Study On Mechanical And Damping Properties Of Ramie Fiber Reinforced Polypropylene Composite For Automobile

With the environmental pollution becoming a global issue,green composites are wildly used in automobile industry.Bast fiber reinforced polymer matrix composites have broad application prospects,because they are lightweight,environmental friendly,biodegradable,and have good mechanical properties,excellent vibration damping and noise reduction properties.The ramie fiber was treated with epoxy-silicone oil(ESO).And the ramie fiber reinforced polypropylene composites(RF/PP)were fabricated by a hybrid molding technology of extrusion and injection.This paper studied the effect of fiber content and fiber treatment on the mechanical properties of RF/PP composites.The modal analysis was used to investigate the effect of fiber content and vibration amplitude on the damping properties of RF/PP composites.The main results are as follows.Both the tensile and flexural properties of the RF/PP composites were higher than pure polypropylene.And the tensile and flexural strength of the RF/PP composites were improved with the increase of ramie fiber content.But the tensile elongation and impact strength of the RF/PP composites showed a declining trend with the increase of fiber content.Compared to pure polypropylene,the tensile and flexural strength of the treated ramie fiber reinforced polypropylene composite with 30wt% fiber content increased by 50.8% and 107.4% respectively.In addition,the tensile,flexural and impact properties of the epoxy-silicone oil(ESO)treated composites were better than that of untreated composites.The SEM observation indicated that the ESO modification enhanced the adhesion strength of the interface between ramie fiber and polypropylene matrix.The natural frequencies of the ramie fiber reinforced polypropylene(RF/PP)composites were significantly higher than that of pure polypropylene.And the natural frequencies of the RF/PP composites linearly increased with increase of ramie fiber content.The first and second damping ratios of the RF/PP composites were higher than that of the pure polypropylene.And they were improved with the increase of ramie fiber content.Compared to of the pure polypropylene,the first damping ratios of the 10wt%,20wt% and 30wt% fiber content RF/PP composites increased by 12.9%,25.8% and 58.1% respectively.It was worth to notice that a critical amplitude(Ac)appeared on the tested amplitude-dependent damping ratio curves.The critical amplitudes for composites with 10wt%,20wt% and 30wt% fiber content were of 6mm,8mm and 10 mm,respectively.The damping ratio almost reached the maximum value at Ac because the highest amount of fiber/matrix slippage happened in composite system.Unlike damping ratio,the vibration amplitude had negligible influence on the natural frequency of RF/PP composites.But the natural frequency of the RF/PP composites presented an increased trend with the increase of the fiber content.The research finding of this paper could promote the study of the mechanical and damping properties of the bast fiber reinforced composites.