Fiber Local Micro Buckling of Continuous Glass-Fiber Reinforced Rectangular Hollow-Cored Commingled Recycled, Plastic Extrusions under Bending

The experimental results of fiber local micro-buckling and partial failure due to the fiber micro buckling of extruded continuous glass fiber reinforced hollow-cored recycled plastic lumber under four point bending are presented in the paper. The test specimens are commercially produced E-glass roving reinforced recycled HDPE extrusions (2.5″ by 3.5″ hollow-cored cross section and 42″ in length) with/without coupling agent and different color pigment. The test results show that the fiber micro buckling causes a significant drop in strength of the extruded lumber and subsequently causes the matrix cracking that will lead to the total structural failure. It becomes a concern for the continuous fiber reinforced plastic beams used in construction fields because most of them are under bending loads. The micro buckling occurs on the compressive half of the hollow beam when it undergoes bending loads. The critical compressive stress is reasonably close to the predictions of Rosen’s model if considering a factor of 0.63 as proposed by Hahn and Williams (1986). For the specimens without the additives and coupling agent, the results show no sign of fiber micro buckling though their strength is much lower than those with the additives and coupling agent. In addition, it is shown that the fiber micro buckling initiates the matrix longitudinal as well as latitudinal cracking.