Tension Modulus Research Articles

Natural coil springs: Biomechanics and morphology of the coiled tendrils of the climbing passion flower Passiflora discophora

Tendrils of climbing plants possess a striking spring-like structure characterized by a minimum of two helices of opposite handedness connected by a perversion. By performing tensile experiments and morphological measurements on tendrils of the climbing passion flower Passiflora discophora, we show that these tendril springs act as coil springs within the plant's attachment system and resemble technical coil springs. However, tendril springs have a low spring index and a high pitch angle compared with typical metal coil springs resulting in a more complex loading situation in the plant tendrils. Moreover, the tendrils undergo a drastic shift from the fresh turgescent stage to a dried-off and dead senescent stage. This entails changes in material properties (elastic modulus in tension), morphology (tendril and helix diameter, number of windings), anatomy (tissue composition), and failure behavior (susceptibility to delamination) and reduces the degree of elasticity and strain at failure of the tendrils. Nevertheless, senescent tendrils remain functional as springs and maintain high energy dissipation capacity and high break force. This renders the system highly energy efficient, as the plant no longer needs to metabolically sustain the died-back tendrils. Because of its energy-storing spring system, its high energy dissipation and high safety factor, the attachment system can be considered a ‘fail-safe’ system. Statement of significanceThe use of coil springs as mechanical devices is not restricted to man-made machinery; striking spring structures can also be found within the attachment systems of climbing plants. Passiflora discophora climbs by using long thin tendrils with adhesive pads at their tips. Once the pads have attached to a support, the tendrils coil and form a spring-like structure. Here, we analyze the form and mechanics of these ‘tendril springs’, compare them with conventional technical coil springs, and discuss changes in the tendril springs during plant development. We reveal the main features of the attachment system, which might inspire new artificial attachment devices within the emerging field of plant-inspired soft-robotics.

Large deformation problem of hyperbolic shallow shells with bimodular effect: A perturbation‐variation method

AbstractAs an important analytical method, the perturbation‐variation method combines the advantages of perturbation method and variational method, and is widely used for the solution of nonlinear plate and shell problems. In this study, the perturbation‐variation method is used to solve the large deformation problem of a flexible hyperbolic thin shallow shells with different moduli in tension and compression (bimodular effect). First, we establish the governing equations expressed in terms of three displacement components, in which the bimodular effect of materials is considered in physical equations and the large deformation of shell is considered in geometrical equations. Next, we use the perturbation‐variation method to solve the governing equations established, obtaining the perturbation‐variation solution up to third‐order. During the application of the method, the displacements are expressed into perturbation formulas of all levels first, and the unknown constants and functions in the perturbation formulas are determined by the extreme value conditions of the functional established (variational principle), hence the perturbation‐variation method gets its name from this practice. The numerical results from FEM basically agree with the perturbation‐variation solution obtained. The method proposed may be extended into the solution of similar partial differential equations established in applied fields.

欧李采后在不同温度下的力学特性研究分析

In this study,the mechanical properties of three varieties of cerasus humilis at different temperatures were systematically investigated by whole fruit puncture test, exocarp uniaxial tensile test and mesocarp uniaxial compression test.It was found that puncture test could not only reflect the shear mechanics of the exocarp in vivo at the tissue level, but also characterize the resistance level of fruit to puncture damage at the macro level.The environmental temperature had significant negative and positive effects on puncture failure stress and puncture failure deformation of cerasus humilis (p<0.05).The stress and elastic modulus of exocarp tension and mesocarp compression were significantly affected by ambient temperature (p<0.05).This study combined with temperature change to study the mechanical properties of cerasus humilis provides a necessary theoretical basis for the prediction of fruit damage and the development of postharvest treatment equipment.

