On the role of the spherulitic microstructure in fatigue damage of pure polymer and glass-fiber reinforced semi-crystalline polyamide 6.6. (September 2019)

• Record Type: Journal Article
• Authors: Raphael, I.; Saintier, N.; Robert, G.; Béga, J.; Laiarinandrasana, L.
• Is Part Of: International journal of fatigue. Volume 126(2019)
• Page Start: 44
• Page End: 54
• Publication Date: 2019-09
• Subjects: Fatigue damage -- Composite material -- Semi-crystalline polymer -- Oriented spherulites; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2019.04.036
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: Fatigue damage progresses in the polymer by opening each spherulite in its equatorial plane. Half of the spherulite can be observed on each fracture surface, with the nuclei being perfectly visible. Injection-molding induces an orientation of the spherulitic structure. Oriented spherulites are intermediate between the usual radial spherulite and the oriented shish-kebab. Abstract: Understanding fatigue damage mechanisms in short fiber reinforced thermoplastics is a key issue in order to optimize material processing and propose physically based multiscale fatigue damage models. The present work aims at further understanding observations of fatigue damage in the polyamide 6.6 matrix with respect to its semi-crystalline structure. In this paper the polymer and associated composite are tested in their ductile regime i.e. above the glass transition temperature. Tomographic and SEM observations are used in order to establish a damage scenario at the spherulitic scale. These observations prove that fatigue damage progresses by intra-spherulitic failure in their equatorial plane. Observations of the spherulite nuclei also evidence the oriented structure of the semi-crystalline polymer induced by the injection-molding manufacturing process.