Mechanical behavior of flexible fabric composite

This dissertation presents a theoretical and experimental study of the constitutive relations of plain weave flexible fabric composites. The major aspects covered are (A) the development of a theoretical model for predicting the nonlinear elastic finite deformation behavior of the flexible fabric composite under biaxial state of stress, and (B) the characterization of such composites with extensive experimentation.; The flexible fabric composites (coated fabrics) studied in this research are based upon elastomeric matrix reinforced by plain weave fabric. This material is often subjected to biaxial state of stress in wide range of practical applications and hence demands an extensive study of its behavior under such condition.; An extensive experimentation has been performed on different material systems. The experimental study includes the evaluation of material properties of the individual constituents, determination of the geometrical structure of the composite and the measurement of the stress-strain data of the composite subjected to different biaxial stress ratios. High degree of nonlinearity contributed by its inherent geometrical structure and constituent material characteristics, is observed in its mechanical behavior. Hence, the biaxial behavior can not be predicted by simply superposing the unidirectional test results.; A theoretical study has been carried out to formulate its general constitutive relation under biaxial state of stress with large deformation using strain energy method. Both geometrical and material nonlinearities are considered in this unit cell model that also accounts for the fiber matrix interaction. Detailed microscopic analysis at the fiber cross over points has been conducted and thickness strain at that point is evaluated by using the laminated composite theory. Theoretical prediction shows good agreement with the experimental results.; Parametric analysis reveals that for a given biaxial stress ratio the mechanical behavior of flexible fabric composite is significantly influenced by the initial crimp and the strength of the fiber within the composite. A method is presented by which these factors can be estimated from the uniaxial test results of the composite. This technique is used to approximate the biaxial behavior of the composite from its uniaxial test results.