Modelling of Environmental Ageing of Polymers and Polymer Composites—Modular and Multiscale Methods

Service lifetimes of polymers and polymer composites are impacted by environmental ageing. The validation of new composites and their environmental durability involves costly testing programs, thus calling for more affordable and safe alternatives, and modelling is seen as such an alternative. The state-of-the-art models are systematized in this work. The review offers a comprehensive overview of the modular and multiscale modelling approaches. These approaches provide means to predict the environmental ageing and degradation of polymers and polymer composites. Furthermore, the systematization of methods and models presented herein leads to a deeper and reliable understanding of the physical and chemical principles of environmental ageing. As a result, it provides better confidence in the modelling methods for predicting the environmental durability of polymeric materials and fibre-reinforced composites.

Environmental Durability of an Optical Fiber Cable Intended for Distributed Strain Measurements in Concrete Structures

The present study investigates the environmental durability of a distributed optical fiber sensing (DOFS) cable on the market, commonly used for distributed strain measurements in reinforced concrete structures. An extensive experimental program was conducted on different types of specimens (including samples of bare DOFS cable and plain concrete specimens instrumented with this DOFS cable) that were exposed to accelerated and natural ageing (NA) conditions for different periods of up to 18 months. The instrumentation of both concrete specimens consisted of DOFS cables embedded at the center of the specimens and bonded at the concrete surface, as these two configurations are commonly deployed in the field. In these configurations, the alkalinity of the surrounding cement medium and the outdoor conditions are the main factors potentially affecting the characteristics of the DOFS component materials and the integrity of the various interfaces, and hence impacting the strain transfer process between the host structure and the core optical fiber (OF). Therefore, immersion in an alkaline solution at an elevated temperature or freeze/thaw (F/T) and immersion/drying (I/D) cycles were chosen as accelerated ageing conditions, depending on the considered configuration. Mechanical characterizations by tensile and pull-out tests were then carried out on the exposed specimens to assess the evolution of the mechanical properties of individual component materials as well as the evolution of bond properties at various interfaces (internal interfaces of the DOFS cable, and interface between the cable and the host structure) during ageing. Complementary physico-chemical characterizations were also performed to better understand the underlying degradation processes. The experimental results highlight that immersion in the alkaline solution induced a significant and rapid decrease in the bond properties at internal interfaces of the DOFS cable and at the cable/concrete interface (in the case of the embedded cable configuration), which was assigned to chemical degradation at the surface of the cable coating in contact with the solution (hydrolysis and thermal degradation of the EVA copolymer component). Meanwhile, F/T and I/D cycles showed more limited effects on the mechanical properties of the component materials and interfaces in the case of the bonded cable configuration. A comparison with the same specimens exposed to outdoor NA suggested that the chosen accelerated ageing conditions may not be totally representative of actual service conditions, but provided indications for improving the ageing protocols in future research. In the last part, an analysis of the distributed strain profiles collected during pull-out tests on instrumented concrete specimens clearly illustrated the consequences of ageing processes on the strain response of the DOFS cable.

Predicting Environmental Ageing of Composites: Modular Approach and Multiscale Modelling

Fibre-reinforced composite materials are used in structural applications in marine, offshore, and oil and gas industries due to their light weight and excellent mechanical properties. However, the exposure of such materials to water leads to environmental ageing, weakening the composite over time. A typical design lifetime of offshore composite structures, being in direct contact with water and humid air, spans 25 years or more. Thus, the prediction and modelling of environmental ageing phenomena has become highly important, especially for predicting long-term environmental durability. In this study, a systematic and modular approach for quantitatively modelling such phenomena is provided. The modular methodology presented in this work can, and should, be further expanded—it is multiscale and scalable. A state-of-the-art degradation framework is not yet complete; however, it is a systematic step towards the multiscale modelling paradigm for composite materials. The topic of the environmental durability of composite materials is being actively developed and is expected to continue growing in the future. There are three constituents in a composite: matrix, fibres, and an interphase. Each constituent degrades differently and may also affect the degradation behaviour of each other. Therefore, a modular multiscale approach is preferred. The modules are based on the physics and chemistry of individual constituents’ interaction with the environment, including the diffusion, molecular mechanisms, and kinetics of environmental ageing [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]. The methodology is seen as a useful approach for both industry and academia, including such use cases as accelerated testing, prediction of the lifetime of composite materials and structures, as well as improving the understanding of environmental ageing effects and the time-dependent properties of composites due to environmental ageing.

Development of an environmentally-durable, low-friction coating

In this communication, we highlight the development of a new coating that offers environmental durability and low-friction characteristics by exploiting the low interfacial bond strength of fillers with lamellar structures. The water-based coating has low volatile organic compound (VOC) content (< 50 g/L), offers the ability to be pigmented, demonstrates resilience against accelerated aging exposures, and exhibits even lower friction with extended weathering. The low-friction coating provides a simple method for modifying surface properties, and has the potential to complement Jersey walls by inhibiting vertical climb and thus decreasing the probability of vehicular roll-over upon impact. Graphic Abstract