@article{stahl_bogdanovich_bradford_2016, title={Carbon nanotube shear-pressed sheet interleaves for Mode I interlaminar fracture toughness enhancement}, volume={80}, ISSN={["1878-5840"]}, DOI={10.1016/j.compositesa.2015.10.014}, abstractNote={Failure of composite laminates is often the result of “secondary” transverse stresses causing delamination. One well known approach to prevent such failure is to incorporate a distinct interleaf material into the interlaminar region in order to increase its fracture toughness and, consequently, its resistance to delamination. In the recent years various carbon nanotube (CNT) interleaves gained much attention. This work presents experimental study of the Mode I progressive fracture of carbon/epoxy composite laminates modified with high volume fraction, aligned, non-functionalized and functionalized CNT interleaves. The interleaves used here are thin solid sheets produced from vertically grown multiwalled CNT arrays by shear pressing method. A dry or resin infused sheet is integrated between prepreg plies prior to the laminate cure. The obtained results show that both dry and pre-infused CNT interleaves significantly, up to two times, increase the critical strain energy release rate of the baseline non-interleaved laminate. Two methods of functionalizing CNTs within the preform are explored: O2/CF4 plasma and H2SO4/KnO4 wet chemical treatments. Both methods maintain the high alignment and aspect ratio of the CNTs. Although, functionalization results in no additional GIC toughening compared to the non-functionalized interleaves, the characteristics of the fracture surfaces are dramatically different.}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Stahl, James J. and Bogdanovich, Alexander E. and Bradford, Philip D.}, year={2016}, month={Jan}, pages={127–137} }
 @article{li_bogdanovich_bradford_2015, title={Aligned carbon nanotube sheet piezoresistive strain sensors}, volume={24}, ISSN={["1361-665X"]}, DOI={10.1088/0964-1726/24/9/095004}, abstractNote={Carbon nanotubes (CNTs) have a unique set of properties that may be useful in the production of next generation structural health monitoring composites. This research introduces a novel CNT based material system for strain and damage sensing applications. An aligned sheet of interconnected CNTs was drawn from a chemical vapor deposition grown CNT array and then bonded to the surface of glass fiber/epoxy composite coupons. Various types of mechanical tests were conducted, accompanied by real-time electrical data acquisition, in order to evaluate the electro-mechanical behavior of the developed sensing material. Specimens were loaded in the longitudinal and transverse CNT sheet orientations to investigate the anisotropy of the piezoresistive effect. The CNT sheets exhibited good sensing stability, linearity, sensitivity and repeatability within a practical strain range; which are crucial sensor features for health monitoring. It was also demonstrated that the CNT orientation in the sheet had a dramatic effect on the sensitivity, thus validating the usefulness of this sensing material for directional strain/damage monitoring. Finally, pre-straining of the CNT sheet sensors was conducted to further enhance the linearity of electro-mechanical response and long-term stability of the sensors during cyclic loading.}, number={9}, journal={SMART MATERIALS AND STRUCTURES}, author={Li, Ang and Bogdanovich, Alexander E. and Bradford, Philip D.}, year={2015}, month={Sep} }
 @article{topal_baiocchi_crocombe_ogin_potluri_withers_quaresimin_smith_poole_bogdanovich_2015, title={Late-stage fatigue damage in a 3D orthogonal non-crimp woven composite: An experimental and numerical study}, volume={79}, ISSN={["1878-5840"]}, DOI={10.1016/j.compositesa.2015.08.020}, abstractNote={Late-stage fatigue damage of an E-glass/epoxy 3D orthogonal non-crimp textile composite loaded in the warp direction has been investigated using a combination of mechanical testing, X-ray micro computed tomography (μCT), optical microscopy and finite element modelling. Stiffness reduction and energy dissipated per cycle were found to be complementary measurements of damage accumulation, occurring in three stages: a first stage characterised by rapid changes, a more quiescent second stage, followed by a third stage where the (decreasing) stiffness and (increasing) energy dissipation change irregularly and then rapidly, to failure. Microscopy of specimens cycled into the transition between the second and third stages showed macroscopic accumulations of fibre fractures in sections of warp tows which lying adjacent to the surface weft tows which are crowned-over by the Z-tows. At these locations, the warp tow fibres are subjected to stress concentrations both from transverse weft tow matrix cracks and resin pocket cracks.}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Topal, Serra and Baiocchi, Luca and Crocombe, Andrew D. and Ogin, Stephen L. and Potluri, Prasad and Withers, Philip J. and Quaresimin, Marino and Smith, Paul A. and Poole, Matthew C. and Bogdanovich, Alexander E.}, year={2015}, month={Dec}, pages={155–163} }
