Dynamic response of polymeric railway sleepers under harsh loading and environmental conditions

Several composite sleeper technologies have been developed, possibly allowing the railway sector to replace wood and concrete sleepers. Although high-magnitude impact loads can occur on the railway track and sleepers due to wheel/rail abnormalities or train derailment, the behaviour of these sleepers under impact loading has not yet been well understood. In this paper, a high-energy drop hammer facility was utilized to investigate the impact behaviour of a polymeric composite rail sleeper made of high-density polyethylene (HDPE) and unidirectional glass fibre reinforced plastic (GFRP). Quasi-static tests and high strain rate tests were conducted on the materials at room and low/high temperatures to gain more insight into the effects of the temperature and strain rate on the mechanical properties of the HDPE and GFRP made of virgin resin. The results suggest that both materials exhibit strong viscoelastic plasticity, temperature softening, and strain rate-hardening effects. High strain rate and low temperature made the GFRP material extremely brittle and prone to develop cracks. Due to the temperature and strain rate dependency of the thermoplastic materials of the sleepers, in addition to impact tests at room temperature (~23°C), impact tests were also performed at low temperatures (~ minus 30°C) on the sleepers. The findings suggest that low-temperature impact assessment should be considered for all polymeric sleepers (to be installed in regions having extremely low temperatures) since these low temperatures affect the ductility of polymers, decreasing the ultimate impact load-bearing capacity of composite sleepers.