Search

ICCE 12. Twelve International Conference on Composites / Nano Engineering. Tenerife, Spain, August 1-6, 2005 In this paper the effect of static biaxial preloading of CFRPs plates under high velocity impact is investigated experimentally. Results are compared with those obtained when no static loads are applied to the specimens. Two magnitudes were measured from the tests: the residual velocity of the impacting projectile and the extension of the damage area in the laminate. The authors are indebted to the Inter-ministerial Commission of Science & Technology of Spain (Project: MAT2001-0735) for the financial support of this work. Publicado

In this paper an analytical static approach to analyse buried tunnels under seismic surface waves (Rayleigh and Love waves), propagating parallel to the tunnels axis, is provided. In the proposed method, the tunnel is considered as a beam on elastic foundation by using a Winkler model to represent the subgrade reaction and the soil-structure interaction. The seismic load is imposed by giving at the base of the soil springs a determined configuration corresponding to the free-field motion. From the solution of the differential governing equations of the problem, results are obtained in form of relative displacements between points of tunnel, and therefore the seismic bending moments and shearing forces, acting on the tunnel cross section, can be computed.

In this paper some aspects of the use of non-reflecting boundaries in dynamic problems, analyzed in time domain, are considered. Current trends for treating the above mentioned problems are summarized with a particular emphasis on the use of numerical techniques, such as Boundary Element Method (BEM) or mixed and hybrid formulations, Finite Element Method (FEM) plus BEM. As an alternative to these methods, an easy time domain boundary condition, obtained from the well known consistent transmitting boundary developed by Waas for frequency domain analysis, can be applied to represent the reactions of the unbounded soil on the interest zone. The behaviour of this proposed boundary condition is studied when waves of different frequency to the one used for its obtention are acting on the physical edge of the model. As an application example,an analysis is made of the soil-structure interaction of a rigid strip foundation on a horizontal non-linear elastic layer on bed rock. The results obtained suggest the need of time domain solutions for this type of problem

Development of composite materials has caused that innovative features and capabilities are being sought for their use in new technology applications. Catastrophic events, like high velocity impacts, are likely to appear in elds where composite materials are being lately applied. Lightweight headgear for modern military ground forces, structural shielding for a knew orbiter spacecraft, or blades intended for high-e ciency wind turbines, are just some examples. The dynamic response of composite materials has become an essential knowledge. New set of tools need to be developed in order to spread this knowledge and decrease design cost. As compared to experimental testing and numerical methods, analytical models stand out as the cheapest and fastest way to provide preliminary results that successfully assist early design stages. The main goal of this project relies on laying the basics for the development of a predesign tool on the implementation of this latter type of models. This tool will support the early design of composite material structural components likely subjected to impact situations. During the last three decades, a great number of analytical models have being developed intended to theoretically predict the behavior under impact of composite materials. The present work covers the basics ndings on the eld. Two models, based on the impact over carbon ber, and glass and polymer ber composites, are selected and thoroughly described in order to evaluate their applicability into a pre-design tool. Description of both models are provided with the needed background and theoretical foundations. In order to evaluate the applicability of analytical models, a simple requirements-based method is presented. It is based on three broad requirements: good predictions, broad applicability and event sensitivity. Both analytical models are evaluated against these requirements. Results of this evaluation show how the rst model (carbon ber model) reproduces one speci c case with accuracy. In spite of this good agreement, there is no possibility to reproduce further environments. This makes the model non optimal to be implemented into a design tool. The second model (glass and polymer ber model) appears to successfully meet the three established requirements. Finally, some guidelines in the development of future analytical models under the method here described, and some possible paths to be followed in the implementation of the pre-design tool, are presented. Ingeniería Industrial

The use of composite materials has grown considerably during recent years, most prominently in the aerospace and automobile industries, as well as in the civil and naval industries. Composite materials display outstanding specific strength and stiffness properties, and a broad capacity for customization. Both qualities have contributed to their application in industries sensitive to the weight of materials such as steel or other alloys. However, composites’ behavior is more difficult to predict due to multiple failure modes. Therefore, complex models and powerful software are normally required to design components made of composite materials, both during the creation of the model and in the results post-processing, adding time to the design process. It would be helpful to automate part of this process in order to speed up the pre-design step. The aim of this project is the development of a tool that will ease the design of composite stiffened panels, reducing the time required to create the model while also allowing fast modifications of a given design in order to maximize the design efficiency. The tool will be able to generate the mesh and geometry from a set of predefined parameters that defines a given panel, and it will compute the critical buckling load of the first five modes, along with the visualization of the deformed panel to ensure quick post-processing. In order to render this tool accessible, it will be implemented in a web environment (CADEC) using advanced features such as object-oriented programming, user authentication and databases. After implementing such a tool in CADEC, it was used to predict the buckling load of several real cases of stiffened panels. Since the results obtained with CADEC generally coincided with the experimental results analyzed, the tool and its results can be safely validated. Ingeniería Industrial