 @article{carvelli_pazmino_lomov_bogdanovich_mungalov_verpoest_2013, title={Quasi-static and fatigue tensile behavior of a 3D rotary braided carbon/epoxy composite}, volume={47}, ISSN={["1530-793X"]}, DOI={10.1177/0021998312463407}, abstractNote={ This paper presents an experimental study of the quasi-static and fatigue behaviour of a three-dimensional braided carbon/epoxy composite. The study involves a three-dimensional braided carbon preform and composite samples produced at 3TEX Inc. on their 576-carrier rotary braiding machine. The first part of the paper describes the preform and composite sample fabrication procedures, the fiber volume fraction determination and the porosity evaluation using micro-computed tomography three-dimensional observation. The second part is devoted to experimental study of the quasi-static tensile response of the material, including the acoustic emission monitoring and the microscopic damage detection. The third part is dedicated to the fatigue tensile–tensile behaviour illustrated by the fatigue life curve and the micro-computed tomography images of the damage imparted after different number of cycles. The fourth part presents results of the quasi-static tensile tests of preliminarily cyclically loaded specimens. These results provide significant insight into the influence of the damage imparted during fatigue loading on the subsequent quasi-static behaviour. }, number={25}, journal={JOURNAL OF COMPOSITE MATERIALS}, author={Carvelli, Valter and Pazmino, Juan and Lomov, Stepan V. and Bogdanovich, Alexander E. and Mungalov, Dimitri D. and Verpoest, Ignaas}, year={2013}, month={Nov}, pages={3195–3210} }
 @article{bogdanovich_karahan_lomov_verpoest_2013, title={Quasi-static tensile behavior and damage of carbon/epoxy composite reinforced with 3D non-crimp orthogonal woven fabric}, volume={62}, ISSN={["1872-7743"]}, DOI={10.1016/j.mechmat.2013.03.005}, abstractNote={This paper presents a comprehensive experimental study and detailed mechanistic interpretations of the tensile behavior of one representative 3D non-crimp orthogonal woven (3DNCOW) carbon/epoxy composite. The composite is tested under uniaxial in-plane tensile loading in the warp, fill and ±45° bias directions. An “S-shape” nonlinearity observed in the stress–strain curves is explained by the concurrent contributions of inherent carbon fiber stiffening (“non-Hookean behavior”), fiber straightening, and gradual damage accumulation. Several approaches to the determination of a single-value Young’s modulus from a significantly nonlinear stress–strain curve are discussed and the best approach recommended. Also, issues related to the experimental determination of effective Poisson’s ratios for this class of composites are discussed, and their possible resolution suggested. The observed experimental values of the warp- and fill-directional tensile strengths are much higher than those typically obtained for 3D interlock weave carbon/epoxy composites while the nonlinear material behavior observed for the ±45°-directional tensile loading is in a qualitative agreement with the earlier results for other textile composites. Results of the damage initiation and progression, monitoried by means of acoustic emission, full-field strain optical measurements, X-rays and optical microscopy, are illustrated and discussed in detail. The damage modes at different stages of the increasing tensile loading are analyzed, and the principal progressive damage mechanisms identified, including the characteristic crack patterns developed at each damage stage. It is concluded that significant damage initiation of the present material occurs in the same strain range as in traditional cross-ply laminates, while respective strain range for other previously studied carbon/epoxy textile composites is significantly lower. Overall the revealed advantages in stiffness, strength and progressive damage behavior of the studied composite are mainly attributed to the absence of crimp and only minimal fiber waviness in the reinforcing 3DNCOW preform.}, journal={MECHANICS OF MATERIALS}, author={Bogdanovich, Alexander E. and Karahan, Mehmet and Lomov, Stepan V. and Verpoest, Ignaas}, year={2013}, month={Aug}, pages={14–31} }
