Static Bending Research Articles

Finite element modeling to explore static bending responses of four-layer FG beam structures considering sliding motions

Finite element modeling to explore static bending responses of four-layer FG beam structures considering sliding motions

Evaluation of static bending caused damage of glass-fiber composite structure using terahertz inspection

Abstract Composite materials find increasing applications in modern industry and transport. However, they may lose desirable mechanical properties due to external mechanical excitations, ultraviolet radiation, moisture penetration, or other factors. Therefore, an effective way to assess the condition of materials is necessary. In this article, a nondestructive evaluation of glass fiber-reinforced composite subjected to five-stage static bending is presented. For this reason, pulsed excitation terahertz imaging was utilized, and a data processing/exploration scheme was proposed. The proposed, novel approach consists of an efficient data registration algorithm based on surface approximation (for surface roughness and unevenness elimination) and a parametrization scheme applied for the signals gained from the time response of the glass fiber-reinforced polymer layer. Obtained parameters enable the global description of the evaluated material state and prediction of failure effectively, even in the early stages of destruction.

Investigation of static buckling and bending of nanoplates made of new functionally graded materials considering surface effects on an elastic foundation

Investigation of static buckling and bending of nanoplates made of new functionally graded materials considering surface effects on an elastic foundation

Analytical solutions for strain-driven Timoshenko nanobeam bending using generalized functions

Static nanobeam bending problems have yielded conflicting results from many researchers. Methods suggested by numerous researchers have shown inconsistencies in capturing size effects and satisfying essential and natural boundary conditions for nanobeam configurations when subjected to different types of loading. This work proposes an alternative approach using Eringen’s strain-driven integral nonlocal elasticity to arrive at analytical solutions. The theory of generalized functions and the Dirac-delta identity are used to revisit Timoshenko nanobeam modeling aspects, focusing on nanobeam elastostatics. Proposed analytical solutions for fundamental and derived quantities based on the strain-driven nonlocal model have been compared with the results of existing approaches. A crucial drawback with the strain-driven models of Eringen in both integral and differential form is its inability to satisfy equilibrium equations, which is addressed extensively in this work.

Clustering of tropical species through multivariate analysis of the bonding properties of edge-glued panels (EGP)

Tropical woods have high added value, and the use of waste for panel production is an initiative to add more value to this material, typically consisting of various species. The use of raw materials from tropical solid wood waste in the Amazon region contributes to the reduction of carbon emissions associated with the burning of this material. In this context, this study aimed to cluster species based on the bonding properties of Amazonian woods by applying multivariate analysis. The apparent density 12% and strength of finger joint and edge-glued joints of Cedrela odorata, Enterolobium schomburgkii, Erisma uncinatum and Qualea paraensis was evaluated which were joined in homogeneous and hybrid configurations with the adhesives PVA and EPI, as spreading rate of 180 g/m2. The treatments were compared by multivariate analysis of variance and discriminant analysis. The discrimination of species and combinations based on wood density (low, medium, and high) revealed that this is the most important characteristic for grouping different species that make up tropical hardwood waste for the production of EGP panels. In practice, the separation of species into groups according to wood densities can contribute to a better definition of the indications for use of edge glued panels of each density class, and assertive targeting for applications according to the strength ranges required. In the static bending, parallel tensile and shear tests all species and their combinations met the minimum requirements normative, indicating the approval of species and combinations studied for the production of EGP panels.

Enhanced Experimental Setup and Methodology for the Investigation of Corrosion Fatigue in Metallic Biodegradable Implant Materials.

