Pultruded fiber-reinforced polymer (FRP) composite is expected to be widely applied for civil infrastructures due to its advantages of lightweight, anti-corrosion, and industrial manufacturing. Its long-term performance has attracted increasing attentions from academia and industry. This paper presents a comprehensive review on experimental studies investigating the mechanical performance of pultruded FRP composites subjected to long-term environmental effects, including water/moisture, alkaline solutions, acidic solutions, low/high temperatures, ultraviolet radiation, freeze-thaw cycles, wet-dry cycles, and in situ environments. Over 1900 experimentally determined mechanical properties of FRP materials were collected, including tensile, compressive, flexural and shear strength and moduli. The reported test data were highly dispersed, and no uniform conclusions could be drawn from these data. Exposure to water and water-based solutions (alkaline and acidic solutions) had detrimental impacts on the mechanical properties of pultruded FRP materials, whereas other environmental effects induced various levels of degradation. The degradation mechanisms for each environmental effect were discussed, and the existing design approaches were presented. Based on the findings from this review, recommendations were proposed for future works. The database presented herein, which is the largest in the available literature, enables a comprehensive understanding of the degradation behavior of pultruded FRP composites. Moreover, this work can serve as a foundation for deriving predictive models for pultruded FRP materials exposed to long-term environmental effects.

A comprehensive review on mechanical properties of pultruded FRP composites subjected to long-term environmental effects

Influence of hygrothermal environment on thermal and mechanical properties of carbon fiber/fiberglass hybrid composites

Acoustic metamaterials with negative dynamic mass density have been shown to demonstrate a five-fold increase in transmission loss (TL) over mass law predictions for a narrowband (100 Hz) at low frequencies (100–1000 Hz). The present work focuses on the scale-up of this effect by examining the behavior of multiple elements arranged in arrays. Single membranes were stretched over rigid frame supports and masses were attached to the center of each divided cell. The TL behavior was measured for multiple configurations with different magnitudes of mass distributed across each of the cell membranes in the array resulting in a multipeak TL profile. To better understand scale-up issues, the effect of the frame structure compliance was evaluated, and more compliant frames resulted in a reduction in the TL peak frequency bandwidth. In addition, displacement measurements of frames and membranes were performed using a laser vibrometer. Finally, the measured TL of the multi-celled structure was compared with the TL behavior predicted by finite element analysis to understand the role of nonuniform mass distribution and frame compliance.

Membrane-type metamaterials: Transmission loss of multi-celled arrays

The task of monitoring asset status and optimizing asset utilization for the T&D industry, given millions of assets and hundreds of thousands of miles of power lines distributed geographically over millions of square miles, seems particularly challenging if not impossible. Given the traditionally high cost of sensing and communications, the grid has minimal 'smarts' with much of the intelligence located at major substations. Dramatic reductions in sensor, computing and communications costs, coupled with significant performance enhancements has raised the possibility of realizing widely and massively distributed sensor networks (SNs) to monitor utility asset status. Under NEETRAC funding, a survey was conducted to review existing sensor technologies and products, and to estimate the possibility of extending these to realize distributed SNs. Possible applications for such SNs were also explored, as was the issue of cost point at which such networks would become commercially viable. This paper provides an overview of the highlights from the detailed survey that was conducted, and identifies 'gaps' in currently available sensor technologies, both from a performance and cost point.

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A Survey on Technologies for Implementing Sensor Networks for Power Delivery Systems

Unidirectional hybrid composite rods were conditioned in humid air to investigate the sorption kinetics and the effects of moisture on mechanical and physical properties. Sorption curves were obtained for both hybrid and non-hybrid composite rods to determine characteristic parameters, including the diffusion coefficient (D) and the maximum moisture uptake (M∞). The moisture uptake for the hybrid composites generally exhibited Fickian behavior (no hybridization effects), behaving much like non-hybrid composites. A two-dimensional diffusion model was employed to calculate moisture diffusivities in the longitudinal direction. Interfaces and thermally-induced residual stresses affected the moisture diffusion. In addition, the effect of hygrothermal aging on glass transition temperature (Tg), short beam shear strength (SBS), and tensile strength was determined for hygrothermal exposure at 60 °C and 85% relative humidity (RH). Property retention and reversibility of property degradation were also measured. Microscopic inspection revealed no evidence of damage.

Moisture absorption of unidirectional hybrid composites

A new type of overhead conductor with a polymer composite core is evaluated in terms of the mechanical properties and operating characteristics. The conductor is composed of trapezoidal O'-tempered aluminum wires helically wound around a hybrid glass/carbon composite core produced by pultrusion. The conductor is intended for electrical power transmission, and is designated ACCC/TW, for aluminum conductor composite core/trapezoidal wire. Measurements of core properties and conductor sag at high temperatures were compared to conventional ACSR (aluminum conductor, steel-reinforced) of the same diameter. The tensile strength of the ACCC/TW was /spl sim/1.5 times greater than conventional ACSR of the same outer diameter. The CTE of the composite core was approximately 4 times lower than the steel core in ACSR. The ACCC/TW conductor exhibited a six-fold reduction in high-temperature sag compared with conventional ACSR (Drake) when operated at the same current. The ACCC/TW conductor also exhibited greater ampacity than ACSR conductor at all operating temperatures.

A. Alawar

Papers

A composite core conductor for low sag at high temperatures

High-temperature strength and storage modulus in unidirectional hybrid composites

A hybrid numerical method to calculate the sag of composite conductors