1,720,966 research outputs found
A new explicit solution for the mode I stress fields in notched orthotropic solids
No full textThis paper deals with the stress distributions in orthotropic solids weakened by hyperbolic-shaped notches and loaded under in-plane tension. A complex potential function and proper boundary conditions are proposed from which, thanks to an optimization algorithm, a new solution is derived that can account for the geometrical features of the notch, such as the notch radius and opening angle, as well as the elastic material properties.A large bulk of results from two-dimensional finite element analyses are then compared with the derived solution, documenting its high accuracy, and showing the improvements with respect to the previous existing solution for the same problem
Modelling the thermoelectric behaviour of composite laminates in the presence of transverse cracks
No full textComposite materials, based on carbon fibres and/or nano-modified polymers, are charac-terised by a thermoelectric coupling. Indeed, an electric potential drop is generated in the presence of a thermal gradient (Seebeck effect), which makes them suitable for thermo-electric applications.In this work, novel analytical models are presented for the calculation of the apparent in-plane electric, thermal and thermoelectric properties of composite cross-ply laminates in the presence of transverse cracks. The aim of this analysis is to understand the variation in the apparent laminate properties if damage takes place in the form of transverse cracks, this being typically the first damage mode occurring in composite laminates under static and cyclic tensile loadings.(c) 2022 Elsevier Inc. All rights reserved
On the use of elemental quantities to compute NSIFs at pointed V-notches with non-regular coarse meshes
No full textIn this work, the possibility to use elemental quantities, computed from non-regular coarse meshes, to assess Notch Stress Intensity Factors at pointed V-notches (with a notch opening angle different from zero) is explored. To this end, the analytical expressions for the Energy Density and averaged stresses over a four sided finite element close to the notch tip are firstly derived, based on Williams equations under pure Mode 1, Mode 2 and Mode 3, as well as for mixed Mode loadings. Subsequently, taking advantage of a large number of examples, non-uniform, coarse, mesh patterns are used to back calculate the NSIF values simply inverting the above-mentioned analytical expressions, also discussing the accuracy, the advantages and the limitations of this approach
Nanomorphology of graphene and CNT reinforced polymer and its effect on damage: Micromechanical numerical study
No full textThe effect of morphology, shapes and distribution of nanoscale carbon reinforcement in polymers on their strength and damage resistance is studied using computational micromechanical modeling. A new software and approach were developed for the automatic generation of finite element unit cell models of nanocomposites with inclusions of arbitrary and complex shapes. The effect of curved, zigzagged, snakelike shapes of real carbon nanotubes, as well as re-stacking of graphene on the damage evolution was studied in the computational experiments based on the developed code. The potential of hybrid (carbon nanotubes and graphene) nanoscale reinforcement was studied with view on its effect of damage resistance. It was demonstrated that idealized, cylinder like models of carbon nanotubes in polymers lead to an underestimation of the stress concentration and damage likelihood in the nanocomposites. The main damage mechanisms in CNT reinforced polymers are debonding and pull-out/fiber bridging, while in graphene reinforced polymers the main role is played by crack deviation and stack splitting, with following micro-crack merging. The potential of hybrid (carbon nanotubes and graphene) nanoscale reinforcement was studied with view on its effect of damage resistance. (C) 2016 Elsevier Ltd. All rights reserved
Characterization and modelling of the microstructural and mechanical properties of additively manufactured continuous fiber polymer composites
No full textThe additive manufacturing of continuous fiber reinforced polymer composites is a technology showing great potential for the production of end-use functional and structural components. The reasons for its still limited use are primarily related to an insufficient knowledge of the mechanical behavior of these composites, especially when considering the features that distinguish the printed components from conventional composite parts. Among these peculiar features, their bead-based architecture has been experimentally and analytically investigated in this study. Following an analysis of the process-morphology correlation, carbon fiber (CF)/polyamide 12 (PA12) specimens were tested to characterize the in-plane quasi-static material properties. Then, a modelling framework has been proposed for assessing the composite elastic properties and average bead stresses. This framework holds the potential to scale up to a structural level, accommodating various fiber trajectories
