• Composites Research
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• v.34 no.1
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• pp.47-50
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• 2021

In this paper, the Curing process for Epoxy Molding Compound (EMC) Package was developed by comparing the performance of the EMC/Cu Bi-layer package manufactured by the conventional Hot Press process system and Carbon Nanotubes (CNT) Heater process system of the surface heating system. The viscosity of EMC was measured by using a rheometer for the curing cycle of the CNT Heater. In the EMC/Cu Bi-layer Package manufactured through the two process methods by mentioned above, the voids inside the EMC was analyzed using an optical microscope. In addition, the interfacial void and warpage of the EMC/Cu Bi-layer Package were analyzed through C-Scanning Acoustic Microscope and 3D-Digital Image Correlation. According to these experimental results, it was confirmed that there was neither void in the EMC interior nor difference in the warpage at room temperature, the zero-warpage temperature and the change in warpage.

• Journal of the Korean Society for Railway
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• v.11 no.4
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• pp.357-363
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• 2008

This study investigates the durability of carbon/epoxy composites for use on train car bodies under a salt water spray environment. Salt water solution with 5% NaCl, similar to natural salt water, was used for the salt water environmental tests. The specimens were obtained from a composite panel consisting of an epoxy matrix reinforced with T700 carbon fabric. The specimens were exposed to the salt water environment for up to 12 months. Mechanical tests were performed to obtain tensile properties, flexural properties, and shear properties. Dynamic mechanical analysis was used to measure such thermal properties as storage modulus, loss modulus, and tan $\delta$. Also FT/IR tests were conducted to investigate changes in chemical structure with exposure. The results revealed that fiber-dominated mechanical properties were not affected much by exposure time, but matrix-dominated mechanical properties decreased with increasing exposure time. Storage modulus was not very sensitive to exposure time, but glass transition temperature was affected, slightly decreasing with increasing exposure time. Although the peak intensity of FT/IR curves was affected slightly by exposure time, the peak shape and peak location of FT/IR curves were not noticeably changed. Carbon/epoxy composites used for this study were relatively stable to the salt water environment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.11-18
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• 2012

This paper deals with the numerical determination of the stress intensity factors of cracked aluminum plates under the mixed mode of $K_I$ and $K_{II}$ in glass-epoxy fiber reinforced composites. For the stress intensity factors, two different models are reviewed such as VCCT and two-step extension method. The p-convergent partial layerwise model is adopted to determine the fracture parameters in terms of energy release rates and stress intensity factors. The p-convergent approach is based on the concept of subparametric element. In assumed displacement field, strain-displacement relations and 3-D constitutive equations of a layer are obtained by combination of 2-D and 1-D higher-order shape functions. In the elements, Lobatto shape functions and Gauss-Lobatto technique are employed to interpolate displacement fields and to implement numerical quadrature. Using the models and techniques considered, effects of composite laminate configuration according to inclined angles and adhesive properties on the performance of bonded composite patch are investigated. In addition to these, the out-of-plane bending effect has been investigated across the thickness of patch repaired laminate plates due to the change of neutral axis. The present model provides accuracy and simplicity in terms of stress intensity factors, stress distribution, number of degrees of freedom, and energy release rates as compared with previous works in literatures.

• Composites Research
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• v.33 no.4
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• pp.228-233
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• 2020

In this paper, a single lap shear test was performed using a glass fiber reinforced composite material (GFRC). Pencil lead drawn paper sensor (PLDPS) was applied for single lap shear test being performed. Bisphenol-A epoxy and amine hardener were used as adhesives combining with composite materials. To make a difference in adhesive properties, the adhesive was cured under different conditions. PLDPS was made of a 4B pencil on A4 paper. Because graphite in a pencil was an electrically conductive substance, electric resistance (ER) could be measured. A change in ER was observed by a position where a PLDPS was attached to single lap shear specimens. It was confirmed that the change in ER was different depending on two attached positions and was observed by lap shear strain as well. In case the lap shear strain was large, the change in ER of PLDPS was high. This was because the larger the extension of the adhesive part, the larger the degree of bending of the specimen and thus the larger the distance change between two electrodes.