Predicting the tensile strength of natural fibre reinforced thermoplastics

Abstract

The tensile strength of short natural fibre reinforced thermoplastics (NFRT) was modeled using a modified rule of mixtures (ROM) strength equation. A clustering parameter, requiring the maximum composite fibre volume fraction, forms the basis of the modification. The clustering parameter highlights that as fibre loading increases, the available fibre stress transfer area is decreased. Consequently, at high volume fractions this decrease in stress transfer area increases the brittleness of the short fibre composite and decreases the tensile strength of the material. A key parameter, the interfacial shear strength, was determined by fitting the micromechanical strength model to tensile strength data at low fibre loading (10 wt%) where there is minimal fibre clustering. To test the modified ROM strength model, compression molded specimens of high-density polyethylene (HDPE) reinforced with hemp fibres, hardwood fibres, rice hulls, and E-glass fibres were created with fibre mass fractions of 10–60 wt%. The modified ROM strength model was found to adequately predict the tensile strength of the various composite specimens.