Biodegradable implants as bone fixations may present a safe alternative to traditional permanent implants, reducing the risk of infections, promoting bone healing, and eliminating the need for removal surgeries. Structural integrity is an important consideration when choosing an implant material. As a biodegradable implant is being resorbed, until the natural bone has regrown, the implant material needs to provide mechanical stability. However, the corrosive environment of the human body may affect the fatigue life of the material. Conversely, mechanical stress can have an effect on electrochemical corrosion processes. This is known as corrosion fatigue. In the presented work, an experimental setup and methodology was established to analyze the corrosion fatigue of experimental bioresorbable materials while simultaneously monitoring the electrochemical processes. A double-walled measurement cell was constructed for a three-point bending test in Dulbecco's Phosphate-Buffered Saline (DPBS- -), which was used as simulated body fluid (SBF), at 37 ± 1 °C. The setup was combined with a three-electrode setup for corrosion measurements. Rod-shaped zinc samples were used to validate the setup's functionality. Preliminary static and dynamic bending tests were carried out as per the outlined methodology to determine the test parameters. Open-circuit as well as potentiostatic polarization measurements were performed with and without mechanical loading. For the control, fatigue tests were performed in an air environment. The tested zinc samples were inspected via scanning electron microscopy (SEM). Based on the measured mechanical and electrochemical values as well as the SEM images, the effects of the different environments were investigated, and the setup's functionality was verified. An analysis of the data showed that a comprehensive investigation of corrosion fatigue characteristics is feasible with the outlined approach. Therefore, this novel methodology shows great potential for furthering our understanding of the effects of corrosion on the fatigue of biodegradable implant materials.

POTENTIAL USE OF Pinus patula WOOD FOR THE PRODUCTION OF PURE AND IN COMBINATION WITH Eucalyptus PLYWOOD PANELS

Plywood panels are products of great importance in the global market, and Brazil is a large producer of conifer plywood, which boosts industrial activities in the south of the country and consequently contributes to the Brazilian GDP. Pinus patula is an unconventional species that requires study for this purpose. Thus, this research aimed to evaluate the potential for using Pinus patula wood for the production of pure plywood panels and in combination with Eucalyptus grandis and Eucalyptus dunnii. 8 treatments were produced, pure and in combination of species, which were glued with phenol formaldehyde adhesive, in a grammage of 180 g/m2 and a solids content from the adhesive formulation of 34%, and pressed at a temperature of 140°C for 13 minutes at a specific pressure of 11 kgf/cm2. Pinus taeda was used as a reference species. The physical and mechanical properties were evaluated according to the ABNT NBR 17002 and ABNT ISO 12466 standards. The results demonstrated that, for the majority of the properties evaluated, the Pinus patula panels were statistically equal or superior in relation to Pinus taeda. The “combi” type panels showed that the Eucalyptus species contributed to improving the static bending property. It is concluded, therefore, that Pinus patula has potential for the production of plywood panels, allowing an increase in the availability and diversity of raw materials for industrial processes, and that the static bending property can be improved with the production of panels of the “combi'' type using Eucalyptus veneers.

Fabrication and Characterization of Flexible CuI-Based Photodetectors on Mica Substrates by a Low-Temperature Solution Process

Both CuI and CuI:Zn semiconductor thin films, along with MSM-structured UV photodetectors, were prepared on flexible mica substrates at low temperature (150 °C) by a wet chemical method. The two CuI-based films exhibited a polycrystalline phase with an optical bandgap energy close to 3.0 eV. Hall effect measurements indicated that the CuI thin film sample had p-type conductivity, while the CuI:Zn thin film sample exhibited n-type conductivity, with the latter showing a higher carrier mobility of 14.78 cm2/Vs compared to 7.67 cm2/Vs for the former. The I-V curves of both types of photodetectors showed asymmetric rectification characteristics with rectification ratios at ±3 V of 5.23 and 14.3 for the CuI and CuI:Zn devices, respectively. Flexible CuI:Zn devices exhibited significantly better sensitivity, responsivity, and specific detectivity than CuI devices both before and after static bending tests. It was found that, while the optoelectronic performance of flexible CuI-based photodetectors degraded under tensile stress during static bending tests, they still exhibited good reproducibility and repeatability in their photoresponses.

