Synopsis

The calculator generates failure envelopes for some of the common lamina-based first-ply failure criteria. This class of failure criteria involves determining the layer-by-layer stress or strain in layer coordinates, and evaluating the criterion for each layer. The plots are presented in average laminate stress space. For most laminates, the ultimate strength is much greater than the first-ply failure stress.

Input

Enter the layer stiffness properties as a list {Ex, Ey, Gxy, nuxy}:

Enter a stacking sequence {theta1, theta2, ...}: Help on advanced stack entry

Enter the default per-ply thickness

Layer Strength Properties

Enter failure stress for stress based criteria. Enter failure strain for strain based criteria such as maximum strain.

Pick a failure theory

Result

Failure Stress in 1-2 Plane

Failure Stress in 1-6 Plane

Failure Stress in 2-6 Plane

Usage Notes

• For the full envelope option, a failure envelope is drawn for each layer. The envelopes are labled with the layer orientation. The curves are also color coded; the color sequence is {red, green, blue, purple}, with the color order corresponding to the layer sequence order. The colors will repeat for more than four layers.
• Because bending is not considered, the actual stacking sequence is not important, only the total thickness for each orientation. A convenient way to represent laminate stacking sequences is with the notation {0//plyThickness[h0], 90//plyThickness[h90],...}, where h0 and h90 are the total thickness of the 0 degree layers and 90 degree layers respectively. This notation eliminates the need for the system to generate multiple identical curves.
• Residual thermal stresses are not included.
• The plots are drawn with a height-to-width ratio of one. This means that the scales on the horizontal and vertical axes may be different. Fixing the aspect ratio enables the system to return readable plots for highly anisotropic laminates, but one should be aware of the possible distortion of the envelopes.
• Another plotting decision is to scale the plot so that the entire envelope is always shown. In some cases, this does not give the most informative plot. However, there is some tradeoff between generality and ease-of-input for a web page calculator.
• The interaction parameter for the Tsai-Wu criteria has been fixed as Fxy=-Sqrt[Fxx Fyy]/2. This selection guarantees a closed envelope.
• The Hashin criterion comes from Hashin, "Failure Criteria for Unidirectional Composites", J. of Applied Mechanics, Vol. 47, June 1980, pp329-334. The plane-stress version has been implemented.

Page History Notes

• Initially placed online Dec. January 1, 2002
• Known issues or bugs
  • Hashin criterion was incorrectly plotting due to divide by zero for certain special cases. Corrected on 9/17/02

Copyright Materials Sciences Corporation, 2001