4. Result and Discussion
Tensile tests were performed to investigate the effect of sandwich
composites in additive manufacturing. The effects on various outer
shells, raster angle, and layer thickness at fabrication were also
measured. All of the experiments were carried out exactly as instructed.
As specified in the experimental design, After tensile testing, broken
test specimens are shown in Figure.1. All the samples were broken in
different ways along the infill direction during the loading.
<<< Figure.1 ASTM Standard Tensile Tested
3D printed Specimens >>>
To generate main plots, the mean of each parameter at all levels was
used. The maximum mean value indicates the optimized parameters for
tensile strength, and the significance of the parameters was determined
using Analysis of Variance (ANOVA). The interaction of process
parameters on tensile strength was investigated in this analysis. The
main plot effect demonstrates the direct impact of independent
parameters, whereas the interaction effect demonstrates the combined
impact of two parameters. The main tensile strength plot for FDM printed
PLA specimens is shown in Figure.2. Tensile strength decreases with
increasing layer thickness and number of shells, but increases with
increasing raster angle. The PLA mean plot analysis shows that a raster
angle of 90 (Level 3), a layer thickness of 0.1 (Level 1), and a number
of shells of 3 produce the best results. The mean plot for PLA analysis
also reveals that the raster angle has the greatest influence on tensile
strength, followed by layer thickness and the number of shells.
<<< Figure.2 Main Plots for printed
samples a)PLA, b)PLA/Al2O3, c)PLA/Cu, d)PLA/CF, e)PLA/Al2O3-SW,
f)PLA/Cu-SW & g) PLA/CF-SW>>>
The PLA/ceramic composite main pot demonstrates that tensile strength
decreases with increasing layer thickness and the number of shells.
increases as the raster angle increases. When compared to PLA,
PLA/Ceramic has slightly higher strength for a layer thickness of 0.2
(Level 2) but lower strength for the number of shells (Level 1).
PLA/Copper composite plots show that the tensile strength varies
similarly to PLA but has less strength than PLA and PLA/Ceramic
composites.
PLA/Carbon fibre composite plots show that tensile strength varies
similarly to PLA for raster angle input parameters, but with less
tensile strength. The layer thickness and number of shells provide
nearly equal strength across all levels (Level 1 to Level 3). The
PLA-PLA/Ceramic sandwich mean plots show a similar variation for the
input parameter but show improved tensile strength over PLA at all
levels (Level 1 to Level 3).A PLA-PLA/Copper sandwich mean plot shows a
similar variation in tensile strength for input parameters such as PLA,
but shows significant improvement over PLA. A mean plot of a
PLA-PLA/Carbon fiber sandwich reveals that the sandwich is unaffected by
layer thickness and behaves like PLA, but the tensile strength increases
as the number of shells from all levels increases (Level 1 to Level 3).
It is also necessary to determine the parameters that have a significant
impact on the tensile strength of the specimen. ANOVA (analysis of
variance) was used to identify the most significant parameters affecting
the response parameter in terms of percentage. The statistical
significance of individual parameters has been represented by the
p-value. According to Taguchi et al. [36], the p-value for the 95
percent confidence level should be less than 0.05. The ANOVA result for
tensile strength means data is shown in Table.6, which shows that the
p-value of the raster angle, layer thickness, and the number of shells
(all input parameters) was less than 0.05 for all materials. However,
the number of shells has a p-value greater than 0.05 for the material
PLA/Carbon fiber composites, and the raster angle has a p-value greater
than 0.05 for the material PLA-PLA/CF sandwich.
<< < Table.7 ANOVA table for Experimental
Results>>>
As a result of these factors having a statistically significant effect
on tensile strength, the confidence interval for PLA material was
96.26%, for PLA/Ceramic composite was 94.08 %, for PLA/Copper
composite was 95.03 %, for PLA/Carbon fiber composites was 95.24 %,
for PLA-PLA/Ceramic sandwich was 94.09 %, for PLA-PLA/Copper sandwich
was 92.36 %, and for PLA-PLA/CF sandwich was 95.08%. As a result, the
raster angle (greater than 34 %.) is the most influenced parameter for
PLA, PLA/Ceramic-composite, PLA/Carbon fiber, and PLA-PLA/Ceramic
sandwich. The layer thickness has the greatest influence on the tensile
strength of the PLA-PLA/Copper sandwich and the PLA-PLA/Carbon fiber
sandwich. The number of shells has the greatest influence on the tensile
strength in PLA/copper composites.