STRAIN RATE EFFECT AND MICROSCOPIC BEHAVIOR ANALYSIS OF SHORT-CUT CARBON FIBER REINFORCED COMPOSITES

In the present paper, strain rate sensitivity has been studied for the 3D-printed short-cut carbon fiber reinforced polylactic acid composite (CF/PLA). Composite specimens have been fabricated through Fused Deposition Modeling (FDM) additive manufacturing (AM) technology and were tested subjected different tensile loading rates. Additionally, a morphological analysis was conducted using scanning electron microscopy (SEM) on the fracture surface of the tested specimens. Initial attention focused on assessing the basic mechanical property of the CF/PLA, that is to study the basic mechanical properties of composite materials, it has been shown that the CF/PLA composites exhibit a rate-sensitivity, with the tensile strength increased slightly from quasi-static to dynamic loading rates. In addition, the SEM observations of the tensile tested pieces at different rates have been obtained. It has been found that the tensile section corresponding to the low loading rate is flat, and the damage exist in the matrix. The exposed fibers were mostly in transverse direction. With the increased tensile loading rate, the section tends to become uneven, and the number of exposed fibers has increased, which are now mainly along the longitudinal direction. This indicates that, under high tensile loading rate, the stress in the fibre is highly concentrated and leads to the initial cracking, which then propagates through the matrix. These eventually form an uneven fracture surface consisting of fibre and matrix damage. It has been clearly shown that the studied short-cut fibre reinforced composite materials present strain rate dependency, by showing different mechanical properties and fracture behaviours subjected to different tensile loading rates.