Effect on dynamic, quasi-static elastic moduli of glass fiber laminates

The use of natural fibers has attracted great interest due to their damping properties, low density and moderate strength. The effect of incorporating chopped natural fibers, as disperse-reinforced phase, on the dynamic or the quasi-static elastic modulus of glass fiber (GF) laminates is presented. The experimental set-up allowed the comparison of adding either coir or extra epoxy when preparing hybrid composite materials using the vacuum bag technique. Squares of 32 cm² plain weave GF pre-impregnated with epoxy resin were used in a stacking sequence [0]₄. The volume fraction of the natural fiber was 30%, and 254-mm-long and 25·4-mm-wide samples were cut and tested at vibration conditions in a cantilever beam arrangement. The vibration frequency was measured by an ADXL335 accelerometer at the z axis, perpendicular to the sample test plane; the elastic modulus was estimated by the cantilever model. The results showed that the samples with coir fiber had an increase in the dynamic elastic modulus value of between 150% and 171% with regard to that of the GF samples without fiber; higher volumes of epoxy improved the coir fiber adhesion preventing delamination, although this lowered the dynamic elastic value. The tensile test confirmed that 30% epoxy addition increased the stiffness of glass/coir lowering their dynamic and quasi-static Young’s modulus.