NUST Institutions Library Catalogue Search for 'kw,wrdl: su-br:an:"11965"'

Analysis of Adhesive Joints using Digital Image Correlation (DIC) /

By Farooq, Muhammad Kashif . . 83p. , In this study, the effect of cork particles on the failure behavior of SLJs was investigated experimentally through tensile testing and non-contact digital image correlation (DIC) methods. Cork particles within size range of 125-250 μm were added at 0, 0.25, 0.50, 0.75 and 1.0% wt. in a brittle epoxy. SLJs with and without cork particles were tested under a displacement control condition of 1.3 mm/min and digital images were captured during the deformation in order to analyze the fracture process. VIC 2D 7 software was used to determine the peel and shear strain distributions in the overlapped area of bonded joints. Tensile test and DIC results reveal that cork particles enhance the strength and ductility of adhesive joints. However, the effect of cork particles on ductility is more significant than strength of joint. The visual inspection of the captured images shows cork particles act as crack stopper and slow down the crack propagation along the bondline. 30cm.

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Effect of Hygrothermal Aging on Strength Performance of Cork Powder Reinforced Adhesive /

By Sohail, Zulekha . . 100p. , Adhesives play a crucial role across various industries and applications due to their ability to bond materials together. They are used in numerous ways, ranging from everyday household applications to industrial and specialized fields. Strength is the most critical factor to analyze before using the adhesive. Various techniques have already been developed and many are being developed to predict and improve the strength of adhesive. The addition of cork powder to the structural adhesives could improve the strength of adhesive joints through mechanical interlocking between the cork cells and the molecules of adhesive. However, even with the nanofiller reinforcement, the strength of adhesive joints is significantly affected by environmental parameters like temperature and humidity. The present study investigated the effect of hydrothermal aging on the strength characteristics of cork powder-reinforced adhesive samples. Reinforced adhesive samples were investigated under two different humidity levels of 80% and 100% RH. The cork powder will be added in concentration of 0.25wt.%, 0.5wt.%, 0.75wt.% and 1wt.% to study the reinforcing effects. The result shows that the saturated mass increased with increased in relative humidity that is approximately 0.4% and 0.9% for 80% and 100% RH respectively. The findings show that the ultimate tensile strength is reduced by the addition of cork powder as well as enhancing humidity. Furthermore, the addition of cork powder makes the sample more brittle, so failure strain and tensile toughness undergo decrement. The above finding indicated that hot-wet environment has a negative influence on strength performance of cork powder reinforced adhesive. In future the same study can be performed to know the strength of SLJ and DLJ to know its effect on joints. 30cm.

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Impact localization on Composite Panel using Fiber-Bragg Gratings optical sensors /

By Arhaam Bin Touqeer, . . 70p. , The advancing use of composites in high stake environments, particularly aerospace industry demands strict monitoring of composite’s health over the entire period of life. Health of composite structures could easily be affected by internal damages like debonding or delamination that are invisible to naked eyes. These damages are normally caused by unexpected impact incidences mid-flight or during ground handling. If these damages are not identified timely, could lead to catastrophic failure. So, there is a need of a system that could timely identify and locate these damages in real-time. FiberBragg Grating sensors have gained confidence with their capability of measuring strains accurately along with their versatile and low-cost integration, particularly in composites. In this research work, FBG sensors have been used to identify and locate impact incidences on a composite laminate. Capability of FBG sensors of measuring strain wave initiated by impact incidence is being investigated. In order to extract quantitative information from strain response for impact localization, novel concepts like Empirical Mode Decomposition (EMD) and Hilbert Huan Spectrum have been used. Lastly, normalized values from spectrum are utilized and Artificial Neural Network has been applied to train the system to differentiate between different damage states. On the bases of predictions made by optimized ANN, comments on FBG sensors reliability have been presented and prospects for future research work discussed. 30cm.

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