Improvement of mechanical properties of ramie/poly (lactic acid) (PLA) laminated composites using a cyclic load pre-treatment method

Ramie/poly (lactic acid) (PLA) laminated composites were fabricated by the compression molding. To improve the mechanical properties of this type of composites, a cyclic load pre-treatment was performed. Ramie plain woven fabrics as the reinforcing material were pre-treated under wet state by cyclic tensile loading several times. The results showed that the fabrics treated by 70% level of the mean fracture load of the untreated ones with 10 cycles had the largest improvement of 38% in tensile strength. As to the mechanical properties of ramie/PLA laminated composites, the treated fabric reinforced composites had 35% higher tensile strength, 32% higher Young's modulus, 20% higher flexural strength and 17% higher flexural modulus than the untreated ones. The X-ray diffraction diagrams indicated that there was no distinct difference in crystallinity and crystalline orientation. The improvement of fabric mechanical properties is likely resulted from the increased orientation of molecules in the fibers and that of the fibers in the yarns.

► Ramie fabrics were cyclically tensile loaded to improve mechanical properties.
► When cyclic loading level reached 70%, tensile strength increased 38%.
► Using the fabric to reinforce PLA matrix composites, tensile strength and modulus increased 35% and 32%.