Experimental and Numerical Investigation of The Mechanical Behavior of Discontinuous Fiber Composite Structures Under Multi-axial Loading

Abstract

Discontinuous Fber composites (DFCs) are widely used in aerospace and other industries. While being not as strong as traditional unidirectional fiber composites, DFCs are still preferred thanks to its lightweight, ease of manufacturing and aesthetic purposes in application that does not require extreme capabilities. However, DFCs have the potential to be used for complex and critical components like joints and braces, of which diffcult to use traditional continuous fiber composites. Such components are naturally subjected to mixed mode loading conditions. The focus of this thesis is to explore the response of DFCs under multi-axial loading conditions to have a better understanding how this material behave. The multi-axial loading was applied using the Arcan rig adapted from Yao et al.. A modification of the Arcan rig system was made to ensure the correct bi-axial failure for DFC coupons. Experimental results showed that the DFC test specimens exhibit similar stiffness and strength to quasi-isotropic layups in pure tension and pure shear, while the energy release per volume amount is lower than the traditional layup. Stochastic finite element model of DFCs adapted from Ko et al. using random platelet generation algorithm combined with Hashin failure criteria was developed to capture the multi-axial behaviors of DFCs. The model managed to capture the strength of DFCs accurately but showed limited accuracy in terms of the non-linear behavior due to shear load. The experimental and numerical analysis of DFCs under the multi-axial loading demonstrated unique structural behaviors of DFCs. This study provides a valuable set of data for engineers and designers who wish to calibrate their model under the multi-axial loading conditions.