Fundamental influences on quasistatic and cyclic material behavior of short glass fiber reinforced polyamide illustrated on microscopic scale

Abstract

In this work, the influences of fiber orientation and weld lines on the morphological structures and the mechanical behavior of polyamide 6.6 (PA6.6-GF35) are investigated. In quasistatic and fatigue tests tensile and 3-point-bending loads are applied. Test temperatures vary between RT and 150 C. Two different specimen types are produced by using injection moulding process to create different fiber orientations as well as weld lines. Fiber orientations are determined using computer tomography. Scanning electron microscopy is used to investigate fracture surfaces of tested specimens. Results show that mechanical properties and morphological structures depend highly on fiber orientation and temperature. Transversely oriented fibers in weld lines result in brittle failure mechanisms and decreased mechanical properties. Different stress distributions in the specimens under tensile and flexural loads have influence on the material behavior as well.

Fatigue Behavior of Short Glass Fiber Reinforced Polyamide 66: Experimental Study and Fatigue Damage Modelling

“…Bernasconi et al [16] showed that increasing specimen orientation angle decreases elastic modulus, ultimate tensile stress and fatigue strength. The same results was found by Zhou and Mallick [15] and Brunbauer et al [17]. Recently, Benaarbia et al [18], reported that ratcheting for fibre reinforced composites oriented at 45° and 90° was much higher than that for 0° composites Moreover, Mallick and Zhou [19] evaluated the effect of the stress ratio on the fatigue behaviour of the PA66-GF33.…”

Fatigue behavior and modeling of short fiber reinforced polymer composites including anisotropy and temperature effects

“…Matrix brittle failure and fiber pull-out were observed in mold flow oriented samples, while brittle fracture surface was observed in samples perpendicular to the mold flow direction of short glass fiber polyamide-6.6 in [15]. As temperature increased, crazes in fibril structure were more pronounced.…”

“…Evolution of hysteresis loops in either their size or slope [2,5], hysteretic energy [7,8], strain energy [9,10], and nonlinear viscoelasticity [11,12] are the parameters typically used for modeling of fatigue damage and accumulation. Fiber orientation is another important factor controlling fatigue performance and the degree of anisotropy of SFRPCs [13][14][15]. The orientation distribution of fibers is mainly controlled by a complex flow field in the injection molding process and also dependent on the geometry of fibers and the component, viscoelastic behavior of matrix, and melt and mold temperatures [16].…”

Multi‐scale analysis of short glass fiber‐reinforced polypropylene under monotonic and fatigue loading

“…The work of Horst and Spoormaker [ 28,29 ] on the damage mechanisms of short glass fiber polyamide 6.6 in quasi‐static and fatigue allowed proposing a scenario of damage in fatigue similar to that of Sato, [ 30,31 ] mainly based on the creation of a vacuum at the matrix fiber interface. Since then, this scenario has been widely validated in the literature [ 32,33 ] and has affirmed its independence from many parameters, including the type of loading and the temperature. For both researchers, the difference between each loading would lead to the level of the kinetics of the damage propagation.…”