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

• Pressure sensitive adhesives provide high toughness at low stress and stiffness. These properties are beneficial for bimaterial bonding. In the present study the tape is modelled with a cohesive layer characterized by a cohesive law. This is suitable for FE-analysis of bonded structures. The cohesive law is measured using a method based on the path independent property of the J-integral. Complementing an earlier study, we here focus on influences of loading rate on the properties of the pressure sensitive adhesive. Transparent PMMA substrates are used with the transparent tape in Double Cantilever Beam specimens. The transparency of both the tape and the substrates provides the possibility of in-situ studies of the fracture process. The results indicate that the fracture energy levels off at about 1 kN/m for small loading rates. Moreover, the cohesive law also appears to level off below an engineering strain rate of about 2 s-1. The cohesive law contains two peak stresses. The first is associated with the nucleation of cavities in the tape. This occurs at a stress level comparable to the critical stress associated with an unbonded growth rate of a spherical cavity in rubber. The second peak stress is associated to the breaking down of walls formed between the fully developed cavities. This process precedes the final fracture of the tape. It also appears as nucleation of cavities is influenced by the strain rate where slower rates give more time for cavities to nucleate. This results in larger cavity density at smaller loading rates. The results also indicate a similarity of the effects of loading rate and ageing of the macroscopic properties of the present pressure sensitive adhesive.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Teknisk mekanik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Applied Mechanics (hsv//eng)

Nyckelord

Experiment

Cohesive law

Elastomer

Cavity

Tape

Mechanics of Materials

Materialmekanik

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)