No abstract

Composite materials have been manufactured using bidirectional jute yarn in a polyester matrix. The manufactured composite has been subjected to water aging for various times of immersion (90, 180, and 270 days). A significant decrease of fatigue strength has been observed during water aging. The number of cycles to failure of the aged and nonaged specimens were correlated using the two-parameter Weibull distribution function to determine the probability of failure and plot the S-N curves at different reliability levels. The results have shown that the two-parameter Weibull distribution describes the fatigue life probability distributions of jute-reinforced polyester composite material with highly significant statistical correlation coefficients.

Randomly oriented short fiber mat reinforced polyester composite laminates immersed in natural seawater for various periods were tested in static and cyclic fatigue loading under three-point bending conditions. Water absorption increased the weight of the specimen while the extraction of soluble compounds induces a weak weight loss. Wöhler curves carried out from repetitive fatigue tests were drawn for the different periods of immersion time. These curves, which are characterized by an important and a significant scatter in their lifetime, were modeled by straight lines. These glass-polyester laminates deteriorate in fatigue tests at a constant rate by cycle decade. This rate increases with increasing immersion time in seawater at a constant speed. A comparison between different mathematical models of endurance curves shows that Wöhler's equation gives a good representation of the average part of the curve.

In recent years, the use of natural fiber composites to provide a possible replacement for synthetic fiber composites for practical applications has been the subject of several studies. This study deals with the fabrication and investigation of jute-polyester composites and the comparison of it with glass-polyester composites. The static mechanical properties of the composites is obtained by testing the composite lamina for tensile and flexural strength. The dynamic mechanical properties of the composites is determined by using the Charpy impact test. By the Williams method based on the principle of linear elastic fracture mechanics, the impact toughness of the composites is deduced. The experimental results were statistically analyzed by using the Weibull theory to better understand the impact behavior of the composites. It is found that the glass-polyester composite has better properties than the jute-polyester composite.