Mechanical Modelling of Bamboo Sawdust/polyester Composites Fabricated by Hot Pressing Method

Bamboo fibres of 1 to 3 mm sizes were milled to particle size of approximately 100μm using a hammer mill. The  bamboo sawdust (BS) was chemical treated using NaOH of concentration 6 % wt/v for 72 h at room temperature.  Dried bamboo sawdust was mixed with polyester at different weight ranging from 0 % to 24 % wt. %. The com posites were tested for the tensile properties. Theoretical mechanical equations were used to predict the proper ties. Polyester curve showed linear deformation behaviour with the stress rising to a maximum value with signs of  yielding before fracture. The tensile strength of polyester was 49.38 MPa, increasing to a maximum of 76.47 MPa  at 24 % wt. of BS. At zero wt. % of BS the modulus was 1381 MPa, and increased to 2587.08 MPa at 24 % wt.  The strain decreased from 5.5 % at pure polyester to 3.32 % at 24 % wt. of BS. A maximum percentage decrease  of ≈ 40 % for the strain was recorded, an indication of the brittleness of the composites. Prediction of mechanical  properties using published theories of mechanical equations (tensile strength and Young’ modulus) with experi mental results of bamboo sawdust reinforced polyester composites was investigated. The models used were rule  of mixture (Parallel and Series), Hirsch’s and Halpin-Tsai models. Irrespective of the equation used tensile  strength increased with increase in the volume fraction of BS. The best correlation between theoretical and exper imental tensile strength was predicted using the Halpin-Tsai model, followed by Hirsch, Parallel and Series re spectively. Depending on the volume or weight fraction the percentage prediction was between 79 and 88 % for  Parallel and Series models and between 97 and 99 % for Halpin-Tsai and Hirsch models