Thursday, December 13, 2007

Composite T-Joint Design Analysis


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This Week's Feature Composite Example

Composite T-Joint Design Analysis

Figure 1 - Configuration and laminate layups of the British Naval composite joint [1]. 

GENOA-PFA is virtual testing software tool simulating both the detailed micro and macro failures occurred in a composite structure throughout the entire loading process. It can greatly reduce the experimental investigation effort and cost involved in structural design. A British Naval composite joint [1, 2] was employed to demonstrate the application of GENOA-PFA in composite structure durability analysis and design. 
Figure 2 - Configuration and laminate layups of the British Naval composite joint [1]. 

Configuration of the T-Joint and the FEM - The joint is comprised of two FRP overlaminates bonded to either side of a web plate and then bonded to the base plate or flange (Figure 1). These overlaminates form a boundary angle connection and are comprised of alternating polyester/E-glass woven roving (WR) and chopped strand mat (CSM) layers. The gap within the boundary angle is filled with a compatible resin. The members being joined are comprised solely of polyester/E-glass woven roving. There are 14616 solid elements in the British joint model (Figure 2). The loading condition is three point bending. The load type is forced displacement. 

Simulation Results - The joint performance was simulated and the failure mechanism, which occurred in the joint, was identified. Figure 3 illustrates the comparison between the simulated and tested load-deflection relationship of the joint. The two results agree reasonably well for both damage initiation and final fracture loads.
Figure 3 - Comparison between simulated and tested load-deflection relationship.

The damage initiated as tensile- driven delamination in the fillets at the juncture area, where the interlamina tensile stress was the largest under the bending condition. Then the delamination failure propagated through the fillet thickness due to stress redistribution to the undamaged layers from the failed layers. The delamination in the fillets reduced their contribution to bending resistance, which finally resulted in the fracture of the flange at the end of the loading process. The entire simulated damage and fracture process of the joint is illustrated in Figure 4 where red areas represent the damage.

Figure 4 - Simulated failure process of the British Naval joint. Red areas represent the failure which was caused by interlamina tensile stress (delamination).

Conclusions
GENOA-PFA computed detailed laminate failure in the composite joint throughout the entire loading process. The load capacity of the British Naval joint was accurately predicted and its underlying failure mechanism was clearly identified, namely, delamination due to interlamina tensile stresses. Hence, GENOA-PFA is a useful virtual testing tool for optimal design of composite structures, e.g. for a composite joints, the fillet radii and thickness can be optimized to reduce the delamination failure and thus maximize the joint durability. 
References:
1. Cody Godines, Frank Abdi, Steven Kiefer and Keith Kedward, "Simplified Analytical Procedure for Prediction of Fracture Damage in Composite Structures", ASTM COMMITTEE-D30 Symposium on Joining and Repair of Composite Structure March 17-18, 2003 Kansas City, MO. Click here to read technical publication.
2. Phillips, H.J., and Shenoi, R.A., "Damage Tolerance of Laminated Tee Joints in FRP Structures", Composites Part A - Applied Science and Manufacturing, Vol. 29, No. 4, pp. 465, 1998. Click here to read technical publication.
 

Did You Know?

Probabilistic Progressive Failure Analysis 

imageGENOA's Probabilistic Progressive Failure Analysis capability enables the prediction of structural reliability in presence of uncertainties in fabrication parameters, cure, material, geometry, and loading. First, perform low fidelity probabilistic analysis to identify influential random design variables. Second, reduce the list of variables to include critical ones and perform high fidelity simulation (e.g. Monte Carlo) to obtain a measure of reliability. As additional benefits, you will obtain a database of competing designs to improve the product performance and reduce the number of unnecessary tests.  For more information on this feature and trying out GENOA through our demos, please contact info@ascgenoa.com.
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Tuesday, November 13, 2007

Delamination Initiation/Propagation Failure Analysis of Reinforced Carbon-Carbon Woven Composite Specimens


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This Week's Feature Composite Example

Delamination Initiation/Propagation Failure Analysis of Reinforced Carbon-Carbon Woven Composite Specimens

Figure 1 - Space Shuttle and Close-Up View of the RCC Panel near the Leading Edge [1]. 

