Thursday, October 4, 2007

Composite Material Modeling


Software Suite for Durability, Damage Tolerance, and Life Prediction
Augments FEA Solvers MSC Nastran*, ABAQUS, ANSYS & LS-DYNA

* Best Performance and Verified Solutions with MSC Nastran



This Week's Feature Composite Example

Composite Material Modeling with GENOA

Figure 1 - Example of Composite Configurations in GENOA Material Modeling
GENOA utilizes a composite micromechanics scheme to compute the mechanical and physical properties of a composite with 1-D, 2-D or 3-D fiber architecture (Figure 1). An illustration of the composite modeling procedure is shown in Figure 2 where stiffness and strength as well as physical properties of each type of reinforcement (e.g. filler, warp and/or through-thickness fiber) are separated into material directions based on fiber angles and contents. These are then combined with matrix properties and/or void contents to create composite unit cell properties. The modeled composite properties include 1) stiffness, 2) Poisson's ratios, 3) strengths, 4) coefficients of thermal expansion, 5) coefficients of hygral expansion, 6) heat conductivities, and 7) moisture diffusivities.
Figure 2 - GENOA's Micromechanics Modeling Procedure for Composites
This composite modeling technique is embedded in the GENOA structural Progressive Failure Analysis (GENOA-PFA) to evaluate both micro failure in the composite unit cell and the overall structural performance. A stand-alone composite property analyzer titled MCA is also presented in the GENOA software suite.

Figure 3 - Modeling the Three Composite Systems in the Army Combat Bridge Design Using the GENOA Composite Micromechanics Technique
GENOA predicted mechanical properties of three polymeric composite systems (a. tri-axial fabric, b. five harness satin weave and c. uni-axial tape carbon fiber reinforced EPON) used in the Army mobile combat bridge design [1, 2] are presented in Figure 3. The simulation results were verified with the Army's test data, which also established A-B base allowable using GENOA's probabilistic module.

Click here to receive demo and presentation of Composite Material Modeling.


References:
1. Ayman Mosallam, Frank Abdi, and Xiaofeng Su, "Virtual Testing And Progressive Failure Analysis Of ARMY COMPOSITE BRIDGE". SAMPE 2004, Long Beach, CA 2004.Click here to read technical publication.

2. Frank Abdi, Zhongyan Qian, Ayman Mosallam, Ramki Iyer, Jian-Juei Wang, Trent Logan, "Composite army bridges under fatigue cyclic loading". Journal of Society of Infrastructure Engineering (SIE), Taylor and Francis Publications, Vol 2, No 1. March, 2006, 63-73. Click here to read technical publication. 
 

Did You Know?

Damage Progression throughout Finite Element Model

imageUnlike many Finite Element Solvers, GENOA accounts for damage progression throughout the model while simultaneously allowing the use of Virtual Crack Closure Technique (VCCT) and Discrete Cohesive Zone Modeling (DCZM) fracture analysis. This feature was recently demonstrated and verified with test data for a bonded three stringer panel.  For more information on this feature and trying out GENOA through our demos, please contact our sales at sales@ascgenoa.com.
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Tuesday, September 18, 2007

Micro Crack Density Prediction of Continuous Fiber Reinforced Polymeric Composites


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Augments FEA Solvers MSC Nastran*, ABAQUS, ANSYS & LS-DYNA

* Best Performance and Verified Solutions with MSC Nastran



This Week's Feature Composite Example

Micro Crack Density Prediction of Continuous Fiber Reinforced Polymeric Composites

Figure 1 - Typical micro cracks in polymer matrix composites
Cryogenic polymer composite propellant tanks are widely employed in Reusable Space Vehicles due to their lightweight. However, micro crack can cause loss of stiffness, stress re-distribution, material degradation due to moisture and oxidation, and leakage when micro-damages exceed tolerable levels which may cause catastrophic tank failure. Micro-cracks (Figure 1), formed in the polymer matrix during manufacturing and service, significantly contribute to the leakage of composite propellant tanks. Therefore, predicting micro-crack formation and development in cryogenic tanks is of great importance to tank design.
Figure 2 - Comparison between the simulated crack densities and test data in 90-degree plies of two IM600/Q1334 laminates under monotonic tension.
GENOA's prediction of the crack density in a polymer composite structure includes three parts: 1) onset of cracks in the structure, 2) multiplication of cracks through the entire structure, and 3) degradation of composite properties due to the existence of cracks at each location. Crack density is obtained at the ply level in the laminate at each location of the structure.
Figure 3 - Crack density development in the 90 degree plies of the IM7/977-2 laminate under tension fatigue in the 0 degree direction. Laminate configuration is [0/45/90/-45]
  
Figure 2 illustrates the micro crack initiation and propagation in two IM600/Q1334 laminates under monotonic tension [1]. The crack density developments in an IM7/977-2 quasi-isotropic laminate under isothermal fatigue loads (room and cryogenic temperatures) were predicted and verified against Air Force test results (Figure 3) [2].

