Episodios

  • Prediction of the tensile strength of FDM specimens based on Tsai Hill criteria

    Prediction of the tensile strength of FDM specimens based on Tsai Hill criteria
    May 22 2025
    This study investigates the mechanical behavior of 3D-printed polyethylene terephthalate glycol (PETG) polymer specimens subjected to tensile and shear testing, with a particular focus on the influence of raster orientation and shell contour. Specimens were fabricated using Fused Deposition Modeling (FDM) at three raster angles (0°, 45°, and 90°) and tested using both a mechanical extensometer and a Digital Image Correlation (DIC) system. The results indicate a significant influence of raster orientation on tensile and shear properties. 0° specimens exhibited the highest tensile strength, as the filament alignment was parallel to the loading direction. In contrast, 45° specimens demonstrated more ductile behavior. While the shell contour had minimal effect on 0° and 45° specimens, it enhanced stiffness and ductility in 90° specimens. Furthermore, the Tsai-Hill criterion was applied to predict the tensile strength at a 45° orientation. These findings contribute to a deeper understanding of the anisotropic behavior of 3D-printed materials and highlight the importance of raster orientation in optimizing mechanical performance.
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    18 m
  • Damage mechanisms in hybrid composites: experimentalcharacterisation and energy-based numerical analysis

    Damage mechanisms in hybrid composites: experimentalcharacterisation and energy-based numerical analysis
    May 21 2025
    This study analyses the failure mechanisms of bilayer hybrid composites, consisting of carbon and glass fibres embedded in an epoxy matrix, under bending loads. The objective is to evaluate how different hybrid configurations influence failure evolution and mechanical performance. To achieve this, specimens are submitted to 3-point bending tests, and 3D finite element models are developed to simulate the experimental setup. The numerical models incorporate a continuum damage mechanics model to capture intralaminar failure and a surface-based cohesive behaviour for interlaminar damage. The results show that hybrid laminates exhibit intermediate strength and displacement values compared to nonhybrid carbon and glass laminates, with the positioning of glass fibers significantly affecting bending force and displacement. Intralaminar damage is the primary failure mechanism in all configurations, followed by delamination. Additionally, placing glass fibers on the compression side reduces the overall damage, whereas placing them on the tensile side increases intralaminar failure before reaching the peak load. These findings contribute to optimizing the design of hybrid composites for bending applications by providing information about the relationship between material configuration and failure mechanisms, ultimately improving their structural efficiency and durability in engineering applications.
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    26 m
  • Parametric study on the effect of anchor’s geometry on the stress distribution and crack initiation direction in a concrete body

    Parametric study on the effect of anchor’s geometry on the stress distribution and crack initiation direction in a concrete body
    May 14 2025
    This work deals with investigations of the stress field distribution around a steel anchor embedded in a concrete. Tensile loading - pulling force of the steel anchor is considered, which is very often connected to concrete cone failure. Numerical simulations via finite element method were performed to obtain results for a large extent of geometrical configurations. In accordance with the basic idea of the maximum tangential stress criterion, the angle where this stress reaches its maximum was determined. The influence of selected geometrical parameters of the system on these angles was analyzed and it was found out that they can significantly affect the angle of the maximum tangential stress and consequently the shape of the cone failure. It was observed that the circumferential crack propagation is flatter with increasing length of the steel anchor’s embedment and with increasing anchor’s outer radius. The results obtained numerically agree sufficiently with experimental results especially when the crack direction is compared. Conclusions presented within this research are important for both design and assessment of anchor/concrete systems subjected to tensile loading.
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    13 m
  • Influence of contact interaction character on residual stresses arising over damaged area in composite plate

    Influence of contact interaction character on residual stresses arising over damaged area in composite plate
    May 13 2025
    New data concerning the values of residual stresses that arise as a result of the contact interaction of a spherical indenter and a flat surface of composite plate have been obtained. The studies are performed for both static indentation and impact influence of a spherical indenter into a flat surface of coupons made of carbon fibre reinforced polymer with cross-ply stacking sequence. The high-quality interference fringe patterns, generated by through hole drilling in contact interaction zone, which are essential for residual stress deriving are visualized and quantitatively processed both inside and outside the contact dimple. The distributions of residual stresses obtained during static and impact contact interaction, which leads to the appearance of dimples of almost the same diameter, are compared. A comparison of the values of the principal residual stress components corresponding to the contact interaction of similar composite plates with a spherical impactor of different diameters for the same impact energy is presented. Several factors have been identified that relate the decrease in the residual strength of damaged specimens to the values of the residual stress components. Evaluation of the influence of coupon’s thickness as well as an impact energy level on the residual stress values inherent in the vicinity of contact dimple is presented.
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    17 m
  • A study on the crack presence effect on dynamical behavior of higher-order Quasi-3D composite steel-polymer concrete box section beams via DQFEM

