The Influence of Alkaline Treatment on Delamination resistance of Woven Flax Fiber-Reinforced Epoxy Composite Laminates

Abstract Delamination is one of the most typical failure modes of fiber-reinforced polymer composite laminates. Thus, investigating and improving the delamination behavior of these laminates are of vital importance. The present research discovers and investigates the role of the alkaline treatment of twill-woven flax fabric on the delamination resistance of flax fiber-reinforced epoxy composite laminates. Initially, flax fibers were treated with different sodium hydroxide solution concentrations (2–5–10%) for 2 h. The influence of alkaline treatment on fiber characteristics was evaluated by performing a single-yarn tensile test, scanning electron microscopy, and Fourier transform infrared spectroscopy analysis for treated and untreated flax fibers. The appropriate treatment condition was selected based on the properties obtained from the tests conducted on the fiber level. Subsequently, to discover the role of alkaline treatment on delamination resistance, flax fabric was treated with the selected treatment condition for further composite fabrication. The treated and untreated flax fiber-reinforced epoxy composites were fabricated using a hand lay-up technique followed by hot compression. Interlaminar shear strength, double cantilever beam, and end-notch flexural tests were carried out for treated and untreated composites to determine the effect of alkaline treatment on the delamination resistance. The results proved that the alkaline treatment of flax fabric significantly improved the delamination resistance of treated composite laminates compared to untreated ones. The interlaminar shear strength, the mode I interlaminar fracture toughness (propagation), and mode II interlaminar fracture toughness were improved by 27.3%, 14%, and 24.9%, respectively, for treated composite laminates compared to untreated ones.