Results Of Compression Tests Research Articles

Sub-regional design of the bionic bone scaffolds using macrostructural topology

With the increasing demand for bone repair, the bionic bone scaffolds have become a research hotspot. A sub-regional design method of the bionic bone scaffolds, using macrostructural topology, is proposed in this paper, aiming to provide a functionally enhanced region division method for the gradient design. The macrostructural topology was carried out by the bi-directional evolutionary structural optimization (BESO), dividing the predefined design domain into sub-region A and sub-region B. Subsequently, a combined probability sphere model and a distance-to-scale coefficient mapping model are established to implement the graded porosification based on the Voronoi tessellation. This approach takes geometric and mechanical continuity into fully account and assures a reasonable distribution of characteristic parameters, yielding to improve the mechanical strength under specific stress conditions. Finally, the scaffolds were fabricated by the laser powder bed fusion (LPBF) process using the Ti-6Al-4V powder. The results of compression tests are satisfactory, showing that the as-built specimens implement sub-regional functionality. The apparent elastic modulus and the ultimate strength range, respectively, between 1.50 GPa and 7.12 GPa (for the first module) and between 38.55 MPa and 268.03 MPa (for the second module), which conform to the required level of natural bone, providing a possibility for clinical application.

Characterization and piezo-resistivity studies on graphite-enabled self-sensing cementitious composites with high stress and strain sensitivity

Carbon-based conductive fillers have recently been incorporated into a cement matrix to develop an intrinsic self-sensing concrete for data monitoring without the need for embedded, attached, or remote sensors while maintaining or improving its mechanical properties and durability. This paper studies cementitious composites filled with graphite as a novel self-sensing construction material. Experiments were systematically conducted to investigate the dispersion, chemical, mechanical, electroconductivity and piezo-resistivity properties of the composites. Experimental results showed an effective mixing with uniform dispersion of the graphite which acted as an inert filler in the mix and did not alter the microstructure of cement hydration products. Isothermal calorimetry, TGA and rheology tests showed good hydration and adequate workability of the composites with low graphite concentration (≤ 10%), while the effect of adding graphite on the compressive strength is insignificant for graphite concentrations of up to 10%. Monotonic and cyclic compressive test results indicated a repeatable piezo-resistivity performance for low graphite concentration cementitious composites whose stress sensitivity values vary from 0.75 to 7.25%/MPa, and strain sensitivity/gauge factor (GF) 150–1250 with some hysteresis. These combinations showed a stable and reliable piezo-resistivity and the ability to detect damage upon failure.

Molecular Dynamics Simulation of High Temperature Mechanical Properties of Nano-Polycrystalline Beryllium Oxide and Relevant Experimental Verification

This article investigated the deformation behavior of nano-polycrystalline beryllium oxide under tensile and compressive stress using the molecular dynamics simulation method. Both the tensile and compressive test results indicate that beryllium oxide breaks mainly along grain boundaries. At low temperature, there is little internal deformation of beryllium oxide grains. When the temperature is above 1473 K, the internal deformation of beryllium oxide grains also occurs, and the phenomenon becomes more obvious with the increase in temperature. This deformation within the grain should be plastic. The flexural strength fracture morphology of beryllium oxide also shows that the fracture mode of beryllium oxide is a brittle fracture at low temperature, while the slip bands appear at 1773 K. This indicates that beryllium oxide, as a ceramic material, can also undergo plastic deformation under high temperature and stress.

Effect of Sandstone Compressive Strength Value on Differences in Physical Conditions in Samarinda City, East Kalimantan Province

Rock strength is the ability of a rock to maintain its strength until it breaks when given force. The purpose of this study is to determine the comparison of rock strength values in different physical conditions, namely natural, saturated, dry conditions and 2 wet-dry cycles on sandstones by testing uniaxial compressive strength according to SNI standards 2825-2008. The results of compressive strength testing at two different locations showed that the condition of the rocks around the Samarinda region was weak to moderate, with strength values at location 1 ranging from 1.61 – 14.31 MPa and at location 2 ranging from 8.26 – 36.27 MPa. The Elastic Modulus obtained at location 1 ranges from 1.88 -18.60 and at location 2 it ranges from 8.26 – 37.928. The more to the West from the city of Samarinda, the strength of the rocks is increasing. With the treatment of rocks that undergo repeated wet-dry processes, it does not cause a decrease in rock strength compared to the condition of rocks undergoing saturation. This is because the amount of water content that is large enough in saturated conditions results in weakening of the rock. The lower the water content, the stronger a rock.

