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This article presents an experimental study to determine the tensile properties of the envelope fabric Uretek3216A under mono-uniaxial, uniaxial cyclic, and biaxial cyclic loading. First, the mono-uniaxial, uniaxial cyclic, and biaxial cyclic tests were carefully carried out on the envelope fabric, and the corresponding stress–strain behaviors were discussed. Then, the elastic constants were calculated from the experimental data of these tests and the influences of the uniaxial loading cycle and the determination options with different stress ratios were discussed. For the biaxial tests, the elastic constants were determined with and without the constraint of the reciprocal relationship to investigate its significance. Finally, a comparison of the elastic moduli between uniaxial and biaxial tensile tests was presented. Results show that the nonlinearity and orthotropy of the envelope fabric could be attributed to the mechanical properties and unbalanced crimp of their constitutive yarns, respectively. The elastic constants vary noticeably with the experimental protocols, as well as the determination options for biaxial tests, and then in the real design practice, elastic constants should be determined for specific loading conditions and stress distributions depending on the project’s needs.

a b s t r a c tA computationally economic finite-element-based multi-linear elastic orthotropic materials approach has been developed to predict the stress-strain and fracture behaviour of ceramic matrix composites with strain-induced damage. The finite element analysis utilises a solid element to represent a homogenised orthotropic medium of a heterogeneous uni-directional tow. The non-linear multi-axial stressstrain behaviour has been discretised to multi-linear elastic curves, which have been implemented by a user defined subroutine or UMAT in the commercial finite element package, ABAQUS. The model has been used to study the performance of two CMC composites: a SiC (Nicalon) fibre/calcium aluminosilicate (CAS) matrix 0°/90°cross-ply laminate Nicalon/CAS; and, a carbon fibre/carbon matrix-SiC matrix (C/C-SiC) plain weave laminate DLR-XT. The global stress-strain curves with catastrophic fracture behaviour and effects of fibre waviness have been predicted. Comparisons have been made between the predictions and experimental data for both materials. The predicted results when fibre waviness is taken into account compare well with the experimental data.

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