PhD Thesis: Spalling, shear banding and fragmentation of metal-matrix composites: experiments and modelling

PhD position in Research Grant funded by:

Ministry of Science and Innovation of Spain

National Research Agency

The purpose of this project is to unravel the mechanisms that govern the formation of instabilities and plastic shocks, leading to the fracture of ductile Metal Matrix Composites (MMCs) subjected to impact loading. This challenge remains unresolved in Solid Mechanics and demands a disruptive, multidisciplinary, and multiscale approach that integrates the latest advances in Manufacturing Engineering and Materials Science with Continuum Mechanics. This fusion aims to open new avenues in the design and analysis of protective structures. To address this challenge, we have devised a three-pronged approach encompassing singular experiments, large-scale computations, and novel theories. These methodologies will be applied to tackle three canonical dynamic fracture problems frequently used to assess the energy absorption capacity of materials under impact: (1) spalling, (2) shear banding, and (3) fragmentation. In MMCs, the microstructure significantly influences the fracture toughness by activating diverse failure mechanisms under different loading conditions. This project seeks to establish a comprehensive research program that ultimately explains the influence of microstructural heterogeneity on dynamic plastic localization and failure.

Specific research tasks

• Development of experimental techniques to perform dynamic fragmentation, shear banding and spall fracture experiments.

• Development of multiscale finite element models to obtain insights into the mechanisms which control plastic shocks and dynamic fracture of heterogeneous materials.

The recruited researcher will have access to the unique facilities of the Impact Laboratory of the Department of Continuum Mechanics of the University Carlos III of Madrid, with all the equipment required to perform plate-impact, dynamic shearing and fragmentation experiments: gas guns to launch strikers at velocities as high as 800 m/s, three high speed cameras with filming rate up to 2.1 Mfps to record the tests, 1 photon doppler velocimetry system and 1 oscilloscope with a sampling rate of 20 Gs/s. In addition, the recruited researcher will have access to all the computational resources of the Nonlinear Solid Mechanics group, including licenses of ABAQUS, Matlab and Mathematica, and several workstations.

Multidisciplinary / international research approach

Experiments – he/she will master singular impact testing techniques using the unique facilities of the IMPACT Laboratory of the UC3M. Theory – he/she will be trained in formulation and calibration of constitutive models for MMCs, with emphasis on mean-field homogenization approaches. Computations – he/she will learn stress integration algorithms for implementation of constitutive and fracture models into finite element codes (including Phase Field), advance scripting for generation of finite element models and image processing techniques for importing microstructures into finite element models. 

Research stays

He/she will conduct research stays at the University of Seville under the supervision of Dr. José Reinoso to implement phase field fracture approaches to model impact failure of MMCs.

Training activities

The successful candidate will have access to the PhD program of the University Carlos III of Madrid as well as to the training activities organized by the Nonlinear Solid Mechanics group. These activities include, among others:

•  Attendance to prestigious international conferences on Solid Mechanics.

•  Attendance to technical courses on materials science and continuum mechanics organized by different prestigious institutions, e.g. the International Center of Mechanical Sciences (http://www.cism.it/).

Benefits

The successful candidate will be employed for 4 years within the framework of a prestigious research grant and receive a generous financial package.