Production parameters of novel geopolymer masonry mortar in heritage buildings: Application in masonry building elements

The aim of this study is to develop an innovative high-strength restoration mortar using recycled materials as an alternative to the mortars used in historical buildings. Compressive strength tests were carried out on the samples and, according to the results, the mortar giving the highest strength was determined as the optimum mixture. The compressive strength, shear strength, displacement and load-carrying capacity values of the masonry units were tested by using the geopolymer mortar with the highest strength among the mortar samples produced. The novelty of this research is that geopolymer repair mortars were produced as an alternative to standard mortars and applied in masonry building units. The results showed that blast furnace slag and brick powder can effectively improve the compressive and bond strength of the geopolymer. In the compressive strength tests performed on the samples, much higher strength results were obtained with geopolymer historical building mortar than standard historical building mortar. In the compressive and shear strength performed on the masonry units, the geopolymer historical building mortar showed higher mechanical properties compared to the standard historical building mortars. When the compressive strength test results are compared, a strength of 1.8 times was observed in the masonry unit (GHB1) produced using geopolymer historical building mortar, compared to the masonry unit (HB1) produced with standard historical building mortar. As a result of the shear strength test, the masonry unit (GHK1) produced with geopolymer mortar demonstrated seven times more load carrying capacity than the masonry unit (HK1) elements produced with standard historical building mortar. Moreover, the masonry arch systems produced with standard historical building mortar showed close load bearing capacity with the geopolymer historical building mortar, but the masonry arch element produced with geopolymer mortar exhibited a more ductile behavior. It has been determined that the use of geopolymer mortars with recycled materials with increasing molarity in masonry arch elements improves the compressive strength and accelerates the geopolymerization mechanism. Innovative high-strength geopolymer mortars used in masonry walls provided good adhesion with the hollow brick, creating a compact structure.

6A13-T6 high-strength aluminium alloy columns under axial compression: Experiments, finite element analysis and design recommendations

Novel high-strength aluminium alloy 6A13-T6 is interesting for its exceptional mechanical properties. Its mechanical performance is understudied, hindering its utilization in the construction industry. This paper reports the experimental results of material tensile and axial compression tests carried out on 8 members. After the test, the finite element models were developed by ABAQUS and validated with the test results. Then, finite element parameter analysis was carried out, and the bearing capacity was compared with the values calculated based on the codes of China and the United States. In addition, column compression's mechanical essence is explored using the finite element refined analysis method. Finally, the overall stability coefficient of the Chinese codes was modified. The results show that the nonproportional yield strength of 6A13-T6 is 340 MPa, the ultimate strength is 352 MPa, and the elongation after fracture is 14.5%, which is much better than other 6-series aluminium alloy materials. Due to the large width-thickness ratio of the section, significant local buckling occurs in all members. With the increase in the slenderness ratio, the failure mode of the member changes from local buckling failure to the coupling failure mode of global buckling and local buckling. Good ductility can fully develop the section stress, so the bearing capacity calculated by the finite element models is greater than the predicted value in the codes. With the adjusted overall stability factor calculation formula, designers and engineers can more economically design 6A13-T6 high-strength aluminium alloy axial compression members.

