Maximum Load Values Research Articles

Prediction of Flexural Properties of Wood Material Reinforced with Various FRP Fabrics by Artificial Neural Networks

Recently, fiber reinforced polymer (FRP) applications have started to be used in the reinforcement of wooden structures, such as in the reinforcement of steel and reinforced concrete structures. It is necessary to strengthen the wooden structures for reasons such as removing the damages caused by external factors and earthquakes in time, increasing the load-bearing capacity of the structure by restoration, preventing early fatigue and breakages that may occur as a result of mistakes made in the design. The necessity to improve the repair and strengthening methods of the structures damaged as a result of the earthquake over time arises. In this study, the maximum load, displacement, flexural strength and modulus of elasticity of the wood material of Iroko and Ash tree species reinforced with 4 different FRP fabrics, namely carbon, glass, aramid and basalt, were determined by bending test. As a result of the experimental study, the maximum load, displacement, flexure strength and elasticity modulus values of the reinforced samples were estimated by artificial neural network (ANN). As a result, it was determined that the flexural properties of a wood material strengthened with FRP by using ANN can be predicted.

ANALISA HASIL UJI KEKUATAN TARIK, TEKAN & STRUKTUR MAKRO SAMPAH PLASTIK JENIS PET, HDPE, DAN CAMPURAN (PET+HDPE)

Plastik is a material which has difficult to decompose. Therefore, the utilization of waste into useful material is important to do. This study aims to identify the tensile strength, bending, and macro structure of recycled PET, HDPE, and PET + HDPE plastik waste mixtures and recommendations for plastik products that fit the characteristics of these plastik types. PET and HDPE plastik waste is melted with oil and reprinted into tensile and bending test samples in accordance with predetermined variations, and then the results of the fracture are analyzed in a macro structure. Based on tensile testing, the tensile strength test results have the highest stress and strain values obtained in the mixture of 40% + HDPE 60% (B2) used oil specimens of 10.58 MPa and strain values of 11.98%. The results of bending strength testing which has the highest bending stress value and maximum load value are obtained in plastik mixture specimens with 30% used oil mixture + 70% HDPE (B1) of 11.58 MPa and for maximum load values of 43.33 KN. Testing the tensile strength and bending strength of the type of plastik mixture Oil and HDPE + PET (50%: 50%), the results obtained can still not be recommended to be used as a paving block product because the value of stress, strain, bending stress, and the maximum load is still relatively low, namely for the tensile test the highest variation of stress value is 5.21 MPa, the highest variation of strain value is 5.23%, the maximum load value is 10 KN, and the highest variation of bending stress value is 40% + 60% by 4.01 MPa.

Weight loss and burst testing investigations of sintered silicon carbide under oxidizing environments for next generation accident tolerant fuels for SMR applications

Accident tolerant fuel (ATF) cladding is one of the most active area for research to advance the global contribution of nuclear energy since ATF will ensure and enhance the reactor safety allowing long refueling cycles and higher burnup. Silicon Carbide (SiC) is one material that can potentially be a solution to this long standing challenge. This study offers both computational reactor physics modeling and experimental investigation to examine the behavior of SiC in nuclear reactor environment. With recent interest in small modular reactors (SMR), this study selected SMR compact core as a reference assembly for Computational Burnup Modeling (CBM). Results of CBM suggest that SiC cladding will provide the highest burnup and maximum uranium utilization. Therefore, subsequent experimental investigations were focused on SiC only. Rhode Island Nuclear Science Center (RINSC)’s nuclear research reactor was used to investigate effects of irradiation on sintered tubular SiC material samples under pure steam at 1 atm, initially at 120 °C, followed by high temperatures between 850 °C and 1350 °C to simulate harsh reactor environment.Experimental analyzes of (a) weight loss and (b) burst testing are considered for SiC samples. For the weight loss experiment, we have considered both types of samples: (1) Non-irradiated and (2) Neutron-irradiated samples. Weight loss was found to be dependent on sample geometry. Irradiated samples show ∼2%–10% higher weight loss per area than that of the non-irradiated samples. Besides, considering the medium flow rate (less than 10 g/min), it has been observed that the irradiated samples exhibit ∼10%–40% higher weight loss than that of the non-irradiated samples over temperatures of 120 °C, 850 °C to 1350 °C. It is also seen that material loss rates are generally more sensitive at higher temperatures than at lower temperatures, and irradiated samples are more prone to weight loss. Furthermore, for the burst testing experimental investigations, experiments were conducted for (1) As-received samples (2) Non-irradiated samples and (3) Irradiated samples. Considering the three types of samples, it was observed that the maximum and minimum peak load values are ∼70% higher and ∼60% lower than the average peak load while fracture hoop stress is consistently ∼70%–75% higher than the internal pressure for all as-received samples. Experimental and computational investigations suggest that SiC is a viable candidate for ATF cladding material.