Comparative experimental investigation on mechanical properties of bamboo scrimber and SPF

This paper presents a comparative experimental investigation of the mechanical properties for bamboo scrimber and spruce-pine-fir (SPF) clear specimens. The primary mechanical properties that were measured and compared included the strengths and moduli in bending, tension, compression, and shear, as well as the Poisson's ratios. The stress–strain curves and failure modes were also presented and compared. The experimental results demonstrated that, for the same category of strength and modulus, bamboo scrimber exhibited values approximately 0.5–5.5 times and 1.2–10.4 times higher than those of SPF, respectively. Bamboo scrimber specimens exhibited greater deformation at the ultimate states compared to SPF specimens. Furthermore, based on the bootstrap method, the characteristic values of the strengths and moduli for both bamboo scrimber and SPF in bending, tension, compression, and shear were determined. The results presented in this paper provide a clearer and more direct comparison of the mechanical property differences between bamboo scrimber and SPF, offering a fundamental reference for theoretical calculations and finite element simulations involving structures made from bamboo scrimber, SPF, and their composites.

A testing theory for simultaneously determining asphalt mixture’s dynamic modulus in compression and tension by use of IDT test

The compressive and tensile moduli of asphalt mixtures are not equal. As a result, in order to obtain reasonable response calculation results, asphalt pavement mechanical analysis should first determine the compressive and tensile moduli of asphalt mixtures separately. Then, it should assign an appropriate modulus to the FEM element based on the stress state of the element. However, conventional uniaxial compression modulus testing protocol is typically unable to determine the actual asphalt pavement's coring specimen due to the limitation that general dynamic modulus testing protocol requires a larger size of specimen and conventional coring specimen from field usually cannot meet the requirement in regard to specimen size. In this case, the dynamic modulus of the asphalt mixture can only be ascertained using the IDT test method.Nevertheless, the current IDT test protocol is unable to distinguish between the compressive and tensile moduli of asphalt mixtures, and the testing results are usually different from those obtained by using the conventional uniaxial compression or tension method. This is because the current IDT test method for determining the dynamic modulus of asphalt mixtures generally treats asphalt mixtures as a kind of ideal elastic material and considers its compressive modulus is equal to its tensile modulus.Consequently, this paper presents a new theory, based on Ambartsumyan's bi-modulus constitutive relation theory, that can use the IDT test method to simultaneously determine the dynamic modulus of an asphalt mixture in both compression and tension. This theory assumes that the stress-strain relationship of asphalt mixture complies with the bi-modulus constitutive relation, and obtains the vertical deformation or horizontal deformation of the IDT specimen by solving a definite integral for the displacement of a small segment on the vertical or horizontal axis, which utilizes the results of the mathematical analysis of the stress distribution of the IDT specimen under distributed strip load. Then, the specimen's dynamic modulus in compression and tension can be obtained via back-calculating method, if the specimen's vertical and horizontal displacement are measured by a physical test in the lab. Obviously, this theory addresses the limitation of the conventional IDT method that cannot reflect the distinction of compressive modulus with tensile modulus, and can be better utilized to simultaneously determine compressive and tensile modulus of cored specimen from field. The verification test also demonstrates, the dynamic modulus determined by this theory are in line with the results of the conventional uniaxial test and is highly practicable.

Investigation of meso-mechanical properties of Jinping dolomitic marble based on flat-joint model

Brittle rock has the mechanical characteristics of a high ratio of uniaxial compressive strength to tensile strength, brittle-ductile transition, and so on. The mineral meso-structure of brittle rock shows the interlocking behavior and there are some microcracks between the mineral grains, so it is difficult to analyze the mechanical characteristics accurately with a regular constitutive model. The previous numerical models have some limitations when applied to brittle rock, that they cannot provide sufficient internal interlocking and are incapable of considering the microcracks. These limitations are addressed by using the updated flat-joint contact model to join notional polygonal particles with an initial gap and increasing the particle coordination number by adding flat-joint contacts to more particles that are within some non-zero distance of one another via the range coefficient contact identification method. A comparison of experimental and numerical results confirms that the updated flat-jointed model provides a good match with the mechanical properties of brittle rock. In this paper, we investigate the influence of mineral meso-structure (micro-cracks, range coefficient, and radius multiplier) on the meso-mechanical properties of Jinping dolomitic marble via the updated flat-joint contact model under direct-tension tests and compression tests. It is found that the updated model can reproduce the microstructure effect of brittle rock and can better simulate the mechanical characteristics of the brittle rock than conventional models, such as high strength ratio, brittle-ductile transition, initial nonlinearity, and different modulus in compression and tension.

