Influence of fiber orientation, temperature and relative humidity on the long‐term performance of short glass fiber reinforced polyamide 6

Abstract

As a result of processing of short fiber reinforced thermoplastics, the fiber orientation varies throughout a product giving rise to a pronounced anisotropic mechanical response. Different flow conditions in a product result in spatial variation in both short‐ and long‐term mechanical properties. In this study, a modeling approach is presented to evaluate the lifetime of short fiber reinforced polyamide 6, both in plasticity‐ and crack growth controlled regions of failure. In the plasticity‐controlled region, a viscoplastic model based on separation of the load angle (by means of Hill's equivalent stress formulation) and time dependence of the yield stress is used in the form of an associative flow rule. The influence of temperature and relative humidity on the magnitude of the plastic flow rate is described by using an apparent temperature approach combined with a Ree‐Eyring formulation. The depression of the glass transition temperature in the polyamide 6 matrix with increasing amount of absorbed moisture was used to predict the anisotropic deformation kinetics in a humid environment. Similar to the plasticity controlled failure, in slow crack growth controlled failure region the effect of temperature, relative humidity, and load angle on the lifetime under a fatigue load is investigated. The apparent temperature approach could also be successfully applied to predict the slow crack growth failure, while the load angle dependence is shown to scale similar to the plasticity‐controlled failure with the Hill's equivalent stress.

An integrated simulation method for analyzing mechanical properties of injection molded fiber‐reinforced polymers

“…Similar conclusions can be drawn from the results of some other researchers. [18,30] In addition, the effect of plaque thickness on fiber orientation and product strength was studied. Figure 7 shows the comparison of simulation and experimental results.…”

“…Existing studies are more inclined to verify the relationship between weld line, fiber orientation and mechanical properties through lots of experiments. [4,[14][15][16][17][18] However, in practice production, optimizing fiber orientation and weld lines through experiments can greatly increase production costs, especially for expensive special engineering polymers such as Polyether ether ketone (PEEK). Therefore, it is of vital importance to analyze the geometric dimensions, mold design, process conditions, and so on through simulation in the design stage to improve the mechanical properties of the products.…”

Novel AA7075/AA2124-SiC-17p laminated structures for aerospace applications: A Comparative study into the mechanical performance of PA6 and PA66 composite interlayers

“…Among thermoplastic polymers, polyamides have received great attention thanks to their unique merit like superior characteristics at elevated temperatures. 27 Polyamide 6 (PA6) with favorable strength, ductility 28 as well as cost-effectiveness, 29 and polyamide 6,6 (PA66) with high mechanical performance 30 and applications in a wide temperature range 31 are of enormous interest by various engineering fields. It is well known that glass fiber (GF) is one of the most popular reinforcing materials for polyamide matrix 32,33 and injection molding is excellent for the fabrication of fiber reinforced thermoplastics due to its performance and cost-effectiveness.…”

Micromechanical Modeling of Anisotropy and Strain Rate Dependence of Short-Fiber-Reinforced Thermoplastics

“…Results from a recent study in our group, however, have opened a new, promising possibility to directly link fiber orientation to the anisotropic time-dependent response [12,13]. In an extensive experimental effort, it was demonstrated that the rate-dependent, anisotropic (yield) strength of short and long fiber-reinforced thermoplastics generally displays a multiplicative decoupling of the effects of strain rate and loading angle [12,13]. Additionally, it was shown that, at a fixed strain rate, the yield strength appears to be uniquely coupled to the average fiber orientation in the direction of testing [14].…”