Reliability Calculations for Strength of a Fibrous Composite Under Multiaxial Loading

There are several interactive failure criteria which give strength predic tions for a composite material subjected to multiaxial loadings. However, if only the average directional strengths are used in the failure criterion, the results give no useful statistical information. A closed form expansion method is introduced which offers a systematic way to calculate statistical in formation for a function of several strength variables. The developed expan sion method is applied to the Maximum Distortional Energy (MDE) criterion using an orthotropic composite material. The results show the expansion technique gives equivalent results to a simulation method for the off-axis ten sile test, but with far less computation. In addition, the expansion technique should prove adaptable to higher order theories such as the Tsai-Wu failure criterion.