Analytical modeling of the mechanical properties of recycled plastics

The widespread use of recycled plastics has been restricted in part because of the limited state of knowledge about the behavior of this recycled material and the lack of unified design procedures. The material behaves differently in tension and compression, and the nonlinear nature of recycled plastic makes traditional terminology such as modulus of elasticity difficult to determine because generally there is no clearly defined yield point. Furthermore, the modulus of rupture, a property determined from beam tests, can vary for different portions of a fabricated beam making these terms specific to the particular beam rather than exclusively a material property. This article investigates the properties of recycled thermoplastics and methods of testing and analyzing recycled thermoplastic members in both axial compression and flexure. In an effort to provide means for analysis of recycled plastic, material tests of discrete portions of beams were performed to develop a uniaxial material model. The model was used to predict member response based on section geometry alone. This enables prediction of member response of sections not yet tested or even constructed with greater accuracy than previously possible, regardless of the differences in tension-compression behavior and material nonlinearities or variations in material properties among manufacturers.