Short Fiber Reinforced Composite Mechanical Properties Prediction

The core role of the researches for the composites' mechanical properties is to establish the academic relationships between the macro-mechanical properties of the composites, its micro-structure and the properties of its ingredients. This can provide necessary academic bases and important means for composites' optimizing design.The objective of the present dissertation is to study the macro-mechanical properties of short-fiber reinforced composites(SFRPs) and its forecasting methods on the basis of micro-mechanics. By using the mechanical models of unidirectional short-fiber reinforced composites, laminate theory of planar composites and fiber orientation tensor, a mechanical model have been developed, which can be used to predict the macro-mechanical properties of composites reinforced by planar or 3 dimensional aligned short fiber. The model established the academic relationships between the macro-mechanical properties of the composites, its micro-structure and the properties of its ingredients to some extent. The following work has been finished in this dissertation:1. The mechanical models of unidirectional short-fiber reinforced composites developed by the former researchers have been analyzed and corresponding computer program of some of these models have been developed, too. It shows that most of these models' numeric results are either larger or smaller and the results achieved by using Tandon-Weng model are relatively precise by the comparison of the calculated results of these programs and results achieved bycorresponding finite element.2. A fiber orientation function and second order fiber orientation tensors are used to represent the fiber orientation state of the short fiber reinforced composites with planar or three dimensional aligned short fiber. And then, the eigenvectors and corresponding eigenvalues are numerated with Yakebi numeric method.3. By using the mechanical models of unidirectional short-fiber reinforced composites, laminate theory of planar composites and fiber orientation tensor, a mechanical model have been developed, which can be used to predict the macro-mechanical properties of composites reinforced by planar or 3 dimensional aligned short fiber. The longitudinal modulus E11, transverse Yang's modulus E22, and shear modulus G12, predicted by this model arerelatively precise and the other results achieved by using this model are exact only when calculate the mechanical properties of composites reinforced by planar aligned short fiber.4. On the basis of numeric results, the laws of how the mechanics of fiber and matrix, the volume fraction, aspect ratio and the orientation state of fiber react to the Yang's modulus, shear modulus, poisson modulus of short fiber reinforced composites are been investigated.