Herein, the influence of distilled water and alkaline solution on the scratch resistance properties of Napier fibre filled epoxy (NFFE) composites were investigated. The particulate Napier fibre form was mixed with epoxy resin to fabricate 5, 10, and 15 wt.% NFFE composites. Moisture exposure tests using distilled water and alkaline solutions were conducted to determine the critical time conditions of the composites. Scratch tests were performed to investigate the scratch resistance properties of the NFFE composites, such as critical normal load, coefficient of friction, penetration depth, fracture toughness and tearing extent. The results showed that with the increasing fibre content of the composites, the scratch resistance properties increased after exposure to distilled water and an alkaline solution. The 10 wt.% NFFE composites had the highest critical normal load and fracture toughness after exposure to distilled water and alkaline solution. Morphological observations showed that severe tearing occurred for all NFFE composites after exposure to the alkaline solution compared to distilled water.