Formulation Effects on the Mechano-Physical Properties of In Situ-Forming Resilient Hydrogels for Breast Tissue Regeneration.

The need for a long-term solution for filling the defects created during partial mastectomies due to breast cancer diagnosis has not been met to date. All available defect-filling methods are non-permanent and necessitate repeat procedures. Here, we report on novel injectable porous hydrogel structures based on the natural polymers gelatin and alginate, which are designed to serve for breast reconstruction and regeneration following partial mastectomy. The effects of the formulation parameters on the mechanical and physical properties were thoroughly studied. The modulus in compression and tension were in the range of native breast tissue. Both increased with the increase in the crosslinker concentration and the polymer-air ratio. Resilience was very high, above 93% for most studied formulations, allowing the scaffold to be continuously deformed without changing its shape. The combination of high resilience and low elastic modulus is favored for adipose tissue regeneration. The physical properties of gelation time and water uptake are controllable and are affected mainly by the alginate and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) concentrations and less by the polymer-air ratio. In vitro cell viability tests were performed on mouse preadipocytes and indicated high biocompatibility. The minimally invasive nature of this approach, along with the excellent properties of the scaffold, will enable the filling of complex voids while simultaneously decreasing surgical costs and greatly improving patient well-being.

Stress distribution in multilayer structural element subjected to skew bending

Results of researches on strength and stiffness of diagonally bending sandwich girders having geometric and/or stiffness asymmetry have been given. A mathematical module for calculation of normal strain (strength) and stiffness on bending at any cross-section point of sandwich girder has been proposed. The kinetics of stiffness on bending and strength variation dependences when geometric parameters of a cross-section and tension modulus ratios of girder layers are changing have been examined. It has been established that the strength of a diagonally bending sandwich girder on the whole depends on the position of the centre of stiffness and the position of the neutral plane.

Analysis of load-bearing characteristics of bi-modulus composite stiffened plates: Numerical simulation method and large-scale experimental verification

A large number of experiments show that composite materials usually show different modulus properties in tension and compression (bi-modulus). However, for actual composite engineering structures, especially complex models, the numerical simulation calculation is usually based on a single modulus. In order to consider the different modulus characteristics of composite materials in tension and compression, researchers put forward simplified constitutive models of dual-modulus materials. However, these constitutive models have not been verified by a large number of experiments, especially by complex models. In this paper, the GWFMM model is simplified and used to analyze complex structures with different modulus in tension and compression. The experimental results of stiffened plate show that the improved GWFMM model can be used to analyze different modulus of tension and compression of complex stiffened structures. In addition, the influence of elastic modulus ratio in tension and compression under different experimental load conditions is further explored, and the influence law of bending and torsion on structures with bi-modulus is discussed. The relevant conclusions provide reference for the design and optimization of full-scale composite structures in marine engineering.

Studying the Structure and Properties of Epoxy Composites Modified by Original and Functionalized with Hexamethylenediamine by Electrochemically Synthesized Graphene Oxide.