Click here to receive demo and presentation of Micro Crack Density.

References:
1. Su, X., Abdi, F. and J. Andre Lavoie, "Prediction of Micro-crack Densities in Cryogenic IM7/977-2 Propellant Tanks", 45rd AIAA Structures, Structural Dynamics, and Materials Conference, AIAA-2006-1933. Click here to read technical publication.

2. Su, X., Abdi, F. and Kim, R.Y., "Prediction of Micro-crack Densities in IM7/977-2 Polymer Composite Laminates under Mechanical Loading at Room and Cryogenic Temperatures," 46rd AIAA Structures, Structural Dynamics, and Materials Conference, AIAA-2005-2226. Click here to read technical publication. 
 

Did You Know?

Modeling Multiple Plies Using a Single Shell Element

imageUnlike many Finite Element Solvers, GENOA is able to model multiple plies (laminate) using a single shell element layer. In many FE solvers, the analyst has to model several layers of shell elements to assign plies in a laminate to each layer which increases the computation time significantly.  GENOA's single shell element modeling of plies offers easier assignment and faster performance.  For more information on trying out GENOA through our demos, please contact our sales at sales@ascgenoa.com.
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Wednesday, September 5, 2007

Impacted Composite Sandwich Panel


Software Suite for Durability, Damage Tolerance, and Life Prediction
Augments FEA Solvers MSC Nastran*, ABAQUS, ANSYS & LS-DYNA

* Best Performance and Verified Solutions with MSC Nastran



This Week's Feature Composite Example

Impacted Composite Sandwich Panels

Simulation of impacted foam core composite panels and calculation of residual strength after impact is a complex and challenging computational process. Accurate prediction requires the integration of material modeling capability with finite element dynamic explicit solution and damage tracking and fracture algorithms. A new computational methodology for assessing impact related damage and determination of residual strength after impact is presented. The analytical procedure relies on both implicit and explicit computational schemes. The degraded damaged properties are progressively updated at every time step of the analysis process.
Table 1: Comparison between Test and Simulation Results for Impact and Post-Impact Compression Analysis of a Foam Core Composite Sandwich Panel
A rigid body impacting a composite sandwich panel with a foam core with high velocity in the center of the panel was simulated. The simulation results indicated local delamination in the panel. The local damage due to impact was then included in the compression analysis. The numerical results obtained from the analytical approach predicted residual strength that is 6% higher than the one from the tests. In all, the analysis predicted that the strength of the sandwich panel in compression was reduced by a factor of 2.25 due to impact. 
Figure 1: Damage Accumulation at the End of Impact Simulation (Left) Damaged Foam (Right) Isolated Ply Damage View of the Foam, Adhesive, and the Face-sheets. Note that both figures show that the adhesive and the face sheets did not accumulate any damage
 
Figure 2: Comparison of Tests and Simulation Results (Left) Load versus Time and (Right) Impact Energy versus Time
 
Figure 3: Failure of the Composite Sandwich Panel during the Post-Impact Compression Simulation (Left) Damaged Panel after Impact Analysis (Right) Failure of the Composite Panel due to In-plane Compression at 24.78 kips
 
Figure 4: Load versus Displacement Curve obtained from Post-Impact Compression Analysis to Assess the Residual Strength
The results validated that the novel progressive failure dynamic approach in GENOA can be reliably used to assess damage growth and residual strength of impacted composite panels.


References:
Garg, M. and Abumeri, G., 2007. Assessment of Residual Strength in Impacted Composite Panels. JEC Composites Magazine (Pending Paper)

 
 

Did You Know?

Faster and Smaller Native .GEN File Format

imageDid you know that GENOA introduced a new native binary file format as of version 4.2? This format is identified with the file extension of ".gen" and supports a highly compressed binary format to allow fast reading and writing of project and data files.  On average, the file size is usually less than 1/10th the size of the previous text format.  For more information on trying out GENOA through our demos, please contact our sales atsales@ascgenoa.com.
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Thursday, August 23, 2007

Virtual Crack Closure Technique (VCCT) and Discrete Cohesive Zone Model (DCZM)


Software Suite for Durability, Damage Tolerance, and Life Prediction
Augments FEA Solvers MSC NASTRAN*, ABAQUS, ANSYS & LS-DYNA

* Best Performance and Verified Solutions with MSC NASTRAN



This Week's Feature Highlight: Crack Growth for Metal and Composite

Virtual Crack Closure Technique (VCCT) &
Discrete Cohesive Zone Model (DCZM)

