Application of the miniature small punch test for the mechanical characterization of polymer materials

Abstract

The aim of this paper is to demonstrate the applicability of the Small Punch Test (SPT) in the mechanical characterization of polymers, following previous achievements in metallic materials. For this purpose, different polymers with a wide variation of tensile properties were examined. The applicability of this type of test to characterize polymeric materials is especially interesting when these products are in the form of films, as their greatly reduced thickness enables an easy preparation of the SPT specimens.\ud \ud All the polymer materials were characterized by means of small punch and tensile tests. The tensile stress-strain curves were compared with the load-displacement SPT curves and the representative SPT parameters were defined accordingly. A good correspondence was found between the tensile elastic modulus and the initial slope of the SPT plot (Slopeini/t), with t being the specimen thickness, and a good correlation was also observed between the tensile yield strength and the SPT Pym/t2 parameter. On the contrary, no corresponding relationship was found to predict the ultimate tensile strength or the failure elongation, since these properties depend greatly on the stress state of the test (uniaxial or biaxial).Peer ReviewedPostprint (author's final draft

A Renaissance in the Use of the Small Punch Testing Technique

“…In another interesting correlation, Rodriguez et al (2012) relate the fracture toughness with the area below the SPT curve until the maximum load W max. .…”

European standard on small punch testing of metallic materials

“…The second proposal estimates the fracture toughness in terms of JIc, by using the effective fracture strain, see equation (14).…”

“…Nowadays, the SP technique is used for the characterization of structural materials for nuclear power plants [8,9]. It is more and more also being used in other industries like aerospace [10,11], automotive [12] or off-shore [13] and for non-metallic materials like polymers [14] or bones [15].…”

Ceramic materials characterization using miniature mechanical tests: comparison between B3B and SPT tests

“…A disc shaped specimen (usually 10 mm diameter and 0.5 mm thickness) is clamped between two rings and deformed by the action of a hemispherical punch that forces the specimen to deform through the internal hole of the supporting ring. This test configuration is widely accepted for the mechanical characterization of steel and other metallic alloys [18][19][20][21] and its applicability has been extended to other types of materials like polymers [22,23].…”