Page 28 - MSAM-2-1

Materials Science in Additive Manufacturing Fast fiber orientation optimization

Figure 5. Top (left) and isometric (right) views of the wrench.

the interval of 10° width around the mean value, a new
iteration is made.
Hence, a sequence of 10 fiber angles for each stack is
obtained at the end of this first step. This result is used as
an input for the second step.
2.2.2. Optimized number of reinforced layers

Once the optimal fiber’s orientation has been computed
inside each stack, it is necessary to reduce as much
as possible the number of reinforced layers because
continuous fiber-reinforced filament is a more expensive
and heavier material compared to the nylon, which is
also available with the Markforged X7 printer used in this
work. To perform this cost reduction, a multi-layered finite
element model only containing nylon at the beginning
is used. A first computation provides the stacks where Figure 6. Mechanical model of the wrench.
the maximal von Mises stress is located inside the nylon
layers. While this maximal von Mises stress is higher correspond to the mechanical tests that we performed on
the printed part.
than the tensile strength of the nylon, the material of the
first unreinforced layer of the stack is replaced by the The optimization model presented in section 2.2 gave
composite, oriented with the angle computed for this layer the same fibers angle repartition for each stack with the
in the previous study. If there are locations where the von following distribution: 2° (70%), −33° (10%), −17° (10%),
Mises stress is higher than the tensile strength of the nylon, and 13° (10%). The two angles of 0° and −30° that could
the loop starts again. be guessed intuitively were therefore found by the first step
of the optimization algorithm depicted in Figure 3 with an
3. Case study angle of 2° close to 0° and an angle of −33° close to −30°.
The specific case of a wrench, which is an easy-to-print Since the stress’ magnitudes were higher in the horizontal
part (Figure 5), is considered. The crooked handle, with section of the handle (frame no. 2 in Figure 7) compared to
an angle of 30° between the two sections, makes the stress the ones in the inclined section of the handle (frame no. 1 in
flow more complex and more interesting to study than a Figure 7), the angle of 2° was logically more represented
straight handle with unidirectional fiber reinforcement. (seven times) than the angle of −33° corresponding to the
Intuitively, the best way to enhance the stiffness of the inclined section. It is also important to note that the model
wrench would be to reinforce equally the two sections, gave two other angles (13° and −17°) corresponding to the
which would result in a 0°/−30° laminate. However, we stress fields inside of the wrench’s head (frames no. 3 and
will see in the next section that two additional angles no. 4, respectively, in Figure 7). The tests performed on the
calculated by our algorithm play a key role in the stiffness printed part demonstrated that these two additional angles
improvement. that cannot be predicted without the help of an optimization
algorithm play a key role to stiffen the wrench.
3.1. Numerical results
3.2. Tests on printed parts
The wrench is locked on the faces, which are supposed to
be in contact with the screw, and a force is applied on the To check whether the proposed method leads to an
top of the handle (Figure 6). These boundary conditions improvement of the performances of the wrench, two

Volume 2 Issue 1 (2023) 5 https://doi.org/10.36922/msam.49