Effect of the Surface Morphology of 3D Printed Titanium Substrates on the Mode I Fracture Toughness of Metal-Metal and Metal-Composite Bonded Joints

Abstract

Parts manufactured with Laser Powder Bed Fusion (LPBF) are drawing interest in the adhesive joints research because of their high surface roughness, which is usually associated with good adhesion. This work aims to assess the adhesion strength of the inherent surface morphology of LPBF manufactured titanium. Double Cantilever Beam (DCB) tests were carried out to determine the mode I fracture toughness of joints comprising as-printed titanium (Ti6Al4V) adherends, namely titanium-titanium secondary bonded and titanium-Carbon Fibre Reinforced Polymer (CFRP) co-bonded joints. The effect of high-temperature oxidation on the fracture toughness was also evaluated by testing a batch of joints in which the titanium underwent a post-printing thermal treatment. The as-printed specimens were compared to the same type of joints but with sandblasted titanium adherends to evaluate the effect of this surface pre-treatment on the value of fracture toughness. The results indicate that non-oxidised titanium joints with untreated adherends had an average of 11% higher fracture toughness than their sandblasted counterparts. On the other hand, sandblasting proved beneficial for oxidised joints, increasing the fracture toughness by 64% on average over the untreated samples.

Michele Guilino

PhD Candidate

My research interests in additive manufacturing of co-bonded CFRP/metallic joints.

Rosemere de Araujo Alves Lima

Postdoc Researcher

I am an MSCA postdoctoral researcher working on toughening and self-sensing strategies for smart, reversible adhesive joints. My research combines 3D printing, structural health monitoring, and multifunctional materials to enable the development of next-generation circular adhesively bonded composite structures.

Sofia Teixeira de Freitas

Principal Investigator

Sofia Teixeira de Freitas researches the structural integrity of bonded and layered materials to enable durable, sustainable structures. She is also an accredited group facilitator, committed to building academic environments grounded in cooperation and inclusion—key to overcoming technological limits and addressing the challenges of a truly sustainable society.