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Introduction: Although ejection fraction (EF) is the cornerstone of the assessment of left ventricular (LV) systolic function, its measurement faces a number of challenges related to image quality, assumptions of LV geometry, and expertise. The aim of this study was to test the inter‐observer variability of EF and GLS measurement in patients with a broad spectrum of LV function, between physicians and investigators (Inv) with different levels of expertise. Methods: In 122 patients, EF and GLS were measured by 4 Inv blinded to each other with different level of experience in echocardiography; EF was measured using 3 methods: visual assessment, biplane Simpson's method, and auto‐EF method. GLS was measured from the 3 apical views. A significant difference for LVEF and for LVGLS was considered to be >10 and >2 absolute values, respectively. Results: Intra‐observer agreement was excellent for visually assessed EF (ICC = 0.87, P <.001) and GLS (ICC = 0.82, P <.001) and good for EF measured by Simpson's method (ICC = 0.70, P <.001) and auto‐EF (ICC = 0.72, P <.001). Intra‐observer and inter‐observer agreements were excellent for GLS with ICCs above 0.8. GLS discordance between the 4 Inv was not significant. Discordance in EF and GLS measurements among the Inv was not related to image quality or wall motion abnormalities. Conclusion: Although EF has proved its prognostic value in various cardiovascular entities, GLS seems to be more reliable for serial assessment of LV function, demonstrating lower intra‐ and inter‐observer variability, even by different physicians with variant level of expertise. [ABSTRACT FROM AUTHOR]

In this study, an optimization of a laser‐based ablation process of aeronautical carbon‐fiber reinforced polymers is aimed via statistical tools such as the design of experiments, the analysis of variance and response surface methodologies. Three basic process parameters and their interactions is under examination that is, the laser beam scanning speed, the pulse repetition frequency and the hatching distance between two scan lines. A green short‐pulsed laser with a central wavelength at 532 nm is for the first time utilized for the ablation task with the purpose of bulk material removal prior to a structural repair. The Box–Behnken Design and a three‐level factorial design are implemented to define the minimum number of experimental trials and build an appropriate test matrix. The results identify the statistically significant parameters that affect five selected responses namely the material removal rate, the shear strength of a stepped‐lap joint and the heat affected zones measured at three locations. Quadratic models are fitted to the experimental data and a near‐optimal solution is identified at the multi‐objective optimization task of laser‐assisted ablation of carbon‐fiber polymer composites. POLYM. COMPOS., 40:3084–3100, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The aim of the present study is to examine and compare the thermal and mechanical properties of epoxy resin/TiO2 particle microcomposites (0.2 μm) and nanocomposites (21 nm). Composite materials consisting of epoxy resin reinforced with different amounts of TiO2 microparticles (1, 5, 10, 15, and 20% wt) and TiO2 nanoparticles (0.5%, 1%, 3%wt) were prepared. The thermal and mechanical properties of the manufactured composites were investigated and compared through differential scanning calorimetry (DSC) and three‐point bending tests (3PB). Lipatov's Theory was then applied on the DSC results, thus leading to the calculation of the particle‐matrix interphase thickness which was correlated to experimental findings. The glass transition temperature (Tg) of the materials was obtained and the effect of the grain size on the measured Tg values was investigated. The data obtained from DSC tests for both micro‐ and nanoinclusions when normalized with respect to the specific surface area of the particles, resulted in a single continuous curve describing the normalized phase transition enthalpy variation with filler weight fraction. POLYM. ENG. SCI., 58:1146–1154, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A study dealing with the effect of the carbon nanotubes (CNTs), at various weight fractions, on the effective thermal conductivity of a CNT-reinforced polymer by associating it with the Kapitza resistance ( RKap) phenomena is presented. The finite element method was utilized as a tool for the models' solution by using the principles of the representative volume element. An intermediate continuum layer between polymer matrix and CNTs was considered for the representation of the RKap phenomena. The influence of the intensity of RKap phenomena at various CNT contents was investigated through the parametric study of the RKap value and the thickness of the intermediate layer. The predicted results were compared against experimental measurements derived from an equivalent CNT-epoxy resin system. The discrepancy between calculated and measured values is diminished when the RKap phenomena are taken into account, thus confirming the existence of thermal resistance between the CNTs and the polymer matrix. The RKap rise as the % CNT weight content is increased. This behavior is correlated to the higher CNT agglomeration at higher CNT contents, which is proven by the scanning electron microscopy and thus providing a first indication of the effect of the CNT agglomeration on the effective thermal conductivity at various CNT contents. POLYM. COMPOS., 35:1997-2009, 2014. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The driver for this study is the observation that heating of carbon nanotubes (CNTs) with electromagnetic field can offer a more efficient and cost-effective alternative in heat transfer for the production of composites. The idea of this study is twofold; CNT can work as microwave (MW) radiation susceptors and they can act as nanoreinforcements in the final system. To test these assumptions, a household oven was modified to control the curing schedule. Polymers with different CNT concentrations were prepared (0.5 and 1.0 wt %). The dispersion of the CNTs in the epoxy was achieved using shear-mixing dissolver technique. MW and conventionally cured specimens were also produced in a convection oven for reference. Thermal and mechanical tests were used as control point. A curing schedule investigation was further performed to quantify the energy and time-saving capabilities using CNT and MWs. The presence of CNTs into epoxy matrix has been proven beneficial for the shortening of the curing time. MW-cured composites showed the same degree of polymerization with the conventionally cured composites in a shorter time period and this time was reduced as the CNT concentration was increased. A good distribution of the CNT is required to avoid hot spot effects and local degradation. Mechanical performance was, in some cases, favored by the use of CNT. The benefit from the use of MWs and CNT could reach at least 40% in terms of energy needed and time without sacrificing mechanical performance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Present work investigates the effect of hydrothermal aging of flax fiber‐reinforced bio‐based epoxy resin laminates on the mechanical and thermomechanical properties of the composites. Three different types of bio‐based resins were used. Plates reinforced with eight layers plain weave flax fibers of 150 g/m2, manufactured using Resin Transfer Molding (RTM), compression molding or autoclave technique depends on type of the resin. One dimensional Fickian behavior shows a good fitting to the experimental data derived from weight measurements. The water uptake at the equilibrium state in the case of 60 °C temperature was slightly greater than that at 40 °C. The mechanical properties after hydrothermal aging show a significant reduction and do not return to their initial values even after the drying process. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48787. [ABSTRACT FROM AUTHOR]

Self‐healing resin (Bismaleimide prepolymer, BMI pp) based on Diels–Alder reaction mechanism was integrated into high performance carbon fiber reinforced plastics (CFRPs). Reference and BMI pp modified CFRPs were manufactured by incorporating grains of the self‐healing agent (SHA) in the mid‐thickness interlaminar region through sieving. First, the effect of the SHA concentration on the toughening and healing performance of CFRPs was studied under mode I fracture loading. The SHA was able to enhance the interlaminar fracture toughness of the composite to a certain extent and also to offer a moderate thermally activated healing functionality. Also, the effect of the curing temperature on the same results was studied; it was found the decrease of the curing temperature slightly decreases the fracture toughness while increases the healing efficiency of the composite. Finally, optical microscopy examinations were conducted and three‐point bending tests were utilized to study the in‐plane mechanical properties of the composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47478. [ABSTRACT FROM AUTHOR]