The Shuttle Reinforced Carbon-Carbon (RCC) leading edge (Figure 1) is a brittle composite system which is subject to cracking and delamination from foreign debris and other impacts. The combination of cracks and delaminations can provide pathways for hot gases to enter the interior of the Shuttle wing during reentry, leading to serious consequences. If an impact occurred during launch, delaminations would be unseen by surface inspection on orbit. An investigation was carried out to demonstrate delamination prediction in RCC when impacts are known to have occurred. 
Figure 2 - Three-Point Bending (a) Test Setup and (b) Schematic and Dimension of the Short Specimen [1].

A detailed failure analysis of two RCC specimens in a three-point bending configuration (Figure 2) was carried out by Alpha STAR Corporation (ASC) using GENOA and compared to NASA tests. GENOA progressive failure analysis (PFA) for 1.0 inch and 1.5 inch three-point bending specimens revealed that the twospecimens exhibit different failure behavior prior to final failure (different delamination initiation and damage/fracture progression). 
Figure 3 - Test (a) versus Predicted [1] (b): Major and Minor Delamination (Initiation & Propagation) Location. Red Indicates Damaged Locations Just Prior to Final Failure. Simulation was based on a Single Layer of Shell Elements as the Finite Element Model.

The finite element models of each specimen was constructed with 200 Mindlin-Reissner shell elements, simulating woven Reinforced Carbon-Carbon (RCC) material properties. Shell thickness was 0.229 inch. The loading was applied using displacement control. Each shell element consisted of 19 plies, significantly reducing the computational time without loss of analysis details such as stresses, strains, and damage information for the individual plies. The material properties were initially calibrated with the 1.0 inch specimen test data.  The material calibration process was presented in one of our previous issues.

The predicted simulation results for the 1 and 1.5 inch specimens compared well with the reported test data (Figures 3 to 5). Alpha Star Corporation (ASC) did not have access to the 1.5 inch long specimen test results prior to submission of the analytic predictions to NASA (Figure 5).

Figure 4 - Calibrated: Load-Displacement Response of 1.0 Inch Three-Point Bending Specimen [1].

Figure 4 shows the test load-displacement behaviour and the corresponding progrssive failure analysis predictions for the three-point RCC bending specimens. Points A through F indicate the onset of various types of damage.


Figure 5 - Measured and Predicted Load-Displacement Behavior for 1.5 Inch Specimen [1].

Progressive Failure Analysis predicted failure loads of 350 lbf and 231 lbf for the 1 inch and the 1.5 inch specimens, respectively (Figures 4 and 5). Measured and predicted failure loads were in excellent agreement, with errors of less than 1% (1 inch specimen) and 5.7% (1.5 inch specimen). Both the shorter and longer specimens were predicted to fail at the specimen mid-section.This was confirmed by the test results.The analyses indicated that the failure mode of the shorter specimen was very different from that of the longer specimen. PFA of the shorter specimen predicted considerable delamination, but longer specimen PFA revealed virtually no delamination. In the shorter specimen, two delaminations were predicted (Points C, D, and E in Figure 4); a primary one and a secondary one.

Figure 3 shows the RCC damage when the load reaches point F (348 lbf) inFigure 4. The delamination, which initiated at load point C and is tracked as excessive relative rotation at ply 3, that is, between plies 2 and 3, and 3 and 4, grows toward the Y-axis (green arrow) as the applied load is further increased (Figure 3). It grows to become a secondary delamination of the specimen.