Micropillar compression investigation on the mechanical behavior of Ni manufactured using laser powder bed fusion

Micropillar compression tests were performed on unalloyed Ni that was manufactured using the additive manufacturing (AM) technique of laser powder bed fusion (LPBF) with micropillar diameters ranging from 1 to 3.5 μm. In all cases, the single crystalline micropillars with the <110> crystallographic orientation, aligned along the build direction of LPBF and the uniaxial compression axis, are tested. In contrast to other LPBF alloys, in which submicron-scale cellular structures decorated with dense dislocation networks are often reported, only dislocation networks with relatively sparse dislocations along the network boundaries are observed in the LPBF Ni. Results of the micropillar compression tests show that the stress-strain responses of the LPBF Ni in the plastic regime are dominated by pronounced serrations and both the yield strength and work hardening behavior are highly dependent on the pillar diameter. Microscopic observations on the deformed pillars show that that the relatively low-density of dislocations in the microstructure of the LPBF Ni do not offer a substantial resistance to the dislocation motion. This is further verified by comparing the mechanical performance of the micropillars of the LPBF Ni with those of the pre-strained Ni, nanocrystalline Ni and 316L stainless steel manufactured via the directed energy deposition AM technique.

Acupuncture for patients with Maigne's syndrome: A case series.

Diagnosing the precise etiology of low back pain (LBP) is crucial for facilitating speedy recovery in patients. Maigne's syndrome (MS), commonly referred to as thoracolumbar junction syndrome, is a condition characterized by pain resulting from nerve entrapment, yet its underlying mechanisms remain poorly understood. This study presents a series of six case reports wherein patients diagnosed with MS received acupuncture treatment. Six individuals with LBP were included in the study, and all were diagnosed with MS. The diagnosis was confirmed in all six patients through pinch-roll and thoracic vertebrae compression tests, indicating the presence of thoracolumbar junction syndrome. Acupuncture treatment was administered to all patients, primarily targeting the T11-L2 facet joints, with additional acupoints selected based on the specific nerve entrapment of MS including the superior cluneal, subcostal, and iliohypogastric nerves. Following acupuncture therapy, all patients reported improvements in their LBP symptoms, while four patients also exhibited amelioration in their thoracic vertebrae compression test results. These findings underscore the significance of promptly diagnosing the underlying cause of LBP and suggest that acupuncture may be an effective approach in alleviating MS-related pain.

Triaxial compression experiment and damage constitutive model of microbially modified strongly weathered phyllite

Microbial improvement of strongly weathered phyllite roadbed can effectively solve the problems of insufficient filling and waste soil in roadbed construction while protecting the environment and considering economic benefits. This paper uses microbially induced carbonate precipitation (MICP) technology to improve the strongly weathered phyllite in the Nanchang area and conducts the porosity and triaxial compression tests on the samples before and after the improvement. According to the strain strength theory of rock and the Druker-Prager yield criterion, the damage constitutive model of the improved sample is established considering the effects of the initial porosity and cementation degradation coefficient on the sample’s mechanical properties. The results show that the strengths of the samples improved by MICP technology are increased by more than 35%, and the porosities are reduced by 15%, which meets the requirements of roadbed filling. The stress–strain curves of the modified samples under triaxial compression can be divided into three stages: elastic stage, elastic–plastic stage and ductile flow stage. The triaxial compression test results of the improved samples show that the damage constitutive model established can describe the stress–strain relationship of the samples well, which verifies the rationality of the model. This model provides a theoretical basis for studying damage softening and mechanical properties of microbially modified strongly weathered phyllite samples.

Environmental and geotechnical properties of lightweight aggregates made of reused solid wastes

This paper presents the environmental and geotechnical characterisation of new synthetic lightweight aggregates (SLAs) composed of reused biomass fly ash and waste plastics, namely high-density and low-density polyethylene (HDPE and LDPE), with a 50:50 fly ash-to-plastic ratio by weight. One-dimensional compressibility, creep properties, compaction features and stress-strain-strength behavior of SLAs were evaluated together with hydraulic conductivity and water absorbability. The fly ash–HDPE aggregate was found to be less compressible upon loading than the companion material made of fly ash and LDPE and similar to traditional natural lightweight expanded clay aggregate. The values of creep coefficient (C αε) were slightly higher than those expected for dense sands, but comparable, or even lower, than those measured for other recycled materials. Peak friction angle (ϕ′) and cohesion intercept (c′), determined by triaxial compression tests, were in the ranges 42.3–46.3° and 1.3–8.6 kPa, respectively with the highest values concerning the fly ash–HDPE aggregate. The hydraulic conductivity (k) was around 3 × 10−4–4 × 10−4 m/s, highlighting favorable permeability properties of both aggregates. Leaching tests and thermal stability analyses proved the sustainability of both aggregates from an environmental point of view. The results obtained in the present study demonstrate the suitability of the investigated aggregates for many geotechnical applications.

