Effects of strain rate on the cohesive properties and fracture process of a pressure sensitive adhesive

Abstract

Pressure sensitive adhesives provide beneficial properties for bi-material bonding and we here focus on influences of the loading rate. The cohesive law for a tape is measured using the J-integral method. In-situ studies of the fracture process are made. The fracture energy and cohesive law levels off below an engineering strain rate of about 2 s −1 . All the cohesive laws include two peak stresses, the first is associated with nucleation of cavities and occurs at a stress level comparable to the critical stress for cavitation in rubber. The second peak stress occurs just before final fracture when walls formed between the cavities break down. Slower rates give more time for cavities to nucleate. A similarity of the effects of loading rate and ageing is also identified.

Comparative Mechanical Study of Pressure Sensitive Adhesives over Aluminium Substrates for Industrial Applications

“…The different cohesion values for the shear and the T-peel tests were related to the direction of the adhesive matrix strain (note that shear and T-peel tests were performed at the same deformation rate). For the shear test, the strain direction was quasi-equatorial, while for the T-peel test the deformation occurred in the axial direction [ 56 ]. When the joints were subjected to shear, the movement occurred in a direction that did not allow the bubbles to grow, leading to a cohesive failure.…”

“…Generally, cavity growth takes place as the joints are subjected to higher stress values, which provokes higher creep rates and shorter fracture times. This reduction in fracture time is due to a faster release of hydrostatic stress after the cavitation process [ 26 , 41 , 56 , 57 , 58 , 59 ]. Therefore, higher stress around the cavities promoted a reduction in the damping behaviour, increasing the cohesive fracture.…”

Rheological and Mechanical Properties of an Acrylic PSA

“…Transparent polymethyl methacrylate (PMMA) was used to manufacture the substrates used in the DCB specimens. This material presents a Young’s modulus of 3 GPa and a Poisson’s ratio of 0.35 [ 34 ]. The use of this material allowed for a better understanding of the fracture process of the PSA in the DCB tests, as it enabled the ability to visually observe the damage process throughout testing, considering its transparency properties.…”

“…Finally, the specimens were assembled with the acrylic PSA in a mould with 23 kPa applied to each joint and then resting for 72 h before being tested. Figure 2 represents the DCB specimens’ geometry, based on the work of Stigh and Biel [ 34 ], where is the thickness of the adhesive tape.…”

“…There are some studies that use this approach, including quasi-static [ 31 , 32 ] and impact [ 33 ] loading conditions, although there is almost no literature on the latter. Stigh and Biel [ 34 ] established the cohesive law for a PSA tape applying the J-integral method, while studying the in-situ fracture process, for different strain rates. They obtained a cohesive law with two stress peaks, the first being related to the cavitation process and the second being associated with the stretching and failure of walls (fibrils) that were created between the cavities prior to the final fracture.…”