• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.418-428
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• 2003

Fiber fracture is one of the dominant failure phenomena affecting the total mechanical Performance of the composites. Fiber fracture locations were measured through the conventional optical microscope and the nondestructive acoustic emission (AE) technique and then were compared together as a function of the epoxy matrix modulus and the fiber surface treatment by the electrodeposition method (ED). Interfacial shear strength (IFSS) was measured using tensile fragmentation test in combination of AE method. ED treatment of the fiber surface enlarged the number of fiber fracture locations in comparison to the untreated case. The number of fiber fracture events measured by the AE method was less than optically obtained one. However, fiber fracture locations determined by AE detection corresponded with those by optical observation with small errors. The source location of fiber breaks by AE analysis could be a nondestructive, valuable method to measure interfacial shear strength (IFSS) of matrix in non-, semi- and/or transparent polymer composites.

• Journal of Adhesion and Interface
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• v.12 no.3
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• pp.88-93
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• 2011

Optimal dispersion and fabrication conditions of carbon nanotube (CNT) embedded in phenolic resin were determined by electrical resistance measurement; and interfacial property was investigated between plasma treated carbon fiber and CNT-phenolic composites by electro-micromechanical techniques. Wettability of carbon fiber was improved significantly after plasma treatment. Surface energies of carbon fiber and CNT-phenolic nanocomposites were measured using Wilhelmy plate technique. Since surface activation of carbon fiber, the advancing contact angle decreased from $65^{\circ}$ to $28^{\circ}$ after plasma treatment. It was consistent with static contact angle results of carbon fiber. Work of adhesion between plasma treated carbon fiber and CNT-phenolic nanocomposites was higher than that without modification. The interfacial shear strength (IFSS) and apparent modulus also increased with plasma treatment of carbon fiber.

• Journal of Adhesion and Interface
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• v.9 no.1
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• pp.3-8
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• 2008

Self-sensing was evaluated for carbon nanofiber (CNF)/epoxy composites with two different aspect ratios via electro-micromechanical technique and wettability test. Volumetric electrical resistance was measured to evaluate the comparative dispersion degree indirectly and it decreased due to the increase of electric contacts with increasing CNF concentration. The dispersion degree was evaluated indirectly by calculating coefficient of variation (COV) of volumetric electrical resistance. The CNF type A with a high aspect ratio showed better self-sensing than the case of CNF type B with a short aspect ratio. The CNF type B/epoxy composite showed little self-sensing at a concentration higher than 2 vol% probably due to poor dispersion. The apparent modulus of CNF type B was higher than that of CNF type A due to the orientation effect and the high surface area. The thermodynamic work of adhesion was consistent with the result of apparent modulus.