Influence of Yttria stabilized zirconia coating on Inconel 625 & Hastelloy X with sodium sulphate molten salt

Molten Salts Energy Storage (MSES) is one of the prime practices with high efficiency and long extended service in thermal energy storage method. The drawback in this MSES technology is storage material is subjected to corrosion and scaling can be formed on the surfaces, since it is continuously exposing to molten salts in aggravated temperature environment. To overcome this problem, the material can be coated with thermal barrier coating. In this current effort, Inconel 625 and Hastelloy X super alloy had been trailed as storage material with Yttria stabilized Zirconia coating. The specimens were heated with sodium sulphate molten salt at 1000 °C for 10, 15 and 20 Hours. The evaluation of both uncoated and YSZ coated specimens was done with test results of Tensile, Compression, Hardness and Impact tests. The Morphological study was done with SEM images and the knowledge on scaling was XRD analysis. The YSZ coated Inconel 625 specimens produced negligible differences in the majority of the experimental test values even after 20 h of heating with sodium sulphate molten salt. The results of the SEM and XRD analyses show that YSZ coated superalloy specimens experience less corrosion and oxidation than untreated specimens. Therefore, it might be advised that specimens of Inconel 625 that have been YSZ coated maintain high levels of corrosion resistance and can be used as MSES storage materials.

A constitutive model of expansive concrete and steel fiber-reinforced expansive concrete under tri-axial compression

Expansive concrete (EC) or steel fiber-reinforced expansive concrete (SF-EC) have been adopted for enhancing the performance of concrete-filled steel tube (CFST) columns, while the investigations on confinement mechanism and theoretical model for EC and SF-EC are limited. This study aims to develop a constitutive model for EC and SF-EC under tri-axial compression. In the first part, the results of tri-axial compression tests on 52 concrete cubes, were summarized and collected to form a database. In the second part, the failure criterions of concrete cubes, and performances of four existing stress–strain models were assessed and discussed using the database. The results of tri-axial compression with equal lateral confining stresses generally complied well with the compressive meridians of Ottosen failure criterion, whereas the Lode angles were around 56°–58° for the true tri-axial compression results. However, the existing models substantially underestimated the axial strains at peak stresses by at least 40%, and thus the predicted stress–strain curves deviated considerably from the test results with much steeper initial ascending slopes. To this end, a modified constitutive model was proposed with Montoya et al.’s model as the base form and the key parameters updated as per the result database. The proposed model had good performances in predicting the peak axial stresses and the corresponding strains (average error at 8% and 19%, respectively), as well as the full axial stress–strain curves.

Empirical correlation of uniaxial compressive and shear strength of jointed granitic rock

Shear Strength of jointed rock plays a significant role in the stability of rock mass structure especially if the developments plan to be constructed adjacent to this formation. However, to get the shear strength of the rock joints is quite costly and difficult to be identified directly at site. This research is conducted to establish the relationship between uniaxial compressive strength (UCS) and shear strength of jointed granitic rock. UCS parameters are quite easily identified and common practise in any construction project such as deep foundation and tunnelling. The result of uniaxial compressive strength test and direct shear test were plotted using 5 samples of cylindrical shape and 5 jointed rock samples respectively. The linear regression analysis produces meaningful correlation with R2 value of 0.8595 and a new correlation to estimate shear strength of jointed rock has been established.

