Tension-tension axial fatigue of E-glass fiber-reinforced polymeric composites: fatigue life diagram

Fiber-reinforced polymeric (FRP) composites have been under analytical and experimental investigations for approx. 40 years in the context of aerospace, marine and mechanical applications. Now the use of FRP composites in civil engineering applications is steadily increasing. For civil engineering structures subject to cyclic loading, one important limit state in design is fatigue. Thus, a review of the existing data is necessary to determine the applicability to civil engineering structures. This review will focus on E-glass FRP compolites under tension-tension axial fatigue with test frequency cif 5 Hz or less, without environmental concerns. Test and material parameters, which define the data, are identified as R ratio, test frequency, load control, specimen shape, type of reinforcement and resin. A fatigue life diagram summarizing the E-glass FRP composite tension-tension axial fatigue data is plotted for normalized stress (maximum fatigue stress divided by ultimate tensile strength) vs. log of fatigue life. This plot reveals a lower bound confidence level, regardless of test parameter combination, such as reinforcement, resin, or R ratio. This lower bound confidence level was challenged via laboratory testing of an E-glass/vinylester composite in tension-tension axial fatigue for R ratios 0.05, 0.1, 0.5 and 0.9, and test frequencies 1, 3 and 5 Hz. The laboratory test data support the lower bound confidence level. This lower bound may be used in designing E-glass FRP composites for use in civil engineering structures conservatively estimating tension-tension axial fatigue life with test frequency 5 Hz or less. This lower bound may be used until further studies refine the effects of the individual test parameters on fatigue life. (C) 1998 Elsevier Science Ltd. All rights reserved.