Srinivasan Arjun Tekalur

Bio: Srinivasan Arjun Tekalur is an academic researcher from Michigan State University. The author has contributed to research in topics: Split-Hopkinson pressure bar & Ultimate tensile strength. The author has an hindex of 14, co-authored 35 publications receiving 959 citations. Previous affiliations of Srinivasan Arjun Tekalur include University of Rhode Island.

Mechanical behavior and damage evolution in E-glass vinyl ester and carbon composites subjected to static and blast loads

Abstract: Fiber based composites have found extensive applications in various fields. In this study, two different fiber materials, namely, E-glass and carbon, with different architecture are chosen. Polymer (vinyl ester) based composites were designed using these fibers and were fabricated using VARTM process. These composites were subjected to quasi-static and high strain rates of loading utilizing different testing methodologies. In quasi-static testing, the tensile, compressive and shear properties were studied using existing ASTM standard testing procedures and the results are reported. The carbon composite showed higher tensile and compressive modulus. In-plane shear properties of both the composites were comparable and inter laminar shear properties of E-glass composites were observed to be better than the carbon composite because of the better nesting between the E-glass fabric layers. A shock tube and a controlled explosion tube were utilized in the study of dynamic damage behavior of these composite materials. Based on the experimental study, it is observed that the carbon fiber composites tend to achieve sudden destructive damage whereas E-glass fiber composites tend to sustain progressive damage, under dynamic loading.

Ballistic Resistance of 2D and 3D Woven Sandwich Composites

Abstract: In the present study, ballistic resistance of sandwich composite structures for vehicle armor panel applications was investigated. The core material of the sandwich structure was a layer of Alumina ceramic and a layer of composite backing, sandwiched between 2D plain weave composite skins. The ballistic performance of sandwich materials with 3D backing was compared to the baseline 2D plain weave backed composites. An IMACON 200 high-speed camera was used to obtain high-speed photographs of the ballistic events of penetration and damage. These images were analyzed to study real time damage mechanism of the strike face surface of several targets and subsequently to obtain average resistive force of target points during impact. Velocities of projectile (armor piercing bullets) were recorded in all the experiments and were found to be in the range of 915 – 975 m/s. Post mortem analyses, which included sectioning of panel, were performed. Results showed that armor panels with 3D woven backing had a higher ballistic efficiency than the 2D baseline panels, strike face damage mechanics were predominantly axi-symmetric about the impact point and panels with 3D backing had controlled delamination and fewer complete penetrations.

Optimal overlap length in staggered architecture composites under dynamic loading conditions

Abstract: Hybrid staggered architecture composites, like nacre and bone, are known for two discernible aspects: superior strength and synergistic toughness. What is lacking is the scientific rationale proving suitability of these materials under impact/time dependent loading. The current investigation aims to address the structure-property correlationship of these materials by development of an analytical model under dynamic rates of loading. Existing literature studies address behavior of staggered materials under quasi-static loading conditions. Critical overlap length was computed for three natural composites-nacre, spider-silk and, collagen in bone/tendon, and showed reasonable agreement with experimental data. Applicability of the analytical approach to predict lap-joint strength has been briefly discussed and quantified against experimental data. Choice of nanometer sized building blocks in natural composites has been addressed and explained from shear transfer efficiency point of view. The potentiality of these composites for use as biomimetic protective material under impact loading has been addressed as well.

Fate decision of mesenchymal stem cells: adipocytes or osteoblasts?

Abstract: Mesenchymal stem cells (MSCs), a non-hematopoietic stem cell population first discovered in bone marrow, are multipotent cells capable of differentiating into mature cells of several mesenchymal tissues, such as fat and bone. As common progenitor cells of adipocytes and osteoblasts, MSCs are delicately balanced for their differentiation commitment. Numerous in vitro investigations have demonstrated that fat-induction factors inhibit osteogenesis, and, conversely, bone-induction factors hinder adipogenesis. In fact, a variety of external cues contribute to the delicate balance of adipo-osteogenic differentiation of MSCs, including chemical, physical, and biological factors. These factors trigger different signaling pathways and activate various transcription factors that guide MSCs to commit to either lineage. The dysregulation of the adipo-osteogenic balance has been linked to several pathophysiologic processes, such as aging, obesity, osteopenia, osteopetrosis, and osteoporosis. Thus, the regulation of MSC differentiation has increasingly attracted great attention in recent years. Here, we review external factors and their signaling processes dictating the reciprocal regulation between adipocytes and osteoblasts during MSC differentiation and the ultimate control of the adipo-osteogenic balance.

Marine Application of Fiber Reinforced Composites: A Review

Abstract: Components and structures working in the marine environment are exposed to high stresses attributable to the action of wind, waves, and tides. Moreover, they have to face hostile and severe environmental conditions during their lifetime, being placed in the splash zone if not even submerged in saltwater. The application of polymer composites in marine systems has been the focus of intensive studies in the last decades, highlighting potential benefits given by the replacement of several components, such as ship hulls, propeller blades, wind, and tidal turbine blades, to cite but a few. The present paper reports the latest advances in this area, addressing the applications of advanced composites in ships and ship components, offshore oil and gas composites, marine renewable energy and underwater repairing.