AMTS STANDARD WORKSHOP PRACTICE. Composite design Section 3 of 3: Composite design and analysis software

Transcription

1 AMTS STANDARD WORKSHOP PRACTICE Composite design Section 3 of 3: Composite design and analysis software Reference Number: Date: November 2011 Version: Final

2 Contents 1 Scope Technical terms Primary references Interacting of Software Comparison between Laminate software Considerations regarding composite software Model creation Material properties Meshing General analysis Failure Analysis Design optimization Manufacturing Links to various software

3 1 Scope A sophisticated analysis plays an important role in the development of aerospace structures. It is required that many specialities are combined on an overall problem in any complex design structure. For each of these specialities the specific knowledge must be known by the designer. [1] This SWP is part 1 of three SWP s which covers the following information: SWP 42: Composite design Section 1 of 3 - Composite definition - Composite classification - Basic terminology - Lamina Theory - Laminate Analysis Theory - Static strength life of composites Theory - Beam Analysis theory SWP 48: Composite design Section 2 of 3 - Fundamentals of Composite design decisions - Advantages / Disadvantages - General guidelines for composite designs SWP 49: Composite design Section 3 of 3 - Interacting of software - Comparison of various software tools - Considerations in software - Links to various software 2 Technical terms Laminate analysis software Classical Laminate Theory Laminate Software tools for the design and analysis of composite material laminates of which the algorithms is based on the Classical Laminate Theory. An approach where the laminates are assumed to be of infinite length and widths, i.e. edge effects are ignored. Plane stress state is assumed and certain stress components are ignored. A thin plate of infinite length and width, made up of one or more orthotropic laminae bonded together, each of potentially different thickness and material, and each with the principal stiffness axis (or Fibres) at a user-defined orientation. 2

4 3 Primary references The main sources used for this document are indicated below. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below: [1] LAP, LAP user manual for Laminate analysis Program version 4.x for windows. Revision 5. Anaglyph [2] LAP, Laminate analysis Program demonstration, Microsoft Power point. Anaglyph. [3] ESACOMP, Quick Start guide for EsaComp version 4.3. [4] Waterman, P.J.1 May Options for Composites Analysis and Simulation. Find your comfort zone with today s software tools. Desktop engineering. [5] Waterman P.J. 2 March Composite Analysis: Making New Choices. An engineering and design gide to choosing software for working with today s composite materials. Desktop Engineering. 3

5 4 Interacting of Software When compared to traditional engineering materials, like steel, the material and manufacturing costs of composites are high; therefore the superior performance of the end product must be achieved by careful designing involving software. The flow chart in figure 1 shows how Laminate Tools interacts with other engineering software applications. [4] The two major different approaches in composite designing software is a CAD environment or an ANALYSIS environment. Any finite element analysis tool, or FEA package, is not sufficient to design, manufacture or create decent composite models, it is only for analysing. [4] The difference in the two approaches is as follow [4]: Design works with very detailed, complete, producible design Analysis work with simplified models made for analysis of buckling, delamination, noise or vibration. Any application should be identified by its complexity as an guide to which approach should be followed. Figure 1: Typical Anaglyph Laminate tools composite analysis flow chart [4] 4

