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Laminated composite materials are used in stiffness critical applications and contain various stress concentration features such as holes, tapers and stiffener attachments. It is these areas which often determine the load carrying capacity of the structural elements and thickness scaling of critical parts. A representative subelement is studied in this work with the aim of evaluating the ability to predict the mechanical response of such critical regions by using discrete damage modeling. Clamped Tapered Beam Specimen (CTBS) designed by Advanced Composite Project Team at NASA LaRC is considered. This specimen allows studying the matrix crack initiation from pristine condition as well as delamination initiation and evolution including migration from one interface to another. Regularized eXtended Finite Element Method (Rx-FEM) is employed for analysis. The Rx-FEM allows modeling the displacement discontinuity associated with individual matrix cracks in individual plies of a composite without regard to mesh orientation by inserting additional degrees of freedom in the process of the simulation. The propagation of the mesh independent crack is then performed by using Cohesive Zone Method (CZM). A simultaneous experimental program was conducted at NASA LaRC and used for the analysis validation. The predicted results showed good agreement with experimental data for ply level transverse strength parameter obtained by using three point bend test method, whereas the results obtained by using a lower value resulting from tensile testing of 90o coupons resulted in under-prediction of the peak load. The distance between the migration location and the load application point is consistent with experimental data.


Engineering | Materials Science and Engineering

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Available for download on Wednesday, January 01, 3000