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Materials Science at Oregon State University

Failure Analysis of pre-notched composite laminated plates under four-point bending conditions

Date: Thursday, Jan 22nd
Presenter: Sergio Arias, OSU Mechanical, Industrial, and Manufacturing Engineering


Ever since composite laminated technology was introduced into the aerospace and automotive industry, there has been a need to fully understand the damage progression experienced by composite laminated plates in the presence of a notch. While numerous research studies have been conducted on this matter when subjected to in-plane loads, not much focus has been directed to the out-of-plane loading conditions. To address this issue, a comprehensive study in partnership with the Boeing Commercial Airplane Company and the Federal Aviation Administration was carried out, using experimental tests and computer simulations, to predict the failure mechanisms of pre-notched composite laminated plates under four-point bending.
A total of 48 pre-notched laminates, varying in size, layer orientations and thickness were tested, and the deformation data was recorded by means of strain gages. Two notch lengths of 1-in. and 4-in. with an end radius of 0.125-in. were considered in the analysis. The laminates were also modeled in the finite element software ABAQUS to determine the concentration factors, and explore the damage progression based on the Hashin criterion. The results were compared to the test data for correlation and validity.
From the simulation results, it was determined that the classical laminated plate models under-predicted the strain concentration factors, and that Reissner?s models should be employed in order to conduct failure analysis on composite laminates when subjected under pure bending. The shell model that takes into account transverse shear effects was then chosen to provide the progression damage simulation. It was found that the results of these theoretical models from ABAQUS were very similar to the results of the test samples generated in our experiments. In general, very good agreement between the simulations and the test results was obtained for the thin laminates. Particularly, as the percentage of 0-degree plies increased, so did the correlation with the test samples. Our theoretical models were capable of reproducing accurately their failure points, by taking into consideration the large deformation effects and damage progression. On the other hand, the thick laminate models were not as successful in predicting failure. In most cases, they computed a failure moment higher than the ones found in the experiment.