Design optimization of automotive carbon fiber composite material floor laminate based on PSO-BFO algorithm

In response to the current challenges of low precision and efficiency in the optimization of composite material layups, the insufficient lightweight of automotive body floors, and the high cost of carbon fiber composites, this study introduces an optimized design method for carbon fiber composite flooring layups. Based on implicit parametric technology, a hybrid PSO-BFO (Particle Swarm Optimization-Bacterial Foraging Optimization) algorithm is employed. This approach achieves an integrated optimization of materials, processes, and structures, thereby balancing and reducing costs. The SFE-CONCEPT is utilized to establish an implicit parameterization model for the body floor, which is validated through experiments and finite element simulation analysis. Concept design and modeling of the carbon fiber composite material floor laminate are performed. Continuous variable optimization is employed to determine the thickness, tile shape, and number of layers for the front, middle, and rear floors. A continuous variable discretization rounding strategy is used to obtain the discrete layer numbers for each laminate orientation of the composite material floor. The continuous fiber lamination strategy is applied to create different shared lamination regions. The PSO-BFO hybrid optimization method is proposed to optimize the lamination sequence as a multi-objective optimization, addressing the challenges of discrete lamination sequence, explosive combinations, and multiple variables in the optimization design of carbon fiber composite material floor laminates. The optimization results demonstrate improvements of 34.4% in floor quality M, 6.0% in static bending stiffness BS, and 5.3% in lightweight coefficient QLX using the proposed PSO-BFO method. PSO-BFO and PSO-GA (Particle Swarm Optimization-Genetic Algorithm) methods are more capable of obtaining global optimal solutions for complex optimization problems than single optimization algorithms. Still, the results obtained by the PSO-BFO method are more balanced.

The application of novel shear deformation theory and nonlocal elasticity theory to study the mechanical response of composite nanoplates

The use of composite structures, which have many layers of materials, has become more prevalent in the field of engineering. One of the advantages of this approach is its ability to use the inherent strengths of the constituent materials, resulting in a substantial increase in their load-bearing capability. Hence, this research represents the pioneering investigation into the static bending and free vibration characteristics of composite nanoplates including several layers of materials, whereby the material layers are interconnected via intricate profiles characterized by square wave and sine waveforms. The purpose of this endeavor is to fully capitalize on the benefits of attending courses in order to enhance practical working efficiency. This study also incorporates the use of two innovative third-order shear deformation theories. Simultaneously, considering the negligible size impact facilitated by the nonlocal theory, the mathematical formulations and equilibrium equations are derived using the Hamilton principle. The issue has been addressed using a four-node element with six degrees of freedom per node. One novel aspect of this study is its consideration of the impact of initial shape imperfections in various manifestations. Additionally, the elastic foundation incorporates characteristics that exhibit spatial variation. This statement provides a somewhat more accurate depiction of the behavior shown by actual structures. The numerical findings have been meticulously computed and thoroughly examined. Notably, it is possible to determine the optimal number of wavelengths in the profile to enhance the load-bearing capability of the structure. The findings derived from this study have significant value in informing the design of operational frameworks in practical settings.

Study on the bending mechanical properties of composite tube and metal joint bonding structure

Abstract The study of the mechanical properties of composite adhesively bonded joints is a very important issue, which directly affects the safety and reliability of the structure. This article studies the bending performance of carbon fiber composite tubes and metal joint bonding structures, as well as obtains the structural bearing capacity, influencing factors, and structural failure modes. Through mechanical analysis and static bending load tests, it is shown that the failure model of composite tube adhesively bonded metal joints under bending load is manifested as the first layer peeling or interlayer failure of the composite material in the bonding area between the tube and the joint, leading to local crushing at the end of the tube. There is no gap between the tube and the joint, which has little effect on the bending bearing capacity. The thickness gradient treatment at the end of the joint does not help improve the bending bearing capacity. The adhesive layer is at a 90 ° angle, which makes it easy for the first layer to peel off; it should be avoided. Other angle layers have little impact on load-bearing capacity. The longer the bonding length is, the stronger the bending capacity is. The adhesive J133 or 420 has a similar load-bearing. Wrapping a carbon fiber unidirectional layer around the ends of tubes and joints is helpful in improving their bending load-bearing capacity.

