Research Projects

Fabric and fabric-reinforced laminate composites are widely used in various applications due to their high specific strength, stiffness, corrosion resistance, and low cost. However, understanding the failure modes of these composites under complex loading conditions, such as biaxial loading, is crucial for safe operations. Fabrics used in high altitude airships, pressure vessels, storage tanks, shear webs, spar boxes, and envelope materials face biaxial stress states during their service conditions. Critic biaxial technique is widely recognized for understanding fabric mechanical behavior under biaxial stress states, but it is relatively rare due to lack of standardized geometry and high testing equipment costs. Additionally, failure outside the test zone of the cruciform specimen is often due to geometrical discontinuities and defects. Therefore, optimization of geometry is essential for valid biaxial failures. This work aims to use novel cruciform specimen geometry optimized through finite element simulations to understand the dominant failure mode of fabric and laminated composites. A miniaturized biaxial test setup with novel specimen fixture assembly will be used for testing, minimizing material and machining costs while maintaining experimental data accuracy. Non-contact strain measurement technique will be employed for continuous monitoring of displacement/strain during biaxial loading, while DIC technique will capture the deformation gradient and damage progression in the test zone. Fractographic analysis will be used to identify the dominant failure mode as a function of stress state. Strength and failure strain under various stress states will be used to construct failure envelopes for glass-fabric and glass-fabric/PTFE laminated composites.