Page 49 - MSAM-3-1

Materials Science in Additive Manufacturing Adhesion study for multi-material 3D printing

tensile coupon was designed and used to facilitate the illustrated in Figure 2C. The intention behind this
evaluation of interlaminar adhesion property between design is to enhance the mechanical bond between
cPLA and TPU materials. The design of the tensile coupons layers through increased physical engagement, akin to
was adopted from ASTM D638. In this work, we focused the interlocking teeth of a zipper. The design of the
on adhesion property between cPLA and TPU materials in interlocking feature was generated using Ultimaker
the build direction (z-direction). The design and the part Cura 5.3.1.
®
orientation used for printing of the tensile coupons are (iii) Top infill modification: The final group of samples
illustrated in Figure 2. includes a modification to the top layer of the bottom
In this study, we conducted a detailed examination of part, designed to augment the effective bonding
interlaminar adhesion by fabricating and assessing three surface area. This was achieved by programming a fine
distinct types of test coupons, differentiated by their 1 mm gap (or groove) on the top layer of the lower
interface treatments: filament segment before depositing the subsequent
(i) Unmodified interface coupons: These samples were material. When printing this variant, the printer’s
produced without any intentional alterations to the nozzle was deliberately positioned closer to the
interface. The printing parameters were set to allow print bed. This adjustment ensures that the extruded
for filament deposition with no gaps, ensuring that filament is compelled into the grooves, forming a
the layers were laid down in direct contact with one mechanical bond on solidification.
another. This standard configuration serves as the
control group, providing a baseline for evaluating the This approach to sample design allowed for the
efficacy of interfacial modifications. comparative analysis of interlaminar adhesion under
(ii) Low-profile mechanical interlocking feature coupons: varying interface conditions. By testing each configuration,
For these specimens, we introduced a mechanical we seek to provide insight on the impact of various
interlocking design, which features two layers of interface designs and the print order of the materials on
interlocking geometry that extends 2 mm into the overall bond strength between the rigid cPLA and the
the material. The precise pattern of this feature is flexible TPU layers in multi-material prints.

A B

C D

Figure 2. Schematic showing the (A) dimensions and print orientation of the tensile coupon for the investigation of interlaminar adhesion property between
cPLA and TPU. (B-D) show the designs of the interfacial feature of multi-material tensile coupon, with (B) showing the normal interface, (C) mechanical
interlocking feature, and (D) top infill modification coupons. Abbreviations: cPLA: conductive polylactic acid; TPU: Thermoplastic polyurethane.

Volume 3 Issue 1 (2024) 4 https://doi.org/10.36922/msam.2672