Viscoplastic deformation of cotton fabric‐reinforced polypropylene composites

In this work, cotton fabric-reinforced polypropylene laminates (CFRLs) were prepared as an example to analyze the effect of viscoplastic deformation on the mechanical properties of natural fiber-reinforced composites. Compared with neat polypropylene (PP), the tensile strength and modulus of CFRLs are significantly enhanced in all directions. However, CFRLs are more prone to plastic deformation than PP during static tensile tests. The tensile strength of CFRLs could be affected by the processing factors. As the drawing speed was reduced from 20 to 0.1 mm/min, the tensile strength of CFRLs decreased by 27%. Cyclic tensile tests were used to analyze the effect of viscoplastic deformation on the tensile strength of CFRLs, and the results showed that when the viscous deformation increased, the strain increased, leading to rapid fracture of CFRLs under cyclic tensile stress much lower than the tensile strength. By simulating the stress conditions of pressure vessels and pipes with different curved surfaces, CFRLs are shown to be more suitable for cylindrical curved structures, which has developable surface; While, they are not suitable for complex curved structures, such as spherical surfaces, that are undevelopable surface.