In this study, we used multilayer graphene oxide (GO) obtained by anodic oxidation of graphite powder in 83% sulfuric acid. The modification of GO was carried out by its interaction with hexamethylenediamine (HMDA) according to the mechanism of nucleophilic substitution between the amino group of HMDA (HMDA) and the epoxy groups of GO, accompanied by partial reduction of multilayer GO and an increase in the deformation of the carbon layers. The structure and properties of modified HMDA-GO were characterized using research methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy and Raman spectroscopy. The conducted studies show the effectiveness of using HMDA-OG for modifying epoxy composites. Functionalizing treatment of GO particles helps reduce the free surface energy at the polymer-nanofiller interface and increase adhesion, which leads to the improvement in physical and mechanical characteristics of the composite material. The results demonstrate an increase in the strength and elastic modulus in bending by 48% and 102%, respectively, an increase in the impact strength by 122%, and an increase in the strength and elastic modulus in tension by 82% and 47%, respectively, as compared to the pristine epoxy composite which did not contain GO-HMDA. It has been found that the addition of GO-HMDA into the epoxy composition initiates the polymerization process due to the participation of reactive amino groups in the polymerization reaction, and also provides an increase in the thermal stability of epoxy nanocomposites.

Simultaneous determination of cement stabilized macadam’s dynamic resilient modulus in compression and tension by bending beam test

Accurately determining the modulus of cement stabilized macadam is a crucial and essential task for effectively calculating the mechanical response or evaluating the performance of semi-rigid asphalt pavement. However, there is currently still no standardized or widely acknowledged method for determining the modulus of cement stabilized macadam, which makes pavement response calculation and performance evaluation more challenging. Therefore, this study first outlines the features of several typical approaches that have been utilized to date to determine the modulus of cement-stabilized macadam while also highlighting the drawbacks of these approaches. Then, based on these analyses and summaries, proposes a new method that uses bending beam test to simultaneously determine the dynamic resilient modulus in compression and tension for cement stabilized macadam. Afterwards, in order to verify the proposed method, this study conducts three different types of dynamic resilient modulus tests for cement stabilized macadam, and compares the test results of these three types of methods to figure out the differences in their mechanical mechanisms. Finally, based on these tests and analysis, some reasonable recommendations about dynamic resilient modulus testing of cement stabilized macadam are provided.

The Effect of Size on the Mechanical Properties of 3D-Printed Polymers

Most of the experiments on additively manufactured polymers are on a small scale, and it remains uncertain whether findings at a small scale can be extrapolated to their larger-scale counterparts. This uncertainty mainly arises due to the limited studies on the effect of size on three-dimensional (3D)-printed polymers, among many others. Given this background, this preliminary study aims to investigate the effect of geometric dimensions (i.e., the size effect) on the mechanical performance of four representative types of 3D-printable polymers, namely, (1) polycarbonate acrylonitrile butadiene styrene (PC/ABS), (2) acrylonitrile-styrene-acrylate (ASA), (3) polylactic acid (PLA) as a bio biodegradable and sustainable material, and (4) polyamide (PA, nylon), based on compression, modulus of elasticity, tension, and flexural tests. Eight different sizes were investigated for compression, modulus of elasticity, and tension tests, while seven different sizes were tested under flexure as per relevant test standards. A material extrusion technique was used to 3D-print the polymers in a flat build orientation and at an infill orientation angle of 45°. The results have shown that the mechanical properties of the 3D-printed polymers were size-dependent, regardless of the material type, with the most significant being flexure, followed by tension, compression, and modulus of elasticity; however, no clear general trend could be identified in this regard. All the materials except for nylon showed a brittle failure pattern, characterized by interfacial failure rather than filament failure. PLA outperformed the other three polymer specimens in terms of strength, irrespective of the type of loading.

The Thermal Stress Problem of Bimodular Curved Beams under the Action of End-Side Concentrated Shear Force.

