Analytical prediction of tensile strength for two-dimensional triaxially braided composite

In this paper, a new analytical model is developed to predict the strength of two-dimensional triaxial braided composite (2DTBC). According to the concept of subcell model, a representative unit cell of braided composite is divided into four subcells, each of which is approximated as a stack of unidirectional composite plies. In order to investigate the interaction of braided angle and effective properties, it is assumed that the unit cell models of different braid angles have the same fiber volume fraction and the same thickness. Then, explicit equations can be obtained to describe the geometric parameters and to quantify the specific dimensions of subcell components based on the manufacture provided properties and microscopic image analysis of realistic specimens. Micro-mechanical models are applied to estimate the elastic and strength properties of unidirectional plies. Classical Laminate theory and Parallel and Series Bridge models are implemented to connect the strain and stress responses of subcell components and effective responses of the unit cell. Hoffman and Hashin failure criteria are used to examine the onset of failure for each subcell component, which can then predict the progressive failure process and global stress-strain response of the unit cell. The developed analytical model will then be utilized to predict the tensile strength (axial tension and transverse tension) of a +60°/0°/-60° 2DTBC and validated against experiments. Finally, the validated model will be used to study strength properties for 2DTBC of different braided angles. The results can provide insights for the design and optimization of composite structures with similar braided architecture.