Program PROGDAM

This program performs a progressive damage analysis of a multi-angle composite laminate subjected to a monotonically increasing stress resultant, in accordance with the discussion presented in Section 3.2 of Chapter 7. The program is limited to symmetric laminates. During execution the user specifies which stress resultant is to be considered (N_xx, N_yy, or N_xy), the amount that the stiffness of a failed ply should be reduced (or “discounted”) at failure, and which failure criterion is to be used during the analysis (Maximum Stress, Tsai-Hill, or Tsai-Wu). The laminate is considered to have failed completely once all plies have failed. As discussed in the text, the user is cautioned that the analysis may be inaccurate after failure of one or more plies, since the basic assumptions of classical laminates theory become less-and-less valid once significant damage has occurred.

The program should be downloaded and saved to a convenient folder location on your computer. Once the program is initiated it will ask whether you wish to read several input values “FROM A FILE? (Y/N)” If you enter a “Y” (or “y”, meaning “yes”) the program will search for a file containing the needed information. If the file is not found you will be directed to enter the values from the keyboard.

Results of the analysis are stored in a file called “FAILURE.txt”. The file will contain a five-line header that includes the type of failure criterion used during the analysis. The header is followed by 9 columns of data. The first column gives the values of the stress resultant (N_xx, N_yy, or N_xy) that cause one or more new ply failures. The next six columns give the midplane strains and curvatures present at the moment of ply failure(s). The last two columns give the failed ply number and fiber angle. The number of rows of data will equal the number of plies in the laminate under consideration. These data can be plotted using third-party software package such as Excel™.

All files created during execution of the program are stored in the folder that contains program PROGDAM.

Warning: The user must input all values using a consistent system of units. For example, using the SI system of units a typical value of Young’s modulus might be 200 GPa = 200 x 10⁹ N/m², a typical ply thickness might be 0.125 mm, and a thermal expansion coefficient might be -1.0 x 10^-6 m/m-°C. These values should be input as 200.0E9, 0.000125, and -1.0E-6, respectively.