A bimodular material is a kind of material that presents two elastic moduli in tension and compression. In classical thermoelasticity, however, the bimodular material is rarely considered due to its complexity in analysis. In fact, almost all materials will present, more or less, bimodular characteristics, and in some cases, the mechanical properties of materials cannot be fully utilized simply by ignoring the bimodular characteristics. In this study, the thermal stress problem of bimodular curved beams under the action of end-side concentrated shear force is analytically and numerically investigated, in which the temperature rise modes in a thermal environment are considered arbitrary. Using the stress function method based on compatibility conditions, a two-dimensional solution of thermoelasticity of the bimodular curved beam subjected to end-side concentrated shear force was obtained. The results show that the solution for a bimodular curved beam with a thermal effect can be reduced to that of a bimodular curved beam without a thermal effect. At the same time, the numerical simulation for the problem verifies the correctness of the theoretical solution. The results may serve as a theoretical reference for the refined analysis and optimization of curved beams in a thermal environment.

Nondestructive Evaluation of 2 by 10 Southern Pine Lumber

Abstract Efficient use of the available wood resources is necessary to sustainably meet the long-term demand for wood products. This paper presents research about the potential of using transverse and longitudinal vibration techniques to evaluate the bending modulus of elasticity MOE (Eb) and tensile properties (Et and UTS) of 2 by 10 No. 2 grade southern pine (Pinus spp.) lumber. A total of 285 lumber pieces were first nondestructively tested using longitudinal vibration (Director HM 200), transverse vibration (Metriguard E-computer), and proof-loading bending tests (Universal Instron Machine). Each specimen was then destructively tested in tension parallel to the grain to determine tension modulus of elasticity (Et) and ultimate tensile stress (UTS). Correlations between growth characteristics, physical, and mechanical properties were analyzed. Excellent correlative relationships between longitudinal and transverse dMOE with the elastic properties Eb, and Et were found. A strong correlation was also found between the elastic properties Eb and Et. The prediction of Eb was improved after adding density to the model. The estimation of UTS was also improved with the addition of density and a secondary nondestructive measurement. Nondestructive techniques are recommended to assess the mechanical properties of southern pine 2 by 10 lumber.

Additive manufacturing of silicone composite structures with continuous carbon fiber reinforcement

AbstractAs a relatively new material deployed in additive manufacturing (AM), silicone and its composites have the potential to realize tunable functionality and heterogeneous, architected properties for a number of applications requiring low modulus, elastic materials. Continuous fiber reinforced composites have been developed for AM to achieve various complex structures that are lightweight with high mechanical properties. AM of silicone‐based composites with direct ink writing (DIW) technology has potential application in medical devices, gasket components, flexible soft electronics, and food packaging. However, DIW printed materials have mechanical anisotropy since the extrusion‐based printing process creates small changes in geometry during the material deposition process. In addition, silicone elastomers are relatively low modulus in tension and can be reinforced with woven cloth or fibers. In this work, a continuous fiber AM machine is developed to manufacture silicone composite structures with continuous fiber reinforcing the printed silicone. Tensile tests show that the anisotropic property of the perpendicular printed specimens, relative to the tension direction, has been significantly improved by continuous carbon fiber reinforcements. This continuous fiber silicone reinforcement printing technique can be applied to tune fiber volume ratios and orientations for different silicone composite structures to meet the desired strength and stiffness.

Investigation on cotton dust-reinforced epoxy composites

A partially biodegradable composite material with cotton dust as reinforcement in epoxy resin matrix has been developed. Composite laminas are prepared with various percentages of untreated and alkali treated cotton dust fiber and their strength and elastic modulus in tension and flexure are determined. Influence of alkali treatment of fibers on mechanical properties of the composite is studied. It is concluded that alkali treatment of fibres has pronounced effect on tensile and flexure properties of the composite.

