Development of beneficial residual stresses in glass fiber epoxy composites through fiber prestressing

Abstract

The undesired residual stresses in fiber reinforced polymer composites are developed during their manufacturing processes due to the thermal and chemical shrinkage of the polymer matrix, which negatively affect the performance of the composites. Applying tensile stress to the reinforcement fibers during the curing of the matrix can reduce or eliminate the undesired residual stresses. Furthermore, the undesired tensile residual stress within the matrix can be replaced with beneficial compressive residual stress which can improve the mechanical properties of the composites. In this study, theoretical stress analysis was performed in order to determine the value of the optimum compressive residual stress that is associated with the highest tensile strength. This value was determined based on the tensile testing result of prestressed composites with a 40% fiber volume fraction. For the composites with different fiber volume fractions, a new approach was introduced to estimate the optimum fiber prestressing level which generates the optimum compressive residual stress within the matrix and consequently, the highest tensile strength can be achieved. In order to validate this approach experimentally, prestressed composites with 25 and 30% fiber volume fraction were prepared by applying the estimated optimum fiber prestressing levels during curing of matrix and tensile testing was performed. The result of the stress analysis showed that the value of the optimum compressive residual stress corresponding to the highest tensile strength is 2.5 MPa approximately. The tensile testing results confirmed the validity of the new approach in estimating the optimum fiber prestressing level for the composites with different fiber volume fractions. For both prestressed composites with 25 and 30% fiber volume fraction, the highest tensile strength was achieved when the theoretically estimated optimum fiber prestressing level was applied to the fibers during the curing of the matrix.

Monitoring of mechanical properties of prestressed glass fiber epoxy composites over 12 months after fabrication

“…16,20,21 Similar to the prestressed concrete, the initial applied prestress in the fiber undergoes two types of losses: (1) instantaneous losses or short-term losses and timedependent losses or long-term losses. In a previous study, Mohamed et al 14 reported two sources of the instantaneous prestress losses. The curing-induced residual stresses that develop during the cooling of composite from the high curing temperature to room temperature is the first source.…”

“…Due to the bond between the fiber and matrix, the tensile residual stress within the fiber is balanced by producing compressive residual stress into the surrounding matrix. 8,10,13,14 The elastic method was the only known method of producing prestressed FRP composites until the late 1990s when Fancey invented a new prestressing method relies on using fibers with a viscoelastic behavior such as nylon. 15 The difference in this method is that the tension force is applied to the fiber for a particular time and released before molding the pre-tensioned fiber into the matrix.…”

Effect of Graphene Oxide-Boron Nitride-Based Dual Fillers on Mechanical Behavior of Epoxy/Glass Fiber Composites

“…Glass fibers have better thermal stability and dimensional stability that initiates their usage in various technological applications [5,6]. In the last few years, material researchers focus on developing advanced materials to decrease fuel [7][8][9][10] consumption in transport industries [11][12][13]. Hence, incorporation of these fibers in polymer material will confidently improvise the stiffness, flexibility, and strength.…”

Mechanical Properties and Thermal Conductivity of Epoxy Resin Reinforced with Functionalized Graphene Nanosheets and Woven Glass Fabric

“…[9][10][11] For this reason, recent studies have investigated the incorporation of glass fibers in petrochemical-based thermoset matrices to overcome these disadvantages and improve their overall mechanical properties. [12][13][14] Today, polyester, [15][16][17] epoxy, [18,19] and phenolic [20,21] resins are the most widely used thermoset matrices for natural fiberreinforced polymer nanocomposites.…”