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

with top infill modification have the highest interlaminar adhesion strength, achieving a minimum enhancement of
adhesion strength. 25% relative to the standard benchmark coupon.
In addition to increasing the surface area, the various These results have far-reaching implications for the design
types of interfaces employed in our study also significantly and manufacturing of multi-material components, where
influenced the diffusion of molecular chains at the interface interlayer adhesion is critical. They pave the way for improved
between cPLA and TPU. This diffusion process is critically application-specific material selection and the development
dependent on the thermal dynamics during printing, where of advanced printing strategies that can enhance the structural
temperature plays a pivotal role. As the printing process integrity of 3D-printed materials. Future work should
35
involves both cooling of the previously deposited layer focus on the optimization of interface designs to maximize
and reheating due to subsequent layer deposition, these adhesion strength, while also exploring the influence of
thermal events occur simultaneously and have a substantial various printing parameters on the mechanical properties
impact on the adhesion mechanism. The reheating of the of multi-material prints. Furthermore, the potential for
underlying layer on deposition of a new layer facilitates scaling these findings to industrial manufacturing processes
the diffusion of molecular chains across the interface, presents a promising avenue for the production of complex,
potentially leading to stronger bonding. This effect is high-strength multi-material assemblies.
particularly pronounced in the presence of mechanical
interlocks, where the increased surface area and complex Acknowledgments
geometries create more opportunities for molecular None.
intermingling. The thermal history of each layer, including
the peak temperature reached and the cooling rate, thus Funding
becomes a critical factor in determining the strength and
quality of the interfacial bond. This complex interplay This research is supported by the Agency for Science,
of temperature, cooling, and reheating underscores the Technology and Research (A*STAR) under its IAF-ICP
importance of optimizing printing parameters to enhance Program I2001E0067 and the Schaeffler Hub for Advanced
molecular diffusion at the interface, thereby improving the Research at NTU and the National Research Foundation,
overall structural integrity of the multi-material print. Prime Minister’s Office, Singapore under its Medium-Sized
Center funding scheme.
4. Conclusion
Conflict of interest
This study provides some insights into the interlaminar
adhesion strength of multi-material interfaces, specifically The authors declare that they have no competing interests.
between cPLA and TPU. In this work, we investigated
three different types of coupons (unmodified interface, Author contributions
interface with interlocking feature, and interface with Conceptualization: Guo Liang Goh
top infill modification) with two opposing print orders. Formal analysis: Guo Liang Goh
Through our experiments, we observed that the failure Funding acquisition: Wai Yee Yeong, Boon Siew Han
of samples predominantly occurred at the interface, with Investigation: Guo Liang Goh, Samuel Lee, Shi Hui Cheng,
most specimens exhibiting a clean break with minimal Pothunuri Laya, Daniel Jee Seng Goh
residual material from the opposing surface. This behavior Methodology: Guo Liang Goh, Samuel Lee
underscores the importance of interface design in multi- Project administration: Boon Siew Han
material 3D printing. We quantitatively assessed the surface Writing – original draft: Guo Liang Goh
roughness characteristics of the fractured interfaces, Writing – review & editing: Wai Yee Yeong, Van Pho Nguyen
employing metrics such as R Sa-A and R . Our findings
a
revealed that the printing order and interface modifications Ethics approval and consent to participate
significantly impact the roughness parameters, which, Not applicable.
in turn, affect the mechanical interlocking and adhesion
properties. In addition, the decrease in porosity at the Consent for publication
interface can be linked to the optimized nozzle positioning
during printing, which promotes the extruded material to Not applicable.
conform into the grooves of the underlying layer, resulting Availability of data
in an increased effective surface area for adhesion. Our
results indicated that the interface incorporating top Data are available from the corresponding author on
infill modifications demonstrated superior interlaminar reasonable request.

Volume 3 Issue 1 (2024) 12 https://doi.org/10.36922/msam.2672