Feature Description

GENOA is an integrated structural analysis/design software suite originally developed to cost effectively predicts strength, reliability and durability of aerospace structural components at the design stage with minimal experimental testing support. GENOA progressive failure analysis predicts the crack initiation, growth, and final failure of monolithic and 2D/3D braided/laminated /stitched/woven composite materials. GENOA evaluates the structural and material response including degradation of material properties due to initiation and growth of damage under static, dynamic, thermal, impact, creep, and low/high frequency cyclic fatigue loading conditions Failure prediction takes into account defects introduced by: 1) manufacturing, 2) in-service operations and environments, 3) fatigue, and 4) material creep.

The modeling of PMC in GENOA considers physics and mechanics of composite materials and structure by integration of a Hierarchical Multi-Level Macro Scale (lamina, laminate, and structure) and Micro Scale (fiber, matrix, and interface) for simulation analyses. Modeling with GENOA involves: 1) ply layering methodology utilizing FEM elements that include through-the-thickness representation, 2) simulation of effects of material properties and defects (voids, fiber weaviness, residual stress) on global static and cyclic fatigue strengths, 3) simulation of crack initiation, and growth to failure under static, cyclic, creep, and impact loads, and 4) progressive fracture analysis to determine durability and damage tolerance, 5) identifying the percent contribution of various possible composite failure modes involved in critical damage events, and 6) determining sensitivities of failure modes to design parameters (e.g. fiber volume fraction, ply thickness, fiber orientation, and adhesive bond thickness) to facilitate targeting design parameter changes that will be most effective in reducing the probability of a given failure mode occurring

Key Analysis Features:

• Virtual Testing- accurate numerical simulation predicting results of experimental testing :
• contour plots of the global strain/stress fields at crack initiation, propagation, and failure
• plot of far-field applied load vs. deflection (deflectometer)
• plot of applied load vs. strain (strain gage)
• photo-elastic fringe simulation (isochromatic, isoclinic, and thermagraphy)
• local and global energy release rates Vs. applied loads representing acoustic emissions
• Plot of Crack Length Vs. Applied Load representing the fracture toughness
• Plots of Stress vs. Strain at selected locations

• Predictions of static failure resulting from discrete source damage ( DSD)

• Prediction fatigue damage Initiation at multiple sites
• Prediction of required tests based on sensitivity of failure criteria

• Durability and Damage Tolerance- accurate numerical simulation in thermal-mechanical and dynamics environments of creep, fatigue, and impact

• Damage initiation and location (fiber, matrix or interface ) within a lamina,
• percent of contributing failure mechanisms
• failure location , and fracture path within lamina, and structure
• residual strength after damage
• Prediction of life cycle
• Prediction of S-N curves, da/dN, and fracture toughness
• Stress intensity factor

• Probabilistic failure analysis - identification and sensitivity of progressive damage parameters
• Uncertainty evaluation of material strength to material parameters
• Sensitivities of design requirements to design parameters.
• Predicting the degree to which design parameters contributed to failure
• Generation of cumulative distribution functions (cdf) for failure strength evaluation
• Probability of time to failure
• Margin of safety predictions

• Manufacturing of Preform Composite Net Part Shape - The process is based on using fiber preforms prepared by reshaping low cost, commercially available, tubular braided/woven fiber textiles by forcing conformance to shaped tooling. Computative prediction of the reshaping process determines:
• Fiber orientation and volume fraction changes,

• Attainable best fit to a shape,
• Minimize occurrences of failure (buckling, fiber wrinkling)
• Simulating multiple reshaped preforms of different sizes interleaved with woven sheet strips
• Transferring fiber orientation data directly to design and manufacturing process software

• Equivalent Material Properties and Degradation of Monolithic, and 2D/3D laminated/woven/braided/Stitched composites

• Equivalent laminate moduli, moisture property, thermal property, , and heat conductivity
• Degradation of material properties due to environmental (moisture, thermal), manufacturing (void, defects, residual strains), etc.

Simulation of discrete source damage effect on Durability and Damage Tolerance of a large Aircraft Wing-Eight three stringer polymer composite Stitched/Resin Film infusion (S/RFI) panels were simulated in support of the NASA-Boeing/Long Beach ACT program for design of a large commercial aircraft wing. Pre test simulation predictions were within 93.5 to 99 percent of subsequent experimental tension and compression strength test results. Further, predictions of damage initiation, damage growth path, strain distributions, and photo elastic fringe patterns correlated well with test results. Sensitivity of damage growth to damage initiation shape was predicted per FAA requirements. Experimental testing was significantly facilitated relative to determination of: 1) load application, 2) strain gage locations, and 3) anticipated crack development.

