Fracture Analysis Of Composites Research Articles

Studies of mechanical properties of carbon fabric-polymer hybrid nanocomposite

The development of nanoparticle reinforced composites is presently one of the most explored areas in materials science and engineering. Multiscale composites can be produced with superior properties by combining nanoparticles with traditional reinforcement materials. This research focuses on the development of such composites, through the use of carbon nanofibers (CNFs), carbon fibers and modified epoxy resin for structural and impact applications. Flexural and tensile behavior of composites has been analysed to investigate the effect of modification of epoxy matrix by adding CNFs on the mechanical properties of composites. Better strengths are obtained at 2.5 wt% of Epoxy terminated butadiene-acrylonitrile copolymer (ETBN) and 2 wt% of Carbon nanofibers (CNF) in the polymer hybrid nanocomposite. Morphological and fracture analysis of composites were performed by SEM DOI: http://dx.doi.org/10.3329/bjsir.v47i2.11451 Bangladesh J. Sci. Ind. Res. 47(2), 191-196, 2012

Fracture analysis of composites by time independent moving-crack orthotropic XFEM

Time-independent orthotropic enrichment functions are introduced for dynamic propagation analysis of moving cracks in composites by the extended finite element method (XFEM). The proposed enrichment functions are derived from the analytical solutions for a moving/propagating crack in orthotropic media, and can be considered as a new extension to the available XFEM techniques for dynamic analysis of stationary and moving cracks in orthotropic materials. They are included within the framework of partition of unity and XFEM to enhance the accuracy of basic FEM solution near a moving crack tip in orthotropic media. The method allows for analysis of the whole crack propagation pattern on an unaltered finite element mesh, which is independently defined from the existence of any predefined crack or its propagation path. A combination of dynamic crack initiation toughness and crack orientation along the maximum circumferential stress is used to design a relatively simple and efficient formulation. Dynamic stress intensity factors (DSIFs) are evaluated by means of the domain separation integral method and the dynamic energy release rate. The time dependent XFEM equations are constructed by discretizing the standard weak formulation of the governing elastodynamics equation. They are solved by the unconditionally stable Newmark time integration scheme. A number of benchmark and test problems are simulated and the results are compared with the available reference results to illustrate the accuracy and efficiency of the proposed scheme.

Contact based delamination and fracture analysis of composites

A new approach based on the concepts of the discrete element method, is presented for impact resistance analysis of composites. The method is capable of analysing the progressive fracturing and fragmentation behaviour, as well as potential post-cracking interactions caused by the newly created crack sides and segments. The imminence of a material crack is monitored by an anisotropic Hoffman model. To avoid the mesh dependency of the results, a bilinear local softening model, based on modes I and II, is also adopted in this study to account for release of energy and redistribution of forces that caused the formation of a crack. A special re-meshing method has been developed to geometrically model an individual crack by splitting the element, separating the failed node, creating new nodes and dividing the neighbouring elements to preserve the compatibility conditions. Numerical simulations have been performed to assess the performance of the proposed algorithm. The method has proved to be an efficient approach for impact analysis of composites undergoing progressive delamination and cracking.

The fracture analysis of composites by a micromechanical approach

An analytical method developed for the analysis of fracture development in composites is described and illustrated for several composite systems. A classical fracture-mechanics modeling technique was employed with the process-zone concept and small- or large-scale analysis. The distinctive characteristic of the method described is an explicit consideration in the analysis of the discrete distribution of the reinforcing components within the composite. The reinforcement mechanisms in composites are based on formation of a system of restrictive forces imposed on the crack surfaces by reinforcing components. The region where these restrictive forces are activated, the so-called fracture process zone, is a subject of the analysis and model development for evaluating composite fracture resistance and strength. Representing the process zone geometry as a line zone allows one to obtain analytical solutions to the representative problems and to investigate detailed micromechanical aspects of the process. The methodology developed was applied to composites formed from a brittle matrix reinforced by unidirectional fibers and to a brittle matrix reinforced by ductile particles.