HyperSizer New Capabilities

Discrete Stiffener Modeling (DSM)

v6A new discrete stiffener model (DSM) analysis capability is available in HyperSizer. Using this analysis capability, unique stiffener buckling, crippling, strength, and local buckling margins of safety may be reported for each skin and panel segment component. This provides the flexibility for designing stiffened panel bays with stiffeners that have varying dimensions and materials. Additionally, the discrete techniques will capture the effects of having non-uniformly spaced stiffeners and stiffener terminations. During the analysis, HyperSizer determines how the stiffener and skins fit together to form a stiffened panel. The software will automatically determine the stiffener spacings, heights, and how to map the loads to perform stiffener analysis like stiffener crippling and flexural torsional buckling.


  • Import discretely stiffened models, multiple techniques
  • Create panel segments in HyperSizer graphics
  • Automatically extract loads from discrete FEM objects
  • Analyze for strength, local buckling, stiffener buckling and stiffener crippling
  • Export updated shell and beam properties

Supported Modeling Techniques


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Laminate Optimization for Manufacturability

v6HyperSizer provides six steps to help design and optimize laminates simultaneously for strength, stability, and manufacturability. It begins by generating composite laminates, defining optimum layup areas and end-of-ply transition zones on the part surface, solving for ply count compatibility across the zones, and then sequencing the actual ply ordering while reducing weight and minimizing ply drops. Factors are provided for controlling which plies to drop, plies to maintain continuous across transitions, and the amount of interleaving. The last step provides convenient ways to perform final edits to the laminates and to export and import from Excel spreadsheets, FiberSIM, and CATIA.


  • Generate discrete laminates automatically
  • Define a Global Stack Sublaminate (GSS)
  • Optimize surface laminates and find multiple optimum solutions
  • Automatic optimization of FEM property zone shapes and sizes
  • Sequence laminates
  • Minimize ply drops
  • Increase total number of continuous full-body plies
  • Interleave dropped plies with continuous plies based on ESDU 91003
  • Identify and track global plies (drawing part numbers)
  • Export/Import laminates to FiberSIM and CATIA
  • Optimize ply compatibility and laminate sequencing of a stiffened panel, sandwich panel, or solid laminate simultaneously as a common active sizing variable that works across multiple groups and components of different panel concepts
  • Graphically plot ply counts (blue font in the image below) and ply drops (red font)

This six-step process establishes a common active laminate sizing variable that works across multiple groups and components of different panel concepts. This common active laminate sizing variable will sequence layups of a stiffened panel skin, sandwich panel facesheet, or a solid laminate simultaneously. The result is laminates that are weight optimum for both stress margins and manufacturing ease.

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Advanced Stiffened Panel Failure Analyses

New analysis predictions are provided for stiffened panels to capture failure modes such as flexural-torsional buckling (FTB), compression, and shear incomplete diagonal tension (IDT) postbuckling based on NACA TN 2661. FTB is frequently the controlling failure mode for airframes, rocket launch vehicles, ship hulls, and rail cars. Postbuckling is a weight-reducing technique that allows the skin of a stiffened panel to initially buckle before reaching the required limit load and is allowed if reserve strength in the panel can be proven by analysis. However, postbuckling analysis is difficult and time consuming to do manually or with nonlinear FEA.

  • Two Flexural torsional buckling (FTB) methods provided: Argyris and Levy
  • Compression post buckling based on iterative method for computing effective width, load redistribution, and updated margins of safety
  • Shear incomplete diagonal tension (IDT) postbuckling implementation of NACA TN 2661
  • Strains in the skin and stiffener are calculated using HyperSizer’s stiffened panel A, B, D matrices
  • Skin postbuckling effects feed into the FTB analysis for combined failure mode interaction
  • User can specify a percentage of limit load for which initial skin local buckling is acceptable
  • FEM is automatically updated with reduced postbuckled stiffness
  • All FTB and postbuckling analyses correlated and validated to test data and included in HVV documents
  • Method developed to apply to both metallic and composite structures
  • Processes thousands of load cases
  • Used during preliminary design optimization
Unsymmetric Stiffened Panel
Unsymmetric Stiffener Cross Section
compression postbuckling

Effective width is computed and displayed for the applied load and failure load. The effective width will always be smaller at the collapse failure load resulting in the most reduced stiffness.

shear postbuckling

The angle of the diagonal tension and the K Factor (degree of tension field vs. shear resistant behavior) is also computed and displayed for the applied load and failure load.

