Characterization of fracture properties of thin aluminuminclusions embedded in anisotropic laminate composites

Abstract

ABSTRACT. The fracture properties of thin aluminum inclusions embedded in anisotropic paperboard composites, of interest for food and beverage packaging industry, can be determined by performing tensile tests on non-conventional heterogeneous specimens. The region of interest of the investigated material samples is monitored all along the experiment by digital image correlation techniques, which allow to recover qualitative and quantitative information about the metal deformation and about the evolution of the damaging processes leading to the detachment of the inclusion from the surrounding laminate composite. The interpretation of the laboratory results is supported by the numerical simulation of the tests. SOMMARIO.Le proprietà di frattura di inclusioni metalliche costituite da sottili stati di alluminio in compositi a base di carta, di interesse nel packaging alimentare, possono essere determinate mediante prove di trazione nonconvenzionali, condotte su campioni di materiale eterogeneo. La deformazione della regione di interesse nel corso della prova viene monitorata attraverso tecniche di correlazione d'immagini digitali che restituiscono informazioni quantitative, oltre che qualitative, sul fenomeno di progressivo distacco dell'inclusione metallica dal composito laminato che la circonda. L'interpretazione dei risultati sperimentali viene supportata dalla simulazione numerica delle prove di laboratorio.

Aluminum Laminates in Beverage Packaging: Models and Experiences

“…This phenomenon has been interpreted at the light of brittle or quasi-brittle fracture models in [2][3][4][5], consistently with the smaller rupture strain and meaningful reduction of toughness exhibited by free-standing thin metal foils compared to the corresponding bulk materials [6,7]. However, fractographical examinations reported in [8] suggest that the material separation may be rather produced by necking, in other words, by a typical elastic-plastic phenomenon.…”

“…The correlation among these images shows that the strain concentrates mostly on the aluminum laminate inclusion. The stiffer paperboard composite undergoes an almost rigid body motion and can be thus considered as an extension of the gripping apparatus [2]. Therefore, the typical load displacement curves drawn in Figure 4 essentially reflect the mechanical response of the cap opening area.…”

“…The response of the aluminum-polymer laminate to different loading conditions and its interaction with the surrounding composite can be reproduced by uniaxial tensile tests [2] or inflation tests [3] carried out on heterogeneous material samples, shown for instance in Figures 2 and 3. The relationship between the applied force (or pressure) and the induced deformation can be complemented by local measurements based on full-field techniques like digital image correlation or laser profilometry.…”

“…The investigations documented in [2,3] show that the material failure is usually initiated by the separation of the aluminum layer from the paperboard composite at the boundary between these dissimilar media. This phenomenon has been interpreted at the light of brittle or quasi-brittle fracture models in [2][3][4][5], consistently with the smaller rupture strain and meaningful reduction of toughness exhibited by free-standing thin metal foils compared to the corresponding bulk materials [6,7].…”

Numerical simulation of non-standard tensile tests of thin metal foils

“…In the usual range of interest (1-100 µm thickness), the metal foils and their composites present a rather brittle failure mode [5][6][7][8]. Their mechanical characteristics are usually inferred from the output of tensile tests performed on narrow material strips, with large length to width (L/W, see Fig.…”