Combined Effect of Cow Dung Ash and Rice Husk Ash on Mechanical Performance of Concrete

Abstract: Rice Husk Ash (RHA) and Cow Dung Ash (CDA) are agriculturally based pozzolanic materials, these materials are available in huge quantities. This final year project report highlights and presents the results of the study on the use of Cow Dung Ash and Rice Husk Ash as partial replacement of cement in concrete. The experiments were conducted to study the impacts of adding Cow Dung Ash and Rice Husk Ash in several percentages by weight (0%, 5%, 10%, 15%, and 20%) of cement and cure for periods of 28 days before testing for compression strength. The consistency, workability, sieve analysis of aggregates were also tested in this research study. The Compressive test results are 37.75 N/mm2, 31.25 N/mm2, 31.25N/mm2 and 25.25 N/mm2 for 0%, 5%, 10% and 15% replacement of cement with Cow Dung Ash and Rice Husk Ash respectively at 28days. The Workability results gives 45mm, 49mm, 56mm, 68mm and 75mm respectively for 0%,5%, 10%, 15%, and 20% replacement of cement with Cow Dung Ash and Rice Husk Ash. The consistency test results are 0.29, 0.32, 0.36, 0.41 and 0.43 for 0%, 5%, 10%, 15% and 20% replacement of cement with Cow Dung Ash and Rice Husk Ash respectively. The bulk density results are 2452.53 kg/m3, 2370.8 kg/m3, 2380.0 kg/m3 and 2348.5 kg/m3 for 0%, 5%, 10% and 15% replacement of cement with Cow Dung Ash and Rice Husk Ash respectively. The main highlights, it should be highlighted that the more quantity of water is required to standard consistency as the percentages of Cow Dung Ash and Rice Husk Ash are added. Dung Ash and Rice Husk Ash concrete is recommended for use when a ten percentage (10%) of Cow Dung Ash and rice husk ash are not exceeded

Strength characteristics of lightweight concrete based on granular foam glass ceramics

Introduction. Over the past 20–30 years, a wide range of effective porous aggregates with a high content of glass phase of various types and low-heat-conducting lightweight concretes of various structures based on them has been developed.In recent years, JSC Research Center of Construction has developed a new highly efficient single-stage technology for the production of porous granular foam glass ceramics (UCS). It is based on the production of raw granules by mixing and granulating a highly porous powder of opal-cristobalite rock with a sodium-containing solution. This ensures the maximum area of the interfacial boundary, the most uniform distribution of all components at the micro level and, as a result, ensures glass formation at a temperature that does not exceed the foaming interval of the finished glass phase.The aim of the publication is to study the problems of the features of the strength characteristics of lightweight concrete on granular foam glass ceramics.Materials and methods. The strength of cubes made of light concrete on the UCS under compression (R) was determined on samples with a size of 10 × 10 × 10 cm and 7 × 7 × 7 cm according to State Standard 10180-2012 with an assessment of strength according to State Standard 18105-2018.The prismatic strength coefficient (Kpp) was determined by the results of compression tests of samples-prisms with dimensions of 10 × 10 × 40 cm and 7 × 7 × 28 cm and samples made from the same batch-cubes with dimensions of 10 × 10 × 10 cm and 7 × 7 × 7 cm.Bending tensile strength (Rtb) (Figure 2) and splitting strength (Rtt) were determined, respectively, on 10 × 10 × 40 cm prism samples and 10 × 10 × 10 cm cube samples according to State Standard 10180-2012 with an assessment of strength values according to State Standard 18105-2018.Axial tensile strength (Rtb) and splitting strength (Rtt) were determined, respectively, on prism samples measuring 7 × 7 × 28 cm according to State Standard 10180-2012. The strength of the prisms (prismatic strength, Rb) was determined on samples of prisms 10 × 10 × 40 cm according to State Standard 24452-80.Results. The article presents the results of experimental and theoretical studies of the basic strength properties of thermal insulation and structural-thermal insulation lightweight concrete on granulated foam ceramic (UCS) with a density of 500 to 800 kg/m3, as well as structural lightweight concrete with a density of up to 1700 kg/m3 of optimal compositions (prismatic compressive strength, prismatic strength coefficient, axial tensile strength, tensile strength during bending and splitting).Various dependencies on the evaluation of the experimental data obtained are analyzed and recommendations are given for inclusion in regulatory documents, in particular, in SP 351.1325800.2017 "Concrete and reinforced concrete structures made of light concrete. Design rules".Conclusions. Experimental data have been obtained on a higher prismatic strength coefficient for lightweight concrete at the UCS, which in the future may be the basis for increasing the standard design strength resistance under axial compression for this type of lightweight concrete.The values and formulas for determining the prismatic strength and the prismatic strength coefficient of light concrete of the tested compositions at the UCS can be used in the calculation and design of large-format wall panels of a new type.Experimental and calculated data on the tensile strength of the tested compositions of lightweight concrete of a porous structure at the UCS have been obtained, which can be taken into account when adjusting regulatory documents.When using lightweight concrete of a porous structure on the UCS to increase the shrinkage crack resistance of such concrete for enclosing structures, it is advisable to use dispersed reinforcement with polymer fiber, which also increases the heat-protective properties of such structures. The article presents the results of studies of the main strength properties of thermal insulation and structural-thermal insulation lightweight concretes on the UCS with a density of 500 to 800 kg/m3, as well as structural lightweight concretes with a density of up to 1700 kg/m3 of optimal compositions.Various dependencies on the evaluation of the experimental data obtained are analyzed and recommendations are given for inclusion in regulatory documents, in particular, in SP 351. 1325800.2017 "Concrete and reinforced concrete structures made of light concrete. Design rules".

