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The development of a robust and reliable material model for fabrics used to prevent fan blade-out events in propulsion engines has significant importance in the design of fan-containment systems. Currently, Kevlar is the only fabric approved by the Federal Aviation Administration to be used in fan-containment systems. However, very little work has been done in building a mechanistic-based material behavior model, especially one that can be used to quantify the behavior of Kevlar when subjected to high-velocity projectiles. Experimental static and high strain rate tensile tests have been conducted at Arizona State University to obtain the material properties of Kevlar fabric. In this paper we discuss the development and verification of a constitutive model for dry fabrics for use in an explicit finite-element program. Results from laboratory tests such as tension tests including high-strain rate tests, picture frame shear tests, and friction tests yield most of the material properties needed to define a constitutive model. The material model is incorporated in the LS-DYNA commercial program as a user-defined subroutine. The validation of the model is carried out by numerically simulating actual ballistic tests conducted at NASA-GRC and fan blade out tests conducted at Honeywell Aerospace (Propulsion Engines). DOI: 10.1061/(ASCE)0893-1321 (2009)22:3(249) CE Database subject headings: Constitutive models; Fabrics; Finite element method; Strain rates.

As product designs have become more sophisticated, both the simulation models (e.g., finite element models) and the design optimization models have grown bigger. To keep pace with this increase in problem size, we present and implement an optimization strategy that can run on a computing cluster with demonstrable efficiency. First, parallelism is implemented in the context of gradient calculations using divided differences. Then, parallelism is achieved in the context of both direction-finding and line-search steps. Parallel direction finding improves the convergence rate as opposed to just cutting down the amount of arithmetic. A new algorithm based on method of feasible directions is discussed that obtains better optima and is also computationally faster. Implementation details regarding distribution of computing tasks to improve scalability and load balancing are presented. Numerical examples show the efficiency of the developed methodology on a relatively small computing cluster. Gains of about 7:1 have been obtainable using 16 processors on some test problems. Importantly, the framework presented can be developed by researchers using other gradient-based optimization codes on different computing platforms.

An experimental and modeling system for the modeling of multilayer composite fabrics used in a gas turbine engine containment system is developed. Specifically, Kevlar 49 (17 x 17) and Zylon AS (35 x 35) fabrics are used in the study. The experimental setup is first used to obtain the material properties of these fabrics. Later, one or more layers of these fabrics is tightly wrapped around a steel cylinder that simulates an engine containment housing. A steel penerator (or a blunt nose) is used in a static test by slowly pushing against the fabric. The resulting load-deflection data are used to compute a variety of parameters, including the energy absorption capacity. The material behavior obtained from the experimental study is then used as the constitutive model in a finite element simulation of the static test. The objective is to develop a procedure for understanding the relative strengths and weaknesses of different fabrics and to aid in the development of finite element modeling of actual fan blade-out events. DOI: 10.1061/(ASCE)0893-1321(2006)19:1(38) CE Database subject headings: Tensile strength: Stress analysis: Stress strain relations; Fabrics; Composite materials; Finite element method; Containment.

Linear elastic fracture mechanics (LEFM) is used together with shape optimal design methodology in studying the connection between structural geometry and the number of life cycles to failure. LEFM results are used in the fatigue model to predict the life of the structure before failure has occurred. The shape optimal design method is used in changing the shape of the structure. Results show that the life of structural components subjected to fatigue can be improved by appropriate shape changes.

Shape optimal design methodology has been used as a design tool in the automotive and aerospace industries for quite some time now. In the present work the hybrid natural shape optimal design approach is used along with a nonlinear programming (NLP) technique to find the optimal shapes of electronic packaging components. The design problems are formulated as min-max problems and linear and materially nonlinear finite element analyses provide the function values. The applicability of the developed methodology is illustrated using a design example that deals with the packaging design of a plastic pad array carrier digital package. The results indicate that the methodology can be used either as an effective way of evaluating different design alternatives or refining existing designs.

The development of energy-efficient building envelopes has been an ongoing effort in many countries owing to the pressing need to achieve energy independence. In this study numerical optimization techniques and finite element analysis provide the means to find a compromise point between adding phase-change materials (PCMs) to a concrete wall, the energy savings and the wall's structural capacity. The primary objective is to minimize the overall lifetime cost of a wall by understanding the implications of PCM layer thickness, material properties and position in the wall on the overall energy consumption. While it is difficult to manually configure a typical wall for the lowest total cost, the developed computational framework provides an automated tool for searching for the best design. The results show that successful designs can be obtained where material and energy costs can be minimized through a judicious combination of existing building materials with thermal energy storage materials. [ABSTRACT FROM AUTHOR]