9727144 Engblom The objectives of this research are threefold and include: (1) the characterization of micromorphology, (2) the determination of life cycle mechanical properties, and (3) the development of a computer-based design methodology, i.e., for fiber-reinforced commingled recycled plastic lumber (CRPL) of efficient structural form. Reinforcements would include hybrid combinations of chopped natural fibers, chopped recycled synthetic fibers, and continuous synthetic fibers. Rectangular hollowcored CRPL profiles will be extruded with variations in wall thickness and reinforcement to obtain mechanical properties equivalent to or better than 2x4 wooden lumber. The design methodology will be developed on the basis of characterizing micro-morphology through microscopy in combination with full scale structural testing. Rectangular hollow-cored CRPL profiles will be extruded with variations in the weight percentages and types of chopped fibers, variations in weight percentages of continuous glass rovings, variations in thermoplastic waste, and variations in compatibilizers. A statistically significant set of samples, of each of these material combinations, will be subjected to tension, compression, flexure, fatigue and creep structural testing to determine short/long term (life cycle) properties. Scanning electron microscopy (SEM) will also be performed on small specimens cut from structural samples to quantify both the micro-morphology and damage mechanisms of the various reinforced CRPL blends. The microscopy data will be essential in developing a finite element (FE) based design methodology. The computer modeling approach taken will be to utilize repeating cells (or super-elements) to model repeating' representative volumes of the commingled thermoplastic matrix with distributed reinforcement. Synthetic lumber has been developed due to the large quantities of dirty and/or mixed thermoplastic waste that is not easily or cost effectively recyclabl e. However, primarily due to their low elastic moduli (stiffness) properties, present unreinforced CRPL products do not compete with pressure treated lumber for load-bearing applications. Perhaps as importantly as finding uses for waste plastics is the need to minimize the environmental impact of deforestation of old growth forests. Additional environmental impact is related to the toxic treatment of lumber. The waste products from pressure treating operations are highly toxic and require elaborate disposal methods. Furthermore, treated lumber itself poses health hazards to people and the environment. Without pressure treatment, the life expectancy can range from 5-10 years for lumber as compared to more that 30 years for plastic alternatives. The significance of the proposed research is, therefore, that both a material properties data base and associated design tools can be developed for hybrid forms of CRPL that can potentially replace pressure-treated lumber in much residential and commercial construction. Long term 'life' material properties data for reinforced CRPL does not presently exist. Since macro-mechanical behavior of reinforced CRPL is strongly related to micro-morphology and to structural form, efficient structural profiles (extrusions) will be utilized in all of the structural testing. The knowledge gained in this research should provide the basis for developing superior construction materials which (1) pose no health hazard, and (2) provide the means of preventing waste plastics from ever entering the waste stream in the future. ***
