Computational Investigation into the Multi-Axial Response of Quasi-Isotropic and Discontinuous Fiber Composites

Abstract

Discontinuous Fiber Composites (DFCs) have surfaced as a feasible substitute fortraditional continuous fiber laminates owing to their superior manufacturability, geo- metric adaptability, low production costs and suitability for high-volume production. Their platelet-based stochastic meso-structure facilitates the formation of intricate shapes while preserving advantageous mechanical properties. The unpredictability in platelet orientation and distribution results in variations in strength, stiffness and fracture characteristics. Despite extensive research aimed at characterizing the ten- sile and shear fracture responses of DFC coupons, most investigations are limited to uniaxial loading conditions. In actual structural components, composite materials are rarely exposed to pure tension or pure shear forces. Brackets, joints, stiffened panels, and molded automotive and aerospace components undergo combined tension-shear loading, with the inter- play of normal and shear loads determining the onset and progression of damage. In multi-axial stress states, fiber-matrix interactions and gradual stiffness degradation are pivotal in the progression of failure. Current strength assessment methods that concentrate exclusively on tensile or shear properties are inadequate for capturing the coupled stress interactions and the nonlinear structural response. his study conducts a computational analysis of the multi-axial behavior of Quasi- Isotropic (QI) continuous fiber and Discontinuous Fiber Composite notched coupons under combined loading circumstances. Experimental data acquired by an Arcan fixture are utilized to determine stress envelopes, load–displacement responses and energy dissipation patterns under different ratios of normal and shear stress. A fi- nite element framework is established in Abaqus/Explicit utilizing the integrated Hashin failure criteria to represent fiber and matrix failure processes. The formula- tion includes damage initiation based on discrete failure modes and gradual stiffness degradation to model failure development in notched specimens under various loading angles. The suggested framework enhances traditional uniaxial composite characterisa- tion by advancing to a comprehensive multi-axial damage evaluation. The model- ing approach facilitates the capture of advanced composite failure mechanisms, such as matrix splitting and distributed fracture processes in QI laminates, along with platelet-driven damage in DFC systems.