 @article{sharp_bogdanovich_boyle_brown_mungalov_2013, title={Wind blade joints based on non-crimp 3D orthogonal woven Pi shaped preforms}, volume={49}, ISSN={["1359-835X"]}, DOI={10.1016/j.compositesa.2013.01.012}, abstractNote={Current industrial designs for joining composite wind blade elements allow unstable crack propagation in the thick adhesive layer within the joint. In this work, a novel integral 3D woven Pi-joint element is developed and implemented in an I-beam joint construction that corresponds to a wind blade’s shear web and spar cap. In a series of iterative design–analysis–fabrication–testing cycles, 2.9 m long I-beams that used the current practice joint and the novel proposed joint were designed, studied theoretically with the use of a 3D Mosaic analysis tool, then manufactured and loaded to failure in a cantilever flexure loading set up. Experimental data showed significant advantage in the load-bearing capacity of the joint structure with the use of novel Pi-joint element. Excellent agreement was observed between the theoretical predictions and experimental data.}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Sharp, Keith and Bogdanovich, Alexander and Boyle, Ryan and Brown, Jesse and Mungalov, Dmitri}, year={2013}, month={Jun}, pages={9–17} }
 @article{bogdanovich_bradford_2010, title={Carbon nanotube yarn and 3-D braid composites. Part I: Tensile testing and mechanical properties analysis}, volume={41}, ISSN={["1878-5840"]}, DOI={10.1016/j.compositesa.2009.10.002}, abstractNote={Macroscopic textile preforms were produced with a multi-level hierarchical carbon nanotube (CNT) structure: nanotubes, bundles, spun single yarns, plied yarns and 3-D braids. The 3-D braided preform was the first of its kind produced by textile processing technique and used as a composite reinforcement consisting solely of carbon nanotubes. Four different epoxy systems that possessed a wide range of mechanical properties (owed to an added modifier) were infused into the CNT yarns and 3-D braids. Mechanical characterization of the resulting composites was conducted through the use of tensile testing. It was found that the tensile strength, stiffness and, especially, strain-to-failure values for each preform type were close regardless of the properties of the matrix whose strain-to-failure values ranged from 3.6% to 89%. This is hypothetically attributed to the nano-scale interaction between individual nanotubes and polymeric macromolecules in the composites. This hypothesis is validated by the Dynamic Mechanical Analysis results in Part II.}, number={2}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Bogdanovich, Alexander E. and Bradford, Philip D.}, year={2010}, month={Feb}, pages={230–237} }
 @article{bradford_bogdanovich_2010, title={Carbon nanotube yarn and 3-D braid composites. Part II: Dynamic mechanical analysis}, volume={41}, ISSN={["1359-835X"]}, DOI={10.1016/j.compositesa.2009.10.003}, abstractNote={Macroscopic textile preforms were produced with a multi-level hierarchical carbon nanotube (CNT) structure: nanotubes, bundles, spun single yarns, plied yarns and 3-D braids. In tensile tests, reported in Part I, composites produced from the 3-D braids exhibited unusual mechanical behavior effects. The proposed physical hypotheses explained those effects by molecular level interactions and molecular hindrance of the epoxy chains with individual carbon nanotubes occupying about 40% of the composite volume. Dynamic mechanical analysis was used in this Part II to study the molecular transitions of neat epoxy resin samples and their corresponding CNT yarn composite samples with varying matrix properties. Dramatic effects on the intensity and temperature at which α-transitions occured, were recorded, as well as a marked effect on the smaller segmental motions, or β-transitions. These changes in the matrix assist in explaining the mechanical test data presented in Part I and the proposed physical explanation of those data.}, number={2}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Bradford, Philip D. and Bogdanovich, Alexander E.}, year={2010}, month={Feb}, pages={238–246} }