Constructing processing map of M50NiL steel by artificial neural network model

The processing map for M50NiL steel was established by hot compression tests at temperatures of 950–1150 °C and strain rates of 0.002–1.0 s−1. Based on the experimental results of hot compression tests, the predictability in both reproducing experimental flow stresses and predicting flow stresses using the Arrhenius, physical-based, and artificial neural network (ANN) models was compared. The results showed that the average absolute relative errors of Arrhenius, physical-based, and ANN models in both reproducing and predicting flow stresses were 6.04 % and 8.01 %, 6.61 % and 7.78 %, and 1.91 % and 4.74 %, respectively. The ANN model had a considerably higher accuracy in reproducing and predicting flow stresses than the other two models. In addition, a processing map of M50NiL steel was established using the predicted flow stresses by the ANN model. This processing map indicated that the optimized processing parameters were 975–1050 °C/0.01–0.002 s−1. Instability occurred during deformation at 950–975 °C at 1.0 s−1 and 1075–1150 °C at 0.01 s−1. The instability prediction was verified by the microstructure evolution.

Design, Preparation, and Mechanical Property Investigation of Ti–Ta 3D‐Auxetic Structure by Laser Powder Bed Fusion

In recent years, Ti–Ta alloy has become a hot material in orthopedic implants. At the same time, the metal lattice structure with a negative Poisson's ratio has a great prospect in the application of implants due to its unique mechanical properties. Herein, an antichiral three‐dimensional polyhedron (A3P) lattice structure with negative Poisson's ratio is designed. This lattice structure is prepared by laser powder bed fusion (LPBF) technology using Ti–Ta alloy as the feedstock material. The surface morphology and relative density of the Ti–Ta samples built with different laser scanning speeds are compared for the optimization of the Ti–Ta's LPBF parameter. Then, the A3P structure of the Ti–Ta alloy is fabricated using the optimized LPBF parameters. The negative Poisson's ratio effect of the A3P structure is verified by finite element analysis (FEA) and compared with experimental results. The compression test results show that the yield strength and elastic modulus of the A3P structure are 9.2 MPa and 0.14 GPa, respectively, which is suitable for the orthopedics application. A3P structure has higher fracture energy compared with diamond structure, indicating it can absorb more energy in the fracture process. A3P shows a promising prospect in the application of orthopedics implantation.

Evaluation of Mechanical Properties and HPM Pulse Shielding Effectiveness of Cement-Based Composites

In today’s world, protection against electromagnetic waves, including high-power microwave (HPM) pulses, is becoming increasingly important. Hence, the aim of this research was to select an absorbing admixture, which, when used in an appropriate quantity, improves the effectiveness of shielding against electromagnetic waves and, at the same time, satisfies the requirements that are important from a construction engineering point of view. Altogether, eighteen admixtures (including two types of fibers), added in different quantities, and three types of aggregate have been tested. The compressive and flexural strength test results show that the greatest improvement in the tested mechanical properties was achieved in the case of admixtures such as steel fibers, carbon black P803, ferrite, and fly ash. Regarding the effect of the admixtures on shielding effectiveness, the best results were obtained for graphite in the form of flakes, graphite in the form of powder, carbon black N990 and P803, polypropylene and steel fibers, and hybrid admixtures, i.e., ashporite aggregate with carbon black and ashporite aggregate with graphite flakes. Regarding both mechanical properties and HPM pulse shielding effectiveness, the best effects were achieved in the case of the specimens with a high steel fiber content.