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Bolted Joint Analysis Automation

v6HyperSizer automates bolt bearing and BJSFM analysis and provides a form to enter data and visualize analysis results. Recent improvements to the bolted joint capability include the automatic extraction of bearing and bypass loads from the FEM without requiring a discretely meshed hole in the laminate. Then the extracted fastener forces are automatically passed to the bolted joint analysis methods to provide a fast, robust solution to reporting bolt bearing and BJSFM margins of safety for every fastener and load case in a global FEM.

With HyperSizer You Can:

  • Extract bearing forces automatically from Nastran CBUSH spring elements or use HyperSizer shear flow method
  • Obtain accurate results with coarse mesh finite element models; unnecessary to discretely model hole in laminate
  • Handle multiple fasteners per laminate
  • Specify joint correction and fitting factors
  • Select lamina failure criteria for reporting BJSFM margins of safety
  • Define material-dependent characteristic distances for both tension and compression bypass loads and apply correction factors to account for laminate thickness and ply percentages
bolted joint analysis

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Data Interaction Through Graphics

v6DirectX graphics features allow HyperSizer users to post-process analysis results such as margins of safety, controlling failure analysis, controlling load case, and ply-by-ply stresses and strains for the controlling ply and for the outer and inner most plies. Also included is the ability to interactively change the component, group, and assembly definitions by selecting regions on the FEM. Many graphics enhancements have been developed and included in HyperSizer to provide frequently used and unique stress analysis features such as free edge forces, FEM connection joints, and cross-sectional EI, GJ properties.


  • Auto-create ply drop fabrication boundaries
  • Auto-compute buckling spans
  • Auto-create FEM connection joints
  • Plot FEM joint force vectors and controlling margins, load cases, and failures
  • Plot ply drop fabrication boundaries
  • Minimize ply drops
  • Plot ply orientation percentages
  • Display numerical ply counts and ply drops across transitions
  • Show global ply coverage on FEM
  • Calculate and display EIyy, EIzz, and GJ stiffness properties for a closed cross section
  • Display CBUSH elements (fasteners)
  • Shortcuts for common plotting functions (i.e. minimum margin of safety)
  • Expanded default color palettes in database template
Edge force vectors and cross sectional EI, GJ properties

Edge force vectors and cross sectional EI, GJ properties

Ply drop boundaries and FEM joint loads

Ply drop boundaries and FEM joint loads

Ply angle percents represented in color hue; Blue =45's, Green=0's, and Red=90's

Ply angle percents represented in color hue; Blue =45's, Green=0's, and Red=90's

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New Panel Concepts

v6Three new composite structural panel concepts have been added to the HyperSizer library. The first concept is a rod/bulb stiffened with integrated frame. Boeing, NASA, and the Air Force Research Labs are developing this structural concept known as PRSEUS for innovative airframes that require biaxial strength and stability. The second concept is a reinforced core foam sandwich with an integral web stiffener. The third concept is a circular tube with integrated tapered ends.

Native sizing optimization and specialized failure analyses are conveniently performed for these concepts without FEA if the loads are known. For vehicle applications that do require FEA for quantifying internal loads, sizing and analyses are conveniently performed for the application using a coarsely meshed, single plane of shell finite elements. Discretely meshed models for the individual panel objects such as the rods, webs, core, and skins are not needed.

The Poltruded Rod/Bulb Stiffener Integrated Frame Concept

This concept has 21 unique cross-sectional dimension and material laminate sizing variables, the most of any HyperSizer panel. In addition to stiffener and skin variables, it has the advantage of including frame specific sizing variables (spacing, height, width, flange width, cap width, foam material, and laminates). Unlike other concepts where the frames of--for example--an airframe fuselage or rocket barrel interstage/intertank are modeled with separate bar elements, the optimum frame spacing can be sized concurrently with the stiffeners and skins. Frame spacing is an important weight-sensitive variable that is highly coupled with skin and stiffener sizing.

The specific Boeing implementation of this concept is stitched flange to skin joints which provide improved damage tolerance and out-of-autoclave curing for reduced manufacturing costs.

The Reinforced Sandwich Concept

This concept is also of high interest due to its improved damage tolerance and out of autoclave curing for reduced manufacturing costs. Common usage is in wind turbine blade and civil construction industries. A commercially available version of this structural panel is Tycore (R) from the Webcore corporation. The internal web provides increased out-of-plane shear load carrying capability in the Qx direction.

