Keywords: Fiber Bragg grating ; optical fiber sensor ; composite joints Reference EPFL-CONF-183849 Record created on 2013-02-18, modified on 2016-08-09

Monitoring strain gradients in adhesive composite joints by embedding fibre Bragg grating sensors

Analysis of flexural failure mechanism of ultraviolet cured-in-place-pipe materials for buried pipelines rehabilitation based on curing temperature monitoring

The steady-state electrical conduction current for single and multilayer polyimide (PI) nanocomposite films was observed at the low and high electric field for different temperatures. Experimental data were fitted to conduction models to investigate the dominant conduction mechanism in these films. In most films, space charge limited current (SCLC) and Poole–Frenkel current displayed dominant conduction. At a high electric field, the ohmic conduction was replaced by current–voltage dependency. Higher conduction current was observed for nanocomposite films at a lower temperature, but it declined at a higher temperature. PI nanocomposite multilayer films showed a huge reduction in the conduction current at higher electric fields and temperatures. The conclusions derived in this study would provide the empirical basis and early breakdown phenomenon explanation when performing dielectric strength and partial discharge measurements of PI-based nanocomposite insulation systems of electric motors.

Steady-State Conduction Current Performance for Multilayer Polyimide/SiO 2 Films.

Marine Environment Induced Failure of FRP Composites Used in Maritime Transport

Fiber reinforced polymer (FRP) composites find ever growing application possibilities in marine structures. Due to harsh environmental operational conditions, failure prediction of such structures is an imperative in this industry sector. For this reason, samples of epoxy/glass and polyester/glass with various fiber layout configurations have been submerged under the sea for prolonged periods (6 and 12 months). On contrary to usual accelerated laboratory experiments, these type of tests in real sea environment and for prolonged periods are rarely done. They are useful to obtain more realistic environmental input parameters for structural modeling of marine structures. Changes in mass, marine microbiology growth, tensile strength and morphological structures were analyzed after submersion and compared with samples exposed to room environment. All samples exhibited an increase in mass due to seawater absorption and microorganism growth in the organic resins used as matrix materials. The dynamic and level of decrease in tensile strength showed dependency on the fiber layout configuration. Optical and scanning electron microscopical investigation showed significant matrix morphological changes primarily due to salt crystal formation and the impact of sea microorganisms embedding in the resin. Results of this experimental work will be used as realistic input parameters for subsequent failure analysis numerical tool that can be applied for life-time behavior predictions of marine structures. 

Joana Sousa

Papers

Mechanical characterization of sandwich composites with embedded sensors

Risk factors associated with the increase of injury severity of powered two wheelers road accidents victims in Portugal.