In situ SEM damage mechanisms investigation of short glass fiber reinforced polyamide composite

Abstract

Injection molded polyamide composite reinforced with short glass fibers has been widely used in automotive industry due to its high strength to weight ratio and the ability of injection process to produce complex parts. A reliable design of components made of this composite should consider the development of progressive properties degradation due to the damage. A better understanding of the damage mechanisms shall contribute to a better formulation of local damage criteria and thus to include with a higher accuracy the physical modeling of their effects to predict the overall mechanical behavior of the composite. For this purpose, in situ SEM tests were performed to observe the damage mechanisms of injection molded polyamide-66 reinforced with 30%wt of short glass fibers (PA66GF30). The observation was focused on dry as mold state (0% water content) of PA66GF30, which correspond to a relative humidity RH=0%. The specimens were subjected to a flexural load using a three-point bending micro-device and were assembled inside an environmental SEM to allow the in situ observations. Specimens were cut following two specific orientations with respect to the mold flow direction (MFD): longitudinal and transverse. Prior to observation, the surface samples were polished and metalized with gold. As the polyamide absorbs water during polishing, the samples were put after polishing inside a vacuum oven at 80 o C for 15h to ensure that the RH content goes back to zero in the whole sample.