Multi‐scale experimental investigation of porosity‐induced damage effects in filament‐wound carbon fiber reinforced epoxy composites used in hydrogen storage tanks

Abstract Hydrogen‐fueled vehicles, recognized for their environmental benefits as they emit only water vapor, represent a sustainable alternative to traditional cars. This paper investigates the relationship between the microstructure and mechanical properties of carbon fiber‐reinforced epoxy composites used to manufacture lightweight hydrogen storage pressure vessels through the filament winding process. This fabrication technique, while common, often results in variable fiber orientations and porosity content that affect the mechanical properties of the composite structures. Our study uses tubes made from carbon fiber reinforced epoxy resin with different angular fiber orientations (±15° and ±30°) and multilayer structures to analyze how these variations impact the mechanical properties and damage behavior of the composites. A series of tests, including physical–chemical characterizations, porosity measurements, and multiscale mechanical assessments such as tensile and loading‐unloading analysis have been conducted. The results demonstrate that porosity, measured in the range of 5%–7%, significantly impacts mechanical performance. Moreover, a 40% decrease in Young's modulus was observed between the ±15° and ±30° fiber orientations, and a 65% reduction was noted for the multilayer structure. Microscopically, the presence of porosity initiates cracks and leads to fiber/matrix decohesion and fiber breakage. Mesoscopically, these defects can merge to form transverse cracks and micro‐delaminations between layers, highlighting the complex behaviors of these composites under loading. This information is critical for improving the design and durability of hydrogen storage systems. Highlights Porosity, measured in the range of 5%–7%, significantly affects mechanical performance, reducing Young's modulus by up to 40% between ±15° and ±30° fiber orientations and by 65% in multilayer structures. Fiber/matrix decohesion and crack initiation due to porosity lead to the formation of transverse cracks and micro‐delaminations between layers, affecting the durability of the composite. Optimizing fiber orientation and reducing porosity are critical to improving the mechanical performance and long‐term durability of hydrogen storage vessels.