 @article{bradford_bogdanovich_2008, title={Electrical conductivity study of carbon nanotube yarns, 3-D hybrid braids and their composites}, volume={42}, ISSN={["1530-793X"]}, DOI={10.1177/0021998308092206}, abstractNote={ Long continuous yarns consisting solely of carbon nanotubes may be the future of specialty composites requiring unique multi-functional properties. Many of such yarns were incorporated in a hybrid composite here, to demonstrate for the first time, their effect on increasing the electrical conductivity of an otherwise insulating composite. Six-ply nanotube yarns produced by University of Texas at Dallas were used as a raw material in this study. Thirty-six ends of such yarn were utilized in a 3-D braiding process along with nine axial bundles of glass fibers. The experimental study of the electrical conductivity of the produced nanotube yarns, 3-D braids and composites made thereof is described; the results for different tested materials are mutually compared and discussed. Some non-trivial effects attributed to the complex multi-level hierarchy and nano-scale building blocks of the studied materials are revealed. Special attention is paid to a proper interpretation of the obtained experimental results, because the tested materials represent complex discrete networks of numerous electrically conductive elements. }, number={15}, journal={JOURNAL OF COMPOSITE MATERIALS}, author={Bradford, Philip D. and Bogdanovich, Alexander E.}, year={2008}, month={Aug}, pages={1533–1545} }
 @article{bogdanovich_bradford_mungalov_fang_zhang_baughman_hudson_2007, title={Fabrication and mechanical characterization of carbon nanotube yarns, 3-D braids, and their composites}, volume={43}, number={1}, journal={SAMPE Journal}, author={Bogdanovich, A. and Bradford, P. and Mungalov, D. and Fang, S. L. and Zhang, M. and Baughman, R. H. and Hudson, S.}, year={2007}, pages={6–19} }
 @article{yushanov_bogdanovich_mohamed_1999, title={Manufacturing and property analysis of a novel class of 3-D woven composites}, volume={12}, ISSN={["0892-7057"]}, DOI={10.1177/089270579901200107}, abstractNote={ Structural and elastic properties of a novel class of 3-D woven orthogonally reinforced composites are studied. Comparative analysis of various theoretical approaches for elastic properties prediction of spatially reinforced composites is carried out. Theoretical predictions are compared with available experimental data. The effect of local yarn waviness on the elastic response of 3-D woven composites is studied using developed novel probabilistic theory. }, number={1}, journal={JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS}, author={Yushanov, SP and Bogdanovich, AE and Mohamed, MH}, year={1999}, month={Jan}, pages={70–82} }
 @article{yushanov_bogdanovich_1998, title={Analytical probabilistic modeling of initial failure and reliability of laminated composite structures}, volume={35}, ISSN={["0020-7683"]}, DOI={10.1016/S0020-7683(97)00081-4}, abstractNote={An analytical approach based on the theory of stochastic processes is developed for the stochastic initial failure analysis and reliability predictions of thin-walled laminated composite structures. The probability of initial failure is calculated using theory of rare passages of the random strain vector field out of the prescribed region of allowable states. The region is limited by the ultimate strain surfaces adopted for each individual layer in the laminate. The surfaces, in their turn, are defined in terms of the scatters in the ultimate strains for the composite layer. Reliability function of a composite layer having random elastic characteristics and loaded with random in-plane tractions is determined through the probability of its initial failure. The reliability function of the laminated composite structure is then calculated through the failure probabilities of individual layers, using the weakest link model. The proposed approach allows one to solve diverse stochastic problems and requires substantially less computational expenses than Monte Carlo simulation technique. The approach may be invaluable for a quick evaluation of various competitive design projects when considering laminated composite structures under the reliability constraint. Applications of the developed approach are illustrated on the examples of reliability predictions of laminated composite cylindrical shells under the effect of random internal pressure and laminated composite plates under random biaxial loading. Numerical results reveal specific probabilistic phenomena related to the effects of ply lay-up, scatters in mechanical and strength characteristics and random loading histories. Results obtained from the developed analytical approach are compared to those calculated with Monte Carlo simulation technique.}, number={7-8}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={Yushanov, SP and Bogdanovich, AE}, year={1998}, month={Mar}, pages={665–685} }