Issue 10

G. Bolzon et alii, Frattura ed Integrità Strutturale, 10 (2009) 56-63; DOI: 10.3221/IGF-ESIS.10.07 56 Mechanical characterization of metal-ceramic composites G. Bolzon, M.Bocciarelli, E.J. Chiarullo Politecnico di Milano , Dipartimento di Ingegneria Strutturale, bolzon@stru.polimi.it R IASSUNTO . I compositi metallo-ceramici rappresentano una classe di materiali per uso strutturale che richiede una adeguata caratterizzazione meccanica. Le difficoltà ed i costi associati con la produzione e la lavorazione di questi compositi scoraggiano l’esecuzione di prove meccaniche tradizionali, che richiedono l’impiego di un numero statisticamente significativo di provini di dimensioni e geometria proibitivi in questo contesto. Risulta invece indicata la prova di indentazione strumentata, rapida ed economica, abbinata a tecniche di analisi inversa che combinano l’informazione sperimentale con la simulazione del comportamento del materiale durante la prova, come si mostra in questo contributo basato sull’esperienza acquisita nell’ambito del Network di Eccellenza su ‘Knowledge-based Multi-component Materials for durable and safe performance’ (KMM-NoE). A BSTRACT . Metal-ceramic composites represent a class of quasi-brittle materials for advanced structural applications that require adequate mechanical characterization. Difficulties and costs associated with material production and specimen extraction prevent the execution of a statistically meaningful number of standard laboratory tests. Parameter calibration methodologies based on instrumented indentation and inverse analysis represent fast and reliable identification procedures in the present context, as shown by the present contribution, based on some experience achieved in the framework of the European Network of Excellence on ‘Knowledge-based Multi-component Materials for durable and safe performance’ (KMM-NoE). K EYWORDS . Metal-ceramic composites; constitutive models; quasi–brittle fracture; mechanical characterization; instrumented indentation; parametric identification; inverse analysis. I NTRODUCTION etal-ceramic composites represent a class of advanced materials of growing interest for their application in several technological fields, ranging from energy production and biomechanics as witnessed, e.g., by the website www.kmm-noe.org . Significant dimensional stability, reduced thermal expansion, increased wear and damaging resistance at high temperature, good mechanical strength (mainly in compression) make these composites interesting replacement of metals as structural components and protective coatings in high demanding applications. Main limitations concerning their usage consist of: difficult processing; high production costs; strong influence on the overall material properties of micro-structural details; brittle behaviour, though mitigated by the metal phase when compared with pure ceramics. The composition and the production process of these composites are usually designed in order to optimize their effective thermo-mechanical response, which require to carefully control the possible presence and the evolution of local damages and defects. The estimation of macroscopic properties is often based on homogenization techniques, which often neglect micro- structural details playing a significant role for brittle and quasi-brittle materials [1-8]. A proper experimental validation of the mechanical properties is therefore mandatory. On the other hand, difficulties and costs associated with specimen production prevent the execution of a statistically meaningful number of standard laboratory investigations. A practical methodology for material characterization is based on instrumented indentation, which represents a fast and economical test, which can be performed at different scales on small material portions, even directly on the structural M