M. Rodríguez-Millán

A review on recent advances in numerical modelling of bone cutting.

Common practice of surgical treatments in orthopaedics and traumatology involves cutting processes of bone. These operations introduce risk of thermo-mechanical damage, since the threshold of critical temperature producing thermal osteonecrosis is very low. Therefore, it is important to develop predictive tools capable of simulating accurately the increase of temperature during bone cutting, being the modelling of these processes still a challenge. In addition, the prediction of cutting forces and mechanical damage is also important during machining operations. As the accuracy of simulations depends greatly on the proper choice of the thermo-mechanical properties, an essential part of the numerical model is the constitutive behaviour of the bone tissue, which is considered in different ways in the literature. This paper focuses on the review of the main contributions in modelling of bone cutting with special attention to the bone mechanical behaviour. The aim is to give the reader a complete vision of the approaches commonly presented in the literature in order to help in the development of accurate models for bone cutting.

Experimental analysis of special tool geometries when drilling woven and multidirectional CFRPs

Drilling is one of the most frequent machining operations for carbon fiber-reinforced polymer composites, carried out prior to assembly between structural components using mechanical joining. Delamination is the main damage mechanism involved during carbon fiber-reinforced polymer composite drilling causing an elevated percentage of workpiece rejection. Tool geometry strongly influences drilling performance. In this paper, an original work dealing with the comparison between three recently developed configurations (Brad center, Step drill and Reamer drills) in terms of drilling forces and delamination both for woven and tape carbon fiber-reinforced polymers is presented. Reamer drill showed the best results concerning productivity and delamination. Strong differences were found when hole quality obtained in tape and woven composite was compared: multidirectional composite presented poorer hole quality than woven composite under the same cutting conditions. The analysis of variance was developed in order to analyze the influence of each parameter showing the importance of feed rate on surface damage.

High impact velocity on multi-layered composite of polyether ether ketone and aluminium

Hybrid structures composed of multi-layer sheets of polymers and metals offer a great potential for impact protection systems in automotive and aeronautics industries. This work presents an experimental and numerical investigation on the perforation behaviour of layered polymer/metal composites. Penetration tests have been conducted on sandwich panels of aluminium 2024-T3 skins and polyether-ether-ketone (PEEK) cores, using spherical projectiles. The perforation experiment covered impact velocities in the range 250–500 m/s. The initial and residual velocities of the projectile were measured, and the ballistic limit velocity was obtained. The impact mechanical behaviour of PEEK core is compared with Ti6Al4V titanium core, for the same areal density of protection. It has been shown high perforation efficiency of PEEK polymer and a promised application for aeronautical protections. A numerical modelling is presented and validated with experimental data.

Numerical analysis for design of bioinspired ceramic modular armors for ballistic protections

The exigent requirements for personal protections in terms of energy absorption and ergonomics have led to increasing interest in bioinspired protections. This work focuses on the numerical analysis of ballistic behavior of different bioinspired geometries under impact loadings. Ceramic armors based on ganoid fish scales (the type exhibited by gars, bichirs and reedfishes), placoid fish scales (characterizing sharks and rays) and armadillo natural protection have been considered. Different impact conditions are studied, including perpendicular and oblique impacts to surface protection, different yaw angle, and multiple impacts. Main conclusion is related to the improved efficiency of modular armors against multiple shots exhibiting more localized damage and crack arrest properties. Moreover, its potential ergonomic is a promising characteristic justifying a deeper study.