Studies On Enhancement Of Mechanical Properties Of Ramie And Flax Composites

The approaches of enhancing the mechanical properties of ramie and flax composites were studied in this paper. The effects of surface pretreatment, fiber content, molding temperature and pressure as well as the effect of electron beam, microwave and ultrasonic wave on the mechanical properties of the composites were explored. The experimental results show that:1. Both ramie and flax are hydrophilic fibers, their thermal stability is not pretty well. The optimal molding temperature and pressure of their composite are 140C and 7.3 MPa.2. The tensile strength, flexural strength and flexural modulus of alkali pretreated ramie/LLDPE composite are increased from 51.2 MPa, 23.1 MPa, 1.58 GPa to 102.6 MPa, 30.4 MPa, 1.66 GPa. Those of silane pretreated ramie/LLDPE composites are increased to 91.1 MPa, 86.3 MPa, and 6.79 GPa respectively. The tensile strength of flax/LLDPE laminates are increased from 84.8 MPa to 96.9 MPa (alkali pretreated) and 115.8 MPa (silane pretreated).3. By means of electron beam irradiation, some oxygen containing groupe are introduced on the molecular chain of LLDPE, the interface compatibility of the composite is improved. The yield strength and young's modulus of ramie/LLDPE are increased from 9.78 MPa, 432 MPa to 13.1 MPa and 633 MPa respectively.4. The presence of microwave or ultrasonic wave, the inter- and intra-molecular complexation of cellulose molecules through hydrogen bonding is weakened, and the complexed polymer of cellulose and nylon formed in situ. The yield strength and young's modulus of the ramie/nylon/LLDPE composites are increased from 9.68 MPa, 260 MPa to 15.7 MPa and 722 MPa respectively.5. The tensile strength and elastic modulus of ramie fiber (RF)/LLDPE are 51.2 MPa ,1.17 GPa; flexural strength and modulus are 23.1 MPa, 1.58 GPa. In case one third of ramie fiber (RF) is replaced by glass fiber (GF), the tensile strength and elastic modulus are increased to 117.7 MPa, 4.85 GPa; flexural strength and modulus increased to 31.5 MPa and 3.65 GPa respectively.