Modeling Mechanical Properties of Carbon Fiber/Vinyl Ester Composites Degraded by Ultraviolet Radiation and Moisture

摘要

Degradation of mechanical properties of fiber-reinforced composites subjected todifferent environmental conditions is a great concern; especially in the case ofoffshore structures and marine application, where UV radiation and sea watersynergistically deteriorate the mechanical properties of the polymeric composites.Here, a method is presented to model changes in mechanical properties ofcomposites and is used to find the fracture initiation energy. The proposed modelpredicts changes in longitudinal modulus, transverse modulus, shear modulus andPoisson’s ratio as a function of thickness of the composite plate for a givenexposure time. For comparison, degraded and undegraded samples in 0 and 90degree fiber orientation are used in tensile test to measure longitudinal andtransverse modulus of the samples. Fracture surfaces of the broken samples andedges of the samples are investigated by optical and scanning electron microscopyto observe the effects of degradation through the thickness of the composites.Effective moduli of samples calculated from the model are compared with theexperiments. Lastly, the composite laminate is considered as a homogenizedorthotropic plate with mechanical property variation based on the developed modeland the fracture initiation energy in flexural test for degraded and undegradedsamples with different fiber orientation is obtained using finite element analysis.The fracture initiation energy is compared to the work of fracture from experiments.