SAMPE Journal - November/December 2021 - 49

Figure 1. Spacecraft antenna mounting bracket, designed and qualified for space applications.
INTRODUCTION
The activity was performed with the objective
of benefiting from additive manufacturing
technologies to design a robust structural
component for spacecraft and significantly reduce
weight and reduce parts counts, at a comparable
cost and lead-time to conventional production.
Very low mass was selected as the main
driver, and Aluminium alloys were the main
focus.
Lattice structure topology, blended with
standard interfaces to attach to the spacecraft
and components, was selected for the component
architecture type. Comparison with the same
component, made by conventional processing was
therefore possible, and the ALM parts could be
subjected to the same loads and other requirements
in the design stage. The study achieved success in
mastering key challenges in the design, inspection,
quality control and potential for cost reduction,
leading to wider acceptance and application in
European space projects.
Outline of Activity
The activity was focused on optimized design
methodologies applied to a spacecraft antenna
mounting bracket. Additive manufacturing (AM),
in this case laser powder bed sintering type, was
used to manufacture the parts. The part was a
combination of lattice structure and reinforcing
framework, with solid attachment interfaces for the
antenna. In this case the design of the AM part had
Figure 2. Lattice cell parameter, increasing density.
significant freedom. The manufacturing aspects associated with AM are more
varied and complex than conventional manufacturing and had to be taken
into account in the design in an iterative way, applying results from sample
tests and detailed inspections in the basic design parameters and results from
component stiffness and strength measurements in component level design
corrections.
The part design employed optimisation algorithms which considered;
* Equipment parameters, mainly build chamber dimensions /
limits, material types
* Cell design & size, in this case lattice type, with associated
parameters of cell geometry, truss dimensions, truss cross-section.
Nominal solid material properties, initially using datasheets,
updated with sample measurements from coupons produced in
representative conditions.
* Component design domain based around CAD geometry of
the reference part (a mounting bracket made in conventional
manufacturing) defining the component geometric envelope,
Interface regions (attachment to spacecraft and antenna).
* Loads, at this stage mechanical, applied as single loads and in
combinations; accelerations, forces and enforced displacements.
* Response, in this case lower eigenfrequency limit, maximum
deformation and maximum stresses.
Using the constraints and targets defined above, the topological
optimisation is run, at each step a FEM analysis is performed and an updated
CAD model generated. The convergence history indicated the effectiveness of
the algorithm at achieving the set objectives.
Figure 2 illustrates 1 parameter, the lattice unit cell density, varying from
a truss thickness of 0.25 mm (slender) in a 10mm cubic cell, to a fully dense
arrangement.
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SAMPE Journal - November/December 2021

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