Papers by Keyword: Tensile Loading

Abstract: The discovery of Carbon Nanotubes (CNT) has opened the doors for revolutionary applications in the mechanical, aerospace, and electrical sectors. However, to fully utilize the potential of carbon nanotubes, there is a persisting need to identify all sorts of structural modifications that can be observed in any type of manufacturing procedure for CNTs. Thus, the presented study investigates the mechanical properties of CNTs with variable waviness and defect density. Furthermore, the study is performed using classical Molecular Dynamics simulations (MD). The structures are then characterized with single or multiple vacancy defects along the axis of the nanotube structure, which is modeled as wavy structures to replicate their natural structure. After the simulation results were analyzed, it was observed that the increase in the surrounding temperature from 300K to 1500K reduces the overall tensile strength of the CNT sample from 89-47 GPa. However, introducing a single vacancy defect to the same structures was shown to reduce the tensile strength to 41 GPa at 1500K and 62 GPa at 300K.

Abstract: In this project, experimental work on tensile behaviour of single lap adhesive joints of sisal, glass and hybrid sisal-glass/epoxy composite laminates has been carried out. Composite laminates were fabricated by hand lay-up method using chopped strand mat sisal and glass fibers with epoxy resin matrix. Lab joints of four interface geometries; straight flat, triangular, rectangular and sinusoidal were fabricated. Tensile load-displacement relations were drawn and discussed. Effect of interface geometry and material type on maximum load and strength of the single lap joint was investigated. Failure mechanism of the fractured specimens was discussed. Results show that the glass/epoxy lap joints with semi-circular adhesive interface geometry supported load higher respectively 14.26%, 26.13%, and 30.79% than rectangular, triangular and straight flat interface geometries. Glass/epoxy lap joint with semi-circular interface geometry supported tensile load higher 5.61% and 21.83% than that obtained from hybrid sisal-glass and sisal/ epoxy adhesive joints. While the shear strength was found higher respectively 6.19% and 18.69%. Adhesive failure mode was observed for most of the single lap joints investigated. Mixed failure mode of adhesive and adherend materials was observed on the sisal/epoxy lap joints.

Abstract: This paper deals with mechanical properties of natural bamboo (Gigantochloa pseudoarundinacea and Gigantochloa apus). Tensile and compression tests were done on these bamboo. It shows that Gigantochloa pseudoarundinacea is better in the field of strength and modulus compared with Gigantochloa apus. Further analysis shows that the specific modulus and strength of these bamboo are better compared the data available in the literature, and even better compared with traditional engineering materials, such as mild steel, polyester resin or Glass Reinforced Plastics. Two parameter Weibull analysis were used to analysis the experimental data.

Abstract: Experimental work on tensile behaviour and failure mechanism of composite double lap bolted joint has been carried out. Chopped strand mat (CSM) coir, glass and coir-glass/epoxy composite plates were fabricated by hand lay-up method. The bolted joint specimens were of 155 mm length and 48 mm width. Steel bolts of 4 mm and 8 mm diameters were used. Effect of material type, number of layers and width to diameter ration (w/d) on tensile load, bearing strength and failure behaviour were examined. Results show that, the maximum load obtained from the glass/epoxy, coir/epoxy and coir-glass/epoxy specimens increased with the increase in the number of layers and (w/d) ratio. Maximum load obtained from the six layers glass/epoxy with w/d ratio of 12 is found higher respectively 15.2% and 50.14% than that obtained from hybrid coir-glass and coir/epoxy composite specimens. The percentages of difference were 14.2% and 42.97% for the specimens with w/d ratio of 6. It has been found that the maximum strength of the six layers glass/ epoxy specimens was found higher in the range between 17.5% to 18.46 % and 51.67% to 57.74 % than the hybrid coir-glass and coir/epoxy specimens respectively. Net tension failure and cleavage failure modes were observed for the two and four layers coir/ epoxy specimens with w/d ratios of 6 and 12. Bearing failure mode was observed for the six layers coir, glass and hybrid coir-glass/epoxy specimens.

Abstract: This paper presents the results of static tests of non-reinforced round timber bolted joints with slotted-in steel plates loaded perpendicular to the grain. This type of joints loading is particularly widespread in truss structures. Round timber test samples series were prepared to validate the behavior of a joint loaded in tension perpendicular to the grain. The joints samples were experimentally tested in the laboratory of the Faculty of Civil Engineering VŠB TU Ostrava. The test results were compared with the calculated load-carrying capacity of joints by Johansen’s yielding theory.

Abstract: The effect of the mechanical properties and geometric parameters on the crack density of the thin film/substrate system under residual stress and uniaxial tensile loading is investigated in this work. The numerical results show that the crack density of the thin film increases with the increase of the Youngs modulus of the thin film and (or) the shear modules of the interface layer, and it decreases with the increase of the thickness of the thin film and (or) the fracture strength of the thin film. These results can help us more deeply understand the fracture behavior of the brittle thin film on the substrate under residual stress and external tensile loading.

Abstract: This paper considers damage development mechanisms in composite laminates subjected to tensile loading. The continuum damage mechanics is the most widely used approach to capture the non linear behaviour of laminates due to cracking. In this study, a continuum damage model based on ply failure criteria, which is initially proposed by Ladevèze has been extended to cover all plies failures mechanisms using an accurate numerical model to predict the equivalent damage accumulation. However, this model requires a reliable representation of the elementary damage mechanisms which can be produced in the composite laminate. To validate this model, a numerical application has been carried on the cross-ply laminates of type [0_n/90_m]_s._. A shear lag model was adapted to calculate the average stress of the 0° and 90° plies. The solution presented is obtained by using finite element analysis which implements progressive failure analysis. The effect of the stacking sequences has been done by varying the thickness of the 90° plies.

Abstract: The mechanical properties of open-cell metal foam structures are investigated using the finite element method. The foam structure is modelled by a regular network of anisotropic Weaire-Phelan cells in which the strands are modelled as 3D finite element beams. We consider four types of strand cross sections: (i) circular, (ii) square, (iii) triangular and (iv) Plateau border shape. The numerical results obtained with our proposed mathematical model are checked against the experimental results obtained on real Nickel metallic foam and an excellent agreement is found. In addition, we conducted a parametric analysis to study the effect of some geometrical characteristics on the elasticity of the metal foam. Among these geometrical parameters, the shape, the dimensions of strand cross section, the inertia, the alignment of strands and the structural network irregularities are investigated, discussed and documented.

Abstract: The fracture behavior of a brittle thin film on an elastic substrate under residual stress and uniaxial tensile loading is investigated. It is assumed that the residual stress in the thin film is not large enough to cause the thin film to fracture. Using a mechanical model presented in this work, the analytical solutions for the distribution laws of the tensile stress developed in the thin film, the shear stress developed along the interface and the relationship between the crack density of the thin film and the applied strain of the substrate can be obtained. The results presented in this work can provide a new analytic solution to the interfacial shear stress for characterizing the interfacial shear strength of the thin film/substrate system when the uniaxial tensile test is adopted to evaluate the mechanical properties of the thin film/substrate system.