JEC COMPOSITES MAGAZINE - Issue #96 - April 2015 - 36

high temperature

Benzoxazine components and OoA manufacturing process for aircraft and helicopters

By
Helder Barros Abreu
Technical Customer Service, Henkel
Dr. Amol Ogale
Program Manager - Materials
Quickstep

T

he use of liquid resin processes such as
resin transfer moulding (RTM) and
vacuum-assisted RTM (VARTM) has
developed rapidly in recent years. There is
a strong desire to use these processes more
extensively in future aerospace structures
because large and complex parts can be
manufactured economically, and the costs
of autoclave processing of prepreg materials
can be avoided. Despite the benefits of
liquid resin processes, there are challenges
to extending their use to primary structure
and high-temperature applications due to
the limitations of the resin systems available,
including:
- Toughness
- High-temperature performance
- Infusion conditions
- Stable viscosity at infusion temperature
- Cost-effective and controlled heating and
cooling during processing
In the study conducted by Henkel and
Quickstep, a benzoxazine resin was combined with a rapid heating and cooling
manufacturing approach to produce hightemperature-resistant composite laminates
and parts at significantly lower cycle times.
Key mechanical strength properties were

Fibre-reinforced polymer composites are increasingly considered
for replacing metals in high-temperature-resistant components
for aircraft and helicopters. With very limited resin options available to manufacture such composite components, Henkel and
Quickstep studied a Loctite benzoxazine resin offering high glass
transition temperatures and excellent hot/wet performance,
combined with room temperature storage and easy processing,
to develop an energy-efficient and manufacturing-friendly out-ofautoclave (OoA) process.
measured. The technique was then applied to
a curved, integrally stiffened composite panel
to demonstrate the ability of the process to
produce complex parts suitable for use in
aerospace applications.

Materials for high-temperature
performance
Epoxy, polyimide, polyurethane, bismaleimide (BMI), benzoxazine and cyanate ester
thermosetting polymers are commonly used
in high-temperature composite applications.
The specific material system is selected
based on the application area. However, the
processing of each resin type differs greatly
and requires attention towards the issues
of foaming, pot life, and the possibility to
use as an infusion resin, including viscosity,
infusion temperature, curing temperature,
etc. Related to the chemistry of phenolic
resins, benzoxazines offer excellent flame
retardancy and very low cure shrinkage. In
contrast to phenolic resins, they cure without
releasing volatile compounds and show
significantly better properties of the cured
material. Henkel has introduced a number of
commercial benzoxazine systems suitable for
use in prepregs, adhesives and infusion processes. For this study, the Loctite BZ 9130
AERO resin was selected and characterized
using the Quickstep process for the infusion

36 jec composites magazine / No96 April 2015

processing. Key characteristics of the resin
include:
- Room temperature stability, requiring no
refrigerated storage
- A one-part system, so no mixing required
by the processor
- Broad processing window, suitable for
large parts and complex shapes
- Stable, low viscosity at infusion
temperature
- Low heat release during cure, reducing
exotherm risk

Fig. 1: Composites for high-temperature-applications: Hat-stiffened curved panel demonstrator
produced using Loctite BZ 9130 AERO resin and
Quickstep curing
JEC COMPOSITES MAGAZINE - Issue #96 - April 2015

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #96 - April 2015
