Multi-scale analysis for mechanical properties of fiber bundle and damage characteristics of 2D triaxially braided composite panel under shear loading

The shear strength and progressive damage responses of 2D-triaxially braided composite (2DTBC) panel under shear loading are predicted by multi-scale modeling approaches. A micro-scale representative unit cell (RUC) model is built to calculate effective properties of bundle under six different loading conditions. At meso-scale, the 3D Hashin criterion and Stassi criteria are adopted to predict damage initiations of bundle and pure matrix. Both components are linearly degraded after damage initiations. A triangle traction-separation law is employed to capture the interface debonding. Effective properties are compared with Chamis' model, which are used as input for meso-scale model. The shear stress-strain response of meso-scale RUC with different boundary conditions (BC) is verified with available experimental results. The shear damage behaviors are analyzed regarding stress distribution and damage characterization. The BC has great effect on shear loading and modulus. Damage modes of bundle, matrix in bundle, pure matrix and interface occur simultaneously. Both bias bundles severely suffer from damage.