6 5 Comparison between Laminate software The following table explains the difference in composite software packages in categories from modelling to general and complex FE analysis[4]: Table 1: Spectrum of composite software [4] CATEGORY EXPLANATION COMPANY (PRODUCT) Laminate analysis packages: Based on LAMINATE ANALYSIS Classical Laminate Theory, these tools Anaglyph (Laminate Analysis Program LAP), allow you to define a flat laminate material Componeering (ESAComp, ComPoLyX), Lindell made of an arbitrary stack of lamina, and (The Laminator) calculate stresses and material failure at a given point under a given load. SUBSTRUCTURE ANALYSIS MICROMECHANICAL STRUCTURE ANALYSIS FINITE ELEMENT ANALYSIS (FEA) FEA OPTIMIZATION FEA-BASED INTERGRATED DESIGN/ANALYSIS/ MANUFACTURE CAD-BASED INTERGRATED DESIGN/ANALYSIS/ MANUFACTURE Substructure analysis: This type of software calculates stresses and material failures in simple composite structures such as tubes, beams and other straightforward configurations. Micromechanical structure analysis: This process creates detailed micromechanical models of a composites structure to calculate elastic and failure properties, particularly progressive failure. These tools are often linked to, or integrated within, non-linear FEA solvers to predict failure. FEA: Most FEA packages allow users to define laminated composite materials on shell elements. More advanced packages support laminated solid and beam elements. A few even support ply-level modeling, where you can define the orientation of the material at each element. FEA optimization software: This software works in conjunction with FEA tools and ties into the manufacturing process by modifying the composites layup on elements, using an optimization strategy to achieve the required structural response. FEA-based Integrated Design/Analysis/Manufacture: In an FEA environment, users can define a highfidelity composites model by simulating the manufacturing process of each ply, building up the stack model. CAD-based Integrated Design/Analysis/Manufacture: In a familiar CAD environment, these tools let users define plies using boundary curves on an underlying surface (rather than specifying shell FEs). Anaglyph (Component Design Analysis CoDA), Componeering (ESAComp) e-xstream Engineering (DIGIMAT), Firehole Composites (Helius:MCT, Prospector: Composites and Helius: CompositePro), Alpha STAR Corporation (ASC) (GENOA), Componeering (ESAComp) ADINA, Altair (HyperWorks), ANSYS, Autodesk (Algor), COMSOL, Cranes Software (NISA), LUSAS (LUSAS Plus Composite), MSC.Software, NEi Nastran, SAMTECH, Siemens PLM Software (NX), SIMULIA (Abaqus/CAE), Strand7, Vanderplaats R&D (GENESIS) Collier Research Corp. (HyperSizer), ESI Group (SYSPLY), e-xstream Engineering (DIGIMAT), Vanderplaats R&D (GENESIS), Componeering (ESAComp) MSC.Software (Patran Laminate Modeler), Simulayt Composites Modeler for Abaqus/CAE (SIMULIA), Simulayt Composites Modeler for Femap (Siemens PLM Software), VISTAGY with ANSYS, Anaglyph (Laminate Tools for Nastran and ANSYS) Dassault Systèmes (CATIA V5/V6 Composites Design) (with Partner Products: ESI Group PAM-RTM for CATIA V5, Simulayt Advanced Fiber Modeler for CATIA V5/V6, Composites Link for CATIA V5/V6), VISTAGY (FiberSIM for NX, ANSYS, Pro/ENGINEER and CATIA V4/V5), Simulayt (Composites Modeler for SolidWorks), Anaglyph (Laminate Tools for SolidWorks) 5

7 6 Considerations regarding composite software. The following list is questions and situations to consider when dealing with any composite design structure. The answers are applicable to durability and manufacturability. [5] 6.1 Model creation Composite-based models for FEA incorporate the general defining of the geometry, material properties and meshing. The difference when working with non-isotropic materials is that the software lets you define the differing nuances of each layer. 3D-CAD and analysis packages do support this in general, but how the software approach it and the other supporting additions need to be considered [5]: Virtually unlimited number of possible layers Different designs calls for different number of layers, some are only 5 layers and others may require thousands. Restrictions in the modelling should not be a problem for any composite software. Import layer data It is important to be able to import layer data such as stiffness and strength from spreadsheets. Easy insertion / deleting of layers Layers should be able to be easily inserted or deleted and any point of the process. Defining of fibre orientation angles The software should be able to handle angles with respect to global axis, local axis, normal to the shell surfaces and a plane defined by two intersecting planes, or along an arbitrary curve. Mixing of composite and non-composite elements It must be possible to mix elements such as beams, springs and shells made of metallic structures with the composite elements. Glues and adhesives modelling between layers It is preferred that the flues and adhesives are surface-based cohesive contact and not just very thin layers. Defining of cores It should be possible to define layers as honeycombs or to be able to include rebar material. Physical property updating It should be possible for the design to have physical holes and updating of thicknesses, angles and material properties should be easy. The modelling process should also be able to correspond to different manufacturing processes like handlayup, filament winding, compression moulding and infusion. 6

