V-Lab Lamina Analysis
Dateline: 09/29/99Opening a Database
The first thing you do when starting V-Lab is open a database. In all of the examples in these side articles, I use the sample database that comes with V-Lab.
If you have opened a database and one or more modules, clicking the open button immediately closes the active database and all modules. It would be nice to leave them open until a database is selected, just in case the user selects cancel. You won't lose any data though: if you have changed anything, you have the option of saving the database or cancelling before anything is closed.
Material Definition
Once you have opened a database, you can start to work with materials. This first screenshot shows the datasheet for a typical material. You can edit properties, or add or remove them from the list. To create a new material, you just create this list from scratch. Although the database supports fiber and matrix properties, you can't create a ply material using micromechanics.
Main V-Lab Window and Material Lab
(This first screen also shows the main V-Lab interface with the left hand icon bar, the menu, and the toolbar. Future shots will show only the client windows.)
Ply Properties
Once a property is defined, you can get the stiffness or compliance matrix. If properties have a temperature or moisture dependency, the matrices will be shown at that condition. The lamina can also be rotated to get the properties in an arbitrary direction.
Constitutive Matrix Calculation
Engineering constants in the rotated direction, which are calculated from the constitutive matrices, are not shown and are not available.
Ply Stress/Strain Analysis
The next option in the Material Lab is stress/strain analysis. Enter stresses (not stress resultants) and calculate strains, or enter strains and calculate stresses. Once again, environmental dependencies and arbitrary ply orientations are supported.
Ply Stress/Strain Analysis
Failure Analysis
Stresses and ply orientation are carried over to the failure analysis screen. Here you can get a plot of the max stress, max strain, and Tsai-Wu criteria.
Ply Failure Analysis
The envelope plot at lower right is common to the Material and Laminate Labs. The greenish box shows the failure envelope and the ball (light green for good, red for failed) shows the point stress location.
The image can be zoomed, panned, and rotated by dragging with various combinations of mouse buttons and control keys. I usually forget what these are: with plenty of screen space, the key combinations could be placed next to the graph. Also, the axis labels don't change position when zooming, so they can disappear from the screen. If you've rotated the image, you may not know which axis you are looking at.
As with the Laminate Lab, the actual failure ratios or indexes are not shown. This is a significant oversight, and should be corrected as soon as possible.
Carpet Plots
The final option in the Material Lab is the Laminate Designer. This is generates a carpet plot of Young's modulus, Poisson's ratio, shear modulus, CTE, or open hole strength (tensile or compressive). The selected property is shown as a function of percent +/-45 plies, percent 0 plies (indicated by the legend), and percent 90 plies (to bring the total to 100%).
Laminate Carpet Plots
This is a nice feature, and in fact is the only place in the program you can get an estimate of laminate engineering properties. I have to say estimate because no numerical values are available, and the plot axes are rather coarse.
Two features would improve the utility of this plot and other numerical plots:
- Give a numerical value in a tooltip or odometer type control as the mouse cursor is moved over the plot.
- Either allow the plots to be resized (which would require resizing of the client window), or have an option to show the plot in a resizeable window.
Finally, all properties must be defined before using the Laminate Designer. For example, to get a carpet plot of Young's modulus, I first had to define ultimate strains. I'm sure that is because strains are required for the open hole strength plots, but it would be more intuitive to disable those plots which are missing data.