Artificial neural-network optimisation of nail size and spacings of plywood shear wall

ABSTRACT The racking performance of shear walls, which is one of the most important elements of light-frame wooden structures, is affected by many factors such as the type of sheathing material, thickness, fibre direction and the size and spacing of the fasteners. Determining the most suitable production parameters is extremely necessary in terms of both time and cost. Therefore, it is aimed to predict the optimum nail size and spacing that gives the best racking performance of plywood shear walls produced with different production parameters using artificial neural networks in this study. The racking performances of shear walls produced with plywood with different wood species, thickness and fibre directions were determined according to ASTM E 72 – 13a standard and the maximum load and displacement values were obtained for each wall model as a result of the test. The prediction models having the best prediction performance were determined by means of statistical and graphical comparisons. It was observed that the prediction models yielded very satisfactory results with acceptable deviations. As a result, the findings of this study could be employed effectively in the building industry to reduce time, energy and cost for experimental studies within the range of experimentation conducted.

Microstructure and mechanical properties of laser welding of AZ31B magnesium alloy and DP590 dual-phase steel with concave groove joint

A novel connection method has been explored for laser welding of AZ31B magnesium alloy and DP590 dual-phase steel, where lap joint with concave groove was added by Sn powder. The influence of groove width on the interface reaction and mechanical properties of the joint was also studied. The result show that the boundary surface of the concave groove was mainly divided into two regions. One was the laser directly irradiated area which was mainly composed of FeAl + Mg2Sn + α-Mg. As the width of the concave groove increased, the phase composition of the interface changed from FeAl + Mg2Sn + α-Mg to FeAl + FeSn + Mg2Sn + α-Mg. The other was the side boundary area of the concave groove, where a large amount of Sn was transferred from the directly irradiated area, thus the columnar Mg2Sn + α-Mg crystal grains were larger than the directly irradiated area. This interface was mainly composed of FeAl + Mg2Sn + α-Mg. The calculation results of the atomic chemical potential were shown that the Al atoms from the base material diffused to the Fe side in the Mg-Al-Sn-Fe system, which made it easier to form the FeAl phase at the interface. At the Fe interface, Fe and Sn atoms were attracted by Al atoms, which promoted the reaction between Fe atoms and Sn atoms. The maximum load value reaches 1711 N with 1.5 mm width of concave groove, representing twice enhancement compared with that with no-concave groove.

Экспериментальное исследование механических свойств ахиллова сухожилия кроликов в процессе его восстановления после травмы