Also at an applied load of 348 lbf additional delamination was observed near the center of the ply stack, ply 9 (Figure 3). This new delamination occurs between plies 8 and 9, and 9 and 10 and is due to excessive transverse normal shear. The delamination originates where the shear is greatest, namely under the applied load and grows to become the primary delamination in the specimen. It reduces the bending stiffness of the specimen in the vicinity of the delamination.

Figure 6 - Photograph of damaged 1.5 inch specimen: (a) Test (b) Prediction at 231 lbf [1].

Photos of the interior of the failed test specimens confirmed the predicted failure behavior. No delamination occurred in the longer specimen (Figure 6), but primary and secondary delaminations occurred in the shorter specimen (Figure 3). Figure 6 shows the similarity between the predicted and the snaps taken at the failure. The simulation results are at 231 lbf.

Conclusions
GENOA PFA predictions confirmed that the 1-inch three-point bending specimen will exhibit two delaminations; a primary one and a secondary one. The primary one results in considerable loss of stiffness prior to failure, whereas the secondary one does not. Photographs of the interior damage in the tested specimens indicated that the two delaminations occur near their predicted locations in the 1-inch specimen.

Confidence in the analytical predictions was reinforced since the predicted load-displacement behavior of both specimens were in excellent agreement with the measured load-displacement behavior. 

References:
[1] Sokolinsky, V. S., Housner, J., Surdenas, J., and Abdi, F., 2006. "Progressive Failure Analysis of Shuttle Reinforced Carbon-Carbon Plate Specimens." AIAA-2006-1789, RI, May 1-5. Click here to read technical publication.
 

Did You Know?

GENOA Custom Failure Criteria

imageGENOA has a recommended 'Custom Failure Criteria' that consists of a set of well known failure criteria, such as Tsai Hill, Puck, Strain Invariant and many more that help predict the strength of composites made up of wide variety of materials and several configuration (2D, 3D braid and woven). The approach is simple to use and allows implication of user defined failure criteria subroutine.  For more information on this feature and trying out GENOA through our demos, please contact info@ascgenoa.com.
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Thursday, October 18, 2007

Prediction and Verification of Metal Fracture Toughness Tests Using Non-linear Static Stress-Strain Curve


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This Week's Feature Metal Example

Prediction & Verification of Metal Fracture Toughness Tests Using Non-linear Static Stress-Strain Curve

Figure 1 -  Full Stress-Strain Curve and Crack Tip Deformation [2] (a) Areas Associated With The Uniform (b) A Center Crack in Wide Panel and Non-Uniform Straining 
Safe life prediction of components must be conducted to ensure the life adequacy of parts during service usage. In many cases fracture properties of material are not available because of 1) cost associated with generating fatigue and fracture data, 2) Inability to conduct tests because of time limitation and deadline set forth by the customers, and 3) lack of analytical tools to conduct a comprehensive crack tip stress analysis. 

New material-physics based computational methodologies for assessing the plane-stress and the plane-strain fracture toughness (KC, KIC) and (da/dN versus Delta K curve) of the material have been used successfully in predicting these fracture allowables, knowing only the complete stress-strain behavior of the material of interest. 
Figure 2 - Typical Crack Growth Rate Versus Stress Intensity Range
Farahmand extended the Griffith theory to estimate fracture toughness value of metals from simple uniaxial tensile tests. Figure 1 illustrates the extended Griffith theory and regions of crack tip plastic deformation. Accounting for the energy absorption rate for plastic deformation at the crack tip is calculated and used to establish a relationship between fracture stress and half critical crack length [1].
On the other hand, fatigue crack growth properties of the material are determined using the well known Newman Forman and Koening (FNK) equation requiring input from fracture toughness theoretical model. The analytical procedure relies on both implicit and explicit computational schemes and evaluates points in the threshold, Paris, and accelerated regions (Figure 2).

