Choosing Your Layup Process – Prepreg vs Traditional

Murphy’s Law: a law of nature, anything that can go wrong,
will go wrong. Especially true in composite fabrication as variables are
always going to exist. Between tooling, plycut, layup, bagging, cure,
demold, and trim, creating or manufacturing a quality composite is no
simple task. Prepreg material can be a great option when things look
like they are getting way too complicated.

Explanation of Benefits of Using Prepreg Material over Traditional Layup Techniques:

A
prepreg material is a pre-impregnated mixture of uncured resin and
fabric that will make a composite laminate. Prepreg material design is
to have an ideal ratio of fabric to resin. This resin ratio provides the
cured composite’s concise properties such as UTS (ultimate tensile
strength) and Modulus (Applied Stress vs. Material Strain). This ratio
eliminates variables due to the traditional hand layup’s likeliness to
variate this resin ratio, consequently altering final composite
properties. Giving that the prepreg material and resin to fiber ratio
will be consistent ensures better laminate properties.

Variation
in ply cutting & layup is mitigated (or limited) by the quality of
the prepreg material. Reputable prepreg material manufacturers undergo
extensive in-house processing and visual testing to ensure to the
customer that material will have a uniform application of resin
throughout the fibers. Uniformity of the material translates to layup as
the parts’ final thickness will be consistent and the process made
repeatable. When planning to manufacture or make multiple parts, prepreg
materials provide a considerable advantage.

Cleanliness,
when using prepreg material, significantly increases. Eliminated are
the problems of rollers, cups, mixing tools, and resin buckets getting
in the way and placing the focus on the details. This focus will provide
the future composite laminate with a patient layup and bagging process.
Prepreg material will also mitigate the waste of resin and fabric
material caused by traditional layup methods.

Prepreg
materials provide peace of mind during layup as the resin cures by heat
and pressure rather than solely on time. Giving time to properly bag or
work through any sudden issues is vital during any layup. Using a
prepreg material provides an advantage over fighting the setup time of
the resin. The surface finish of a composite part is also easily
achieved relative to traditional hand layups.

When
debating on what process to go with, whether it be a traditional layup,
using prepreg, or infusion, it is essential to ask the following
questions before coming to a decision:

What quantity of parts for fabricating needs to be considered?

If
making a single part for anything fabricated, using a prepreg material
may not make economic sense. The advantages of prepreg materials lie in
producing 20-30 to even hundreds of parts. Using traditional layup
techniques may be more feasible when making only a single part or if the
mold requires future modifications due to design changes. Notably
important is that advanced planning will significantly reduce the mess
that traditional layups bring.

What is the complexity of the contours of the part?

When
planning a layup that goes over multiple changing angles in a tool, it
is vital to understand the workability of prepreg material is greater
than that of traditional methods. However, for simple contours,
traditional layups would suffice for many situations.

Have
questions on what would be the best layup process for your project & if Prepreg is the right way to go?
Contact us here at Composite Envisions, and we’ll be happy to help and
set you on the correct path.