Effect of cycling frequency and self-heating on fatigue behavior of reinforced and unreinforced thermoplastic polymers

Abstract

An experimental study was conducted to evaluate the effect of frequency and self‐heating on fatigue behavior of two unreinforced and two short glass fiber reinforced thermoplastic polymers. Load‐controlled fatigue tests were conducted under fully reversed (R = −1) and R = 0.1 conditions with specimens loaded in either longitudinal or transverse direction to the mold flow direction. Effect of frequency on fatigue life was evaluated at 23 and 125°C and for a range of frequencies between 0.063 and 20 Hz. Incremental step frequency tests were also performed at different stress ratios and stress levels. Surface temperature rise was found to be material, frequency, and stress level dependent. Three energy‐based models were applied to the incremental step frequency data and relationships were developed for each material to estimate surface temperature rise as a function of test frequency and stress level. Relationships were also developed to assess critical frequency for the unreinforced thermoplastics at a given stress level above which surface temperature does not stabilize. POLYM. COMPOS., 55:2355–2367, 2015. © 2015 Society of Plastics Engineers

Fatigue behaviour and modelling of talc‐filled and short glass fibre reinforced thermoplastics, including temperature and mean stress effects

“…Energy-based models based on hysteresis energy loss and steady state heat conduction have been utilized to calculate temperature rise and correlate experimental fatigue life data. [8][9][10] A beneficial effect of frequency on fatigue behaviour of some polymers has also been observed. In a study by Eftekhari and Fatemi,11 this beneficial or strengthening effect of frequency on fatigue behaviour of injection moulded neat, talc-filled, and short glass fibre reinforced thermoplastics was investigated.…”

“…Self‐heating is the major detrimental effect of cycling frequency on fatigue behaviour of polymers, resulting from viscous energy dissipation and frictional heating. Energy‐based models based on hysteresis energy loss and steady state heat conduction have been utilized to calculate temperature rise and correlate experimental fatigue life data . A beneficial effect of frequency on fatigue behaviour of some polymers has also been observed.…”

Tensile, creep and fatigue behaviours of short fibre reinforced polymer composites at elevated temperatures: a literature survey

“…The emphasis of their review was on fatigue crack initiation behaviour of synthetic SFRPCs, mainly processed with injection moulding and mostly used in automotive applications. Mortazavian and Fatemi have also considered several of these effects including temperature, water absorption, anisotropy, mean stress, stress concentration and cyclic frequency, on fatigue behaviour of two commonly used short glass fibre composites in recent publications …”

“…Mortazavian and Fatemi have also considered several of these effects including temperature, water absorption, anisotropy, mean stress, stress concentration and cyclic frequency, on fatigue behaviour of two commonly used short glass fibre composites in recent publications. 12,42,[62][63][64][65] Jia and Kagan 31 investigated effects of ageing time and temperature on tension-tension, R = 0.1, (R is the ratio of the minimum to the maximum stress) load-controlled fatigue behaviour of short glass fibre (33 wt% glass) polyamides-6 and polyamide-6.6. Typical S-N curves were used to represent the experimental fatigue data.…”

A Study of the Thermal Runaway Phase Generated During Cyclic Loading of Viscoelastic Materials Accounting for the Prestress

“…However, the combined effects of static and dynamic loadings and the thermal runaway phase have not been addressed by the authors. Mortazavian et al (2015) have performed an interesting experimental study to evaluate the effects of frequency and self-heating on fatigue life of reinforced and unreinforced thermo-plastic polymers. Braeck and Podladchikov (2007) have performed a theoretical investigation of the thermal runaway failure mechanism of viscoelastic materials without considering the prestressed.…”