Predicting the response and perforation of fibre metal laminates subjected to projectile impact

Purpose The purpose of this paper is to predict the response and perforation of fibre metal laminates (FMLs) subjected to impact by projectiles at different velocities. Design/methodology/approach A finite element (FE) model is constructed in which recently proposed dynamic constitutive models for fibre reinforced plastic (FRP) laminates and metals are used. Moreover, a recently developed dynamic cohesive element constitutive model is also used to simulate the debonding between FRP laminates and metal sheets. The FE model is first validated against the test data for glass laminate aluminum reinforced epoxy (GLARE) both under dropped object loading and ballistic impact, then used to perform a parametric study on the influence of projectile nose shape on the perforation of FMLs. Findings It is found that the present model predicts well the response and perforation of GLARE subjected to impact loading in terms of load-time history, load-displacement curve, residual velocity and failure pattern. It is also found that projectile nose shape has a considerable effect on the perforation of GLARE FMLs and that the ballistic limit is the highest for a flat-ended projectile whilst for a conical-nosed missile the resistance to perforation is the least. Originality/value Recently developed constitutive models for FRPs and metals, together with cohesive element model which considers strain rate effect, are used in the FE model to predict the behaviour of FMLs struck by projectiles in a wider range of impact velocities; the present model is advantageous over such existing models as Johnson-Cook (JC) + Chang-Chang and JC (+BW) + MAT162 in terms of failure pattern though they produce similar results for residual velocity.

A 3D FEM Mesoscale Numerical Analysis of Concrete Tensile Strength Behaviour

A three-dimensional (3D) finite element method (FEM) based on an inserted cohesive element numerical analysis procedure was developed for concrete mesoscale systems on the ABAQUS platform with python scripts. Aggregates were generated based on dividing the existing geometrical element algorithms to randomize arbitrary spheres. Simultaneously, randomizations of the maximum aggregate size and uniform distributions of aggregate particles were also considered. An FEM for the mortar phase in concrete mesoscale systems was generated along with the interfacial transition zone (ITZ) by inserting a cohesive element. Numerical parameter analyses were performed for nine different concrete systems by varying the coarse aggregate volume fraction (α) and the ITZ tension strength (ITZ-S). The mechanical performance of concrete systems with the coupling effects of α and ITZ-S was evaluated for simulated tensile loading. The results of the numerical simulations for mechanical properties, such as the simulated tensile strengths and tension damage behaviour of concrete systems, were verified with experimental results. The proposed aggregate and ITZ generation approach and numerical simulation procedure can be used by researchers to better understand how aggregate volume fraction and ITZ strength affect the tensile behaviour of concrete mesoscale systems.

Study on the cohesive edge crack in a square plate with the cohesive element method

The size of the fully developed process zone (FDPZ) is needed for the arrangement of displacement sensors in fracture experiments and choosing element size in numerical models using the cohesive element method (CEM). However, the FDPZ size is generally not known beforehand. Analytical solutions for the exact FDPZ size only exist for highly idealised bodies, e.g. semi-infinite plates. With respect to fracture testing, the CEM is also a potential tool to extrapolate laboratory test results to full-scale while considering the size effect. A numerical CEM-based model is built to compute the FDPZ size for an edge crack in a finite square plate of different lengths spanning several magnitudes. It is validated against existing analytical solutions. After successful validation, the FDPZ size of finite plates is calculated with the same numerical scheme. The (FDPZ) size for finite plates is influenced by the cracked plate size and physical crack length. Maximum cohesive zone sizes are given for rectangular and linear softening. Further, for this setup, the CEM-based numerical model captures the size effect and can be used to extrapolate small-scale test results to full-scale.

Simulation of Slip-Oxidation Process by Mesh Adaptivity in a Cohesive Zone Framework

Adaptive oxide thickness was developed in a cohesive element based multi-physics model including a slip-oxidation and diffusion model. The model simulates the intergranular stress corrosion cracking (IGSCC) in boiling water reactors (BWR). The oxide thickness was derived from the slip-oxidation and updated in every structural iteration to fully couple the fracture properties of the cohesive element. The cyclic physics of the slip oxidation model was replicated. In the model, the thickness of the oxide was taken into consideration as the physical length of the cohesive element. The cyclic process was modelled with oxide film growth, oxide rupture, and re-passivation. The model results agreed with experiments in the literature for changes in stress intensity factor, yield stress representing cold work, and environmental factors such as conductivity and corrosion potential.