Enhancement of mechanical property and formability of CFRP core sandwich sheets by additive manufacturing process-induced material and structural anisotropies

Abstract

The additive manufacturing (AM) of fiber reinforced plastics has gained much interests in the design of lightweight structures with superior mechanical performance. Strong anisotropy can be induced during the extrusion process owing to the preferentially orientated fiber reinforced plastics with high aspect ratio. To make better use of AM-induced material anisotropy, an integrated material-structure-performance design strategy for AM-produced carbon fiber reinforced plastic (CFRP) structures was proposed, in which the microscopic material and mesoscopic structural anisotropies were integrated to achieve enhanced macroscopic mechanical performance of CFRP core structures and sandwich sheets. The effects of AM process parameters including the layer thickness and build orientation on microscopic material anisotropy of the AM produced CFRP were firstly investigated and the strong relationship between material anisotropy and AM process parameters was confirmed by extensive mechanical tests and microscopic observations. A new core structure possessing the arbitrary bending anisotropy was proposed and the relationship between structural anisotropy ratio and bending stiffness was clarified. In addition, the mechanical properties of core structures were tested and superior mechanical performance can be achieved by tailoring the combination of material and structural anisotropies. The effects of structural anisotropies on mechanical properties and face buckling behaviors of sandwich sheets were investigated and found that face buckling is the dominant failure behavior. The new finding that the integration of microscopic material anisotropy and mesoscopic structural anisotropy induced by AM could enhance the mechanical property and formability of CFRP core sandwich sheets is of great significance in the design of lightweight structures. • An integrated material-structure-performance design strategy for additive manufacturing (AM) produced fiber reinforced plastic structures • The effects of AM process parameters including layer thickness and build orientation on microscopic material anisotropy of CFRP are clarified • Structure that can achieve an arbitrary bending anisotropy is proposed • The relationship between structural anisotropy ratio and bending stiffness is investigated • Better mechanical performance can be achieved by the integration of material and structural anisotropies