Manufacturing Technology, Experimental and Numerical Analysis of Static Bending of Three-Layer Composite Plate with Honeycomb Structure

The use of thin-walled constructions with honeycomb structure manufactured using additive technologies has several advantages compared to the constructions manufactured using traditional technologies. First of all, this is explained by the fact that additive technologies greatly simplify the production of honeycomb structures. A technology for manufacturing a three-layer composite plate with a honeycomb structure obtained using additive technologies is proposed in the paper. PLA plastic was chosen as the material for the honeycomb structure production. Printing was carried out using a "Delta" printer with parallel kinematic chains using FDM technologies. The printing temperature was 215 °C, table temperature – 60 °C. A fundamentally new scheme of an experimental plant for studying the bending of a three-layer plate is proposed. The aim of the research is to conduct tests of samples of a three-layer honeycomb panel for static bending when one edge of the sample is rigidly pinched. For the tests, a certified TiraTest 2300 universal testing machine (UTM), which allows to perform tensile and compression tests at a given traverse speed and measure the load with a relative error of 1%, was used. The UTM allows to load the sample and measure the load and displacement of the traverse. A sixteen-channel strain gauge station is used to measure the surface deformations of the housings. Transverse displacements of a three-layer plate were obtained as experimental data. The bending of the three-layer plate is modeled in the commercial package ANSYS. The results of experimental and numerical analysis coincide well.

Hybrid panels produced with particles and veneers of pine wood in different compositions

Hybrid wood panels can be produced with different particle or veneer sizes, forest species or even mixtures of synthetic materials, with the aim of reusing wood particles and generating new products. The present study aimed to verify the production process of hybrid panels formed with particles and veneers of Pinus taeda wood and urea‒formaldehyde resin. The panels were produced in four different compositions, with a nominal density of 0.65 g/cm³, and their quality was evaluated through their physical and mechanical properties. The addition of veneers in the traditional particleboard system increased the density of the hybrid panels and improved the mechanical properties. The properties of the MOR and MOE in static bending and screw withdrawal were favored using veneers on the panel faces. The internal bonding of the panels was not affected by their composition. The addition of veneers to the particleboard improved the dimensional stability of the panel.

PRODUCTION OF MDP PANELS WITH YERBA MATE HARVEST RESIDUES

The quality of MDP panels produced with Pinus taeda wood particles mixed with yerba mate harvest residues was evaluated. Monolayer panels were produced with the addition of 0. 20. 40. 60. 80 and 100% proportion of yerba mate waste, with a nominal specific gravity of 0.65 g.cm-³, using 12% urea-formaldehyde resin, 0.5% paraffin and 2% ammonium sulfate catalyst. The panels were pressed for 10 minutes at a temperature of 140°C and pressure of 40 kgf/cm². The physical properties of apparent density, moisture content, water absorption and thickness swelling (2 and 24 hours) were evaluated, as well as the mechanical properties of static bending (MOR and MOE), internal bonding, screw withdrawal on the face and Janka hardness. There was a trend towards an increase in internal bonding with an increase in the proportion of yerba mate residue in the panels, but the opposite occurred for the other mechanical properties studied. Some physical properties such as water absorption and thickness swelling resulted in better performance when yerba mate particles were added. In view of this, it can be concluded that it is possible to produce panels with the addition of yerba mate up to 40% in the composition with yerba mate particles, without affecting the quality of the properties.