Hierarchical nanoreinforced composites: Computational analysis of damage mechanisms
Full text linkThe potential of hierarchical composites with secondary nanoreinforcement is discussed and analysed on the basis of the computational modelling. The concept of nanostructuring of interfaces as an important reserve of the improvement of the composite properties is discussed. The influence of distribution, shape, orientation of nanoparticles (carbon nanotube, graphene) in unidirectional polymer matrix composites on the strength and damage resistance of the composites is studied in computational studies. The possible directions of the improvement of nanoreinforced composites by controlling shapes, localization and other parameters of nanoreinforcements are reviewed
Energy-based evaluation of the stress concentration factor with highly non-regular coarse meshes: Theoretical formulation and practical validation
No full textThe main aim of this work is to propose a simple and highly accurate approach to evaluate the stress concentration factor of notched solids under Mode 1 loading by using non-regular coarse meshes and the elemental averaged strain energy. As a first step of the analysis, the analytical expression for the Strain Energy averaged over a four-sided and three-sided finite element located at the notch tip is derived, taking advantage of Filippi-Lazzarin-Tovo equations for rounded notched plates under pure Mode 1 loading. Subsequently, the accuracy of the proposed approach is widely validated taking advantage of a large number of examples related to U-shaped notches and rounded V-shaped notches with different notch root radii
A Semi-Analytical Solution for the in-plane Stress Fields in Isotropic Convex Finite Solids with Circular Holes Reinforced with Cylindrically Orthotropic Rings
Full text linkIn this paper a semi-analytical solution for the stress distribution in a finite convex plate with a reinforced hole and subjected to a general loading condition is presented. The method described accounts for the geometrical parameters of the plate, as well as material properties and loading conditions, which can be applied internally to the hole boundary and externally to the outside boundaries of the plate. An extensive validation of the proposed solution is carried out comparing the theoretical predictions with results from various finite element analyses, showing an excellent agreement
Improving the antimicrobial and mechanical properties of epoxy resins via nanomodification: An overview
Full text linkThe main purpose of this work is to provide a comprehensive overview on the preparation of multifunctional epoxies, with improved antimicrobial activity and enhanced mechanical properties through nanomodification. In the first section, we focus on the approaches to achieve antimicrobial activity, as well as on the methods used to evaluate their efficacy against bacteria and fungi. Relevant application examples are also discussed, with particular reference to antifouling and anticorrosion coatings for marine environments, dental applications, antimicrobial fibers and fabrics, and others. Subsequently, we discuss the mechanical behaviors of nanomodified epoxies with improved antimicrobial properties, analyzing the typical damage mechanisms leading to the significant toughening effect of nanomodification. Some examples of mechanical properties of nanomodified polymers are provided. Eventually, the possibility of achieving, at the same time, antimicrobial and mechanical improvement capabilities by nanomodification with nanoclay is discussed, with reference to both nanomodified epoxies and glass/epoxy composite laminates. According to the literature, a nanomodified epoxy can successfully exhibit antibacterial properties, while increasing its fracture toughness, even though its tensile strength may decrease. As for laminates—obtaining antibacterial properties is not followed by improved interlaminar properties
Exact in-plane stress field solution for isotropic plates with circular holes reinforced with cylindrically orthotropic rings
Full text linkIn this paper an analytical solution for the stress distribution in an infinite plate with a concentrically reinforced hole under a general loading condition is derived. The developed solution explicitly accounts for the elastic properties of the plate and of the reinforcing annulus, for the hole radius to reinforcing ring thickness ratio, as well as the loading conditions, including loads applied onto the hole boundary and on the plate, far away from the hole. A careful validation of the proposed framework is carried out by comparing the newly developed solution with the results from a number of finite element analyses, documenting a very satisfactory agreement. The solution derived represents a useful tool toward the understanding of the stress fields in polymeric components with reinforced holes and made with fused deposition modelling technologies
- …