Актуальность. Проблема лечения больных с повреждениями сухожилий остается нерешенной. Неудовлетворительные результаты после хирургического лечения, по данным разных авторов, составляют от 15 до 62 %. Функциональный результат после хирургического восстановления поврежденных сухожилий трудно прогнозировать из-за высокого риска образования рубцового блока, препятствующего их свободному скольжению. Спайки нарушают растяжимость сухожилий, что, в свою очередь, сказывается на их прочности. Цель: исследовать в эксперименте прочностные свойства ахилловых сухожилий после их хирургического восстановления с дальнейшим использованием различных медикаментозных препаратов. Материалы и методы. Проведены исследования механических свойств ахилловых сухожилий кроликов, на которых была создана модель их частичного повреждения путем пересечения на 1/2 диаметра. Травмированное сухожилие ушивалось сухожильным швом. В ходе эксперимента изучали 5 групп препаратов ахилловых сухожилий кроликов с пяточной костью по 3 препарата в каждой группе. 1-я группа — контрольная. После выполнения сухожильного шва рану ушивали. Во 2-й группе животным вокруг сухожильного шва вводили препарат нолтрекс. В 3-й группе вводили препарат гиалуроновой кислоты, в 4-й — препарат лидазы. 5-я группа — норма, препараты неоперированных ахилловых сухожилий интактных животных. Все животные были выведены из эксперимента на 60-е сутки. По результатам испытаний рассчитывали величину модуля упругости и предел прочности препарата. Результаты. Наибольшее удлинение под действием растягивающей нагрузки величиной 30 Н было достигнуто на препаратах неоперированных ахилловых сухожилий кроликов — 2,96 ± 0,22 мм. Наименьшая величина удлинения была получена на препаратах контрольной группы — 0,83 ± 0,37 мм. Остальные группы препаратов показали промежуточные значения. Наибольшим значением модуля упругости обладают препараты ахиллова сухожилия кроликов контрольной группы — 0,216 ± 0,123 МПа. Наименьшее значение модуля упругости выявлено при изучении нетравмированных препаратов ахиллова сухожилия — 0,051 ± 0,004 МПа. Наибольшей прочностью обладали препараты контрольной группы (величина предельно допустимой нагрузки 81,81 ± 0,34 Н). Наименьшую прочность продемонстрировали препараты нетравмированных ахилловых сухожилий кроликов (величина предельно допустимой нагрузки 69,72 ± 0,18 Н). Выводы. В процессе восстановления ахиллова сухожилия кроликов после травмы наблюдается увеличение значений показателей, характеризующих прочностные свойства тканей, — модуля упругости, предельно допустимой нагрузки и предела прочности. Величина показателей, характеризующих пластические свойства тканей, уменьшается, что может стать одной из причин развития посттравматических контрактур. Наилучшие показатели с точки зрения пластичности тканей наблюдались в группе препаратов ахиллова сухожилия кроликов, леченных с помощью гиалуроновой кислоты. Наихудшие — в контрольной группе.

Biomechanical evaluation of the pedicle screw insertion depth and role of cross-link in thoracolumbar junction fracture surgery: a finite element study under compressive loads

Introduction. The thoracolumbar junction is one of the most frequently damaged parts of the human spine when exposed to a traumatic factor. Corpectomy in combination with posterior decompression and restoration of the spinal support function is often performed using an interbody implant and posterior transpedicular stabilization to achieve adequate decompression and stabilization in severe traumatic injuries of this level. The surgery of this type is characterized by significant instability of the operated segment and determines increased requirements for the rigidity and reliability of posterior fixation. We have modeled the situation of a two-level corpectomy with subsequent replacement of bodies with a mesh implant and posterior transpedicular stabilization with 8 screws. Objective. To study the stress-strain state of the thoracolumbar spine model after resection of the Th12-L1 vertebrae with different variants of transpedicular fixation under the influence of a compressive load. Materials and methods. A mathematical finite element model of the human thoracolumbar spine has been developed, the components of which are the Th9 ‒ Th11 and L2-L5 vertebrae (vertebrae Th12-L1 are removed), as well as elements of hardware - interbody support and transpedicular system. Four variants of transpedicular fixation were modeled: using short screws and long screws passing through the cortical layer of anterior wall of vertebral body, as well as two cross links and without them. The stress-strain state of the models was studied under the influence of a vertical compressive distributed load, which was applied to the body of the Th9 vertebra and its articular surfaces. The load value was 350 N, corresponding to the weight of the upper body. Results. d It was found that transpedicular fixation of the thoracolumbar vertebrae with the use of long screws reduces the level of tension in the bone elements of the models. In the area of screw entry into the pedicle of the T10, T11, L2 and L3 vertebral arch, the load when using short screws was 3.1, 1.7, 3.9 and 12.1 MPa, respectively, when using bicortically installed screws - 2.9, 1.8, 3.8 and 10.6 MPa. The addition of two cross-links also reduces the maximum load values in critical areas of the model to a certain extent. In case of short screws combination and two cross-links, the load in these areas was 2.8, 1.7, 3.6 and 11.5 MPa, when using bicortical screws and cross-links - 2.8, 1.6, 3.3 and 9.3 MPa. The study of the stress-strain state of other parts of the model revealed a similar trend. Conclusions. The use of long screws with fixation in the cortical bone of anterior part of the vertebral bodies reduces the level of tension in the bone elements of the models. The use of cross links provides greater rigidity to the transpedicular system, that also reduces the tension in the bone tissue.

