Numeričko modeliranje udarnih oštećenja sandwich konstrukcija pri malim brzinama udara

master's thesis

• Title (english): Numerical modeling of low velocity impact damage in sandwich structures
• Author: Matej Markulin
• Mentor: Darko Ivančević (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2018-05-18, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

U ovom radu provedeno je numeričko modeliranje udarnih oštećenja sandwich konstrukcija pri malim brzinama. Modeliranje će se vršiti na dva načina. Prvi je da jezgra bude modelirana kao homogenizirano tijelo. Drugim načinom će se modelirati stvarna geometrija saća. Materijal jezgre je NOMEX, dok se vanjski slojevi izrađuju od ugljičnih vlaknima ojačanih kompozita. Pretražena je dostupna literatura o navedenom području. Potom dane su osnove kompozitnih materijala, te temeljne jednadžbe za analitički proračun sandwich konstrukcija. Prikazani su modeli oštećenja jezgre i vanjskih slojeva, svojstva materijala i njihovi materijalni modeli. Proces modeliranja započinje s opisom numeričkih modela za homogenizirani i stvarni model za slučaj savijanja u linearno elastičnom području, koji će se kasnije validirati s teorijskim pristupom, te će se pronaći veza između krutosti homogeniziranog i saćastog modela. Potom opisan je postupak numeričkih modela za modeliranje udarnih oštećenja. Numeričko modeliranje oštećenja se sastojalo od variranja nekoliko brzina i nekoliko kutova udara. Zatim su se prikazali rezultati ovisnosti kontaktne sile o vremenu, te kako oni ovise o promjenama brzine i kuta udarca, te je na kraju će se sve usporediti s rezultatima dobivenim eksperimentom. Dodatno, može se vidjeti usporedba oštećenja vanjskih slojeva dobivena eksperimentalnim i numeričkim putem. Na samom kraju, ocijenjene su obje metode s obzirom na provedeni eksperiment.

Abstract (english)

This thesis deals with numerical modeling of low velocity induced impact damage in honeycomb sandwich structures. The finite element modeling was performed employing two methods. The first method uses homogenization technique (the honeycomb core is modeled as a homogenized body), while the second model of honeycomb core represents the actual geometry. The investigated sandwich panel consists of a carbon fibre reinforced composite as facesheets and NOMEX honeycomb core. In the first, introductory section, the review of available literature is presented. In addition, the basics of mechanics of composite materials are presented, as well as the fundamental analytical equations for analysis of sandwich structures. Furthermore, FE impact damage models of core and facesheets are presented and the appropriate constitutive material model is elaborated. The finite element modeling begins with the description of numerical models for aforementioned modeling techniques of a honeycomb core. The numerical results for linear elastic bending are compared with reference theoretical data and relation between stiffness of homogenized and honeycomb model is presented. Moreover, the course of creating numerical impact damage models is shown, as well as a number of velocity and impact angle variations. The results of conducted analyses are presented in terms of time-dependent contact force during impact. Additionally, the contact force - time results dependent on the velocity and impact angle variations are shown. Finally, the obtained results are compared to the available experimental data, which enables the validation of both modeling techniques.

• Keywords: saće; modeliranje; udar; sandwich; NOMEX; oštećenje; homogeniziran; male brzine udara
• Keywords (english): honeycomb core; modeling; impact; sandwich; NOMEX; damage; homogenized; low velocity impact
• Language: croatian
• URN:NBN: urn:nbn:hr:235:947051
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-22 22:24:14