The automotive industry is increasingly focusing on lightweight and high-performance materials to meet stringent environmental and efficiency standards. Polymers play a pivotal role in this shift, as they offer design flexibility and significant weight reduction. Injection moulding is one of the most widely used manufacturing processes for producing high-quality plastic components in the automotive sector. A critical application area is in hydrogen fuel cell vehicles, where the integrity and durability of Type 4 hydrogen storage tanks depend on the strong adhesion between the polymer liner and the composite structure. Enhancing this bond is crucial to ensuring safety and performance under high-pressure conditions. By tailoring the surface microstructure of polymer liners through advanced injection moulding techniques, the adhesion to composite materials can be significantly improved. Despite the detailed mechanical properties provided in the technical data sheets of polymers, fatigue characteristics are often not included, even though many automotive plastic components are exposed to repetitive stresses during their operational life. This research aims to investigate the effect of microstructures created by modern manufacturing technology, which is currently undergoing significant development for automotive applications, particularly in relation to hydrogen technology.