periodic representative volumeelement (RVE) model was generated and the displacement difference boundarycondition was applied. In this model the different model scales, anisotropy of sprucefiber, random fiber position, both the random orientations of fiber material and fiberattitude, aspect ratios and volume contents were considered roundly. The equivalentelastic property of the material was calculated with homogenization methods. Theinfluences of model dimension scale on the equivalent modulus were investigatedbased on two fiber volume fractions model. The results showed that, in the fiber scale,the composite presented obviously anisotropic, and as the scale enlarged, the effectiveproperty tended to be homogenous isotropy.Both the compression and the cyclic compression behavior of the compositeswere conducted by means of experimental methods. The cohesive zone model wasused to characterize the mechanics behavior of the interface in a numericalcompression model. The influences of the interface parameters on the compressionmodulus were studied in detailed. It showed that the compression modulus wassignificantly affected by normal interface stiffness among the other interfacialparameters such as the tangential interface stiffness, effective displacement at damageinitiation, and the effective displacement at complete failure.