School of Mechanical and Industrial Engineering

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Browsing School of Mechanical and Industrial Engineering by Subject "ABAQUS"

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    Fractural Analysis of S2 glass fiber/ SC15 Epoxy Reinforced composite Material using Numerical Method
    (Addis Ababa University, 2024-06) Bereket Teshome; Mulugeta Hailemariam (PhD)
    Composite materials are utilized more extensively as a metal structure replacement in weight sensitive applications where energy and the environment are a real concern. This is due to their attractive properties as high strength-to-weight ratio and stiffness-to-weight ratio. Therefore, the replacement materials need to be studied and this research focused on numerical analyses of the interlaminar fracture behavior of S2-glass/SC15 epoxy composite. Glass fiber reinforced plastic (GFRP) composite structures are prone to fracture at interfaces or within the matrix which may not be visible from outside. Thus, a thorough knowledge of the initiation and propagation of cracks in GFRP composites is necessary. In this study, fracture mechanics approaches used to analyze fracture parameters of Mode I and Mode II. A numerical method was used to model the S2-glass/SC15 epoxy composite as a plain weave lamina. According to ASTM standards, Double Cantilever Beam (DCB) and End-Notched Flexure (ENF) specimens were used for Mode I and Mode II interlaminar fracture behavior analysis, respectively. The Virtual Crack Closure Technique (VCCT), a finite element method was applied to study crack propagation using Abaqus software. The analysis was performed to study the loads at which the model begins to delaminate. The two models showed delamination within the range of the load application. The strain energy release rate along the delamination directions and across the crack fronts were also determined. The strain energy release rate value of the S2 glass / SC15 epoxy composite for mode I and mode II loading conditions were found to be 0.92 J/m² and 1.1 J/m² respectively. Through the determination of the strain energy release rate and analysis of load-displacement responses, significant findings were obtained. The study successfully characterized the delamination behavior of the composite laminate under both Mode I and Mode II loading, providing insights into its fracture mechanics properties. The investigation into the strain energy release rate offered a quantitative measure of the energy required for crack propagation, aiding in understanding the material's resistance to delamination.
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    Fracture Analysis of Shaft due to the Second Higher Critical Speed (Vibration) for AISI 1018 Steel Shaft
    (Addis Ababa University, 2021-03) Semihar, Ayalew; Samuel (PhD)
    This paper was devoted to analyze fracture of shaft failure due to the second higher critical speed for AISI 1018 steel shaft. In this particular research, the influence of transverse cracks in a rotating shaft was analyzed by comparing with the un-cracked shaft which deflects at the second higher critical speed. The paper addressed the two distinct issues of the changes in critical speed and the influence of crack on dynamic response of shaft during operation. Moreover, the evolution of catastrophic failure of a cracked rotor near the second higher resonance frequency was investigated. Numerical calculation was made to calculate the critical speed and other dynamic fracture parameters. ABAQUS was used to present the simulation result. The research utilized whirling machine for experimental investigation to find out the critical speed and the crack developed at the shaft. For homogeneity confirmation SPECTRO MAXX was employed. The dynamic response obtained from simulation and experimental investigation was compared with those evaluated through numerical integration. It was observed that the critical speed of the cracked shaft decreases by 8.2% and 6.93%. Combined mode I & III of crack had been seen in the shaft.
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    Modeling the Interfacial Shear Strength of Natural Fibers Epoxy Matrix by Pullout Failure Mode
    (Addis Ababa University, 2022) Fasil, Henok; Samuel, Tesfaye (PhD)
    Recently natural fiber composites are overtaking the place of synthetic fiber composites for many applications, so it seems crucial to model interfacial shear strength of it and study the load transfer efficiency between the fiber and the resin, which plays a significant role in determining the mechanical properties of the fiber reinforcement which the is fiber-epoxy matrix. In this paper two fiber; Pineapple fiber and kapok, which has the highest and lowest young’s modulus are chosen. Twelve models, six for each kind of fiber, are developed using ABAQUS software considering different conditions, such as various fiber embedment lengths, fiber diameter, and void sizes for fiber pullout failure of the interface between the fibers and epoxy. Parameters studied are fiber embedded length of 3 mm and 0.1 mm; fiber diameter 48 for pineapple and Kapok fiber with a length of 1mm and 0.1 mm with a diameter of 33 is taken. The effect of the presence of voids on the interface of fiber and epoxy is studied. The average interfacial shear strength obtained, between epoxy and fiber interface, are for pineapple and for kapok. This study shows the interfacial shear strength is dependent on the elastic modulus and density of the fiber but the change in the interfacial contact surface area due to change in embedded length of fiber has no significant effect on the interfacial shear strength value. But the change in diameter of the fiber and void ratio affects interfacial shear strength. Rather the presence of void does have a positive effect on the incremental of the value interfacial shear strength.