MECHANICAL BEHAVIOR OF BANANA REINFORCED EPOXY COMPOSITE BY FINITE ELEMENT METHOD

In the recent years, there is a shift in interest of engineers and researchers to natural fibres from synthetic fibres. Natural fibres have high strength, are light weight and are also inexpensive than the traditional synthetic fibres. In addition, the fibres obtained naturally are biodegradability and eco-friendly in nature. Banana fibre is a derived product by cultivation of banana fruit and thus plentiful in environment. Banana fibre is classified among the strongest naturally obtained fibre and therefore when reinforced with other few binding resins can be utilized for different applications. Epoxy resin are suitable matrix for composite creation since they have outstanding binding characteristics. The (FEA) Finite Element Analysis of epoxy-banana composite shows that the maximum value of impact, flexural and tensile load that the composite can bear is 1000 N, 900 N and 2100 N respectively. According to this investigation it can be concluded that because of their outstanding load bearing characteristics epoxy-banana composite can be utilized for several medium load industrial uses to high load industrial uses. It is observed that the composite with least volume percent of epoxy has better mechanical strength and can bear higher deformation under higher load for tensile and flexural tests and for the impact strength results, the increase in fibre % results in lower impact strength. Also, the increase in higher vol. % of epoxy results in lower stiffness and higher deflection in the specimens, except for the specimen with 40% vol. of epoxy which obtained the most optimal results.

Biomechanical behavior of endodontically treated premolar teeth restored with novel endocrown system: 3D Finite Element and Weibull analyses

ObjectiveTo date, there is no clear consensus in the literature which endocrown design with which material is the most effective treatment option to restore endodontically treated maxillary premolars with extensive loss of tooth structure. The aim of this study was to evaluate the stress distribution pattern and failure probability of maxillary first premolars restored with a novel endocrown system compared to the conventional one by means of Finite Element and Weibull analyses. Materials and methodsTwo finite element (FE) models representing two endocrown systems used for restoration of severely-destructed endodontically treated maxillary first premolar tooth were generated: model C for the conventional monolithic IPS e.max CAD endocrown and model P for the novel bi-layered endocrown (PEKKTON ivory coping veneered with cemented IPS e.max CAD). A static occlusal compressive load was axially and centrally-applied. Modified von Mises and maximum principal stress values on the remaining tooth structure, cement lines and restorative materials were evaluated separately. Weibull function was incorporated with FE analysis to calculate the long term failure probability. ResultsRegarding stresses occurred in the remaining tooth structure (enamel and dentin), model P transmitted less stresses than model C. The individual enamel of model C showed about 5% and 40% risk of failure at normal and maximum occlusal load values, respectively, while for model P, it had no failure risk at both values. For dentin, model C showed about 13% failure risk at the normal masticatory force, while model P showed only 2%. At clenching value, model C dentin showed about 44% failure risk, while only 9% was resulted for model P. ConclusionsCompared to the conventional endocrown system, the positive impact of the studied novel endocrown system on the stress distribution pattern and also on the survival/failure probability of the restored severely-destructed endodontically treated maxillary first premolar teeth was reflected (more tooth-friendly), not only at normal masticatory forces but also at the maximum functional loads. Clinical significanceThe novel endocrown system using a PEKK coping veneered with cemented IPS e.max CAD can be considered a favorable option for restoration of severely-destructed endodontically treated premolar teeth, with more protection for residual tooth structure. Despite the conventional endocrown system may benefit the durability of tooth bonding, it should not be selected for restoration of clenching cases because of the too high overall failure risk.

