Fundamental Understanding of the Effect of Paper Filler on the Mechanical Property Behavior of Hybrid Paper/LDPE/Oak Composites

Wood plastic composites (WPC) are the generic classification used to describe cellulose filled polymer matrices. The largest commercial use of wood plastic composites is in the building and construction sector as a replacement for wood in exterior applications due to its superior dimensional stability and rot resistance. It has been found that wood plastic composite decking is a well suited application for converting and reclaiming large amounts of recycled plastic waste as well as waste wood fibers and has evolved as a sustainable sector of manufacturing. Commercial wood plastic composites have continued to improve but are still limited by inherent limitations in strength and stiffness (as compared to wood) for structural applications.;The primary objective of this research is to study the effects of paper fiber filler content on the mechanical properties of a hybrid wood plastic composite. It is hypothesized that the addition of high aspect ratio paper fibers to a conventional wood plastic composite will enhance the mechanical properties of the composite by significantly increasing interfacial area resulting in better stress transfer potential between phases. It is postulated that incorporation of paper fibers in the composite will create the formation of a 3D reinforcing network within the matrix.;The secondary objective of this research is to develop and validate a hybrid composite rule of mixtures model to predict the mechanical properties of a hybrid composite at various paper contents based on the average measured mechanical properties of its constituent composites. It is hypothesized that even though fillers of different type and geometry are used for each constituent composite, an equivalent strain assumption will be valid given that they are compounded in the same grade of resinous matrix. With this assumption, a relationship is derived where the properties of the hybrid system are related linearly to the volume fraction of the constituent composites.;The objectives were obtained through the design and synthesis of a controlled series of experiments examining hybrid paper/low density polyethylene (LDPE)/oak composites at 60 wt% LDPE and paper concentration at eight levels varied from 0--40 wt%. Experimental outputs from the study are density, tensile modulus, tensile strength, tensile strain at break, flexural modulus, and flexural strength. The test results showed that all mechanical properties significantly improve with increased concentrations of paper fiber in the hybrid composite. The test results also showed that the hybrid rule of mixtures model based on volume fraction correlated very well with experimental data. Scanning electron microscopy was used on select tensile fracture specimens to identify and propose mechanisms responsible for observed behavior.