    A study on the crack presence effect on dynamical behavior of higher-order Quasi-3D composite steel-polymer concrete box section beams via DQFEM
    May 11 2025
    This paper presents a dynamic and critical buckling analysis of the presence of a crack of steel-polymer concrete composite beams modelled using a refined quasi 3D beam theory. The beam model is a hollow steel box section filled with a composite concrete material. The presence of the crack is assumed on both inner concrete core and outer steel layer box, incorporating its effects into the mechanical behavior of the beam. The governing equations for the box beam are derived using the Differential Quadrature Finite Element Method (DQFEM) combined with Lagrange’s principle. The study investigates the natural frequencies and critical buckling loads of steel-polymer concrete composite beams under various crack location and crack depth. Validation is performed by comparing the results with numerical methods and experimental results available in the literature, demonstrating high accuracy. The findings of this research provide valuable insights into the dynamic and stability behavior of box-section beam with composite infill, offering practical guidelines for the design of material-based structures in engineering applications.
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    14 m
  • Predictive modeling of PMMA-based polymer composites reinforced with hydroxyapatite: a machine learning and FEM approach

    Predictive modeling of PMMA-based polymer composites reinforced with hydroxyapatite: a machine learning and FEM approach
    May 7 2025
    This research examines the mechanical characteristics of polymer composites (PMMA) that are reinforced with Hydroxyapatite (HAp), with a particular emphasis on the Elastic Modulus and Compressive Strength. The investigation employs a multifaceted approach that integrates experimental methods, micromechanical analysis, and machine learning techniques. Experimental assessments of Elastic Modulus and Compressive Strength were conducted at various HAp concentrations (5%, 15%, and 30%) and were compared with theoretical predictions derived from Representative Volume Element (RVE) and micromechanical frameworks, including Voigt and Reuss bounds. Various machine learning algorithms, such as Feedforward Neural Network (FFNN), Radial Basis Neural Network (RBNN), and Support Vector Machine (SVM), were used to predict the mechanical properties. The RBNN exhibited high accuracy (R² = 0.92; MAE = 0.05) for intermediate HAp levels (20-30%) but displayed instability at the extremes % of reinforcements values . The FFNN consistently provided lower estimates of the properties, whereas the SVM yielded robust and stable predictions that closely matched both experimental and theoretical results with the error of (2-5) % (Result value). This research highlights the effectiveness of integrating micromechanical modeling with machine learning to improve the prediction and comprehension of composite behavior, thereby offering valuable insights for the design and application of advanced materials.
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    14 m
  • Flood-induced load effects on real-scale structures: a 3D multilevel dynamic analysis

    Flood-induced load effects on real-scale structures: a 3D multilevel dynamic analysis
    May 6 2025
    In this work, the structural behavior of masonry buildings under flash flood actions is analyzed by using a novel 3D multilevel fluid/structure model. The proposed numerical framework consists of a macro-scale model based on the computational fluid dynamic, able to simulate the dynamic free-stream flow of a fluid impacting rigid solids and a meso-scale structural model that employs a coupled damage-plasticity approach to describe the nonlinear behavior of the masonry buildings, subjected to the fluid dynamic pressure extracted by the macro-scale fluid analysis. The integrated model was employed to assess the fluid-structure interaction effects on the global structural response, in terms of load-carrying capacity and damage patterns, of a real-scale masonry structure subjected to flood-induced loading conditions. Finally, a parametric analysis is performed in order to understand the influence of the fluid inlet velocity and water depth on the failure mechanisms of the structure. The results highlight the good numerical capabilities of the proposed multilevel model, establishing it as a valuable numerical tool for the structural vulnerability assessments under flood actions.
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    11 m
  • Experimental investigation on mechanical behavior of sandwich structures using Digital Image Correlation (DIC)

    Experimental investigation on mechanical behavior of sandwich structures using Digital Image Correlation (DIC)
    Apr 26 2025
    The aim of this work is to investigate the mechanical behavior of sandwich structures when subjected to edgewise and flatwise compression loadings, using 2D Digital Image Correlation (DIC). These structures are made of Glass Fiber Reinforced Polymer (GFRP) skins with polyurethane foam (PU) core. Initially, the mechanical characterization of each component within the sandwich structure is exanimated. Subsequently, flatwise and edgewise compression tests are conducted on the sandwich panels, in accordance with ASTM C365 and ASTM C364 standards, respectively. Different geometries are studied by testing various lengths of sandwich structures exposed to edgewise compression loads. The DIC technique is applied to analyze and comprehend the deformation and failure mechanisms of GFRP skins and sandwich structures. The results of the present study indicate that the flatwise compression test revealed condensation and densification of PU foam, accompanied by microcracks in GFRP skin. On the other hand, the edgewise compression test on sandwich structures with an equal length-to-width ratio identified several distinct failure modes, including skin-core debonding, shear sliding damage of the skin, and localized buckling. This localized buckling was initially observed in the mid-section of the specimens, followed by skin cracking on both sides, which then propagated across the width of the samples. For other geometric configurations of the sandwich structures, the Euler general buckling mode was observed. The results show that the length of samples has a significant effect on the collapse modes of sandwich structures under edgewise compression.
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    7 m
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