Application of the Variational Method to the Large Deformation Problem of Thin Cylindrical Shells with Different Moduli in Tension and Compression

In this study, the variational method concerning displacement components is applied to solve the large deformation problem of a thin cylindrical shell with its four sides fully fixed and under uniformly distributed loads, in which the material that constitutes the shell has a bimodular effect, in comparison to traditional materials, that is, the material will present different moduli of elasticity when it is in tension and compression. For the purpose of the use of the displacement variational method, the physical equations on the bimodular material model and the geometrical equation under large deformation are derived first. Thereafter, the total strain potential energy is expressed in terms of the displacement component, thus bringing the possibilities for the classical Ritz method. Finally, the relationship between load and central deflection is obtained, which is validated with the numerical simulation, and the jumping phenomenon of thin cylindrical shell with a bimodular effect is analyzed. The results indicate that the bimodular effect will change the stiffness of the shell, thus resulting in the corresponding change in the deformation magnitude. When the shell is relatively thin, the bimodular effect will influence the occurrence of the jumping phenomenon of the cylindrical shell.

Load-bearing characteristics of marine complex sandwich composites considering unequal elastic modulus in tension and compression

The panel and core materials of sandwich composite usually have the characteristics of unequal elastic modulus in tension and compression. However, in the numerical calculation of sandwich composite, it is usually considered as the material with the same tensile modulus or compression modulus, which often leads to larger calculation errors. The test results show that when the elastic modulus of tension and compression is about 10 times different, the maximum calculated stress and maximum deflection will be more than twice different. In view of the complexity of sandwich composite structure, based on the bi-modulus model of laminated plates, a simplified theoretical formula and numerical calculation method are proposed for bi-modulus sandwich composite structures in this paper. Furthermore, the accuracy of the proposed numerical calculation method of bi-module is verified by the experimental study of composite single-layer plate structure and sandwich composite cabin structure. The results show that the error between the improved numerical calculation method and the experimental measurement results is basically within 6%. Meanwhile, the numerical method based on field variables has wide application range and high convergence, and can be used to calculate complex marine composite structures.

A Bi-Modulus Material Model for Bending Test on NHL3.5 Lime Mortar

The research provides an innovative contribution to the interpretation of three-point and four-point bending tests on mortars by employing a bi-modulus material model, which assumes an asymmetric constitutive law, i.e., different elastic moduli in tension and in compression. To this aim, Euler-Bernoulli and Timoshenko bi-modulus beam models are defined, and the related displacement fields are reported for three-point loading, and provided for the first time for the four-point bending layout. A wide experimental campaign, including uni-axial tensile and compressive tests, three-point and four-point bending tests, and on notched specimens three-point tests for mode-I fracture energy, has been carried out on lime mortar specimens exploiting traditional contact (CE-DT) and contactless (DIC) measurement systems. Experimental results provided the values of tensile and compressive mechanical characteristics, which are employed to validate estimations of the analytical model. The tension-to-compression moduli ratio experimentally observed is on average 0.52. Experimental outcomes of the DIC analysis proved the bi-modulus behaviour during the four-point bending tests showing visible shifting of the neutral axis. The bi-modulus analytical model provides closer results to the experimental ones for the slender specimens subjected to four-point bending.

Study of the physicochemical and mechanical stability of an edible leather of mango (Mangifera indica) and pineapple (Ananas comosus) pulp

Mango (Mangifera indica) and pineapple (Ananas comosus) are two important fruits with many industrial uses and excellent sensory, nutritional and functional characteristics. In this research work, the development of intermediate moisture edible leathers obtained by convective drying technology of the mixture of mango and pineapple pulp at 60 and 70 °C was carried out, evaluating their physicochemical characterization and stability under controlled storage conditions at 25 and 35 °C. The results showed that leathers subjected to drying at 60 °C and stored at 35 °C presented a significant increase in water activity. Leathers stored at 35 °C showed greater browning due to the effect of storage temperature. The highest resistance to cutting and tension was observed in edible leathers dried at 70 °C and stored at 25 °C. The Young's Modulus in tension varied between 1.317 and 2.22 MPa. The greatest degradation of vitamin C (57%) was found in leathers dried at 70 °C and stored at 35 °C. It was possible to conclude that the mango and pineapple pulp-based leathers stored for 4 weeks presented physical-chemical and techno-functional characteristics that make them suitable for consumption.