The objective of this research is to establish a long term durability data base and material resistance factors for FRP composites with exposure to complex infrastructure environments, and provide recommendations for materials selections based on application and environmental types. The major part of this research program is to deal with fundamental studies regarding the durability of FRP composites for civil infrastructure applications. Multidisciplinary research methodologies will be adopted, which include composites material science, building material science, experimental science, and polymer composite materials science. Close corporation will be also given to the composite materials scientists from FRP composites industry.
Determine the durability of the available FRP products and those made with
the best combination under various critical aging and loading conditions.
Environmental durability will be determined for FRP composites with exposure to
moisture, alkaline/salt, thermal cycles, wet\dry cycles, freeze/thaw cycles, and
U.V. radiation, different loading conditions and the combination of these
conditions. Mechanical durability i.e. creep/relaxation and fatigue, as well as
physical and chemical aging of these FRP composites will be investigated to
establish relationships between stress, strain , time and other environmental
parameters such as , temperature, alkali, and moisture. The performance and
properties of the samples will be examined physically, microscopically,
mechanically and chemically in the laboratory. The surface degradation of resin
and the environmental penetration into fibres will be examined by different
micro-structural modern techniques. Comparison will be made among these FRP
composites to identify the degradation mechanisms involved. The role of resin
matrix, fibres, in controlling long term durability will be revealed. Special
attention is also given to the interface between fibre and matrix, which is
known to be more critical for the long term durability of FRP composites with
exposure to complex infrastructure environment. With suitable fibre surface
treatments or fibre sizing, the adhesive strength between fibre and matrix can
be improved, which therefore, improves the properties of composites. The effect
of sizing agents on properties of FRP composites under some critical defined
aging conditions will be studied. Changes observed in surface chemistry,
micromechanics, and composite properties as the function of sizing agents’ type
will be correlated.
In parallel to this experimental work, theoretical modeling will be conducted to predict the response of FRP composite materials to exposure conditions or to determine acceleration methods such as Arrhenius relationship, and modified Arrhenius relationships to predict diffusion coefficients as function of temperature as accelerating agent. Predictive models based on either matrix plasticization (related to Tg measurement), or on maximum fibre strain will be developed and used to perform accelerated tests in a rational manner. This research activity includes the following tasks.
This activity intends to provide the physical and mechanical properties of both FRP products and FRP/concrete specimens. CFRP, GFRP, and FRP products based on PNC (Polymeric Nano-Composite) in the form of rods, plates, laminates, sandwich panels, tubes, and structural shapes will be obtained directly from the manufacturer and suppliers. Before starting the accelerated ageing tests, the material properties (mechanical and physical) of the FRP products and of the concrete will be determined and the resulting data will be used as references for the analyses and comparisons in the research program.
The accelerated ageing technique developed at the Université de Sherbrooke has shown great promise in predicting the long-term durability of FRP bars, and FRP reinforced concrete structures (See the 48-month progress report). This accelerated ageing method will be used in this research activity, and will be further developed as the project progresses. Based on literature review, the following accelerated ageing schemes, which represent the most common and aggressive service environments for civil infrastructures, will be employed. However, tests will not necessarily be limited to only these.
Immersed in water, alkaline, and saline solution at different temperatures
Thermal (cold and heat)
Wet-dry cycles in saline solution
Exposure to alkaline solution
Freeze-thaw cycles in air, alkaline solution, and saline solution
Stressed in air, alkaline solution, and saline solution
Immersion in other aggressive chemicals
After a defined period of accelerated ageing tests and field exposure, the specimens will be removed for micro-structural analysis, to obtain the fundamental material properties of the FRP products for further analysis. The fundamental material parameters include the degradation mechanism of the FRP products (i.e. fibre dominated mechanism, matrix dominated mechanism, interface dominated mechanism, or combined mechanisms), and chemical penetration into FRP products, which are the fundamental properties required to better predict service life. Various micro-structural analysis techniques will be employed: matrix degradation will be studied by infrared spectroscopy (IR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), while matrix cracking will be investigated by energy dispersive X-ray (EDX), X-ray elemental mapping (XEM), optical light microscopy (OLM), and SEM analysis. Fibre damage and interface damage will be observed by OLM and SEM technology. Each of these modern techniques is critical to the complete characterisation of these with respect to environmental exposure and mechanical loading.
In parallel to the accelerated ageing tests and field exposure of the FRP composites, a theoretical analysis will be conducted to obtain the correlations between exposure/loading conditions, micro-cracking and residual properties for FRP products/systems. The final stage of this research activity will consist of developing credible service life prediction models to quantify the synergistic interactions between mechanical and environmental processes. The models will be further calibrated with field ageing data. From this analysis, an analytical model to describe the stress-corrosion behaviour of FRP products/systems in various aggressive environments and loading conditions will be developed. The analytical model will take into account fracture mechanics and shear lag theory.