scholarly journals Modern testing machines for investigation of wood and timber-based composite materials

2021 ◽  
pp. 73-80
Author(s):  
С.С. Гомон ◽  
В.О. Савчук ◽  
Ю.А. Мельник ◽  
О.В. Верешко
Keyword(s):  
Composite Materials ◽  
Testing Machine ◽  
Measuring Instruments ◽  
Strain Diagram ◽  
Timber Species ◽  
Recording Device ◽  
Stress Strain ◽  
Test Mode ◽  
Deformation Properties ◽  
Strength And Deformation

A detailed analysis of test machines and presses operating in both soft (increasing loads) and hard test mode (displacement increase) has been performed. The results of tests of deciduous, coniferous and tropical timber species on modern test machines of foreign production under a strict test regime were analyzed. The results of tests of timber and concrete on advanced presses of old production with the help of additional equipment are also given and analyzed. With the help of such equipment it is possible to build a "stress-strain" diagram completely on the ascending branch and partially on the descending branch. And also allows you to more widely establish the strength and deformation properties of concrete and timber. It was found that the influence of age on the main strength and deformation parameters has not been studied. In recent decades, testing machines and presses have begun to appear, which allow to investigate these or those materials from the beginning of loading and to its full destruction. That is, to analyze the work of different materials (metal, timber, concrete, etc.) on the ascending and descending branches, and in particular in the so-called supercritical stage of work. At the end of the 20th century, scientists developed electromechanical and servo-hydraulic universal testing machines, which make it possible to test samples from the beginning of loading until complete destruction (rigid test mode for incremental displacements), while fixing all the necessary strength and deformation indicators on the ascending and descending branches of the diagram "stress - strain", setting the necessary modes and loading speeds. Measuring instruments determine the forces and deformations at different stages of testing and transmit the measurement results to the recording device or means of information accumulation. The characteristics of modern testing machines, in particular electromechanical and servo-hydraulic, are given: WDW (Time Group Inc.), INSTRON (USA), REM (Russia), LFM (Switzerland). The possibilities of the STM-100 servo-hydraulic testing machine for the study of timber and composite materials based on it are described in detail..

scholarly journals INFLUENCE OF INCREASED TEMPERATURE ON THE DYNAMIC PROPERTIES OF ASPEN

2021 ◽  
Vol 83 (1) ◽  
pp. 5-21
Author(s):  
A.M. Bragov ◽  
A.Yu. Konstantinov ◽  
A.K. Lomunov ◽  
T.N. Yuzhina
Keyword(s):  
Experimental Data ◽  
Elevated Temperatures ◽  
Dynamic Properties ◽  
Stress Strain ◽  
Horizontal Section ◽  
Mean Values ◽  
Damping Material ◽  
Deformation Properties ◽  
Relaxation Of Stresses ◽  
Strength And Deformation

As a damping material in the structures of containers for the transportation of hazardous materials, along with plastic metals, fiber-claydite concrete and synthetic foams, it is proposed to use wood of different species. Since containers are transported in different climate regimes, there is an urgent need to study the properties of wood at elevated temperatures. The paper presents the results of dynamic tests of aspen under uniaxial compression under conditions of temperature increased to +60°C. The tests were carried out according to the Kolsky method on a Hopkinson split-bar setup. To study the anisotropy of properties, aspen samples were made and tested by cutting samples along and across the direction of the grains. As a result of processing the experimental data, dynamic stress-strain curves were obtained. According to the experimental data, there are determined the stresses at which the integrity of the samples were violated. The mean values of the moduli of deformation in the active loading regions of stress-strain curves are also presented. The highest slope of the load sections and the highest breaking stresses were observed for the specimens when loaded along the grains, and the smallest values of these parameters were noted when loaded across the grains. For specimens loaded along grains at strain rates above 1500 s–1, after reaching the limiting stress values, a decrease (relaxation) of stresses is observed with increasing deformations. For specimens loaded across the grains, an almost horizontal section the diagrams of deforming or even with some strengthening is more typical. The effect of elevated temperature on the strength and deformation properties of aspen is estimated. There is a tendency towards some decrease in the diagrams at a temperature of +60 °C in comparison with the diagrams at room temperature. In this case, both the moduli in the loading and unloading sections and the limiting (breaking) stresses decrease. The obtained features of the behavior of aspen specimens at elevated temperatures should be taken into account when modeling deforming wood.

