Stiffness Reduction of the Laminates

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StiReL v1.0 is a MS Windows  95/98/NT 32-bit application.

StiReL (Stiffness Reduction of the Laminates) is a software tool for the analysis of the composite laminates with damage. Symmetric laminates containing 90-layer in the middle can be analyzed, such as [S/90n]s for example. Where S is sub-laminate with complicated lay-up, it should be balanced laminate, like for instance S = [+45/-45] or S = [+30/0/-30], etc. In such laminates [S/90n]s loaded in axial direction x, first damage that occurs is matrix cracking in the middle layer or so called transverse cracking.
Due to this damage that accumulates with increasing strain, stiffness of the laminate as well as Poisson's Ratio are decreasing. In order to design composite structures properly it is very important to know level at which its elastic properties can drop due to damage.

StiReL is using algorithm for stress analysis based on very well known models (such as Shear Lag, Hashin's etc.) initially developed for cross-ply laminates and adopted for laminates with more complicated outer layer lay-up.

Engineers and students can use StiReL as a design tool. It has the following features: 

  • laminate contains 90-layer in the middle and sub-laminate with complicated lay-up as an outer layer;
  • uniaxial loading transverse to the 90-layer is assumed;
  • only constants of the UD composite and some parameters for particular models are needed as input data; 
  • elastic constants of the laminate as well as of the sub-laminate are calculated;
  • changes of the longitudinal Young's modulus and Poisson's Ratio as a function of the crack density in 90-layer are calculated;
  • six different models are available for prediction of the stiffness degradation: three modifications of the Shear Lag model, two variational models and model based on FEA.

StiReL is designed for Windows and uses all advantages of its graphical interface: 

  • attractive, efficient and easy-to-use interface; 
  • effective means for creating new sets of data, as well as storing, browsing opening, and editing the existing sets of data; 
  • set of options that allows to configure data format, content of report and screen options; 
  • built-in small text editor allowing to observe and compare the results of various calculations in the text mode;
  • data representation in text mode and in scientific graph mode;
  • simultaneous output of experimental and predicted curves for comparison.

Minimum hardware requirements:

  • IBM PC-compatible computer, with 80486 processor or higher (it should be able to run Windows 95/98/NT).
  • VGA video adapter;
  • 3.25" FDD and HDD with approximately 1 Mb to install program and store results.