Study On Hygrothermal Ageing Of Ramie Fiber Reinforced Polymer Composites

With the growing environmental consciousness, Nature Fibre ReinforcedPolymer (NFRP) has been given more attention. Compared with traditional syntheticfiber composites, NFRP has the following advantages: small density, low price, lessenergy consumption, sound insulation, shock absorption, noise reduction and impactresistance.However, NFRP gain more weight after moisture absorption, mechanicalproperties decreased significantly and size is not stable. In order to promote safe andreliable application of NFRP in practical engineering structure, it has a remarkablesignificance to research degradation laws of moisture absorption and mechanicalperformance in thermal and humid environment.During the wet and heat resistance research， environmental temperatureincluding20℃(room temperature),40℃and60℃, environment humidityincluding50%RH,85%RH to98%RH have been focused. The performance testsof composite sheet include water absorption and diffusion, mechanical properties(such as tensile properties, flexural properties and short beam shear performance)and glass transition temperature, etc. Wet and heat endurance performance testperiod is6months. The test results are as follows:1）Based on moulding process, the ramie fiber fabric reinforced phenolic resinmatrix composite sheet has been prepared. Fiber Bragg grating (FBG) sensor hasbeen used to conduct real-time monitoring of the moulding process. The sheetinternal temperature and the strain of the change have been tested. The experimentalresults show that the plate internal produce a large contraction deformation.2）In thermal and humid environment, the moisture diffusion rate of NFRPcomposite sheet is influenced by temperature while the equilibrium moistureabsorption rate affected by humidity. Before the moisture absorption equilibrium (1~2weeks), mechanics performance declined faster. Mechanics performancedecreased significantly with the increase of humidity, but less affected bytemperature factors. In addition，the degree of modulus degradation is greater thanstrength.3）After completely drying, the mechanical properties of NFRP have a greatrecovery, closed to the initial value. Hygrothermal environment has a littleirreversible effect on NFRP.