Composites are increasingly used in engineering applications due to their superior strength- to-weight ratio and ability to manufacture them as per the design. The composites might be subject to complex combined loading in critical components like pressure bottles, wind blades etc. Hence conducting biaxial studies is crucial because multiaxial characterization of composites will improve our understanding of their mechanical behavior and characterization. This study mainly focused on the development of the bi-axial test specimen for study of several composite laminates with the aim of achieving the pure bi-axial stress field in the gage area itself. Also, developed the bi-axial test set-up to load the materials under different bi-axial loading conditions to test their behavior and tested glass/epoxy composite laminate with quasi-isotropic lay-up [00/-600/600]. The study is further extended in performing finite element simulations with different ply sequence to understand the material bi-axial stress behavior which will enable the better design of composite laminates under multi-axial loading conditions. Based on the bi-axial stress-strain behavior [00/- 600/600] laminate configuration is more promising compared to other layup configurations for bi- axial loading conditions.

•Based on the displacements mentioned in Table 5, except uni directional laminate, rest of the laminate configurations are yielding equi bi-axial displacement field in the desired gage area. •The cross-ply laminate configuration [00/900/900/00] shows the same displacement field in primary X and Y directions, but the strains are slightly higher in X and Y directions compared to quasi-isotropic laminate configurations. [00/-600/600] laminate configuration is more promising compared to other layup configurations for bi-axial loading conditions. However, depending on the desired load ratios in X and Y directions, the layup stack-up can be modified based on the established stress-strain field using the finite element simulations with different configurations.

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