Focusing now on the differences between the different APF classes, the [0°] class appears to have overall degraded properties (viz. lowest ductility, stiffness and strength). Although the only difference with the [90°] class is the direction of loading with respect to the printing di- rection, a significant decrease in UTS and stiffness is observed. This highlights an anisotropy in the behavior which is related to the for- mation of bonds between droplets and beads during the APF process: the interfacial bonding between two adjacent beads is stiffer than the interfacial bonding between two consecutive droplets of a same bead. Bellehumeur et al. [44] have described the formation of bonds between polymer filamentsintheFDMprocess.Theyexplainedthatthe firststep of bond formation is the establishment of interfacial molecular contact by wetting. The molecules then undergo motions towards preferred configurations to achieve an adsorptive equilibrium. Molecules diffuse across the interface, forming an interfacial zone, and/or react to form primary chemical bonds across the interface. The randomization can be reached only after extensive inter-diffusion of chain segments under critical conditions. In another study, Sood et al. [45] have clarified that a small air gap helps to create a strong bond between the two rasters and thus improves the strength of the component. But a small air gap restricts heat dissipation; thus increasing the chance of stress accumu- lation.
Focusing now on the differences between the different APF classes, the [0°] class appears to have overall degraded properties (viz. lowest ductility, stiffness and strength). Although the only difference with the [90°] class is the direction of loading with respect to the printing di- rection, a significant decrease in UTS and stiffness is observed. This highlights an anisotropy in the behavior which is related to the for- mation of bonds between droplets and beads during the APF process: the interfacial bonding between two adjacent beads is stiffer than the interfacial bonding between two consecutive droplets of a same bead. Bellehumeur et al. [44] have described the formation of bonds between polymer filamentsintheFDMprocess.Theyexplainedthatthe firststep of bond formation is the establishment of interfacial molecular contact by wetting. The molecules then undergo motions towards preferred configurations to achieve an adsorptive equilibrium. Molecules diffuse across the interface, forming an interfacial zone, and/or react to form primary chemical bonds across the interface. The randomization can be reached only after extensive inter-diffusion of chain segments under critical conditions. In another study, Sood et al. [45] have clarified that a small air gap helps to create a strong bond between the two rasters and thus improves the strength of the component. But a small air gap restricts heat dissipation; thus increasing the chance of stress accumu- lation.
การแปล กรุณารอสักครู่..
