Technical literature on the subject of environmental exposure effects related to determining accelerated test methods for the prediction of long-term performance of FRP composite materials for highway structural applications is reviewed in this paper. Effects of environmental exposure of a chemical and a thermal nature on fiberreinforced polymer (FRP) composites are considered. Such exposures include temperature, moisture and chemicals in liquid solutions or in gaseous mixtures. The effects include the changes in the physical and mechanical properties of the composite materials. Such changes are typically related to the degradation or deterioration of the composite material. Synergistic effects of mechanical load and exposure are also reviewed. The review is divided in topics entitled Materials, Exposure Conditions, Experimental Techniques, Failure Mechanisms and Theoretical Modeling.

Studies of the reactions between rare earth salts and phosphoric acid in aqueous or ethanolic media have shown that in both cases stable gels can be formed. Upon drying, gels prepared in aqueous environments yield macrocrystalline REPO 4 products similar to those produced by conventional precipitation and drying. Gels prepared in ethanol, on the other hand, undergo dehydration to form dense microcrystalline products. This observation is based on optical and scanning electron microscopy, as well as on x-ray diffraction studies and infrared spectroscopy. These techniques, as well as differential thermal analysis, indicate that crystal growth of these products takes place around 600-700 ± C. The composition of the dehydrated gels produced in both the aqueous and ethanolic systems corresponds to an orthophosphate structure. Other characteristics of the microcrystalline REPO 4 products include high resistance to attack by water, absence of coloration upon exposure to gamma rays, and a high index of refraction.

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Slow processes in viscous liquids: Stress and structural relaxation, chemical reaction freezing, crystal nucleation and microemulsion arrest, in relation to liquid fragility AIP Conf.The question of relaxation time distributions in viscous liquids is examined by observing time-dependent behavior of optically active elements of the liquid structure, both intrinsic and otherwise, in response to perturbations from equilibrium states. As a suitable medium for this study the polyalcohol sorbitol C 6 Hg{OH)6 is adopted. Equilibrium distributions of intact and broken hydrogen bonds in the pure sorbitol have been determined using near IR spectra, and the loss of, and re-establishment of, this equilibrium, during down and up temperature ramping processes, has been monitored and analyzed. The hydrogenbond equilibrium is established on essentially the same time scale and with essentially the same distribution ofre1axation times as for the enthalpy. (The latter has been monitored by differential scanning calorimetry). Analysis shows that the kinetics of the bond-breaking process are well accounted for by a relaxati0f, function, near equilibrium, of the formwith J3 = 0.55 ±0.03. As extrinsic probes, two carbocyanine dyestuffs have been introduced in low concentrations into the sorbitol, and the equilibrium distribution of monomer and dimer species has been determined as a function of temperature. The loss and recovery of the equilibrium has also been monitored during down and up temperature ramping experiments. It is found that these equilibria are lost and recovered at temperatures far above that at which solvent structure equilibrium is established on the same time scale, showing that equilibration times for the monomer-

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