DUGi

Novel methodology for predicting delamination in 3D composite structures under multiple loading conditions and large process zones

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@25945

ENG- The overall objective of this thesis is to provide a tool for predicting delamination in composite materials under different static and fatigue loading conditions in 3D structures. The methodology is intended to be a practical guide for industry, providing a flexible tool capable of predicting the delamination behaviour of new polymeric materials in an agile manner. A review of the state of the art has shown that there is still some missing link between the physics responsible for delamination and the state of the art models, especially for materials with large delamination process zones. There is also a lack of validation tests that challenge the delamination predictions under different loading conditions in 3D structures. This work contributes to the field of delamination characterisation in composites with large process zones and builds a modelling and simulation strategy capable of predicting delamination in composites with large process zones. A comprehensive validation of the delamination prediction is also presented. For delamination characterization, test procedures and data reduction methods that are suitable for characterizing the delamination properties are summarized and the most suitable techniques for characterizing large process zones are discussed and selected. For the modelling and simulation strategy, the Cohesive Zone Modeling (CZM) approach is selected to predict the delamination behavior. State-of-the-art static and fatigue CZM models are used as the core of the simulation strategy, while novel developments are integrated, aimed at linking the simulation approach with the physics of the delamination observed experimentally. To validate the modelling and simulation strategy, a novel delamination benchmark test concept for composite materials that allows non-straight crack fronts and non-self-similar delamination in characterization specimens under complex loading conditions is presented. As validation of the modelling and simulation strategy, a blind simulation of the benchmark test is proposed to evaluate the predictive capabilities of the methodology. Finally, the proposed methodology is exemplified by a case study illustrating the application of the methodology to a real composite material with a large process zone. The material used in the case study is the AS4D/PEKK-FC thermoplastic composite, exhibiting large delamination process zones

CAT- L鈥檕bjectiu general d鈥檃questa tesi 茅s proporcionar una eina per a la predicci贸 de la delaminaci贸 en materials compostos sota diferents condicions de c脿rrega est谩tica i de fatiga en estructures 3D. La metodologia pret茅n ser una guia pr脿ctica per a la ind煤stria, proporcionant una eina flexible capa莽 de determinar la forma 谩gil el comportament de la desminaci贸 de nous materials polim猫rics. Una revisi贸 de l鈥檈stat de l鈥檃rt ha puesto de manifiesta que encara falta algun eslab贸 entre la f铆sica responsable de la delaminaci贸 i els models de l鈥檈stat de l鈥檃rt, especialment per als materials amb grans zones de proc茅s de delaminaci贸. Tamb茅 faltan assaigs de validaci贸 que han posat a prova les prediccions de delaminaci贸 sota diferents condicions de c脿rrega en estructures 3D. Aquest treball contribueix al camp de la caracteritzaci贸 de la delaminaci贸 en materials compostos amb grans zones de proc茅s i construye una estrat猫gia de modelitzaci贸 i simulaci贸 capa莽 de determinar la delaminaci贸 en materials compostos amb grans zones de proc茅s. Tamb茅 es presenta una validaci贸 exhaustiva de la predicci贸 de la delaminaci贸. Per a la caracteritzaci贸 de la delaminaci贸, es repr猫n els procediments d鈥檃ssaig i els m猫todes de reducci贸 de dades adequats per caracteritzar les propietats de la delaminaci贸 i discutir i seleccionar les t猫cniques m茅s adequades per caracteritzar grans zones del proc茅s. Per a l鈥檈strat猫gia de modelitzaci贸 i simulaci贸, seleccioneu l鈥檈nfocament de modelitzaci贸 de zones cohesives (CZM) per determinar el comportament de la delaminaci贸. S鈥檜tilitzen models CZM est脿tics i de fatiga d鈥櫭簂tima generaci贸 com a nucli de l鈥檈strat猫gia de simulaci贸, al temps que s鈥檌ntegren desenvolupaments nous, destinats a vincular l鈥檈nfocament de simulaci贸 amb la f铆sica de la delaminaci贸 observada experimentalment. Per validar l鈥檈strat猫gia de modelitzaci贸 i simulaci贸, es presenta un nou concepte d鈥檃ssaig de refer猫ncia de delaminaci贸 per a materials compostos que permeten fronts de grieta no rectos i delaminaci贸n no autosimilar en probes de caracteritzaci贸 sota condicions de c脿rrega compleja. Com a validaci贸 de l鈥檈strat猫gia de modelitzaci贸 i simulaci贸, es proposa una simulaci贸 ciega de l鈥檃ssaig de refer猫ncia per avaluar la capacitat predictiva de la metodologia. Per 煤ltim, la metodolog铆a proposta s鈥檈xemplifica amb un cas pr脿ctic que il路lustra l鈥檃plicaci贸 de la metodologia a un material compost real amb una 脿mplia zona de proc茅s. El material utilitzat en el cas d鈥檈studi 茅s el compost termopl谩stico AS4D/PEKK-FC, que presenta grans zones de proc茅s de deslaminaci贸

Programa de Doctorat en Tecnologia

Universitat de Girona