Simulation of full scale Mini Space Plane Vehicle-in support of the Air Force-Boeing/Seal Beach Mini Space Plane Technology (MIST) program. The GENOA-PFA software successfully predicted damage tolerance limits and failure criteria of the Mini Space Technology Plane (MIST) by using a building-block strategy to numerically) calibrate material strength and stiffness properties with data from tape and fabric composite coupon tests, and 2) predict the D&DT (involving damage initiation, accumulation, and residual strength) of the full scale test article under combined longitudinal, torsional, and shear loads. GENOA-PFA used finite element models (FEMs) to analyze subcomponents made of composite materials, taking into account ply drop-off, voids, and fiber volume ratios. Details of composite thickness, lay-up configuration, voids and flaws were provided by Boeing Tulsa Division from results of ultrasonic jet flow machine inspection of fuselage crown, side, and bottom areas. Verification was achieved by successfully predicting test results of 1) residual strength (within 1.0%), 2) multiple crack initiation and growth locations , and 3) strain measurements. It was shown that global fracture initiation and fracture propagation occur at maximum and minimum of the Total Energy Release Rate (TDERR) values, respectively.

Simulation Acoustic Fatigue effects on Durability of Lockheed F22- Aircraft Composite Panel - Damage initiation, growth, accumulation, and propagation to fracture due to cyclic fatigue were simulated. Results showed the damage progression sequence and the changes in the structural response characteristics during different degradation stages and allowed. assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions. Significant findings were: 1) the number of load cycles to failure was an approximately exponential function of the acoustic amplitude, 2) degradation of the first natural frequency was a function of the number of acoustic load cycles, 3) the first damage growth stage affects the fundamental structural response significantly, and 4) the damage propagation stages immediately prior to structural fracture do not influence the first natural frequency very much.

Probabilistic Fatigue Life Analysis of Boeing Crown Panel, and Integrally Assembled (IAS Panel Lap Joint In The presence of MSD –The Progressive Failure Analysis by probabilistic fatigue life and durability and damage tolerance computative simulation analyses of a lap joint in an IAS coupon and in IAS panel structures with multi site damage. Deterministic progressive failure analysis (PFA) simulations were performed by Alpha STAR Corporation using its GENOA software and information obtained from Boeing. Finite element models, meshes of a test coupon and two test panels, with and without multi site damage, were prepared. Test results from the coupon with static and cyclic fatigue simulation analyses were conducted to determine in detail the effects of multi site damage on ultimate loads and cycles to failure after calibrating the software. In the course of these simulation analyses, damage initiation and progression were determined as functions of static and cyclic loading.

Deterministic accomplishments of this effort were: 1) PFA verification with data from five coupon tests, crown panel static test, and the crown panel fatigue test, 2) PFA analysis of the static lap joint model (extracted from the Boeing crown panel FEM model), 3) PFA analysis of the fatigue lap joint model (extracted from the Boeing crown panel model), and 4) PFA analysis of the fatigue lap joint model (extracted from the Boeing crown panel FEM model) using 5 percent variation of lap joint thicknesses. A comparison of simulation and experimental test results is shown in Table 1-1.

Probabilistic analysis accomplishments of this effort were probabilistic simulation of: 1) the static lap joint model for critical failure modes at the crack initiation site (at pressure load of 29.4 psi), and 2) fatigue of the lap joint model for critical failure modes at the crack initiation site (at pressure load of 29.4 psi). 

Probabilistic Assessment of Fracture in Stitched and Unstitched Composite Laminates-Structural response is assessed probabilistically during degradation. The effects of design variable uncertainties on structural damage progression are quantified. The Fast Probability Integrator is used to assess the response scatter in the composite structure at damage initiation. Sensitivity of the damage response to design variables is computed. Methods are general purpose in nature and are applicable to stitched and unstitched composites in all types of structures and fracture processes starting from damage initiation to unstable propagation and to global structure collapse. The methods are demonstrated for polymer matrix composite panels under edge loads. Results indicate that composite constituent properties and fabrication parameters have a significant effect on structural durability. Design implications with regard to damage progression and damage tolerance of composite structures are examined.