Based on fracture mechanics approach, VCCT (Virtual Crack Closure Technique) and DCZM (Discrete Cohesive Zone Model) can be used to simulate crack growth and are supplementary to the PFA (Progressive Failure Analysis) of GENOA. VCCT is applicable to linear elastic materials. It can also be used as a tool to compute the strain energy release rate and to estimate the fatigue life and residual strength. DCZM has the capability to model the material softening. They are applicable to, but not limited to, delamination of face sheets/cores in sandwich materials, failure analysis of adhesively bonded joints; fast crack propagation and arrest in pipe lines; interface failure analysis in MEMS devices; and crash and crush analysis.

Click here to receive demo and presentation of VCCT & DCZM.

Figure 1 - Boeing 747 Crown Panel Fuselage Section

Figure 2 - NASA Push-off Test with Honeycomb, Adhesive Bond, & Polymer Composite

VCCT and DCZM Features:  
  • Not sensitive to the FEA mesh size.
  • Not require the singular crack element and therefore, they are easy to apply without much extra work in mesh preparation.
  • Calculations are based on the nodal displacements and nodal forces and therefore, they do not increase the problem size and thus are computational efficient.
  • Work with most of commercial FEA software such as MSC.NASTRAN, ABAQUS, ANSYS, LS-DYNA, MSC.MARC and MHOST. 
  • Can be used with material strength theory.
  • Virtually represents damage propagation by element removal, node split, and adaptive meshing techniques. 
  • Supports various loading conditions such as quasi-static, impact, cyclic (low, high and two stage fatigue, random fatigue, PSD fatigue) and creep.
  • Delivers robust computational performance, rapid convergence and efficient CPU time.
  • Captures the load vs. displacement curve after the ultimate load. 
References:
1. De Xie, Zhongyan Qian, Dade Huang, and Frank Abdi, "Crack Growth Strategy in Composites under Static Loading", 47th AIAA-2006-1842, Newport, RI, May 1-5, 2006.  Click here to read the publication document. 

2. Thomas S. Gates, Xiaofeng Su, Frank Abdi, Gregory M. Odegard, and Helen M. Herring, "Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures", Journal of Composite Science and Technology, 2006.
Click here to read the publication document. 

Did You Know?

Trying GENOA on the Web

imageDid you know that you may try out material modeling or 3D analysis through the web without installing GENOA software?  With our Collaborative Virtual Testing software, we allow customers and clients to login to our secure public CVT website and perform analysis on our server. For more information on trying out GENOA through the web, contact our sales at sales@ascgenoa.com.
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Friday, August 10, 2007

Filament Winding (FW) Analysis


Software Suite for Durability, Damage Tolerance, and Life Prediction
Augments Solutions for NASTRAN, LS-DYNA, ABAQUS & ANSYS

This Week's Feature Highlight

Filament Winding (FW) Analysis

As part of the GENOA family, Filament Winding (FW) supports design and analysis of composite over-wrapped pressure vessels (COPVs). FW utilizes advanced composite mechanics and generates information that can be included in the PFA analysis of a COPV design. It can duplicate the manufacturing process by generating the correct tape schedule at each location on the COPV FEM model and calculate the residual stresses caused by the filament winding process.
Filament Winding (FW) Features:  
  • Import finite element models from other software formats.
  • Generate pressure vessels: liner only, composite over-wrap only, or combined liner and composite over-wrap. 
  • Control the bonding between the liner and the composite over-wrap. 
  • Accounts for residual stresses due to the winding procedure and curing during the manufacturing procedure.
  • Outputs the node/element ply schedules (including orientations, materials, and thickness) and internal stress distribution, which depends on the geometry, loads, material properties, environment and filament winding process.
  • Generate finite element model of pressure vessels of several shapes and sizes.
    Supports cylinders with circular, elliptic cross-sections and end caps with elliptic, spherical, geodesic, and toroidal shapes. 
  • Automatically generate filament winding ply schedules upon giving the definition of hoop and helical winding with greater control over the material and fabrication parameters.
  • Allows to simulate complete manufacturing to certification process (static, mechanical and thermal fatigue, and dynamic loading).
  • Design of filament wound pressure vessels for defense, automotive and aerospace applications that account for filament winding processes.
  • Predicts failure location and corresponding load.
  • Create design configurations with increased durability and damage tolerance.

Did You Know?