The Reinforced Sandwich Concept

The Tapered Tube Concept

This composite concept can be sized using FEA loads or with an integrated spreadsheet that computes loads closed form for the overall truss structure. Extreme lightweight aerospace applications include struts of NASA's lunar lander. Other applications include bicycle frames.

The Tapered Tube Concept

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Integrated Test Database

v6More test data has been added to the test database and three additional failure analyses are fully populated with test data. They are composite crippling analysis, compression and shear post buckling, and stiffened panel flexural-torsional buckling. These failure modes are now validated. Additionally, major simplifications have been made to the test database correlation visual display.

The term validation, as used in HyperSizer, refers to correlating an analysis failure prediction with a test result. With HyperSizer, you can validate analysis methods using the same process used to perform an analysis. Once the part dimensions, materials, layup, applied loads, and boundary conditions have been entered into HyperSizer to perform the analysis prediction, the only additional step is entering the test failure load. Once established, the data resides in a Workspace project in the HyperSizer database and is easily maintained and retrieved for decades to come and can be exported to a detailed stress report with equations included.

Existing data contained in the HyperSizer test database may be all that your design project needs for certification of a particular analysis method.There are over 500 unique tests covering several different failure analysis modes. However, you can easily add your own test data to supplement existing data or use only your own test data to certify a unique concept or fabrication process.

A new simplified view of the correlation is available for users requiring quick and easy access to correlation data.

Tsai Hahn

  • The ratio of test failure load divided by analysis (theoretical) prediction is displayed as a single point
  • Green points are “conservative”--failure load exceeds predicted load
  • Red points are “non-conservative”--failure load is less than predicted load
  • Test data can be viewed with and without histograms, statistical markers, and user-defined correlation factors
  • Typical material allowables are used, so a good correlation has most of the test results centered around the analysis prediction with approximately an equal amount of green and red points

Once predicting average test failure load is achieved, the next step is to establish correction factors for required conservatism such as B basis design-to allowables. This same data correlation process is used to establish consistent conservatism and certification documentation for all other analyses such as crippling, panel buckling, etc.

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FEM Laminate Zone Shapes and Sizes

v6The software now identifies and controls ply drop/add boundaries for defining the best laminate transitions and ply patterns. This includes automatic assignment of finite elements to optimum laminate zones to achieve light weight and manufacturability. The number, shape, and size of the sizing components (zones) is now part of the design optimization process.

A designer or analyst will not know the optimum layout of areas where the laminates should be the same or be allowed to be different. The issue is trading lightest possible weight versus manufacturability. Typically, the analyst will make the initial definition of which elements of the model are assigned the same laminate property. FEM preprocessors such as Femap, Patran, CATIA, and NX are currently used for this tedious manual assignment. Now the process is automated with HyperSizer and both minimum weight and manufacturability are achieved.

The image below is the root section of a wind turbine blade. The colors represent different laminate stacking zones. Most of the plies are continuous across laminate transition boundaries. Overall, the number of ply drops are substantially reduced for the part. This process is useful for nearly all composite structures including airframe wings and fuselages, engine ducts, cowling, fixed structures, etc.

Step 2 Wind Blade

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Analysis Methods Documentation

v6Twelve new analysis methods documents have been added to the documentation library. The methods and equations documents explain the theory and list the governing equations. Verification and validation documents compare the methods with published solutions, finite element analysis, and test data.

Methods & Equations (HME)

  • Composite strength, ply-based
  • Compression post buckling
  • Shear post buckling
  • Plate and shell buckling equations
  • Panel buckling
  • Beam buckling
  • Local buckling
  • Stiffener flexural-torsional buckling
  • Sandwich flatwise tension
  • Required values (stiffness, deformation)

Verification & Validation (HVV)

  • Compression & shear post buckling
  • Stiffener flexural-torsional buckling
  • Crippling

Refer to the Help System for the full documentation list.

Integrated Help System

v6Over 500 context-sensitive topics accessible directly from the interface. While using the software, click the green question mark icons or press [F1] to activate the help documentation. The Help System is installed locally with the software and is also hosted online at hypersizer.com/help (registration required). Topics are illustrated with full-color screenshots for ease of use. Find the topic of interest using the built-in search and index capabilities.


View Complete Press Release

HyperSizer v6 Released with Improved Design and Manufacturability Optimization for Composites 468KB PDF May 11