Studies of hygrothermal degradation of a single fiber composite: An iterative approach with embedded optical sensors and numerical analysis

The hydrothermal ageing of glass/epoxy interface is investigated using an experimental numerical approach on cylindrical epoxy specimens with centrally located optical fibers. A 24 mm long Bragg grating sensor is inscribed on the optical fiber and used to monitor strains along the fiber, due to processing and subsequent ageing in water at 50 degrees C. The distributed strains are used to: (a) evaluate the residual strain field developed during processing, employing a parametric finite element identification scheme, (b) monitor the evolution of the moisture induced strains during ageing using linear and non-linear responses for the epoxy recorded experimentally, (c) track debond growth at the interface, generated during ageing, by adopting a concentration dependent cohesive finite element model. Good agreement is found between experimental data and simulations until 47 days of immersion (or 63% of saturation). Afterwards, the model is not quantitatively accurate but indicates well the trend of the experimental data. (C) 2014 Elsevier Ltd. All rights reserved.