8 6.2 Material properties The applicable software should be able to define specific material properties. It should either have its own database or it should be capable of importing material properties from commercial services such as MatWeb and Matereality. The following questions should be asked regarding material properties [5]: Does it allow unit-cell-based micro-material models? Can it also incorporate continuum material models? Can it handle a mix of elastic and inelastic materials? Can you designate fibre packing as well as braided or woven configurations? Can you introduce random variations in fibre orientation to allow for manufacturing realities? Can you enter equivalent stiffness s as a starting point, especially early in the design phase, and then replace those values on a layer-by-layer basis? Does the software allow user-defined equations in the property matrix? Is any necessary unit-conversion handled automatically? 6.3 Meshing After the completion of the model there should be options for directing the meshing (FE definition) process. The two different approaches are solid elements or layered shell elements. Mostly analysts starts by modelling the structure as a layered shell element and then switch to a detailed solid element mesh for the understanding of, for example, interlaminar shear stresses. Such a change should be automatically extracted, especially from the mid-planes. [5] 6.4 General analysis Both implicit and explicit solvers should be offered by the software, as well as macro- and micro-mechanical analysis at the following levels [5]: Global level: Structure Deflection, buckling, natural frequency Ply/layer level: inter-laminar shear formations and stresses Matrix level: detailed stress distribution within a single layer Other important functions within general analysis of the software should include, if possible, [5]: The same FEA model use for both implicit and explicit solutions. Should be able to handle metal-matrix, ceramic-matrix and polymer-matrix composites An option should be available to compute equivalent material properties in either the pre-processor or the solver. Material properties should be able to change in proportion of the geometry and shape. 7

9 It should be able to account for heat transfer effects and solve simultaneously for multi-physics like conductivity, thermal and fluid structure interactions. It should account for initial strains in the different composite layers, like preloaded layers during manufacturing. Should be able to compute out-of-plane stress (Stress in the z-axis), inter-laminar shear and peel stresses. (In addition to the classical laminate theory in-plane stresses and strains.) All the mentioned properties will make visualization harder and thus more critical. The following display options should be available at orientated angles and normal layer-by-layer [5]: Stress results for core, worst and specified lamina Strain for composite elements (initial, mechanical and total) Damage energy density 6.5 Failure Analysis Damage modelling of composite structure is critical in the analysis software. The failure modes of composite and laminate materials are subject to different failure modes than those found in single-material structures. Degradation of the performance is subjected to both delamination (Laminate based failure) and fibre/matrix breakdown (ply based failure) on different levels of severity. For example, the outer layers can wrinkle, crimp or dimple and damage of one layer can equate to failure of the entire part or not. [5] BVID (Barely visible impact damage) investigation should be possible for the software with the definition allowable damage tolerance and own macros. Simple values like maximum strain and stress, quadratic Tsai-Wu, Hill, and Hoffman failure modes should be included. Some of the newer criteria will account for fibre/matrix failure separately using models like Hashin-Fabric, Hashin-Tape and Puck.[5] Other properties that could be useful include [5]: Crush simulation Public-domain VCCT code for post processing and re-meshing of progressive crack growth propagation between bonded surfaces. Immediate or gradual stiffness reduction for matrix and fibres Damage addition at simulation De-activation of simulate material removal/breaking Fatigue analysis (rare capability on composite analysis) 6.6 Design optimization Typically the composite material is optimized for the perfect strength to weight ratio. The large number of variables, however, makes the optimization an important task and may lead to overall conservative designing. The following should be kept in mind: Provision for interactive optimization capabilities to determine for a given load environment the lightest weight combination of material systems and ply layups. 8

10 Easy re-orientation of layers, stacking sequences or material type change to compare behavioural differences. Optimization of a complete structural entity such as wings or fuselages. Handling of sandwich/ solid-laminate structures. Coupling with other solver software and pre/post-processors. Tolerances in design parameters and variation of it. Objective optimization like low vibration/multiple objectives. 6.7 Manufacturing The simulations can provide insight to the model, but only theoretically and a real product must still be manufactured. An interface between the analysis software and the various manufacturing solution packages should be available. The some of the following terms should be available; draping, taping, braiding, flat-patterns and ply drop-offs. The software must also be able to help with incorporate non-geometric details such as glues, fasteners, coatings and sealants, and predict any expected shrinkage, thermal warping and spring-back. [5] 7 Links to various software LAP: ESAComp: PATRAN: NASTRAN: SOLIDWORKS: =58&productID=833 9