Microstructure-property relationship for impact energy absorption of functionally graded porous structures of acrylonitrile butadiene styrene (ABS)

Functionally graded (FG) structures are advanced class of composite materials where the microstructure is gradually continuous. This continuity eliminates problems like stress jumps and delamination that are encountered with conventional composite materials. FG porous structures have the added advantage of high strength-Toweight ratio compared to the solid FG materials. Strengthto- weight ratio can be tailored with controlled fabrication processes to satisfy certain design requirements. Microstructure-property relations help in selecting the appropriate microstructure for required strength and provide a guide to fabrication procedures. In this work, FG porous structures of ABS are fabricated with thermally activated microspheres and compression moulding with a special mould design. Gradient in the porous structure is created by inducing thermal gradient across the thickness. SEM images of the porous structure were analyzed by locally adaptive thershoulding technique which is based on minimizing an energy functional of the thresholding surface through a variational Minimax algorithm. The purpose of local threshoulding is to extract accurate information about the microstructure like pores' diameters and porosity. This information is then utilized to run correlation analysis between microstructure to processing and microstructure to impact energy absorption. The results showed the potential to control microstructure and hence tailor impact energy absorption. Impact energy is shown to be more correlated to pores' average diameter than to porosity.