Computer modelling of porous composite structures with advanced pore morphology

doctoral dissertation

Aljaž Kovačič (Author), Zoran Ren (Mentor)

Abstract

Advanced pore morphology (APM) structures are composite metal foams, which are assembled from a large number of small spherical elements with cellular structure, and are bonded into a composite with polymeric adhesive. The result of such composition is a wide spectrum of achievable mechanical behaviour in APM structures. To explore their full potential, efficient computational models are needed, which allow for simple parameter variation. Unfortunately, the current computer models do not allow for efficient simulations of porous composite structures with advanced pore morphology, as they employ complex discretisation approaches. A new approach to simulation is presented in this work, based on the discrete particle method (DPM), where every element of APM structure is discretised with a single node. This enables more efficient simulations of APM structures, while still allowing for simple variation of structural parameters. The DPM method was augmented with constitutive models of normal and tangential contact behaviour of APM elements and bonds between them, which were formulated based on an extensive experimental study of APM structure's geometry and mechanical behaviour. Consequently, the models enable simulations of large APM structure's behaviour by modelling the contact behaviour of individual elements. The implementation of new models was verified on a set of analytically solvable examples, and the accuracy of the models was validated with very good correspondence between computational and experimental results. Moreover, the models were validated on a wide set of examples, also taking into account the various strain rates and the absence of the bonds. The applicability of new models was demonstrated in a comprehensive parametrical study, where the influential structural parameters and properties were identified for low and high strain rate deformations. The study also demonstrated the possibility of customising the mechanical behaviour with property gradation, and with introduction of regular, as well as geometrically complex APM element assemblies. The possibility of coupled discrete particle method and finite element method simulations was also addressed. The newly developed models represent a breakthrough in the field of computational investigation of APM structures, and provide for simpler and more efficient investigations of APM structures in the future.

Keywords

metal foams;advanced pore morphology;composite materials;mechanical properties;contact modelling;discrete particle methods;computer simulations;

Data

Language:	English
Year of publishing:	2016
Typology:	2.08 - Doctoral Dissertation
Organization:	UM FS - Faculty of Mechanical Engineering
Publisher:	A. Kovačič]
UDC:	004.942:[620.17/.18:669-1-026.747](043.3)
COBISS:	284066816
Views:	1825
Downloads:	144
Average score:	0 (0 votes)
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Other data

Secondary language:	Slovenian
Secondary title:	Računalniško modeliranje poroznih kompozitnih struktur z napredno morfologijo por
Secondary abstract:	Strukture z napredno morfologijo por (APM strukture) so kompozitne kovinske pene, sestavljene iz velikega števila majhnih okroglih elementov z celično notranjo zgradbo, ki so spojeni v kompozit s polimernim vezivom. Rezultat takšne zgradbe je širok spekter dosegljivega mehanskega obnašanja v APM strukturah. Za raziskanje njihovega resničnega potenciala potrebujemo učinkovite računske metode, ki omogočajo preprosto variiranje parametrov. Trenutni računalniški modeli žal ne omogočajo učinkovitih simulacij poroznih kompozitnih struktur z napredno morfologijo por, saj temeljijo na kompleksnejših pristopih k diskretizaciji. V tem delu je predstavljen nov pristop k simulacijam, ki temelji na metodi diskretnih delcev (metodi DPM), v kateri je vsak element APM strukture diskretiziran z enim samim vozliščem. To omogoča učinkovitejše simulacije APM struktur, vendar še zmeraj omogoča preprosto variiranje strukturnih parametrov. DPM metoda je bila razširjena s konstitutivnimi modeli normalnega in tangencialnega kontaktnega obnašanja APM elementov in njihovih povezav, ki so bili oblikovani na osnovi obširne eksperimentalne študije geometrije in mehanskega obnašanja APM struktur. Modeli zato omogočajo simulacije mehanskega obnašanja velikih APM struktur na osnovi modeliranja kontaktnega obnašanja posameznih elementov. Izvedba novih modelov je bila preverjena na nizu analitično rešljivih primerov, natančnost modelov pa je bila potrjena z zelo dobrim ujemanjem med računskimi in eksperimentalnimi rezultati. Modeli so bili tako potrjeni na širokem nizu primerov, ki so zajemali tudi različne hitrosti deformacije in odsotnost vezi. Uporabnost novih modelov je bila dokazana v obsežni parametrični študiji, v kateri so bili identificirani vplivni strukturni parametri in lastnosti pri majhnih in velikih hitrostih deformacije. Študija je tudi dokazala možnost prirejanja mehanskega obnašanja s stopnjevanjem lastnosti ter z vpeljavo urejenih, kakor tudi geometrijsko zapletenih sestavov APM elementov. Naslovljena je bila tudi možnost sklopljenih simulacij po metodah diskretnih delcev in končnih elementov. Novo razviti modeli predstavljajo preboj na področju računalniških raziskav APM struktur ter zagotavljajo enostavnejše in učinkovitejše raziskave APM struktur v prihodnje.
Secondary keywords:	kompozitni materiali;celična gradiva;mehanske lastnosti;kovinske pene;napredna morfologija por;modeliranje kontakta;metoda diskretnih delcev;računalniška simulacija;Materiali;Disertacije;Računalniško modeliranje;
URN:	URN:SI:UM:
Type (COBISS):	Dissertation
Thesis comment:	Univ. Maribor, Fak. za strojništvo
Pages:	XXIII, 286 str.
ID:	9122782