Strength prediction for bi-axial braided composites by a multi-scale modelling approach

The final publication is available at Springer via http://dx.doi.org/10.1007/s10853-016-9901-z.Braided textile-reinforced composites have become increasingly attractive as protection materials thanks to their unique inter-weaving structures and excellent energy-absorption capacity. However, development of adequate models for simulation of failure processes in them remains a challenge. In this study, tensile strength and progressive damage behaviour of braided textile composites are predicted by a multi-scale modelling approach. First, a micro-scale model with hexagonal arrays of fibres was built to compute effective elastic constants and yarn strength under different loading conditions. Instead of using cited values, the input data for this micro-scale model were obtained experimentally. Subsequently, the results generated by this model were used as input for a meso-scale model. At meso-scale, Hashin’s 3D with Stassi’s failure criteria and a modified Murakami-type stiffness-degradation scheme was employed in a user-defined subroutine developed in the general-purpose finite-element software Abaqus/Standard. An overall stress–strain curve of a meso-scale representative unit cell was verified with the experimental data. Numerical studies show that bias yarns suffer continuous damage during an axial tension test. The magnitudes of ultimate strengths and Young’s moduli of the studied braided composites decreased with an increase in the braiding angle

A consistent experimental protocol for the strain rate characterization of thermoplastic fabrics

International audienceThis paper introduces an experimental procedure aiming at performing a consistent mechanical characterization of textile composites behavior, under static and dynamic loadings, and particularly their macroscopic strain rate-dependent mechanisms. The procedure includes the design and validation of a reduced specimen adapted to dynamic testing, which guarantees the consistency of the identified macroscopic properties under a wide range of strain rates. An interrupted high speed tensile apparatus was also developed to investigate the strain rate sensitivity of the nonlinear constitutive behavior from math formula = 10 − 4 s − 1 to 102 s − 1. The originality of this experimental device lies in its ability to stop high speed loadings before ultimate failure, at adjustable, accurate strain levels. Finally, an extensive characterization campaign was performed. Results reveal a high strain rate dependency of the linear and nonlinear behavior. The procedure therefore generates consistent characterization data that may trustworthily be used for modeling purposes