Road guardrail beam made of natural stem (Stipa tenacissima L.) eco-composite: Impact energy absorption improvement by stems and pre-tensioning

Reducing accidents, deaths, and serious injuries is an objective to be achieved by every health and road authority. To avoid road leaving, rigid barriers or stretched cables are used at the edges of the roads. These structures are based on metallic materials. This paper presents an innovative structure based on a composite reinforced with natural esparto stems as road barriers absorbing shock energy. The structure is lightened and reinforced by tensioned cables to ensure the prestressing of the whole. Prestressing is a technique widely used in civil engineering but rarely in composites. To develop new crash beam barriers based on Epoxy/Alfa10% material, Charpy tests were conducted to determine the absorbed energy per section of material per weight. Knowing the energy to be absorbed, the section and weight of the barrier can be designed. In this paper, physical tests were conducted on solid, solid-compressed, perforated, and perforated-cable-reinforced specimens according to the ASTM E23-18 standard. The results show that the compression prestressing improves the Epoxy impact energy absorption by 37.22%. The Epoxy/Alfa10% composite compression prestressing improves the absorbed energy by 67.7%. The Epoxy/Alfa10% compressed, perforated, and reinforced by cables composites gives a better result than the raw Epoxy material, with a minimum improvement of 22.69% with respect to the ratio Resilience value of Charpy V-notch specimen (KCV)/weight. Reinforcement of holed samples with cables gives the best energy absorption results on all experimental tests for both materials with a value of 8.83 J. Finite element models calibrated on Aluminum to be predictive are developed for the four types of specimens.