KTMM Seminar:Dynamic failure of curved CFRP composite laminates

Merhabalar, 

09 Mayıs  Çarşamba günü, 13:50-14:40 saatleri arasında Kompozit Teknolojileri Mükemmeliyet Merkezinde;Assoc.Prof.Demirkan Coker  "Dynamic Failure of Curved CFRP Composite Laminates Under Quasi-static Loading" başlıklı seminer verecektir.

 Sabancı Üniversitesi -Teknopark Gidiş 

Teknopark- Sabancı Üniversitesi Dönüş

Araç Hareket Alanı : KTMM Binası Önü    

Title:                   Dynamic Failure of Curved CFRP Composite Laminates Under Quasi-static Loading

Speaker:            Assos.Prof.Demirkan Coker

Time:                  Mayıs 09, 2018, 13:50-14:40

Place:                 Teknopark- KTMM

Abstract: 

In aerospace and wind energy industries, new advances in composite manufacturing technology and high demand for lightweight structures are fostering the use of composite laminates in a wide variety of shapes as primary load carrying elements. However, once a moderately thick laminate takes highly curved shape, such as an L-shape, Interlaminar Normal Stresses (ILNS) are induced together with typical Interlaminar Shear Stresses (ILSS) on the interfaces between the laminas. The development of ILNS promotes mode-I type of delamination propagation in the curved part of the L-shaped structure, which is a problem that has recently raised to the forefront in in-service new composite wind turbines. Delamination propagation in L-shaped laminates can be highly dynamic even though the loading is quasi-static.  An experimental study to investigate dynamic delamination under quasi-static loading is carried out using a million fps high-speed camera. Simulations of the experiments are conducted with a bilinear cohesive zone model implemented in user subroutine of the commercial FEA code ABAQUS/explicit. Results for three different CFRP lay-ups are presented: [0] UD, [0/90] UD, and woven L-shaped laminates.  For the woven laminate, a single delamination is found to initiate at the 5th interface during a single drop in the load. The delamination is then observed to propagate to the arms at intersonic speed of 2200m/s. The results obtained using cohesive zone models in the numerical simulations were found to be in good agreement with experimental results in terms of load displacement behavior and delamination history.  The failure mechanisms of different lay-ups are shown to be different from each other.

Biograph:

Dr. Coker is Associate Professor in Aerospace Engineering and Director of Structural Mechanics and Materials Laboratory at RÜZGEM, METU.  He acted as a vice-Chair of the Dept. of Aerospace Engineering from 2009-2012.   Dr. Coker holds a B.S. degree in Aeronautical Engineering from METU, an M.Sc. degree in Aerospace Engineering from University of Dayton, an M.Sc. degree in Applied Mathematics from Wright State University and a Ph.D degree in Aeronautics with a minor in Geophysics from California Institute of Technology (Caltech).  After he obtained his B.S., he started his career as a research engineer at the UDRI and at the Materials Lab/Wright Laboratories, Dayton, carrying out research on thermomechanical fatigue of novel high temperature composite materials for the hypersonic National Aerospace Plane project.  During his Ph.D. studies at Caltech he carried out groundbreaking experimental work on dynamic fracture of composite materials.   Afterwards he worked as a Post-Doctoral research associate at Brown University on dynamic friction modeling (2001-2004) and worked as an Assistant Professor at Oklahoma State University (2004-2008).  He also worked as a visiting Professor at KITP, the University of California at Santa Barbara and EPFL in Lausanne.  Dr. Coker has published over 30 peer reviewed articles and 40 conference proceedings, gave more than 100 international conference talks and more than 30 invited talks in the fields of fatigue, fracture mechanics, friction, dynamic failure, experimental mechanics, computational mechanics and composite materials.  In addition, he has been instrumental in setting up the undergraduate aerospace labs at METU, Structures and Materials labs at RUZGEM and micro-and nano-mechanics laboratory at Oklahoma State University.