The Ways to Develop Steel Reinforcing and Concrete Cohesion Testings

2018 ◽  
Vol 931 ◽  
pp. 624-627
Author(s):  
Lyubov V. Morgun ◽  
Anton V. Visnap ◽  
Vladimir N. Morgun
Keyword(s):  
Corrosion Resistance ◽  
Composite Materials ◽  
Carbon Fiber ◽  
Experimental Evaluation ◽  
Strength Assessment ◽  
Real Nature ◽  
Reinforced Polymer ◽  
Deformation Properties ◽  
Strength And Deformation ◽  
Compatibility Of Materials

The article oversees the topicality of an appropriate strength assessment of bonding of steel reinforcing rod with concrete. It is shown that in the technology of reinforcing concrete framing, metal reinforcing has seen a new alternative in the form of fiberglass, basalt plastic reinforced polymer and carbon fiber. Efficiency of application of reinforcing construction made of composite materials includes not only increased corrosion resistance, but also better compatibility of materials in strength and deformation properties. The article suggests experimental evaluation of the adhesion of the steel reinforcing with concrete to account for its real nature.

New Autographic Machine for Testing Tensile Properties of Rubber

1931 ◽  
Vol 4 (4) ◽  
pp. 591-600
Author(s):  
George J. Albertoni
Keyword(s):  
Tensile Strength ◽  
Tensile Properties ◽  
Cross Section ◽  
Test Piece ◽  
Testing Machine ◽  
Recording Device ◽  
Stress Strain ◽  
Strength Of Materials ◽  
Considerable Deformation

Abstract A description is given of a testing machine for the measurement of the tensile strength of materials having considerable deformation, such as rubber. A stress-strain recording device is described in which the strain recorded responds to the separation between a pair of independently movable pointers which may be made to follow the separation of two marks, spaced upon the sample before insertion in the machine. Mechanical means are also described to correct for variations in the test-piece cross section, and to produce equal chart displacements for equal angular deviations of the inclination balance.

scholarly journals A General Temperature-Dependent Stress–Strain Constitutive Model for Polymer-Bonded Composite Materials

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1393
Author(s):  
Xiaochang Duan ◽  
Hongwei Yuan ◽  
Wei Tang ◽  
Jingjing He ◽  
Xuefei Guan
Keyword(s):  
Composite Materials ◽  
Constitutive Model ◽  
Model Parameters ◽  
Temperature Dependent ◽  
Stress Strain ◽  
Proposed Model ◽  
Single Temperature ◽  
Testing Data ◽  
Bonded Composite ◽  
Tension And Compression

This study develops a general temperature-dependent stress–strain constitutive model for polymer-bonded composite materials, allowing for the prediction of deformation behaviors under tension and compression in the testing temperature range. Laboratory testing of the material specimens in uniaxial tension and compression at multiple temperatures ranging from −40 ∘C to 75 ∘C is performed. The testing data reveal that the stress–strain response can be divided into two general regimes, namely, a short elastic part followed by the plastic part; therefore, the Ramberg–Osgood relationship is proposed to build the stress–strain constitutive model at a single temperature. By correlating the model parameters with the corresponding temperature using a response surface, a general temperature-dependent stress–strain constitutive model is established. The effectiveness and accuracy of the proposed model are validated using several independent sets of testing data and third-party data. The performance of the proposed model is compared with an existing reference model. The validation and comparison results show that the proposed model has a lower number of parameters and yields smaller relative errors. The proposed constitutive model is further implemented as a user material routine in a finite element package. A simple structural example using the developed user material is presented and its accuracy is verified.

scholarly journals Acoustic Emission and K-S Metric Entropy as Methods for Determining Mechanical Properties of Composite Materials

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 145
Author(s):  
Lesław Kyzioł ◽  
Katarzyna Panasiuk ◽  
Grzegorz Hajdukiewicz ◽  
Krzysztof Dudzik
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Composite Material ◽  
Composite Materials ◽  
Testing Machine ◽  
Measurement Data ◽  
Entropy Method ◽  
Displacement Sensor ◽  
Metric Entropy ◽  
Plastic Phase

