Effect that natural fibres have on the quasi-static and dynamic elasticity modulus, and damping ratio of glass fibre laminates obtained by the vacuum bag technique

The use of natural fibres is gaining interest because of their potential in the development of human and environmentally friendly materials with very high mechanical stability. Natural fibres contribute with good damping... [ view full abstract ]

The use of natural fibres is gaining interest because of their potential in the development of human and environmentally friendly materials with very high mechanical stability. Natural fibres contribute with good damping properties, low density and moderate strength. The effect of incorporating short and long length chopped natural fibres, as disperse reinforced phase, on the dynamic and quasi-static elastic mechanical properties of glass fibre laminates is presented. The volume fraction of untreated and treated short natural fibre in the first configuration was 30% and its mass fraction 6%, while in the second configuration, short and long natural fibre volume fraction was 15% and 40%, with a mass fraction of 4.7% and 4.3% respectively. The dynamic elasticity modulus and damping ratio was estimated with a cantilever model set up. Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials (ASTM D3039) was also used to further characterize the thin samples (≈0.7mm, ≈1.3 mm for each configuration). The results showed that treatment had a poor effect and that the samples with short coir fibre showed an increase in the dynamic elastic modulus value of 22% with regard to that one of glass fibre samples without coir fibre and samples with long coir fibre ones showed a decrease of 22%. The variation of damping ratio of samples with both short and long coir fibre increased significantly in comparison to the control samples (25% and 57% respectively). The tensile properties obtained are lower for both short and long coir fibre samples than the ones without. Quasi-static elasticity modulus decreased 21% and 30% for short and long coir fibre samples respectively. In conclusion, beside human and environment friendship, the study suggests that addition of coir fibre layers in hybrid composite glass fibre laminar arrangements must significantly improve fatigue life and acoustic properties due to better damping properties. Natural fibre length affected samples vibration frequency differently suggesting a higher rigidity for short length fibres.

Keywords:
Coir fibre, hybrid reinforcement, dynamic elastic modulus, quasi-static elasticity modulus, Young’s modulus, damping rate.