Constraint-satisfying planar development of complex surfaces

Engineering With Computers, 1995

Fibre-reinforced laminate composites have attractively high stiffnesses and strengths and low densities. However, designing with laminate composites is more difficult than designing with metals because (a) it involves the design of the material itself, and its manufacturing route, at the same time, (b) laminates are highly anisotropic, and (c) they have complex failure modes. The failure modes and anisotropy combine to make design details unintuitively important and small detailed-design oversights have been responsible for most failures in composite structures. Design is ‘the process of converting an idea into information from which a product can be made’. Thus the central role of information processing in any design activity implies that software should be able to help. Here we show three different ways in which laminate stacking sequences can be designed.

Major market growth in the area of advanced composite materials has spurred the development of methods to streamline the analysis and optimization of these materials. A computer tool has been developed to automatically create a finite element model with greater detail than previous zone-based methods. This tool can save practitioners dozens of hours during the pre-processing stage of analysis. It can also be used in an optimization to find the best possible lay-up for a laminate composite part. A method to automatically apply boundary conditions and solve the finite element model is also presented. This method is used in conjunction with the automated composite finite element tool in an iSight optimization to optimize the modal frequencies of a composite wing model.

Composites Science and Technology, 2005

The design and computation of laminated composite structures in terms of their strength is a complex task because many different mechanisms are involved in the damage and rupture to which these materials are subject. The great diversity of the damage mechanisms and their patterns of evolution make it extremely difficult to estimate the strength margins. In the case of woven plies laminates, the number of damage mechanisms is fairly small (no transverse rupture occurs and the material has a greater resistance to delamination) and the behaviour of the material is fairly simple to model up to rupture. The strategy adopted in this study on designing laminated composite structures is based on the choice of materials (woven or unidirectional plies) and the use of simple models (focusing on the rupture of the first ply) with which industrial structure analyses can be carried out. The choice of materials does not depend only on mechanical criteria but also on the simplicity of the corresponding modelling procedures.

Guidelines for a Decision Support Method Adapted to NPD Processes, 2007

This paper presents a methodology for the conceptual design synthesis and subsequent automated structural analysis of the material topology in composite structures. The long-term goal of this approach is to obtain a conceptual design language which is able to generate a multitude of composite structure topologies along with an automated analysis. The design language constitutes a graphgrammar based synthesis approach, which is well adapted to the topological layout problems. Ultimately, by integrating the design language and the analysis processes into one design loop, the presented approach shall lead to an optimization tool which yields topologically and functionally optimized composite structure designs. First layouts and analysis' of composite laminate structures which were generated using this approach shall be presented in this work, along with a brief description of how the methodology is currently applied to model existing structures and to generate new design topologies.

IEEE Expert, 1995

, and ring Ding, Michigan State University range of problem-solving types and approaches, making it difficult to reduce all descriptions of the various design approaches to a common model. However, many design problem-solvers generate designs by performing a state-space search that combines simulation with optimization.' Simulation 42

International Journal for Numerical Methods in Engineering, 1989

Finite element models of the continuumsbased theories and two-dimensional plate/shell theories used in the analysis of composite laminates are reviewed. The classical and shear deformation theories up to the thirdorder are presented in a single theory. Results of linear and non-linear bending, natural vibration and stability of composite laminates are presented for various boundary.conditbns and lamination schemes. Computational modelling issues related to composite laminates, such as locking, symmetry considerations, boundary conditions, and geometric non-linearity effects on displacements, buckling loads and frequencies are discussed. It is shown that the use of quarter plate models can introduce significant errors into the solution of certain laminates, the non-linear effects are important even at small ratio of the transverse deflection to the thickness of antisymmetric laminates with pinned edges, and that the conventional eigenvalue approach for the determination of buckling loads of composite laminates can be overly conservative. I. INTRODUCTION Increased utilization of composite materials in a variety of structures, including space and underwater vehicles, autotnotive parts, electronic and medicai devices, and sports equipment, has led to increased research activity in the mechanical characterization, structural modelling, and failure and damage assessment of composite materials. While composite materials offer many desirable structural properties over conventional materials, they also present challenging technical problems in the understanding of their structural behaviour, manufacturing, and in the damage and failure modes developed during their service:The subject of composite materials is an interdisciplinary area where chemists, materials scientists, chemical 'engineers, mechanical engineers, structural engineers and manufacturing engineers contribute to the overall product. From computational mechanics considerations, the study of composite materials involves modelling of fabrication processes (heat and mass transfer, and fluid flow) and structural response including micromechanics aspects, inelasticity and damage. Laminated composites consist of two or more different composite materials that are bonded together to achieve the best properties of the constituent layers. Most composite laminates are made of layers of the same orthotropic material, with the material coordinates of each layer oriented differently with respect to the laniinate coordinates .

The design of non-planar laminate composite parts is a difficult and time consuming process. To streamline the process, a composite design automation program was written that uses CAD independent methods available in GSNLib. This program utilizes the speed and portability of CAD independent algorithms while incorporating the benefits of visualization, simplicity and data storage of a CAD centric approach. The program takes the outer composite surface definition, translates it into its NURBS surface representation, automatically creates the ply lay-up and translates it into the CAD system for visualization. In addition, it automatically pre-processes a finite element model of the composite lay-up for engineering analysis.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2000

In a rapid prototyping process, the time required to build multiple prototype parts can be reduced by building several parts simultaneously in a work volume. Interactive arrangement of the multiple parts, called three-dimensional nesting, is a tedious process and does not guarantee the optimal placement of all the parts. The three-dimensional nesting is well known as a problem requiring intense computation. Thus, an efficient algorithm to solve this problem is still under investigation. This paper presumes that the three-dimensional packing problem can be simplified into a set of two-dimensional irregular polygon nesting problems for each layer to take advantage of the characteristic of a rapid prototyping process, i. e. the process eventually uses two-dimensional slicing data of the STL file. The proposed algorithm uses a no-fit polygon (NFP) to calculate the allowable locations of each slice of a part such that it does not overlap other existing slices in the same z level. Then th...

Composite Structures, 2001

Various numerical formulations of elastomeric lami®ed composite structures have been described. We underline the strengths and weaknesses of each of them. We then suggest and study various strategies for the numerical implementation on parallel computers. The numerical and mechanical results relate to an industrial¯exible composite structure.

Computers & Structures, 1991

belong to the category of designable materials that can be designed and constructed to specified structural requirements because of their special features of anisotropicity and heterogeneity. For these materials, the concept of thickness is generally replaced by reinforcement and matrix percentages, number of laminate layers and fibre orientations. This means that a suitable structural design methodology must be able to determine the number and orientation of the laminae subjected to known loads. A calculation program was designed and developed in view of these requirements. The program is capable of optimizing laminates in relation to specific structural requirements, providing the designer with solutions in terms of number, layer orientation, and layer sequence. Additional routines were implemented in order to evaluate laminate behaviour with thermal variations and dynamic excitations and to analyse the risk of delamination. The program, implemented on a PC, has been validated numerically and experimentally.