Estimation of the interfacial shears strength, orientation factor and mean equivalent intrinsic tensile strength in old newspaper fiber/polypropylene composites

The present paper investigates the suitability of old newspapers (ONPs) as a source of reinforcing fibers for composite materials. Different percentages of ONP fibers were compounded with polypropylene (PP). A coupling agent was added to the compound to improve the interface between matrix and reinforcing fibers. Tensile test were performed to obtain the mechanical properties of the composite materials. Micromechanics of the fibers were obtained using Hirsch model, Bowyer–Bader methodology and Kelly–Tyson equations. Due to the presence of a percentage of calcium carbonate in the obtained fibers (10%), the computed intrinsic characteristics were addressed as equivalent. The most important results were the mean equivalent intrinsic tensile strength of the ONP fibers, the mean orientation angle and the mean interfacial shear strength. The contributions of the matrix, the subcritical and the supercritical fibers to the tensile strength of the composite material were also computed.