Flexoelectronics of a centrosymmetric semiconductor cylindrical nanoshell

Cylindrical shell-type semiconductors are essential for sensing and energy harvesting when integrated into surfaces of certain equipment, such as spacecraft, marine devices, and portable electronics, where mechanical forces play a significant impact on charge transport. Traditionally, such functionalities are only manifested in piezoelectric or pyroelectric crystals that possess non-centrosymmetry. Here, we theoretically investigate electronic behaviors driven by strain gradient-induced flexoelectric polarization in a centrosymmetric semiconductor cylindrical nanoshell, expanding the flexoelectronics in shell structures. The governing equations and accompanying boundary conditions are formulated simultaneously using the principle of virtual work and the fundamental lemma of the calculus of variation. Electromechanical interactions through static bending and forced vibration analyses of the newly developed model are systematically investigated. Under localized force excitation, the distribution of mobile charges is manipulated by tuning loading magnitudes and areas. The effects of doping levels on electric potentials and mobile charges are explored to show the interaction mechanism between flexoelectric and semiconducting properties. Moreover, the natural frequencies and modes of all mechanical displacements, electric potentials, and carrier concentration perturbations within the shell are identified. This paper provides a new approach for designing shell-shaped sensors and energy harvesters specifically for centrosymmetric semiconductors.

On the nonlinear mechanics of hybrid skew aerospace structures

This study proposes a functionally graded (FG) nanocomposite hybrid skew plate element which is fabricated from a polymeric matrix and is reinforced with two well-known nanoscale reinforcements, namely, carbon nanotubes (CNTs) and graphene platelets (GPLs). The Mori–Tanaka approach, the Halpin-Tsai scheme and standard rule of mixtures are employed to estimate the effective mechanical properties of the hybrid plates. To model this structural element, Reddy's third-order shear deformation theory (TSDT) is used. By considering the von-Kármán assumptions and using the Hamilton's principle, the nonlinear static bending and free vibration governing equations are determined. Then the isogeometric analysis (IGA) is employed to establish the structural stiffness and mass matrices of the skew hybrid plates. After validating the correctness of the presented solution procedure with the previously published results, the effects of various variables such as number of layers, distribution pattern of reinforcements (CNTs and GPLs) and their volume fractions, skew angle and width-to-thickness ratio are investigated. It is found that with considering nonlinear von-Kármán relationship in the strain field, the distributions of σxx and σyy about the mid-plane are no longer symmetric.

Effect of different initiators on the properties of diacetone acrylamide grafted starch-based adhesive

Environmentally friendly and non-toxic bio-based adhesives are emerging as the most promising substitutes for petroleum-based adhesives, attracting increasing attention. This work involved the synthesis of a starch-based adhesive for particleboards by grafting diacetone acrylamide (DAAM) onto starch. The graft polymerization was initiated using three different initiators: ammonium persulfate (APS), hydrogen peroxide (H2O2)/ammonium ferrous sulfate system, and ceric ammonium nitrate (CAN). A comparative study was conducted to assess the varying effects of these initiators. The results showed that in the graft copolymerization of starch with DAAM, different initiators produced different types of free radicals, and CAN initiation produced alkyl radicals and long-chain alkyl radicals with a peak total spin value of 3.96 × 1015, and thus had the highest grafting efficiency and grafting rate of 72.59 % and 16.75 %, respectively. From the comparison of the total number of spins, it can be seen that CAN is more targeted for starch initiation. In addition, characterization results from Fourier transform infrared spectroscopy and confocal Raman spectroscopy showed that DAAM underwent a graft copolymerization reaction with starch. Notably, the adhesive initiated by CAN demonstrated the highest water resistance and mechanical strength, with an absorption thickness expansion and static bending strength of 8.52 % and 10.56 MPa, respectively.

