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Highlights • A novel test method for accelerated interlaminar shear fatigue of marine composites. • Comparison of dry and immersed interlaminar fatigue shear testing. • Matrix creep induced fatigue damage in dry samples. • Cracks growth induced fatigue damage in immersed samples. Abstract Exposure to marine environment causes a degradation of the interlaminar shear performance of composites. This effect has been reported in several studies, but the mechanisms that lead to failure in composites subjected to cyclic loading under water exposure are still not fully understood. In this work a novel test method, the I-beam short beam shear, was used to determine shear properties and accelerate fluid saturation in glass fiber epoxy specimens. The interlaminar shear performance of the material was studied experimentally. From the analysis of the cyclic parameters recorded during the test and from optical micrographs it was possible to observe a change in failure mode between dry samples and conditioned samples. The failure of dry samples was a creep dominated effect, which led to inter-ply cracks, while the failure of conditioned samples was a damage growth dominated effect, which led to intra-ply failure. Optical micrographs showed that fiber/matrix debonding occurs in conditioned samples prior to mechanical loading, which are potential damage onset spots. [ABSTRACT FROM AUTHOR]

Polymers and polymer composites are negatively impacted by environmental ageing, reducing their service lifetimes. The uncertainty of the material interaction with the environment compromises their superior strength and stiffness. Validation of new composite materials and structures often involves lengthy and expensive testing programs. Therefore, modelling is an affordable alternative that can partly replace extensive testing and thus reduce validation costs. Durability prediction models are often subject to conflicting requirements of versatility and minimum experimental efforts required for their validation. Based on physical observations of composite macroproperties, engineering and phenomenological models provide manageable representations of complex mechanistic models. This review offers a systematised overview of the state-of-the-art models and accelerated testing methodologies for predicting the long-term mechanical performance of polymers and polymer composites. Accelerated testing methods for predicting static, creep, and fatig ue lifetime of various polymers and polymer composites under environmental factors' single or coupled influence are overviewed. Service lifetimes are predicted by means of degradation rate models, superposition principles, and parametrisation techniques. This review is a continuation of the authors' work on modelling environmental ageing of polymer composites: the first part of the review covered multiscale and modular modelling methods of environmental degradation. The present work is focused on modelling engineering mechanical properties. [ABSTRACT FROM AUTHOR]

This work investigates the combined effect of water immersion and temperature on the interlaminar shear static and fatigue strength of glass fiber epoxy composites. Interlaminar shear tests were performed on I-beam shaped samples which enable faster fluid saturation at 20, 40 and 60 °C, both in air and in immersion. Analysis of fatigue parameters and optical micrography enabled understanding the phenomena that govern the static and fatigue degradation for each case. The dry properties are dominated by the matrix resistance at room temperature and by fiber/matrix interface strength for higher temperature. The immersed properties are dominated by the fiber/matrix interface degradation. An analytical model based on Arrhenius theory is presented for building a fatigue mastercurve that accounts for both temperature and water immersion. The effect of water immersion is modelled by accounting for the change of glass transition temperature of the material. The results show that the mastercurve describes well the conditions tested, provided that the material remains below its glass transition temperature. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced composites are exposed to hydrolytic degradation in subsea and offshore applications. Fiber-matrix interphase degradation was observed after the matrix was fully saturated with water and typical water absorption tests according to ASTM D5229 were stopped. Due to water-induced dissolution, fiber-matrix interphase flaws were formed, which then lead to increased water uptake. Cutting sample plates from a larger laminate, where the fibers were running parallel to the 1.5 mm long short edge, allowed the hydrolytic degradation process to be studied. The analysis is based on a full mechanistic mass balance approach considering all the composite's constituents: water uptake and leaching of the matrix, dissolution of the glass fibers, and dissolution of the composite interphase. These processes were modeled using a combination of Fickian diffusion and zero-order kinetics. For the composite laminate studied here with a saturated epoxy matrix, the fiber matrix interphase is predicted to be fully degraded after 22 to 30 years. [ABSTRACT FROM AUTHOR]