Computational and Experimental Characterization of Continuously Fiber Reinforced Plastic Extrusions: Part II – Long-Term Flexural Loading

Experimental characterization of time-dependent properties for rectangular hollowcored, continuous fiber reinforced, commingled recycled plastic extruded forms under long-term (creep) flexural loading has been presented in this paper. Finite element based computer models have been developed to predict the effects of damage progression in such reinforced extruded plastic forms. In the long-term (creep) tests, reinforced and unreinforced extrusions with varying compositions were used as specimens. These extruded specimens were submerged in heated water and subjected to different loads. Experimental results indicate that fiber micro-buckling and fiber–matrix interface failure occur during the creep loading environment. The fiber micro-buckling occurs over time, compared with similar but dramatic damage that occurs in a short-period of time during short-term (static) loading, as discussed in Part I of this work. Experimental data also shows that these damage modes significantly reduce the long-term (life cycle) flexural properties, and the specimens with a coupling agent demonstrated much better performance. “Damage dependent” finite element models were developed using different material property types to represent the glass-fiber roving, fiber–matrix interface and plastic matrix respectively. Material nonlinearity of the plastic matrix has been incorporated along with stress-based failure criteria to account for fiber–matrix interfacial shear failure and local fiber micro-buckling. A user-defined material model has been incorporated into an industrial standard finite element software package to accommodate damage progression. The developed finite element based model(s) have correlated well with the long-term (creep) test results, and can provide a valuable tool in designing reinforced plastics for long-term loading conditions.