Papers by Keyword: Computational Modelling

Abstract: Computational modelling of quasi-brittle fracture in cement-based composites needs to cover both i) the damage caused by micro-fractured zones, referring to some nonlocal strain-stress relations, respecting quite different behaviour of such composites in tension and compression, and ii) the initiation and propagation of macroscopic cracks, exploiting the cohesive zone model, handled by some modification of the finite element technique, together with the discretization in time. A fundamental issue for such model is the introduction of a traction-separation (stress-displacement) relationship. This contribution pays particular attention to the design, identification and estimation of material parameters for the traction separation law suitable for predicting the deformation behaviour of samples of materials and structures.

Abstract: The paper presents selected results of experimental and computational modelling of composite material samples of tires with cord ply (casing) and breaker textile reinforcement. The computational modelling included applications of finite element methods. The output is to determine and verify the influence of material parameters of textile reinforcement. The results were confirmed by the experiment and computational modelling verification. For elastomeric matrices hyperelastic behavioural patterns of this material were considered.

Abstract: Computational modelling of the crack growth in brittle and quasi-brittle materials used in mechanical, civil, etc. engineering applies the cohesive zone model with various traction separation laws; determination of micro-mechanical parameters comes then from static tests, microscopic observation and numerical calibration. Although most authors refer to ill-possedness and need of artificial regularization in inverse problems (identification of material parameters), some difficulties originate even in nonlinear formulations of direct and sensitivity problems. This paper demonstrates the possibility of proper analysis of the existence of a weak solution and of the convergence of a corresponding numerical algorithm for such model problem, avoiding non-physical assumptions.

Abstract: Bioinspired design involves the use of concepts observed in natural biological materials in engineering design. The hope is that the leveraging of biological materials in the engineering domain can lead to many technological innovations and novel products. This work presents the initial material characterization of kinixys erosa tortoise shell using a combination of x-ray diffraction, optical/scanning electron microscopy and micro-mechanical testing. The results were used in the analytical/computational modelling of shell structures. The potential implications or the results were then discussed to give fundamental understanding of deformation and stress responses of shell structures

Abstract: European directive on energy performance of buildings (2010) and related national technical rules force reduction of energy consumption of both new and reconstructed buildings due to the so-called passive standard. Consequently the thermal design of such buildings, utilizing advanced materials, structures and technologies, requires proper analysis of relevant physical processes, unlike classical evaluations of thermal resistance from one-dimensional stationary heat conduction. The paper demonstrates a possibility of compromise between complicated multi-physical models and realistic thermal estimation of buildings, as well as some optimization procedures in building design leading to energy reduction.

Abstract: The optimal design of the heat storage, as a part of the Czech-Swedish project of the development of original equipment for exploiting solar energy using optical fibres, requires a reliable evaluation of thermal conductivity of powdery materials for insulation layers, both under normal air pressure and in vacuum. The standard evaluation of thermal conductivity of such materials makes use of the stationary ball-shape measurement device, with the strong requirement to the of the ball vessel, to the thermal contraction of applied materials, as well as to all temperature sensors. The paper presents the original alternative non-expensive measurement equipment with the cylindrical vessel, supplied with the ANSYS-supported computational tool, producing results of comparable validity.

Abstract: The paper shows the possibilities of the arrangement of particular layers of vegatative roofs for building structures and the influence of soil on the distribution of temperature in a roof structure, using the software based on the non-stationary thermal analysis.

Abstract: Computational modelling is the most important method in research for their low cost, high efficiency. A porous particulate composite material made of glass flam and phenolic coating was studied in the paper. The particle in the composite is glass foam but simplified as non-porous solid ball to reduce simulation cost. A series of the composite material model with ball size range of 0.5-2 mm diameters, different unit cell size, interface thickness and compression speed were simulated and analysed in the manuscript.

Abstract: A concept for improving the impact resistance of carbon fibre reinforced plastic (CFRP) laminates by using a carbon nanotube (CNT)/epoxy surface coating is presented. An initial parametric numerical study shows the effects of interphase properties on the macroscopic stress-strain behaviour of carbon nanotube/epoxy nanocomposites. Finite element (FE) simulations carried out for fully aligned single-walled CNTs (SWCNTs) and double-walled CNTs (DWCNTs) investigated the influence of properties of the polymer/CNT interphase and the interwall phase of DWCNTs. They reveal that a high shear stiffness of the CNT/polymer interphase is essential to take the full advantage of the load-bearing ability of the inner wall of the DWCNT, and thus enhance the mechanical performance of the nanocomposite. Furthermore the interphase shear stress distributions in interwall and CNT/polymer interphase of a DWCNT point out the relationship between CNT/epoxy interphase damage propagation and shear stress in the interwall phase.

Abstract: Crystal structure of an aromatic polysulfones containing biphenylene units was elucidated using diffraction simulation technique extracted from X-ray data and interfaced with computational modeling. The chain conformations and configurations were derived from a synthesized oligomer and several analogous structure of past studies. It was found that the polymer adopt an orthorhombic Cmcm with the adjacent aromatic rings attached to the sulfone linkage orthogonal to each other whilst the biphenylene unit are coplanar. The chain conformation and crystal systems are consistent with the analogous polymer containing wholly uniphenylene unit.