Bulk fatigue damage evolution in polyamide-6 and in a polyamide-6 nanocomposite

Abstract

The mechanical response of a polyamide‐6 montmorillonite clay nanocomposite and of a polyamide‐6 was monitored during axial fatigue tests performed at R‐ratios of 0.1 and −1. For both materials, two transitions were usually observed in the evolution of all the stress‐strain‐time parameters studied after similar numbers of loading cycles, suggesting interrelationships between the mechanisms of molecular reorganization. Fatigue test monitoring indicated an initial decrease in the storage modulus and a subsequent trend for this modulus to increase, especially in polyamide‐6. During all tests, a partially recoverable strain was accumulated because of viscoelastic deformation. Nanoparticles reduced this strain in the initial cyclic straining regime but not in the last regime, probably because such particles cannot inhibit viscoelastic events constrained in a volume larger than their interaction volume within the matrix. Based on the accumulated volume variation measured, the nucleation and growth of microvoids can be expected to occur in the last cyclic straining regime. POLYM. COMPOS., 26:636–646, 2005. © 2005 Society of Plastics Engineers

A novel model to predict the fatigue life of thermoplastic nanocomposites

“…They have focused on experimental methods and tried to find the optimum weight ratio of nanofillers added into thermoplastic polymers and reported improvements in fatigue behavior of nanocomposites under load or displacement control conditions. [1][2][3][4][5][6][7][8][9] Mallick et al 1 studied the fatigue behavior of PP and polyamide-6 (PA6) nanocomposites (PA6NC) filled with montmorillonite silicate clay particles. Ramkumar and Gnanamoorthy 2 studied the effect of nanoclay addition on the temperature rise and modulus drop during the axial cyclic loading in PA6 and PA6NC and claimed that the addition of nanoclay improved the modulus of nanocomposites in comparison to pristine polymers.…”

“…They performed the fatigue tests under displacement controlled conditions and demonstrated a marginal improvement in fatigue life of the specimens due to the addition of the nanoclay. Bellemare et al 4 performed axial fatigue loading tests on PA6 montmorillonite clay nanocomposites and pure PA6 at stress ratios of 0.1 and À1. Their results indicated an initial and a subsequent decrease in the storage modulus.…”