Failure Analysis of Polymer Composite Stiffened Laminates Using the Finite Element Method

A finite element method is adopted to study the initiation of damage (ply failure) of polymer composite stiffened laminates under static loading. Lightweight and high strength advanced composite materials are nowadays extensively used in aircraft and automobile industry. These structures on various occasions are subjected to point load or uniformly distributed load. Under these loads the stress level at a point may be high enough to initiate a local failure and a reduction in strength. So, a first-ply failure analysis (initiation of damage) of plated structures are often necessary. The procedure adopted here is based on the first-order shear deformation theory and a tensor polynomial failure criteria. As a special case, Tsai-Wu failure criteria is incorporated in the computer code. A number of problems for which experimental and theoretical results are available, have been analysed in the present investigation to check the code developed, and finally, analysis of stiffened composite plate problems with various laminae orientation, stiffener eccentricity etc. have been put forward for first ply failure load as new results for future reference. The results can be compared to find the best possible ply group against failure under transverse loading. According to author's knowledge, this is perhaps the first attempt to apply first ply-failure analysis in any stiffened configuration.