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https://www.nist.gov/itl/math/acmd-seminar-regularized-finite-element-modeling-methodology-predicting-discrete-damage

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# ACMD Seminar: Regularized Finite Element Modeling Methodology for Predicting Discrete Damage-Based Strength and Durability of Laminated Composite Structures

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Endel Iarve*Mechanical and Aerospace Engineering Department, University of Texas, Arlington*

Tuesday, October 8, 2019, 3:00–4:00 PM	Building 101, Lecture Room D	Gaithersburg

Tuesday, October 8, 2019, 1:00–2:00 PM	Building 1, Room 4072	Boulder

This talk will be broadcast on-line using BlueJeans.  Contact acmdseminar [at] nist.gov (acmdseminar[at]nist[dot]gov) for details

**Host:** Jeffrey Fong

**Abstract:**

Laminated composite materials represent a fundamentally important form of composites critical for various types of highly loaded structures in aerospace and automotive industry alike. Development of automated manufacturing methods such as automatic tape and tow placement techniques has enabled repeatable and efficient manufacturing of complex shapes with composite materials. The cost of such advanced structures is, however, determined in significant measure by the design and qualification process involving large amounts of testing on various structural levels of the building block approach. Detailed modeling of deformation and fracture of composite materials is widely considered a critical step towards a new design and qualification paradigm where significant amounts of testing will be replaced by computational simulation. 

Static and fatigue properties of CFRP were studied intensively in the past and satisfactorily described for most isolated damage modes. What represents a challenge however is the structural response to fatigue loading, which is characterized by evolution and interaction of various modes of damage. Adequate simulation as well as experimental verification of fiber failure, matrix cracking and delamination mode interaction represents a formidable problem not only under fatigue but static loading as well. Recently proposed methods for mesh independent modeling of matrix cracking combined with cohesive zone based simulation of delamination have shown promising results in quasi-isotropic laminates with and without stress concentrations. These methods employ variants of eXtended Finite Element Methodology (X-FEM) and its regularized implementation (Rx-FEM) in particular.

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 cracks is then performed by using cohesive zone method.

The RxFEM methodology will be demonstrated on a range of examples varying from basic flat and open hole coupons to subelement level composite structures under static and fatigue loading.

**Bio:**

Dr. Iarve was educated at the Latvia State University, Riga, Latvia, with B.S. and M.S. (1983) degrees in physics, and at the St. Petersburg University, St. Petersburg, Russia, with Ph.D. (1989) in mechanical engineering.  From 1983 to 1991, he also worked as research scientist and engineer-designer at various institutes of the Latvian Academy of Sciences.  In April 1991, Dr. Iarve came to the United States and worked for 4 years as research scientist at AdTech Systems Research, Inc., Dayton, OH, and then 20 years at the University of Dayton Research Institute (1995-2015) and as Professor of Engineering at the University of Dayton (2013-15). Dayton, OH.  In October 2015, Dr. Iarve joined the Mechanical and Aerospace Materials Department at the University of Texas at Arlington in Arlington, Texas at the rank of Professor.

Dr. Iarve's research career is focused on understanding and computational modeling of deformation and failure mechanisms of current and emerging composite materials. In the 1980-1990’s, Dr. Iarve was one of the pioneers in the application of B-spline approximation to stress analysis in laminated composites, including dynamic problems and impact loading. Dr. Iarve’s research areas included refined plate and shell theories, biomimetics, composite repair, composite bolted joints, chopped fiber composites and textile composites. In the past 10 years, Dr. Iarve’s research interests have concentrated on the development of novel Discrete Damage Modeling methodologies for laminated composite materials based on Regularized eXtended Finite Element Method (Rx-FEM). His research was and continues to be funded by the United States Air Force, NASA and other government agencies and industry, including Boeing and Lockheed-Martin Corporation. Dr. Iarve has published 4 book chapters and over 40 archival journal papers. His professional service included manuscript and proposal review as well as Chair Position of the Joining and fastening Committee of the ASME.

**Note:** Visitors from outside NIST must contact Cathy Graham; (301) 975-3800; at least 24 hours in advance.

MaterialsMathematics and statistics

## Contacts

                -  Jeffrey T. Fong  jeffrey.fong@nist.gov      (301) 219-9333   
                -  Stephen Langer  stephen.langer@nist.gov      (301) 975-5423   

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