Search

This study aims to propose a method for mapping the implementation of active learning approaches by quantifying engineering teachers' self-perception. It also seeks to examine the correlations between the implementation of active learning approaches and training, as well as publications focused on active learning. To conduct the study, active learning concepts were defined, and a set of approaches were selected for consideration in the survey. A questionnaire was developed to collect data, which was completed by teachers of 246 courses from 14 engineering programs within a school of engineering. The findings revealed that only 11% of the courses studied did not implement any active learning approach. Project-Based Learning emerged as the most implemented approach, which aligns with the context of the engineering school. Additionally, positive correlations were found between training and the implementation of active learning approaches. This work makes contributions both to the theory, as it presents a way for measuring the perceived implementation of active learning approaches and the correlation with training and publications, and for institutional policy, as it shows the importance of training for that same implementation. [ABSTRACT FROM AUTHOR]

In this work, we present a study on numerical and experimental approaches aiming to improve our understanding about the relation between the flow conditions and the strength of weld lines in extruded profiles. For this purpose, a prototype extrusion die that comprises a movable spider leg is used to produce tapes under different flow conditions, by varying the location of the spider leg and the flow rate. The same case studies are numerically studied, considering a viscoelastic Giesekus constitutive model. The numerical results are then investigated to identify potential relationships between the flow conditions, in which the weld lines are formed, with the strength of the weld line experimentally characterized. The results obtained allow identifying a clear correlation between the flow conditions and the weld-line strength., INTRODUCTION The formation of weld lines occurs when two or more different flow fronts merge or when the flow encounters an obstacle that forces two portions of fluid to separate [...]

In this work we present improved design guidelines to support the die designer activity, when searching for the flow channel geometry that allows the achievement of a balanced flow distribution, in complex profile extrusion dies. The proposed methodology relies on surrogate models, obtained through a detailed and extensive numerical study, carried out with the open source computational library OpenFOAM®, in which an appropriate numerical solver for the problems under study was implemented. The main contribution of this work is to further enlarge the applicability of the simplified design methodology (Rajkumar A, Ferrás LL, Fernandes C, Carneiro OS, Becker M, Nóbrega JM. Int. Polym. Proc. 2017, 32, 58-71.) previously proposed by this group for similar purposes, by considering the effect of processing parameters and material rheology. The sensitivity analyses performed showed that, among the studied parameters, the power-law exponent was the only one that affected the system behavior. Thus, the previous proposed surrogate models were modified to include the effect of this parameter. Verification studies performed for three geometries and different rheological and process parameters evidenced the effectiveness of the proposed simplified design methodology. [ABSTRACT FROM AUTHOR]

The preparation of microfibrillar composites (MFCs) based on oriented blends of polyamide 6 (PA6) and high-density polyethylene (HDPE) is described. By means of conventional processing techniques, the PA6 phase was transformed in situ into fibrils with diameters in the upper nanometer range embedded in an isotropic HDPE matrix. Three different composite materials were prepared through the variation of the HDPE/PA6 ratio with and without a compatibilizer: MFCs reinforced by long PA6 fibrils arranged as a unidirectional ply; MFCs containing middle-length, randomly distributed reinforcing PA6 bristles; and a nonoriented PA6-reinforced material in which the PA6 phase was globular. The evolution of the morphology in the reinforcing phase (e.g., its visible diameter, length, and aspect ratio) was followed during the various processing stages as a function of the blend composition by means of scanning electron microscopy. Synchrotron X-ray scattering was used to characterize selected unidirectional ply composites. The presence of transcrystalline HDPE was demonstrated in the shell of the reinforcing PA6 fibrils of the final MFCs. The impact of the compatibilizer content on the average diameter and length of the fibrils was assessed. The influence of the reinforcing phase on the tensile strength and Young's modulus of the various composites was also evaluated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [ABSTRACT FROM AUTHOR]