Characterizing Stiffness and Strength Properties of Glass-Fiber Reinforced, Hollow-Cored Recycled Plastic Extrusions

Hollow-cored structural profiles have been processed using blends of polyethylene with continuous glass-fiber roving reinforcement through an offset extrusion process. These profiles have been produced with and without coupling agents. The intent has been to achieve high bending stiffness (El) by locating the reinforcing fibers in the mid-plane of the extrusion walls. However, the process was not optimally tuned which results in the fibers being nearer the inner surfaces of extrusion walls. Four-point bending and compression tests have been performed on the hollow-cored beams according to ASTM D6109 and ASTM D61 12. The nonlinear elastic nature of the unreinforced plastic blends has been quantified by performing tensile tests according to ASTM D638. A finite element-based computational model has been developed through the assembly of "repeating cells" representing individual fiber rovings and neighboring plastic. Comparing experimental and computational results demonstrates the validity of the model in predicting bending stiffness (El). Furthermore, simple multi-material beam models are shown to over-predict bending stiffness. The experiments also provide evidence suggesting shear failure at fiber-matrix interfaces.