Rigidity coefficients of rubber belts for dynamic testing of modulus of elasticity and shear modulus of non-wood engineered board

To determine the appropriate stiffness coefficient k values for rubber belts used in dynamic testing of the elastic modulus and shear modulus of timber and solid wood composite materials, this study employed three different thicknesses of rubber belts. Dynamic tests were conducted on straw boards, Laminated Veneer Lumber (LVL), and Spruce-Pine-Fir (SPF) materials, and the results were validated and analyzed using static four-point bending tests. The conclusions drawn from this research indicate that the range of stiffness coefficient k values for the rubber belts obtained through dynamic testing fell between 0.05 and 0.28 N/m. The correctness of the dynamic testing method was verified through static four-point bending tests. The error levels for elastic modulus E and shear modulus G of the same type of board measured using the three different rubber belts were below 9.5% and 9.8%, respectively.

The Influence of Hemp Fibers (Cannabis sativa L.) on the Mechanical Properties of Fiber-Gypsum Boards Reinforcing the Gypsum Matrix.

The modern construction industry is looking for new ecological materials (available, cheap, recyclable) that can successfully replace materials that are not environmentally friendly. Fibers of natural origin are materials that can improve the properties of gypsum composites. This is an important issue because synthetic fibers (hardly biodegradable-glass or polypropylene fibers) are commonly used to reinforce gypsum boards. Increasing the state of knowledge regarding the possibility of replacing synthetic fibers with natural fibers is another step towards creating more environmentally friendly building materials and determining their characteristics. This paper investigates the possibility of manufacturing fiber-gypsum composites based on natural gypsum (building gypsum) and hemp (Cannabis sativa L.) fibers grown in Poland. The effect of introducing hemp fibers of different lengths and with varying proportions of mass (mass of gypsum to mass of fibers) into the gypsum matrix was investigated. The experimental data obtained indicate that adding hemp fibers to the gypsum matrix increases the static bending strength of the composites manufactured. The highest mechanical strength, at 4.19 N/mm2, was observed in fiber-gypsum composites with 4% hemp fiber content at 50 mm in length. A similar trend of increased strength was observed in longitudinal tension. Again, the composite variant with 4% fiber content within the gypsum matrix had the highest mechanical strength. Manufacturing fibers-gypsum composites with more than 4% hemp fiber content negatively affected the composites' strength. Mixing long (50 mm) hemp fibers with the gypsum matrix is technologically problematic, but tests have shown a positive effect on the mechanical properties of the refined composites. The article indicates the length and quantity limitations of hemp fibers on the basis of which fiber-gypsum composites were produced.

EVALUATION OF PROPERTIES OF WOOD PLASTIC COMPOSITES MADE FROM SEVEN TYPES OF LIGNOCELLULOSIC FIBERS

This article aims to investigate the characteristics of wood plastic composites (WPC) prepared from polyethylene (PE) reinforced with lignocellulosic fibers derived from the xylem and bark of Masson pine, fir, cypress, as well as from Moso bamboo. The surface polarity and elemental composition of fibers were determined through contact angle measurements and X-ray photoelectron spectroscopy (XPS). The lignocellulosic fiber/PE composites were manufactured through hot-pressing technique, and their water absorption, mechanical properties, and mildew resistance were evaluated. The results revealed that the surface free energy of xylem fibers was higher than that of bark fibers among the three conifer species. XPS analysis showed that the O/C ratio of bark was consistently lower than that of xylem fiber. Among the three conifers, the Masson pine bark had the lowest O/C ratio (22.25%), while its xylem fibers had the highest ratio of 41.64%. WPC made with bark fibers had better water resistance. Additionally, the composites reinforced with xylem fibers showed superior static bending strength, impact strength, and mildew-resistant properties as compared to the composites reinforced with bark fibers. WPC made from bamboo fibers exhibited the best water resistance, with a water absorption rate and thickness swelling rate of 1.83% and 1.42%, respectively. They also had the highest static bending strength, elastic modulus, and impact strength, at 41.31 MPa, 3.82 GPa, and 10.24 kJ/m2, respectively. The WPC made from fir xylem fibers showed the most effective mildew resistance, with the smallest damage (0.50).