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Software Review: The Laminator

Dateline: 09/08/97

Last week, I promised an article on the FORTE satellite. That article will appear next week. One of the people I am interviewing for that article has been out of town. Rather than presenting an incomplete story, I decided to delay the article by a week so I could complete the interviews.

This week, I'm beginning an occasional series of articles covering software used for compsoite analysis. I'll begin with shareware programs, and move to commercial programs as I am able to get access to them.

The first program in this series the The Laminator, written by Mike Lindell. The Laminator began as a text-based FORTRAN program written as a homework assignment for a composite materials class at Virginia Tech. Mr. Lindell converted it to a GUI program as an excercise in learning C++.

The Laminator is a simple Windows program for composite plate analysis using Classical Laminated Plate Theory (CLPT). You enter material properties (engineering constants and strengths), stacking sequence, and loads; the program calculates laminate properties, constitutive matrices, stresses and strains, and failure indices. The capabilities are basically the same as Think Composites' GENLAM, but with a much nicer interface and a much lower price.

Installation is incredibly easy: just unzip the archive file and you're ready to go. The program consists of one executable file; you also get a sample input file and a readme.txt file. There are no registry entries (so you can easily move the executable to a new location) and no INI files. You have to create your own icon, but that's a good trade for simple installation.

The main program window consists of a simple dialog box divided into Input Options, Output Options, Results Options, and Setup and Analysis. Help consists of individual dialog boxes. These are modal windows, so you can't keep them on-screen while entering data, but the forms are so simple you shouldn't really need help.

Input can be either interactive or from a file. The file format is a simple text file containing material properties, the stacking sequence, and the load vector. Once an input file is read in, all input values can be modified or added to interactively. The input data can be saved to a file by selecting an option; the save is done when the results are calculated. There is no master database: material properties are stored in the input file with the laminate definition and load vector.

Material properties and the stacking sequence are entered in tables. One-half the stacking sequence can be entered for symmetric laminates, but that is the only shortcut available. In particular, you can't insert or delete rows in existing tables. Each layer can have a separate material, ply angle, and thickness. The number of layers allowed is very large, but the program is limited to five materials at once. My only complaint about the entry form (aside from the lack of editing features) is a minor one: the width is just small enough to require horizontal scrolling; a small increase would make entry more convenient.

The author pointed out to me, after I wrote this review, that all windows can be resized by the user. Thus, you can make the stacking sequence window large enough to not require horizontal scrolling. The new window size is remembered for the current session, but not between sessions, so you will need to resize for every new run.

The load vector can consist of any combination of mechanical loads (force and moment resultants, or strains and curvatures), thermal loads (uniform temperature change), and moisture loads (uniform percent moisture content).

Results are output in a simple plain text format which is displayed on the screen and can optionally be stored in a file. The results can also be printed from the display screen. To redisplay the results page from within the program, you must rerun the solution, but solution speed is fast (less than one second for the sample 8 ply laminate). The results you can view are shown on the main dialog; for unsymmetric laminates, the engineering constants include shear coupling coefficients.

The calculations are accurate. I ran several sample problems and compared them to other programs I have verified against textbook and literature results. In all cases, The Laminator gave the correct solution.

The only bug I found was in printing. When I pressed the Print button from the results display screen, then pressed cancel, the proigram shut down with an illegal operation error. This was a graceful crash, however, affecting no other running programs (under Windows 95). Also, the input data is saved when the analysis is run, so I didn't lose any data (just make sure you select the save input data option).

The author has posted a revised version (2.03) which corrects this bug. You can now cancel a print operation without crashing the program.

If you need a program to do some quick plate analysis, this is a good choice. It has a nice, simple interface, and the price can't be beat ($20 shareware, the download is fully functional). Mr. Lindell has no current plans to update the program, but he is willing to make revisions or updates if he gets enough feedback.

Program Details

The Laminator
Written by Mike Lindell
Classical Laminated Plate Theory analysis of composites
Mechanical, thermal, and hygral loads
For Windows
Shareware: $20

About the Author

Mike Lindell graduated from the University of Delaware in 1981 with a Bachelors degree in Mechanical Engineering. He earned a Masters degree in Engineering Science and Mechanics while working for NASA. Mr. Lindell currently works for NASA at the Langley Research Center in Hampton, VA. His work involves finite element analysis of space and aircraft structures and experiments.

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