Optimal vulcanization of unbonded fiber reinforced elastomeric isolator devices

Elastomeric seismic isolation is a technique diffused in civil engineering to protect existing and new structures against earthquakes. It consists in introducing between the superstructure and the foundation several devices (called seismic isolators) having the property to carry vertical loads maintaining at the same time the shear modulus small, increasing considerably the natural period of the structure, where the spectral acceleration drops down (Habieb et al., 2020 and 2019a, 2019b, 2019c, 2019d, 2018). This study investigates the possibility of using recycled rubber in the form of reactivated EPDM (made by 2/3 of regenerated rubber and 1/3 of virgin rubber) for the production of low cost rubber isolators (Habieb et al., 2020). A Fiber Reinforced Elastomeric Isolator FREI prototype constituted by five EPDM pads and four GFRP laminas interposed between contiguous pads is cured in the lab at 130°C and the level of vulcanization is experimentally provided measuring Shore A hardness on several points. A 3D numerical model based on both finite differences and FEM is proposed to predict the degree of vulcanization of the FREI numerically. It is found that the crosslinking density obtained is suboptimal (but still acceptable for an engineering point of view) and that it is required to increase the vulcanization temperature to obtain a full and homogeneous curing