Due to the unique properties of polymer composites, these materials are used in many industries, including shipbuilding (hulls of boats, yachts, motorboats, cutters, ship and cooling doors, pontoons and floats, torpedo tubes and missiles, protective shields, antenna masts, radar shields, and antennas, etc.). Modern measurement methods and tools allow to determine the properties of the composite material, already during its design. The article presents the use of the method of acoustic emission and Kolmogorov-Sinai (K-S) metric entropy to determine the mechanical properties of composites. The tested materials were polyester-glass laminate without additives and with a 10% content of polyester-glass waste. The changes taking place in the composite material during loading were visualized using a piezoelectric sensor used in the acoustic emission method. Thanks to the analysis of the RMS parameter (root mean square of the acoustic emission signal), it is possible to determine the range of stresses at which significant changes occur in the material in terms of its use as a construction material. In the K-S entropy method, an important measuring tool is the extensometer, namely the displacement sensor built into it. The results obtained during the static tensile test with the use of an extensometer allow them to be used to calculate the K-S metric entropy. Many materials, including composite materials, do not have a yield point. In principle, there are no methods for determining the transition of a material from elastic to plastic phase. The authors showed that, with the use of a modern testing machine and very high-quality instrumentation to record measurement data using the Kolmogorov-Sinai (K-S) metric entropy method and the acoustic emission (AE) method, it is possible to determine the material transition from elastic to plastic phase. Determining the yield strength of composite materials is extremely important information when designing a structure.

Mechanical characterization of a woven multi-layered hyperelastic composite laminate under uniaxial loading

2021 ◽  
pp. 002199832110115
Author(s):  
Shaikbepari Mohmmed Khajamoinuddin ◽  
Aritra Chatterjee ◽  
MR Bhat ◽  
Dineshkumar Harursampath ◽  
Namrata Gundiah
Keyword(s):  
Composite Materials ◽  
Energy Function ◽  
Strain Energy ◽  
Strain Energy Function ◽  
Mechanical Tests ◽  
Stress Strain ◽  
Aerospace Applications ◽  
Envelope Material ◽  
The Individual ◽  
High Dielectric

We characterize the material properties of a woven, multi-layered, hyperelastic composite that is useful as an envelope material for high-altitude stratospheric airships and in the design of other large structures. The composite was fabricated by sandwiching a polyaramid Nomex® core, with good tensile strength, between polyimide Kapton® films with high dielectric constant, and cured with epoxy using a vacuum bagging technique. Uniaxial mechanical tests were used to stretch the individual materials and the composite to failure in the longitudinal and transverse directions respectively. The experimental data for Kapton® were fit to a five-parameter Yeoh form of nonlinear, hyperelastic and isotropic constitutive model. Image analysis of the Nomex® sheets, obtained using scanning electron microscopy, demonstrate two families of symmetrically oriented fibers at 69.3°± 7.4° and 129°± 5.3°. Stress-strain results for Nomex® were fit to a nonlinear and orthotropic Holzapfel-Gasser-Ogden (HGO) hyperelastic model with two fiber families. We used a linear decomposition of the strain energy function for the composite, based on the individual strain energy functions for Kapton® and Nomex®, obtained using experimental results. A rule of mixtures approach, using volume fractions of individual constituents present in the composite during specimen fabrication, was used to formulate the strain energy function for the composite. Model results for the composite were in good agreement with experimental stress-strain data. Constitutive properties for woven composite materials, combining nonlinear elastic properties within a composite materials framework, are required in the design of laminated pretensioned structures for civil engineering and in aerospace applications.

The mechanical behavior of the Kettle Point oil shale

1986 ◽  
Vol 23 (1) ◽  
pp. 87-93 ◽  
Author(s):  
Maurice B. Dusseault ◽  
Matthias Loftsson ◽  
David Russell
Keyword(s):  
Oil Shale ◽  
Clay Content ◽  
Organic Content ◽  
Point Load ◽  
Brazilian Test ◽  
Point Load Strength ◽  
Triaxial Strength ◽  
Deformation Properties ◽  
Strength And Deformation ◽  
Oil Shales

Samples of eastern black shale (Kettle Point oil shales, Ontario) were subjected to extensive mineralogical and geomechanical tests. We prove that the mineralogy, as measured by the ratio of quartz to illite, controls strength and deformation properties, and the organic material plays no significant role. The reason is that increasing clay content dilutes the rigid quartz–quartz grain contacts that are responsible for the high strengths and stiff behavior. Tests of temperature effects on point load strength of another low organic content oil shale confirm that organic matter is not important to mechanical properties in matrix-supported shales. Key words: shale, mineralogy, Brazilian test, triaxial strength, organic content, slake durability, thermogravimetry.

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