Interfacial Coupling in Kevlar-Epoxy Composites for Production of Improved Filament Wound Casings

Abstract

The present invention relates to a method for improvement in mechanical properties of aramid fiber epoxy composites for applications in filament wound casings and CNG cylinders. More particularly, a process employing an interfacial agent that chemically links the said fiber surface with the epoxy matrix, providing an improvement in the dynamic elastic modulus of the said composite. The chemical interaction between this interfacial agent and fiber is confirmed by Differential Scanning Calorimetry (DSC) and Fourier Transform infrared (FTIR) spectroscopy. More specifically, the said fiber surface is treated with phthalic anhydride interfacial agent and subsequently processed using a prepeg machine to yield the desired composite exhibiting an order of magnitude enhancement in the dynamic modulus of the said composite. Dynamic Mechanical Testing (DMA) confirms the said improvement in the dynamic modulus. Additionally, surface modification of the said fiber by the said treatment also improved the adhesion to epoxy resin by 21%, as measured by fiber bundle pullout technique whereas the composite interlaminar shear strength increased by 16%. As opposed to prior art treatment methods based on plasma and chemical etching techniques, the method of the present invention achieves the said improvement in the elastic modulus of the said composite without incurring loss of strength in the aramid fiber.