Load testing and health monitoring of monolithic bridges with innovative reinforcement

PurposeThe paper aims to investigate effectiveness of the strengthening method, the construction process monitoring, fielding-load tests before and after strengthening, and health monitoring after reinforcement were carried out. The results of concrete strain and deflection show that the flexural strength and stiffness of the strengthened beam are improved.Design/methodology/approachThis paper describes prestressed steel strand as a way to strengthen a 25-year-old continuous rigid frame bridge. High strength, low relaxation steel strand with high tensile strain and good corrosion resistance were used in this reinforcement. The construction process for strengthening with prestressed steel strand and steel plate was described. Ultimate bearing capacity of the bridge after strengthening was discussed based on finite element model.FindingsThe cumulative upward deflection of the second span the third span was 39.7 mm, which is basically consistent with the theoretical value, and the measured value is smaller than the theoretical value. The deflection value of the second span during data acquisition was −20 mm–10 mm, which does not exceed the maximum deflection value of live load, and the deflection of the bridge is in a safe state during normal use. Thus, this strengthened way with prestressed steel wire rope is feasible and effective.Originality/valueThis paper describes prestressed steel strand as a way to strengthen a 25-year-old continuous rigid frame bridge. To investigate effectiveness of the strengthening method, the construction process monitoring, fielding-load tests before and after strengthening and health monitoring after reinforcement were carried out.

I-fiber implantation robot for composite parts

I-fiber implantation is a new stitching technology that can effectively enhance the interlayer performance of laminated composites. This paper presents and evaluates the design and implementation of the I-fiber robot implantation system integrated for producing high-performance fiber preforms for advanced composites. The system was constructed and validated through I-fiber robot implantation experimentation. It was demonstrated that automated I-fiber implantation could be achieved by use of an industrial robot. The programming method and computer-aided manufacturing software of the I-fiber implantation robot were feasible and effective. The double-cantilever-beam (DCB) experiments showed that the implantation of I-fiber significantly improved the interlaminar fracture toughness of the laminated composite, where the maximum load value increased by up to 106%. The DCB load–displacement curve presented a zigzag shape, where the peaks and valleys were the location points of the I-fiber break. It was also found that for the reinforced laminated composite without an I-fiber head, the delamination failure was manifested as resin cracking and I-fiber pullout, while for the I-fiber with a certain head length, the I-fiber failure mechanism was brittle fracture. I-fiber with a certain head length could significantly improve the interlayer performance of the composite. In addition, DCB experiments also revealed that the implantation matrix had little effect on the interlayer performance of I-fiber reinforced composites, and the failure load value and the I-fiber implantation volume showed an obvious proportional relationship.

ANALYSIS OF STRENGTH CRITERIA IN THE DESIGN OF PRODUCTS FROM COMPOSITE MATERIALS

Technological progress gives rise to the continuous expansion of the class of structural materials and the improvement of their properties. The appearance of new materials is due to the natural desire to increase the efficiency of the structures under development. One of the most striking manifestations of progress in the development of materials, structures and technology is associated with the development and application of composite materials. Composites have a number of obvious advantages over other materials, in particular over metals. Such advantages are high specific strength and rigidity, high corrosion resistance, good ability to withstand alternating loads and others. It should be noted another, perhaps the most important feature of composites - is the ability to change the properties of the material in accordance with the purpose of the structure and the nature of its load during operation.
 Under the influence of loads on the structure, its strength is estimated by the ultimate state of the materials of the structural elements. When a boundary state arises in a material, its transition to another mechanical state - elastic, plastic, or fracture state - occurs. This article aims to determine the optimal criterion for the strength of composite material that takes into account different values of ultimate stresses not only in different directions of the coordinate axes, but also to stretch and compress and further calculate the maximum allowable load for single-layer unidirectional composite material
 During the research the main properties of composite materials, methods of manufacturing parts from composite material, their main properties and methods of destruction were considered. The characteristics of the strength criteria of composite materials are given, the most suitable for calculating the maximum value of the allowable load for a single-layer unidirectional composite material is determined. The proposed approach to the optimal design of elements of single-layer composite structures may be of interest to developers of numerous and analytical methods for solving problems of optimal design of more complex structures.

