Static Crack Propagation of Carbon Nanotube through Non-Bonded Interface of Nanocomposites

This study presents an analytical shear-lag model to illustrate the interface crack propagation of carbon nanotube (CNT) reinforced polymer-matrix composites (PMCs) using representative volume element (RVE). In the model, a 3D cylindrical RVE is picked to present the nanocomposite in which CNT/polymer chemically non-bonded interface is taken into consideration. In the non-bonded interface, the stress transfer of CNT is generally considered to be controlled by the combined contribution of mechanical interlocking, thermal residual stress, Poisson’s contraction and van der Waals (vdW) interaction. Since CNT/matrix interface becomes debonded due to crack propagation, vdW interaction which is a function of relative radial displacement of the CNT/matrix interface makes the modeling of the interface tricky and challenging. In order to solve this complexity, an iterative approach is proposed to calculate the vdW interaction for debonded CNT/matrix interface accurately. The analytical results aim to obtain the characteristics load displacement relationship in static crack propagation for CNT reinforced PMCs.

Numerical investigation of tunneling induced surface movement:A case study of MRT line 1,Dhaka

The proposed underground tunnel for Mass Rapid Transit Line 1,Dhaka brings immense attention to the engineers and experts not only because of its construction challenges through a densely-built city,but also for the potential tunneling-induced ground settlements.This very preliminary study investigates the ground surface movement due to the progression of the tunnel boring machine(TBM)using numerical analysis.A series of finite element(FE)models have been developed using PLAXIS 3D,in which Mohr–Coulomb(MC),modified Cam-Clay(MCC),and hardening soil(HS)have been considered.The in-field data of Mashhad Metro Line-2 have been compared to verify PLAXIS 3D’s efficacy in tunnel modeling.Subsequently,the outcomes of the FE analyses are compared with the existing empirical formulas.The PLAXIS 3D analysis considering the MCC soil model exhibits strong agreement with the real monitored data,with a variance of only 3.85%.After simulating different stages of the tunnel construction,results are reported in terms of the distance of the inflexion point from the center,the settlement trough pattern,the maximum transverse settlements,and the vertical settlements.They are also compared with the established empirical formula.In order to comprehend the surface settlement with various tunnel depths and diameters,a parameter dependency study has been carried out.The analysis findings showed that increasing the TBM’s depth and radius causes the inflexion point’s distance from the center of the tunnel to increase by 4%and decrease by 5%,respectively.It is also observed that as tunnel depth increases,the overall settlement of the tunnel lowers by 11%for every additional 5 meters of depth.The MCC model,out of the three,exhibits the most accurate value of the settlement compared to that obtained from the empirical solutions,and also the best-fit form to the Gaussian curve.