Fig. 7: DCB specimen manufactruing.

Labeled schematic of the modified DCB specimen (A). The backing was made of PLA (black), while the thermoplastic was made of PLA, ABS, PVDF, 5% PCL, or 10% PCL (white). A PLA spacer (black) was included to maintain separation between the backing and thermoplastic layer during casting but was removed before testing. The interface (initial crack) was created by inserting 6 cm of packing tape across the thermoplastic layer surface before casting. The HTPB layer (clear) was cast between the thermoplastic layer and the backing. The XY orientation (B) was used to create all thermoplastic layers except for the PVDF-S and PVDF-M specimens. All thermoplastic layers printed in the XY orientation, except for the PVDF-B specimen, used the top surface (including PVDF-T). The XZ orientation (C) was used to create the PVDF-S surfaces.