Effect of compression parameters on stress relaxation behavior of bamboo fiber reinforced polypropylene composites

Abstract A self‐made thermal mechanical analyzer was manufactured to characterized the compression and bending stress relaxation behavior for bamboo fiber reinforced polypropylene composite with different bamboo fiber and coupling agent concentration. The effects of bamboo fiber concentration, interfacial strength, load controlling method, compression speed, and temperature on composite stress relaxation parameters were investigated. The obtained results show that two‐stage relaxation process could be observed for both compression and bending test while shearing relaxation process was a single exponential decay. The relaxation time for slow exponential relaxation process was two orders of magnitude to that for fast relaxation process and the force decay amplitude on the first linear stage was about 3.5 times as much as that on the second exponential decay stage. Both the filling of bamboo fiber and coupling agent could increase the stress relaxation time but higher temperature would promote the movement of polymer chains and lengthen the stress relaxation time. The insights obtained from the experiments and fitting results can offer valuable reference to precisely controlling of dimensional accuracy and production efficiency for the composite products of irregular structure.