Allied Signal Engine Combustor Development- The effort centered on enhancement of GENOA_TM, to simulate 2D/3D-braided/woven CMC material to simulate: 1) 3D-woven/braided fiber architecture, and 2) track micro/macro damage (initiation, accumulation, stable growth, and fracture). GENOA predictions made for code verification by comparison with CMC coupon and combustor test data from: 1) Nicalon/SIC CMC compact tension coupon test results reported in the literature, and 2) Sylramic/MI CMC coupon tests (bending, flexural, open hole (0.25, 0.38 in diameters) tension and unnotched) available from an Alpha STAR cooperative effort with GE/NASA’s HSR-EPM program and AE full-scale combustor rig test. Verifications of GENOA predictions were made relative to CMC strength, stiffness, and creep rupture. AE’s CMC combustor model was simulated to predict fracture paths and life cycles under service conditions. GENOA predictions correlated well with the fracture pattern exhibited on experimental testing of AE’s Nicalon/SiC CMC combustor. GENOA was also used to predict the fracture path in AE’s projected Sylramic/MI CMC combustor for comparison with their Nicalon/SiC CMC combustor.

Air Born Laser -The STI-optronics laser reactor housing of the airborne laser laboratory is a lightweight structure that is made of composite materials that are loaded statically and dynamically. Alpha Star Corporation (ASC) has conducted static stress analysis to determine which areas are highly loaded and areas, which require design modifications to prevent structural failure. The GENOA durability and damage tolerance (D&DT) simulation software has been successfully used to predict susceptibility to damage under service loading of the STI-optronics laser reactor housing. The GENOA analysis combines details of the composite structure lay-up, a rough finite element model defining the geometry, material properties and structural loading with advanced methods of damage tolerance fracture mechanics to provide crack initiation, crack growth and lifetime fatigue predictions. The GENOA simulation evaluated one piece and adhesive bonded structural designs of the STI-optronics housings made of: 1) carbon-carbon composite and fiber glass honeycomb core, and 2) carbon-carbon composite and titanium honeycomb core. Simulation of D&DT was achieved by utilizing CATIA for solid geometric modeling, and GENOA for mathematical modeling of progressive failure and reliability. The results of the GENOA simulations have provided insight needed for significant reduction of the time and cost required for the design of the 21st century commercial laser reactor housing structure.

Verification with coupon test results

Strength and fracture pattern Simulations - of (S/RFI) Polymer composite compact tension, center cracked, and inclined cracked coupons were made and verified, to be within 99% of corresponding test data from NASA.

Strength and stiffness Simulations-of (S/RFI) Polymer composite. open-hole tension, open-hole compression, Isopescue shear, unnotched compression and unnotched tension coupons were made and verified to be within 97% of corresponding test data from University of California at Santa Barbara (UCSB).

Strength and Stiffness Simulations-of ten lightly and heavily compacted woven composite coupons were made and verified to be within 97% of corresponding test data from Rockwell Science Center.

Product Strategy

GENOA is a modular, heterogeneous software system that can be easily ported to any hardware platform using a UNIX, and NT operating systems. Several stand alone modules are offered as a package or selectively purchased according to the users specific needs. The Graphic User Interface (GUI) and Executive Controller System (ECS) together make up the main driver for one or all of the modules and are a required part of GENOA. The GUI provides the pre and post processor visualization capability while the menu driven ECS connects all the modules. The following is a brief description of GENOA’s drivers and modules.

Graphic User Interface (GUI) - - A visualization system based on ICONS and menus. The main functions of GUI are: 1) to provide visualization to view results, 2) to import CAD models from PATRAN or NASTRAN, and 3) to export data to other software systems such as NASTRAN or PATRAN. GUI is written in C language and employs a standard graphical library such as X11 Motif and OPENGL, on-line help options spanning from input deck preparation, post processing plots, and contour plots. GUI allows visualization of the updated Lagrangian: 1) FEM model, 2) FEM stresses/strains/photo-elastic fringe pattern, 3) ply stresses, 4) micro-stresses, 5) damage locations, 6) percent contribution of failure mechanism to failure, 7) location of failed nodes, and 8) XY plot history of strain, TDERR, DERR, %damage, and strength degradation plots.

Code Name: GENOA

Source: Alpha STAR Corporation

Cost: Please contact us.

Outputs: Graphical representation of Damaged plies/nodes, photo-elastic fringe, stress/strain field, damage history profile.

Documentation: User’s manual, and Training Manual, on line help menu

Interface: Interfaces with other Commercial analysis codes: PATRAN, ANSYS, and NASTRAN

Supported Computer Platforms: Silicon Graphics, Hewlett Packard, WINDOWS, UNIX, LINUX

Additional Software or Hardware Required: 500 MB Storage, 512 MB Memory