Behavior of an Internally Confined Hollow Reinforced Concrete Column with a Polygonal Cross-Section

The new supporting structure, internally confined hollow reinforced concrete (ICH RC), was suggested by former researchers. It maintains the material saving effect, which is the advantage of the hollow concrete structure, and it solves the brittle fracture problem of the inner wall by the inner steel pipe to make it into the 3-axis confinement state. However, until now, its design and analysis model has been limited to a circular cross-section. In this study, to expand the applicability, research and development of an ICH RC structure with a polygonal cross-section were performed. The material model was developed by defining the constraint stress in the members of the concrete and deriving a reasonable stress-strain relationship. For the column model, it was developed to predict the behavior of the polygonal ICH RC columns by analyzing the axial force-moment correlation, moment-curvature, and lateral force-displacement relationship. Each model was verified not only by comparing with the results of previous experiments but also by analyzing the results according to parameters. The maximum load and ultimate displacement values through the developed model showed the difference with the experimental results within 6% of mean error. It was verified that the proposed analytical model reasonably reflects the behavior of actual columns.

Modeling and calculation of the fatigue crack growth life in structural steels

The kinetics of fatigue crack growth has been studied in tensile testing of compact steel tensile specimens (S(T)-type) in the middle section of the kinetic diagram of fatigue fracture (fatigue crack growth diagram) under regular and irregular loading with different asymmetry and maximum load values. The samples were tested on a BISS Nano-25kN servo-hydraulic machine. Standard loading spectra typical for different technical objects exposed to alternating loading during operation were used. The values of the crack growth rate per cycle in the loading block were obtained. Parameters for assessing the character of irregular loading and crack closure, namely, the irregularity factor and crack closure coefficient were proposed. When calculating the effective value of the range of the stress intensity factor (SIF) at the crack mouth, we propose also to take into account the loading irregularity in addition to the closure coefficient. With this approach, the obtained fatigue crack growth diagrams can be grouped into one equivalent curve, which is characteristic of regular loading with R = 0. Moreover, grouping of the fatigue crack growth diagrams provided the use of unified parameters when calculating the crack growth kinetics, regardless of the type and parameters of loading, which rather simplified the crack growth determination. The fatigue crack growth life was predicted taking into account the crack «closure» and the nature of loading according both to the approach developed by the authors and by cyclic calculation method (cycle-by-cycle). All the data obtained are tabulated and classed according to the type of loading. The calculation results and experimental data showed good convergence, which was confirmed by the high values of the correlation coefficient.

PULL AND BENDING FORCE USING FIBERGLASS WR EPOXY COMPOSITE MATERIALS AND FIBER CARBON EPOXY

Bending testing is carried out in the lab. Nurtanio Adisutjipto College of Technology Yogyakarta uses the Gotech Testing Machine INC (Universal Testing Machine) UTM testing machine where the results obtained in the test are in the form of a graphic in which the maximum load value, elastic modulus, area, yield point and span have been obtained. From the results of these tests, we can compare the average value of the maximum load and the modulus of elasticity received in each specimen with variations in carbon fiber and WR fiberglass.

Study on Buckling Behavior of Glass Fiber Sandwich Structure

A range of glass fiber sandwich structures were manufactured utilizing VARI technology and hydrothermal accelerate aging tests were carried out for them at four temperatures (25°C, 40°C, 55°C, 75°C) with three durations (10 days, 20 days, 30 days). Subsequent buckling tests on these structures recognized the principal failure mode as overall buckling, additionally, interface debonding and foam shearing were observed, moreover, the maximum load value is negatively related to the above two hydrothermal parameters and decreased by 19.53% and 17.27% respectively after 30-day aging and the exposure at 75°C. Furthermore, SEM images of the structures’ surface suggest that as temperature and time increase, the resin dissolution are escalated contributing to more distinct undermining of buckling capacity.

Mechanical Properties Of Sandwich Composites Used For Aerofoil Shell Structures Of Wind Turbine Blade

The grid-scored foams contribute significantly to the overall mechanical properties of the sandwich structures, such as aerofoil shell structure of wind turbine blades which are subjected to different loads under operating conditions. The goal of the present paper is to examine the four-point bending, flatwise and edgewise compression and in-plane shear behaviour of sandwich panels composed of composite face sheets of E-glass/ bisphenol-A epoxy resin and plain and grid-scored PVC foams. The four-point bending failure load of the grid-scored foamed sandwich beams increased by 28.1% compared to the plain foamed ones. The flatwise compression strength of samples with grid-scored foam increased by 546% compared to plain foamed samples. The resin grids contributed to an increase in the flat-wise compression stress inducing the core crushing. Under the edgewise compression load, using the grid-scored foam increased the maximum load values by only about 2.9% relative to the plain foam. The reason for this small difference can be addressed as the facings are more effective in carrying the edgewise loadings. With the use of the grid-scored foam, an increase of 38.2% was obtained in-plane shear strength compared to plain foamed sandwich beams. The resin grids improved bonding between the facings and PVC foam.

