Moisture and Temperature Induced Degradation in Tensile Properties of Kevlar-Graphite/Epoxy Hybrid Composites

Abstract

This paper presents results of a comparative study of the effects of moisture and temperature on tensile properties of Kevlar 49/epoxy, graphite/epoxy, single fiber and Kevlar 49-graphite/epoxy hybrid composites. The work reported here shows variations in tensile strength, elastic modulus and Poisson's ratio with changes in the hygrothermal conditions. A temperature range of 23°C to 150°C was considered for both dry and wet specimens exposed to moisture for 200 days. Moisture was introduced into the specimen by immersion in distilled water. Effects of the kind of outer fiber of the same hybrid system was also studied for better understanding of the behavior of hybrid composites. Variation in the tensile modulus determined by various test methods is also reported.The results indicate that moisture and temperature degrade the tensile strength of hybrid and single fiber composites. The tensile modulus of Kevlar 49-graphite/epoxy is comparatively higher than that of Kevlar 49/epoxy. The degradation of the tensile modulus is mostly temperature dependent. The presence of moisture either increases or decreases the tensile modulus depending upon the laminate and exposure conditions. Poisson's ratio in general appears to increase with temperature. In the presence of moisture the Poisson's ratio further increases between the temperatures of 45°C to 150°C.

Failure Load of Mechanically Fastened Immersed Composite Laminated Plates under a Preloaded Moment

“…The bolted joint was constructed for carrying the preload moment. Some specimens were observed in dry and unimmersed conditions; meanwhile, some specimens were kept for 200 days 21 in sea water taken from the İzmir Gulf.…”

Moisture Absorption/Desorption Effects on Flexural Property of Glass-Fiber-Reinforced Polyester Laminates: Three-Point Bending Test and Coupled Hygro-Mechanical Finite Element Analysis

“…The “hot/wet” exposure is supposed to be the severest environmental condition to degrade the performance of polymeric materials [9,10,11,12,13,14,15,16,17], which decreases the service-life of FRP composite bridges. The influence of moisture absorption on mechanical properties of FRP composites is well documented in literatures [9,10,11,12,13,14,16,17,18,19,20,21,22,23,24,25,26], regarding the tensile, interlaminar shear and flexural properties. Shao et al’s research [9] found that the tensile strength of the aged composites decreased with the increase of percent absorption.…”

Coupled Hygro-Mechanical Finite Element Method on Determination of the Interlaminar Shear Modulus of Glass Fiber-Reinforced Polymer Laminates in Bridge Decks under Hygrothermal Aging Effects

“…A comprehensive understanding of the mechanisms of the hygrothermal aging-related degradation on FRP composite materials is necessary for the purposes of evaluating and predicting the service life and durability of FRP infrastructures. In the literature, the influence of moisture absorption on the mechanical properties of FRP composites is well documented [9,10,11,12,13,14,17,20,21,22,23,24,25,26], regarding the tensile, interlaminar shear, and flexural properties as well as toughness. Generally, the combination of moisture and temperature effects seriously degraded the mechanical properties of FRP composites.…”