Experimental Study of Mechanical Properties and Failure Characteristics of Coal-Rock-like Composite Based on 3D Printing Technology.

Coal contains cracks and has strong heterogeneity, so the data dispersion is large in laboratory tests. In this study, 3D printing technology is used to simulate hard rock and coal, and the rock mechanics test method is used to carry out the coal-rock combination experiment. The deformation characteristics and failure modes of the combination are analyzed and compared with the relevant parameters of the single body. The results show that the uniaxial compressive strength of the composite sample is inversely proportional to the thickness of the weak body and directly proportional to the thickness of the strong body. The Protodyakonov model or ASTM model can be used as a verification method for the results of a uniaxial compressive strength test of coal-rock combination. The elastic modulus of the combination is the equivalent elastic modulus, and the elastic modulus of the combination is between the elastic modulus of the two constituent monomers, which can be analyzed using the Reuss model. The failure of the composite sample occurs in the low-strength material, while the high-strength section is rebounding as an extra load on the low-strength body, which may cause a sharp increase in the strain rate of the weak body. The main failure mode of the sample with a small height-diameter ratio is splitting, and the failure mode of the sample with a large height-diameter ratio is shear fracturing. When the height-diameter ratio is not greater than 1, it shows pure splitting, and when the height-diameter ratio is 1~2, it shows a mixed mode of splitting and shear fracture. The shape has a significant effect on the uniaxial compressive strength of the composite specimen. For the impact propensity, it can be determined that the uniaxial compressive strength of the combination is higher than that of the single body, and the dynamic failure time is lower than that of the single body. It can hardly determine the elastic energy and the impact energy of the composite with the relationship to the weak body. The proposed methodology provides new cutting-edge test technologies in the study of coal and coal-like materials, with an exploration of their mechanical properties under compression.

Enhanced mechanical property and freeze-thaw stability of alkali-induced heat-set konjac glucomannan hydrogel through anchoring interface effects of carboxylated cellulose nanocrystals

The alkali-induced heat-set konjac glucomannan (KGM) hydrogels have drawn increasing attention due to their high absorbency and thermal irreversibility ability, but pure KGM hydrogels generally have defects of low strength and high syneresis rate. Cellulose nanocrystals and their derivatives, which have a very high specific surface area, good biocompatibility, biodegradability, and low toxicity, are promising candidates to solve this challenge. In this work, we propose the use of carboxylated cellulose nanocrystals (C–CNCs) as nanofillers for the strengthening of KGM hydrogels. The effects of the C–CNCs content on the microstructure and physical properties of the KGM hydrogels and their possible mechanism were investigated. The compressive test results indicate great improvement in the mechanical properties upon the addition of the C–CNCs for the KGM hydrogel and reached a maximum value at 20% loading. The microstructure analyses of the KGM hydrogel revealed that the well-distributed C–CNCs can act as a physical cross-linker to connect the neighboring KGM chains to strengthen the resultant hydrogel, based on their strong interactions, including hydrogen bonding and chain entanglements. Moreover, adding 20% C–CNCs can significantly decrease the syneresis after five repeated freeze-thaw cycles of the KGM hydrogels. Compared to pure KGM hydrogels, KGM/C–CNCs nanocomposite hydrogels demonstrated higher water-binding capability based on Low-field nuclear magnetic resonance. These findings indicate that C–CNCs are considered anchors for KGM chains as well as reinforcement fillers in the polymer matrix, which contributes significantly to the mechanical property of the nanocomposite. Therefore, C–CNCs were a promising material to be applied for modulating the mechanical and freeze-thaw stability properties of the polysaccharide-based hydrogel in food and biomedical applications.