Osseointegration evaluation of UHMWPE and PEEK-based scaffolds with BMP-2 using model of critical-size cranial defect in mice and push-out test

It the present study the push-out mechanical test was adopted for mouse model of implantation in critical-size cranial defects to evaluate the effectiveness of implant-skull fusion. As implants, disks of porous ultra-high molecular weight polyethylene (UHMWPE) and polyetheretherketone (PEEK) with hydroxylapatite (HA) with and without loading of recombinant bone morphogenetic protein-2 (BMP-2) were used. Implantation results were evaluated using histology and micro-computed tomography (micro-CT). In the case of both UHMWPE/HA and PEEK/HA, BMP-2 loading resulted in a significant increase in the amount of bone tissue in the implantation area, especially at the edges of the defect, and an increase in the value of BV/TV (bone volume/tissue volume) during micro-CT. There was a high correlation of BV/TV values with the maximum load and elastic modulus measured during the puch-out test. The maximum load values showed good convergence within the groups and are comparable to the maximum load values obtained by other authors in the rat model of implantation in critical-size cranial defects. An adapted push-out test can be used to evaluate the quality of osseointegration of the implanted materials.

Suggested Modifications of the ASTM D2344-16 Short-Beam Shear Test Method to Be Applied to Fiber Metal Laminates

Abstract ASTM D2344/D2344M-16, Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates, is used to test fiber-metal laminates (FMLs), although its scope is limited to high-modulus fiber-reinforced composite materials. These two groups of materials have differences in their mechanical behavior, and it is possible that this standard cannot be employed in FMLs in its current status. To verify this, short-beam shear (SBS) tests were performed in aramid aluminum laminate (ARALL) 3 4/3 specimens employing two sets of rollers diameters. One set was in accordance with ASTM D2344/D2344M-16, whereas the other made use of smaller diameters. The options to stop the tests presented in the standard were not adequate for the ARALL specimens using the normalized rollers diameters. Modifications to the standard in order to include FML specimens are suggested as follows: to include a test rig with reduced roller diameters, to observe of delamination at one side of a specimen as a new option to stop the test, and to define the short-beam strengths (Fsbs) as that corresponding to the maximum load value observed previous to a total load drop-off of 30 %. The difference between the means of Fsbs obtained with both set of rollers was not significant when using these modifications.

Bending Strength of Wood Treated with Propolis Extract and Silicon Compounds.

The modification of wood and its treatment with various preservatives may affect its mechanical properties, hence the knowledge of the character changes in wood caused by impregnation is of great importance. Therefore, the aim of the research was to determine the effect of impregnation, with the propolis-silane preparation (EEP-MPTMOS/TEOS) consisting of the propolis extract (EEP) and silicon compounds: 3-(trimethoxysilyl)propyl methacrylate (MPTMOS) and tetraethoxysilane (TEOS), on the bending strength of treated wood. Moreover, in the study wood treated with components of the propolis-silane formulation was used, namely 70% ethanol, the propolis extract, and silanes (MPTMOS/TEOS). In order to determine whether the impregnation of wood affects its long-term bending, creep tests were performed depending on the humidity. The impregnation of wood with the propolis extract and the propolis-silane preparation (EEP-MPTMOS/TEOS) contributed to the increase in modulus of rapture and work to maximum load values compared to the untreated wood. In dry wood condition, the wood treated with EEP and EEP-MPTMOS/TEOS was characterized by lower modulus of elasticity values than the control samples. In turn, in wet wood condition, wood treated with the propolis-silane preparation showed an increase in the MOE value. Moreover, the impregnation of wood had an influence on the wood creep process under bending loads. The treated wood was characterized by higher relative creep compliance than the untreated wood. The exception was the wood impregnated with EEP-MPTMOS/TEOS, which showed comparable relative creep compliance to the control samples. The presented results indicate that wood treated with a bio-friendly preparation based on propolis and silicon compounds can be used in various application and also in variable humidity conditions.