Fong, Collin Hock Ling (2023) Experimental and finite element study of eggshell powder on shear strength of adhesively bonded joints. Masters thesis, Universiti Tun Hussein Onn Malaysia.

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Abstract

Eggshells are daily food waste disposed of in landfills, producing environmental issues and an unpleasant odour. Eggshells were crushed to form eggshell powder and may be suitably applied as a filler in epoxy resins to improve their mechanical properties as neat epoxy resins have the drawbacks of low shear strength, low fracture toughness. In this study, dog-bone specimens were fabricated to investigate the mechanical properties of toughened epoxy with eggshell powder (TEEP), such as the elastic modulus, Poisson's ratio and tensile strength. Double Cantilever Beam (DCB) and End-Notched Flexure (ENF) tests were used to determine the Mode-I and Mode II fracture energy of TEEP specimens, respectively. For this purpose, oven-dried eggshells were crushed to obtain particles with a size of 150 μm. The volume fraction of eggshell powder in epoxy was designated as 0%, 2.5%, 5%, and 10%, respectively. The epoxy resin system was made by mixing EPIKOTE Resin 828 and Hardener 651 with a mixing ratio of 5:2 by weight. The results showed that the tensile strength, elastic modulus, Mode I and Mode II fracture energies of TEEP were optimum at 5% eggshell with the enhancement of 36.8%, 24.9%, 60.3% and 166.3%, respectively than those of neat epoxy. This is due to the ability of eggshell powder as a crack arrestor, indicated by rough fracture surfaces. However, 10% TEEP prone to agglomeration of eggshell powder lead to poor bonding with epoxy resin and substantially reduces mechanical properties. Subsequently, the shear strength of the single-lap joint (SLJ) with the 38.1mm overlap length, bonded with 5% TEEP has improved up to 72.7% compared to that of neat epoxy. The finite element modelling framework was developed using the Cohesive Zone Modelling (CZM) technique by incorporating the traction-separation relationship as a constitutive model. Here, the measured values were adopted, and good agreement with experimental datasets was found with average discrepancies less than 10.8%

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