Soon-Chul Kwon

Fatigue durability of FRP composite bridge decks at extreme temperatures

Decks manufactured with Fibre-Reinforced Polymer (FRP) composite materials are used in bridges. A performance evaluation of FRP composite decks subjected to simulated traffic loads that induce repetitive stress cycles under extremely high and low temperature is presented. Fatigue testing of three FRP composite bridge deck prototypes and one FRP-concrete hybrid bridge deck prototype under two extreme temperature conditions: −30°C (−22°F), and 50°C (122°F) was conducted. The fatigue response of the deck prototypes was correlated with the baseline performance of a conventional reinforced-concrete deck. Design loads were applied simultaneously at two points. Quasi-static load-deflection and load-strain characteristics were determined at predetermined fatigue cycle levels. No significant distress was observed in any of the composite deck prototypes during ten million load cycles. The effects of extreme temperatures and accumulated load cycles on the load-deflection and load-strain response of FRP composite and FRP-concrete hybrid bridge decks are discussed based on the experimental results.

Effect of Particle Size on Fracture Toughness of Spherical-Silica Particle Filled Epoxy Composites

We investigated the particle size effects on the fracture toughness of epoxy resin composites reinforced with spherical-silica particles. The silica particles had different mean particle diameters of between 1.56 and 0.24µm and were filled with bisphenol A-type epoxy resin under different mixture ratios of small and large particles and a constant volume fraction for all particles of 0.30. As the content with the added smaller particle increased, the viscosity of each composite before curing remarkably increased. We conducted the single edge notched bending test (SENB) to measure the mode I fracture toughness of each composite. The fracture surface with the small particle content exhibited more rough areas than the surface with larger particles. The fracture toughness increased below the small particle content of 0.8 and saturated above it. Therefore, near the small particle content of 0.8, the composite had a relatively low viscosity and a high fracture toughness.

Mechanical Properties of Nano/Micro-Silica Particles Bidispersed Epoxy Composites

Mechanical properties of nano/micro-silica particles bidispersed epoxy composites were investigated based on experimental results. The composite specimens varied with different compositions of nano and micro-silica particles (240 nm and 1.56

Fracture toughness of nano-and micro-spherical silica-particle-filled epoxy composites

m) were prepared with the constant volume fraction, 0.30. The thermo-viscoelastic properties for the composites and the neat epoxy measured in the temperature ranges from 123 K to 523 K and compared to theoretical results according to Lewis and Nielsen’s law with the maximum particle packing given by Ouchiyama and Tanaka’s model. In addition, fragility derived from the thermo-viscoelasticity measurements was used to characterize the strength and fracture toughness of the composites. From results, we found that the thermo-viscoelasticity of the composite was dependent on nano and micro-particles packing, and its strength and fracture toughness were effectively evaluated by fragility.