Industrial Verification Examples

imageDid you know that there are over 30 industrial verification examples to browse on the official GENOA website?  In addition there are example videos of case models that demonstrate the capabilities of the GENOA modules. Find out more here! 
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Wednesday, July 25, 2007

Collaborative Virtual Testing (CVT) Remote Client Analysis


Software Suite for Durability, Damage Tolerance, and Life Prediction
Augments Solutions for NASTRAN, LS-DYNA, ABAQUS & ANSYS

This Week's Feature Highlight

Collaborative Virtual Testing (CVT) Remote Client Analysis

Multiple users can login to a central server from remote workstations
As part of the GENOA family, CVT 2.0 is an add-on package that allows users to use GENOA through the internet using a remote-client framework. CVT allows GENOA to be installed on a central server where multiple users may simultaneously login and perform analysis jobs. The clients do not need to install GENOA on their remote workstation and only require a common internet web browser (Internet Explorer, Netscape, etc.) to access GENOA. This may be helpful for environments where multiple GENOA licenses may be difficult to install or for remote users wishing to access GENOA from remote geographical regions. CVT may be customized for an internal private corporate intranet or to the outside public internet.
The clients may access the CVT analysis server using standard HTML web pages and Java 3D applets through their internet web browser.
CVT 2.0 Features:  
  • Allows GENOA users/engineers to remote access a central server through an internet browser.
  • Ideal for customers to use GENOA within their own intranet and for remote purposes.
  • Utilizes web server to monitor user logins and launch GENOA GUI as Java applet
    through client browser.
  • Creates user accounts, monitors analysis jobs, and records logs of user logins and
    analysis runs.
  • Upload/Download files and models through web server interface.
  • Supports internet browser from any platform (Mac, UNIX, Windows, Linux, etc.) that
    supports Java & Java3D plug-in.
  • Includes Documentation and Step-by-Step Tutorial Example.
  • Cross-platform capability such as Windows client accessing Linux server, Linux
    client accessing Windows server, etc.

Did You Know?

GENOA Download Demo and Web Demo

imageDid you know that it is easy to evaluate and try GENOA?  Simply go to the Download section of www.ascgenoa.com and select either Demo Download or Web Demo.  The Web Demo is the fastest way to test and requires only a Java plug-in with your internet browser.  Find out more here! 
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Monday, July 9, 2007

Fatigue Prediction & Verification of 3D Woven Composite


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Augments Solutions for NASTRAN, LS-DYNA, ABAQUS & ANSYS

This Week's Feature Composite Example

Fatigue Prediction & Verification of 3D Woven Composite

Figure 1 - 3D Weave Architecture
3TEX 3Weave (3D woven fiberglass mat)/vinyl-ester (Dion 9800) composites (Figure 1) have been investigated as a candidate material in the DOE-Delphi-NCC (National Composite Center) Composite Chassis Cross-Member program. One of the most important mechanical properties for qualifying these composites for such applications is the mechanical fatigue longevity. The math-based GENOA methodology effectively tracks the details of damage initiation, growth, and subsequent propagation to fracture, for composite structures subjected to cyclic fatigue, thereby predicting the fatigue life.
The utility of the GENOA technology was demonstrated by predicting premature and extended fatigue lives in tensile mode of various 3TEX 3Weave/Dion composites (Figure 2). The simulated fatigue longevity of 3D woven ISO coupons agrees well with those measured in actual tensile-tensile fatigue tests using the R (minimum-to-maximum stress ratio) value of 0.1 (Table 1). Furthermore, GENOA PFA simulations quantitatively predicted the effect of the void content on premature fatigue failures.
Table 1 - Comparison between fatigue life cycles for composites with high and low void contents
Indeed a 10% volume fraction of void defects reduces the fatigue life of the 3D woven composite by a factor of 40 at the tensile load of 30% composite ultimate strength (Table 1). Finally, the sensitivities of composite fatigue life to manufacturing anomalies were calculated using GENOA Probabilistic PFA for future design of the composite structure (Figure 3). This math-based predictive methodology is currently being used in the DOE-NCC Composite Chassis Cross-Member program.
Figure 2 - Failure mechanisms for the tensile-tensile fatigue of the composite tensile test coupon
Figure 3 - Sensitivities of composite fatigue life to its constituent parameters

Did You Know?

Five Reasons to Use GENOA for Aerospace Applications

image
  • Accurate prediction of loads that produce damage and fracture initiation and propagation in composite/sandwich/metallic structures.
  • Assessment of damage initiation and growth under static, impact (low and high velocity), thermo-mechanical fatigue (quasi-static, harmonic, and random), and creep loading.
  • Prediction of failure modes (including delamination, fiber micro-buckling, fiber crushing, etc.) in composite structures.
  • Simplified representation of all types of composites including tape, 2D-3D weave and braids and stitched (polymers and ceramics).
  • Ability to select from a range of competing designs that would improve the product performance and delivery time to market through virtual testing and accelerated certification processes.
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