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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.7, #1)
Fracture of Plain and Fiber-Reinforced High Strength Mortar Slabs with EA and ESPI Monitoring by Luigi Biolzi; Sara Cattaneo; Gian Luca Guerrini (pp. 1-12).
The failure of cement-based materials is associated with the development of a damaged zone in the form of a more or less large region of microcracking. The development and the evolution of the damaged zone is of fundamental importance in defining the mechanical response in terms of both structural behavior and peak strength. For geometrically similar beams of different sizes, this paper presents and discusses experimental evidence from interferometric measurements (ESPI) and locations of acoustic emission (AE) of the damaged zone development, at the peak load, in terms of shape and size. The cement-based materials had an aggregate/binder ratio of 1.5, a microsilica/binder ratio of 0.1 and a water binder ratio of 0.22. Beams made with (2% by volume) and without steel reinforcing microfibres were considered. It is shown that the size effects appear to be reduced in the fibre- reinforced materials.
Keywords: cement mortar; fracture; fiber-reinforced mortar; ESPI; acoustic emission
Physical Modelling of Engineering Problems of Composites and Structures by Peter W. R. Beaumont; Hideki Sekine (pp. 13-37).
There is an alternative way for starting the design process of composite materials and structures (particularly, but not exclusively, aerospace structures) made from advanced composite laminate. It is based on sound fundamental understanding of the mechanisms by which damage accumulates with time in the laminate and structure across several orders of magnitude of size: fibre breakage and matrix cracking that lead progressively to ply fracture, followed by laminate cracking (delamination and splitting) that leads to component failure. Application of this approach to a predictive design methodology requires the identification and understanding of failure mechanisms in the material at the micron level of size and fracture of the component on the size scale orders of magnitude greater.
Keywords: physical modelling; composite laminates; cracking mechanisms; predictive failure
Numerical Analysis of Stress Concentration for Brittle Matrix Composites by Yang Wang; Yuan-Xing Zhou; Yuan-Ming Xia (pp. 39-49).
A FEM numerical model is constructed of SiCf/LASIII glass-ceramic uni-direction plate under tension loading. The smeared crack method is used to deal with the failure point of fiber and matrix elements. The solution of the model gives the distribution of meso-stress of SiCf/LASIII glass-ceramic uni-direction plate. The stress concentration factor K and the size of stress concentration effect zone are also analyzed. The average saturation cracking space is obtained by a numerical method. The mesh length of the elements is also studied.
Keywords: numerical analysis; stress concentration; brittle matrix
Advanced Modeling Strategies for the Analysis of Tile-Reinforced Composite Armor by C. G. Dávila; Tzi-Kang Chen (pp. 51-68).
A detailed investigation of the deformation mechanisms in tile-reinforced armored components was conducted to develop the most efficient modeling strategies for the structural analysis of large components of the Composite Armored Vehicle. The limitations of conventional finite elements with respect to the analysis of tile-reinforced structures were examined, and two complementary optimal modeling strategies were developed. These strategies are element layering and the use of a tile-adhesive superelement. Element layering is a technique that uses stacks of shear deformable shell elements to obtain the proper transverse shear distributions through the thickness of the laminate. The tile-adhesive superelement consists of a statically condensed substructure model designed to take advantage of periodicity in tile placement patterns to eliminate numerical redundancies in the analysis. Both approaches can be used simultaneously to create unusually efficient models that accurately predict the global response by incorporating the correct local deformation mechanisms.
Keywords: composite armor; tile-reinforced sandwich structure; finite element analysis; element layering; superelements