Session: 02-14-03 Structural Analysis of Marine Structures 3

Submission Number: 176216

Internal Structure Optimization for Additively Manufactured Marine Propeller Blades 

Marine propeller manufacturing faces increasing demands for improved efficiency, reduced material consumption, and shortened production cycles. While traditional casting methods constrain designers to solid geometries, Wire Arc Additive Manufacturing (WAAM) enables the integration of complex internal structures that significantly reduce weight while maintaining structural integrity. This research presents a comprehensive investigation of optimized internal architectures for WAAM-manufactured propeller blades, addressing both design methodologies and practical manufacturing constraints.

Three distinct internal structure approaches were developed and analyzed for a five-blade marine propeller geometry. First, topology optimization with Siemens NX generated branch-like internal supports that efficiently distribute loads along principal stress paths. Manufacturing constraints necessitated simplification into two configurations: a straight-bridge structure and a Warren truss design. Second, bio-inspired gyroid lattices were implemented, leveraging their proven isotropic stiffness and superior strength-to-weight ratios demonstrated in compression testing. For the gyroid design even the outer shell thickness of the blade could be reduced.

Finite element analyses in ANSYS evaluated each configuration under realistic hydrodynamic loading conditions representative of operational pressure distributions on suction and pressure blade surfaces. The gyroid structure demonstrated optimal performance with average Von Mises stress of 22.57 MPa while achieving 45-65% material density relative to solid construction. The truss structure showed intermediate performance (27.37 MPa average stress, 60-70% density), while the straight-bridge design exhibited higher stress concentrations (41.61 MPa, 60-70% density). All configurations remained well within allowable stress limits for the selected high-strength bronze alloy, chosen for its superior corrosion resistance and WAAM processability.

Manufacturing feasibility studies validated the production of inclined struts up to 35° using Cold Metal Transfer (CMT) and Pulse Multi Control (PMC) welding processes. Critical manufacturing parameters were established regarding minimum feature sizes, layer heights, and post-processing requirements. Prototype blade sections at reduced scale successfully demonstrated consistent bead geometry and dimensional accuracy, confirming the viability of the proposed internal structures.

While the gyroid configuration offers superior mechanical performance, current WAAM technology limitations—specifically minimum feature sizes and restricted tool access for complex curved paths—prevent immediate implementation and require sophisticated solution strategies. The truss structure emerges as the optimal near-term solution, balancing manufacturability with approximately 30% mass reduction and acceptable stress distribution. The path planning for the lattice geometry and contour of the ship propeller can be seamlessly integrated into existing hybrid WAAM milling workflows, enabling practical implementation without significant changes to the robot-assisted systems.

This research establishes a framework for designing and manufacturing lightweight marine propellers using additive technologies. The methodology combines mathematical optimization, bio-inspired design principles, and practical manufacturing constraints to achieve components that meet stringent classification society standards while reducing material consumption. The findings demonstrate that internal structure optimization can revolutionize propeller manufacturing, with immediate applications for the truss design and future potential for gyroid structures as WAAM technology advances.

Future work will focus on full-scale prototype testing, fatigue characterization under cyclic loading per DNV guidelines, and development of specialized WAAM strategies for complex lattice geometries. The integration of topology optimization with manufacturing constraints provides a pathway toward next-generation marine propulsion systems that are both lighter and more resource-efficient.

Presenting Author: Christian Klötzer-Freese Mecklenburger Metallguss GmbH

Presenting Author Biography: 11/2013: Finishing Studies in Mechanical Engineering at University of Rostock, M.Sc.

03/2022 – Present: Project Engineer Process Management & Business Development
Mecklenburger Metallguss GmbH, Waren (Müritz)
Department: Process Management & Business Development
- Leadership of "Production Controlling" committee, strategic and operational production controlling
- Management and coordination of production engineering research projects
- Further development and optimization of existing manufacturing processes
- Project management of special projects
- Development of strategic ideas and targeted business plans

02/2014 – Present: Research Associate
Fraunhofer Institute for Large Structures in Production Engineering (IGP), Rostock
Department: Automation Technology and Prototype Construction
- Planning, design, and commissioning of automation solutions with focus on robotics
- Development, acquisition, and execution of research topics
- Instruction and supervision of research assistants and student theses
- Primary point of contact for CAD and additive manufacturing within the institute

Authors:

Muthair Saeed University of Rostock
Christian Klötzer-Freese Mecklenburger Metallguss GmbH
Gunnar Kistner University of Rostock
Jörn Klüss Mecklenburger Metallguss GmbH
Patrick Kaeding University of Rostock
Thomas Lindemann University of Rostock