Effect of through-thickness compression on in-plane tensile strength of glass/epoxy composites: experimental study

The effect of through-thickness compression on in-plane tensile strength of glass/epoxy composites with random microstructure was investigated experimentally. The studied composite laminates were man- ufactured with a self-regulating Resin Transfer Moulding device. Their mechanical behaviour was assessed in pure in-plane tensile and through-thickness compressive tests, followed by biaxial tests combining both loading modes; indenters with a radius ranging from 5 to 25 mm were used to impose a compressive mode. The obtained results demonstrate a nonlinear decreasing trend for the in-plane tensile strength under the growing through-thickness compressive stress. All the failed specimens showed catastrophic brittle failure with a specific fracture orientation that mainly exhibited a tensile mode of fibre fracture for smaller radii of indenters and a combination of matrix crack, fibre fracture and typical shear failure for larger radii

Failure analysis of a frangible composite cover: A transient-dynamics study

A transient-dynamics model based on the approximate Riemann algorithm is proposed for the failure analysis of a frangible composite canister cover. The frangible cover, manufactured with a traditional manual lay-up method, is designed to conduct a simulated missile launch test using a specially developed test device. Deformation of the cover’s centre is determined using a transient-dynamics finite element model; failure pressure for the frangible cover is obtained based on a failure criterion and compared with simulated experimental results. Weak-zone position of the frangible cover has a significant effect on failure pressure compared to that of deformation of the cover’s centre. With the same structure of the weak-zone, an increase in its height can first raise and then reduce the level of failure pressure of the frangible cover. Close agreements between the experimental and numerical results are observed

Tensile properties of 3D multi-layer wrapping braided composite: Progressive damage analysis

An experimental and numerical study on mechanical properties and damage behavior of 3D multi-layer wrapping braided composite under axial tensile load is presented. The braiding process of this material is introduced and its tensile properties are obtained in tensile tests. Numerical simulations employ periodical boundary conditions, with interface elements between yarns and matrix added to improve the accuracy of prediction. 3D Hashin-type criteria and Von-Mises stress criterion are employed as damage initiation criteria for yarns and matrix, respectively. The obtained numerical results show a good agreement with the experimental data. The load-bearing capacity and failure mechanisms of 3D multi-layer wrapping braided composites under axial tensile loading are also discussed. A stress distribution shows that the axial yarns are the main load-bearing component of the composite. The main failure mode of the yarns is the yarn-matrix tensile cracking in the width direction, followed by the yarn-matrix tensile cracking in the thickness direction and fibre tensile failure. When the fibres in axial yarns begin to break, the material loses its load-bearing capacity

Failure analysis of plain woven glass/epoxy laminates: Comparison of off-axis and biaxial tension loadings

© 2017 Elsevier Ltd An experimental study was focused on investigation of the failure properties of plain woven glass/epoxy composites under off-axis and biaxial tension loading conditions. Four fibre orientations (0°, 15°, 30° and 45° with respect to the load direction) were considered for off-axis tests and two biaxial load ratios for biaxial tests to study failure characteristics and mechanism. Four classical polynomial failure criteria - Tsai-Hill, Hoffman, Tsai-Wu and Yeh-Stratton - were analysed comparatively to predict off-axis and biaxial failure strength of the composites. For failure prediction of the plain woven composites under multiaxial tension loads, the Tsai-Wu criterion was modified by introducing an interaction coefficient F12 obtained from 45° off-axis or biaxial tension tests and the Yeh-Stratton criterion was modified with the interaction coefficient B12 = 0 or obtained from the biaxial tension test. The former criterion was found to have higher accuracy. Finally, according to macroscopic and microscopic studies, the failed specimens showed mostly distinct failure with a specific fracture orientation, mainly exhibiting fibre or fabric tensile fracture mode and a combination of matrix cracking and delamination, both in off-axis and cruciform samples