Once the fracture allowables are determined, the values can be further used to predict the S-N curve of the component using finite element method approach with Virtual Crack Closure Technique (VCCT). The formulation extends to fatigue crack growth and strength life prediction of notched and unnotched components. Scientists at Alpha STAR and TU Delft are extending the algorithm to composites.
Figure 3 - Process and Comparison of Fracture Toughness Versus Thickness [FTD] and da/dN Versus Delta K Curve [FCG] With The Test Data Provided in NASGRO for Ti-6Al-4V (Mill Annealed) [2].

Figure 3 shows the process and comparison of the results obtained using the two methodologies (Fracture Toughness Determination [FTD] and Fatigue Crack Growth [FCG]) for a Titanium alloy. Similar verification has been done with several other pure and alloyed materials, such as Aluminum alloy, Inconel, Steel, and many more.

Figure 4 - Metallic Center Cracked Panel Subjected to Quasi-Static Fatigue Loading [2]
The virtual testing technique was later used to generate the high cycle fatigue data (the S-N curve). The fracture allowables predicted from the FTD/FCG modules in GENOA for a center-cracked specimen were used to assess the total life of uncracked specimen made of Ti6-4MA and 7075-T6 Titanium and Aluminum alloys, respectively (Figure 4). The panels were subjected to quasi-static fatigue loading using progressive failure analysis in conjunction with Virtual Crack Closure Technique (VCCT) (A link to the past news letter). The comparison of the predicted and test results is tabulated in Table 1 for four tests.

The capability of the three step approach: 1) Fracture Toughness Determination, 2) Fatigue Crack Growth Determination, and S-N curve Determination was demonstrated Life Assessment of Boeing 747 crown Panel Fuselage Section (Figure 5).

Table 1 - Comparison between Test and Simulation Results for Life Assessment of Metallic Center Cracked Panel, As Shown In Figure 3 [2]
The results validated that the novel Fracture Toughness Determination, Fatigue Crack Growth Determination and Life Assessment Methodologies in GENOA indicating further that GENOA can be reliably used to assess fracture allowables for a materials extremely quickly and with reasonable accuracies.
Figure 5. Three Step Approach to Assess Life of the Stiffened Curved Panel Made of Aluminum Alloy [2]
In addition, a probabilistic analysis of the fracture toughness and fatigue crack growth can also be performed using the Probabilistic Fracture Toughness (PFTD) and Probabilistic Fatigue Crack Growth (PFCG) modules in GENOA (Figures 6 & 7). The probabilistic capability allows monitoring the sensitivity of the response (KC, KIC, and da/dN versus DK curve) to different input variables [3].
Figure 6 - Variation of Fracture Toughness with Variable Thickness [3]
Figure 7 - Variation of Plane Stress (KC) and Threshold (Kth) Fracture Toughness Due to Variations in Material Properties. [3]

Click here to receive demo and presentation of FTD & FCG.

References:
1. Farahmand, B., Fatigue and Fracture Mechanics of High Risk Parts, Chapman and Hall, 1997.
2. Farahmand, B., Saff, C., Xie, D., and Abdi, F., 2007. Estimation of Fatigue and Fracture Allowables for Metallic Materials Under Cyclic Loading. AIAA-2007-2381.Click here to read technical publication.
3. Farahmand, B., and Abdi, F., 2002. Probabilistic Fracture Toughness, Fatigue Crack Growth Estimation Resulting From Material Uncertainties. ASTM International Paper. Click here to read technical publication.
 

Did You Know?

Benefits from Virtual Simulation of ASTM Tests

imageVirtual simulation of ASTM tests using GENOA enables the qualification and characterization of aerospace materials. The successful replication of these tests provides the designer and analyst with a reliable tool to evaluate the component performance. Iterative designs can be made with GENOA until satisfactory performance is achieved. This capability eliminates redundant tests thereby expediting the component certification and delivery to market.  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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Thursday, October 4, 2007

Composite Material Modeling


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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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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


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

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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)


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

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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


Software Suite for Durability, Damage Tolerance, and Life Prediction
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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