Abstract
In recent years there has been a resurgence of interest in the usage of natural fiber reinforced composites in more advanced structural applications. As a result, the need for improving their mechanical properties, as well as service life modeling and predictions have arisen. In this study effect of alkaline treatment of flax fiber as well as addition of 1% acrylic resin to vinyl ester on mechanical properties and long-term creep behavior of flax/vinyl ester composites was investigated. To perform the alkaline treatment, fibers were immersed into 1500 mL of 10 g/L sodium hydroxide/ethanol solution at 78 °C for 2 h. Findings revealed that alkaline treatment was successful in increasing interlaminar shear, tensile and flexural strength of the composite but decreased the tensile and flexural modulus by 10%. Addition of acrylic resin to the vinyl ester resin improved all mechanical properties except the flexural modulus which was decreased by 5%. In order to evaluate the long-term behavior, creep compliance master curves were generated using the time-temperature superposition principle. Results suggests that fiber and matrix treatments delay the creep response and slows the process of creep in flax/vinyl ester composites in the steady state region, respectively.
Highlights
Smaller microfibrillar angle will result in a moProelymriegrsi2d015fi,b7,eprag[e1–6pa].ge According to Bledzki et al [18], the secondary wall contributes to up to 70% aofmtohree rfiigbiedrfiYbeoru[n1g6]’.sAmccoodrduilnugst,otBhleerdezfkoireet ahli.g[1h8e]r, tcheelsluecloonsedacroynwteanlltcownitlrlibruetseuslttoiunphtoig7h0e%r otfensile moduthleusfib[1er8]Y.oung’s modulus, higher cellulose content will result in higher tensile modulus [18]
Alkaline treatment was successful in increasing interlaminar shear strength and tensile and flexural strength of the composites
The highest gain was observed where vinyl ester containing 1% acrylic resin was reinforced with alkaline treated flax fiber except for tensile modulus
Summary
Due to their superior advantages, natural fibers, such as flax, have been the center of attention as natural reinforcement in composite materials for the past couple of decades. The first layer dispositioning during plant growth is a thin primary wall containing both cellulose and hemicellulose and has a thickness of around 0.2 μm [16,17]. The middle layer of secondary wall, is thicker than first and third layer and contributes to the strength of the fiber. The secondary wall includes three layers which consists of helically wound highly crystalline cellulose chains called microfibrils. These microfibrils are made up of 30 to 100 cellulose molecule chains which are oriented with approximately 10 ̋ angle with the axis of the fiber. Smaller microfibrillar angle will result in a moProelymriegrsi2d015fi,b7,eprag[e1–6pa].ge According to Bledzki et al [18], the secondary wall contributes to up to 70% aofmtohree rfiigbiedrfiYbeoru[n1g6]’.sAmccoodrduilnugst,otBhleerdezfkoireet ahli.g[1h8e]r, tcheelsluecloonsedacroynwteanlltcownitlrlibruetseuslttoiunphtoig7h0e%r otfensile moduthleusfib[1er8]Y.oung’s modulus, higher cellulose content will result in higher tensile modulus [18]
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