SAMPE Journal - July/August 2020 - 22

FEATURE / FIBER BED ARCHITECTURE
Figure 3. Topographical image of the plain weave
fabric.

ting the square out. Edges are secured with tape to
prevent frayed edges from lifting up and ruining
the fabric.
A 3D image of the surface is obtained using an
optical microscope (VHX-5000). The microscope
image generates 3D data used to create a topographical map, as well as a 150x image. Cropped
versions of these images are used in Figure 2. An
example of the topographical map is shown in Figure 3.
The topographical mapping will be used to obtain a more concrete measure of the variation in
surface uniformity and roughness that arises from
the different weaves. A pinhole is a much more severe height difference than a tow over/underlap, as
can be seen in the Figure 3.
Droplet Deposition Test
The droplet deposition test is the main way in
which data was gathered for this test. Two separate
views of the droplet were recorded with separate

devices. A goniometer (Ramé-Hart Model 500) was
the main device used during this test, providing the
stage for the fabric sample, as well as the syringe
system for dispensing a droplet. The fabric sample was secured to the goniometer stage with tape
along the edges to ensure the sample remains flat.
The goniometer recorded a side view of the
droplet, while a digital camera (LUMIX GH4) was
used to record the top view. A syringe was used to
deposit a 5mL droplet onto the fabric, at with both
recording devices starting to record once the droplet began falling under its own weight.
Images were recorded every two seconds by
the goniometer and every ten seconds by the topdown camera. These two sets of images were separately analyzed. An example of these images can be
seen in Figure 4.
The data gathered from each of the views is the
following: The side view allows for measuring the
height of the droplet that is above the fiber bed
surface. The top-down view is used to measure the
area being covered by the droplet over time.
RESULTS
Height Over Time
The height of the droplet over time is measured
using an automated MATLAB script. Given that the
goniometer images are output in greyscale, such
measuring is simple to do. Using the final image in
the sequence, a baseline for the final height is set,
and then for each individual image, the height of
the droplet is compared to that.
A measure of the height over time was determined to be the time it takes for the height to stop
changing. While ideally, this would be the time it
takes for the height to reach zero, in some cases
the droplet never is fully absorbed into the fabric,
particularly for the lighter areal weight fabrics. This
time will be referred to as the time to full absorption (th0) .

Figure 4. Images captured during the droplet
deposition test for the plain weave fabric sample. Side view images (above) are taken with the
goniometer, while top-down images (below) are
taken with a camera. The images on the left are
immediately following deposition, while those on
the right are after 1000 minutes, at the end of the
test.

SAMPE JOURNAL

J U LY/AU G U S T 2 0 2 0

w w w. s a m p e . o r g

http://www.sampe.org

SAMPE Journal - July/August 2020

Table of Contents for the Digital Edition of SAMPE Journal - July/August 2020