Fiber micro-buckling of continuous glass-fiber reinforced hollow-cored recycled plastic extrusions under long-term flexural loads

Experimental results on fiber micro-buckling of continuous glass-fiber reinforced hollow-cored recycled plastic extrusions under creep tests are introduced in the paper. The full size specimens with dimensions in were submerged in warm water at a temperature of 125 °F when they were under a four-point bending creep test. The results show that the micro-buckling of the embedded glass-fiber roving occurs along 90% the length of the specimen on the upper inner surface (compressive side) and mainly during the time between 5 and 100 h from the initial loading moment. The micro-buckling causes the steady-state apparent flexural modulus of the composite drop faster, and it also causes the plastic matrix local crackling which subsequently leads to the structural failure of the composite. The stress level has little effect on the steady-state creep rate. The results also show some evidence that the plastic matrix becomes more brittle when it is submerged in warm water for certain long time. From the results, it is indicated that the pattern or distribution of the micro-buckling is significantly different from that of short-term four-point bending test for the same composite materials, for which the fiber micro-buckling occurs locally only on the middle section of the specimen.