Association Mechanical Engineers Technicians Slovenia
Abstract
The development of a new composite that is compounded of natural fibres and low price polymers such as
HDPE or PP began in the 90’s of the past century. Because this material is rather new on the market and due to
random characteristics of the fibres no attempts have been made to analytically define the mechanical
properties of this material. In this article the micromechanical approach called the Generalised Method of Cells
(GMC) is introduced to describe the properties of injection moulded wood-plastic composites compounded of
polypropylene (PP) or polystyrene (PS) and of wood or cellulose short fibbers. The main problem of analytical
approach is that natural fibbers are not uniform in shape and size, which makes them hard to fit into the
standard mathematical models. In this article average values of fibre size have been used. Materials were first
scanned with optical and electron microscope to determine the fibre properties and their scatter. These values
were then used in determining elastic and plastic response of the composite alongside with the maximum
strength and elongation of the composite where the Tsai-Hill failure criterion was used. The results were then
compared to the experimental data in order to evaluate the practical usefulness of this method
