Fatigue life predictions of porous composite paper coatings

Low-cycle strain-controlled fatigue tests were carried out to determine the influence of porosity, binder volume and binder type used within a calcium carbonate based composite. Fatigue lifetime, degree of plastic strain, maximum cyclic stress and hysteresis loops were analysed. Porosity influenced by binder volume was identified as the main factor to effect a change in fatigue lifetime. Increasing polymer content by ten times led to a similar lifetime at 30 times the amplitude. Lower Tg polymer binder improved lifetime for high percentage volume binder by 2–5 times, but its effects were not noticeable in lower amounts. There was little degradation in compressive strength as a function of number of cycles but tensile load bearing resistance depreciated noticeably throughout testing due to areas of low binder leading to widespread areas of crack propagation. Hysteresis loops show that for lower polymer concentrations little plastic damage occurs within the compressive portion of the fatigue cycles. This was due to the hard pigment particles dominating compressive behaviour.