This document discusses out of autoclave composite manufacturing and resin transfer molding (RTM) as alternative processes to traditional autoclave curing. RTM involves placing fiber reinforcement in a closed mold and injecting resin under pressure and heat without an autoclave. The resin cures as it flows through the mold. RTM produces high strength, lightweight composite parts with complex shapes. It is commonly used for aircraft, boat, and wind turbine components. The document provides overviews of RTM and out of autoclave processes, companies that use RTM, benefits, applications, and references for further information.

1. Composite Structure Manufacturing
RTM ( RESIN TRANSFER MOLDING )
Cairo University
Faculty of Engineering
Aerospace Department
UDC xPlatform Training
Prepared By:
Mohamed Adawy

2. Out of autoclave composite manufacturing
Out of autoclave composite manufacturing is an alternative to the traditional high pressure autoclave curing process
commonly used by the aerospace industry for manufacturing composite material. Out of autoclave (OOA) is a process
that achieves the same quality as an autoclave but through a different process.
Out of autoclave manufacturing processes
OOA curing achieves the desired fiber content and elimination of voids by placing the layup within a closed mold and
applying vacuum, pressure, and heat by means other than an autoclave. An RTM press is the typical method of
applying heat and pressure to the closed mold. There are several out of autoclave technologies in current use including
resin transfer molding RTM), Same Qualified Resin Transfer Molding (SQRTM), vacuum-assisted resin transfer molding
(VARTM), and balanced pressure fluid molding. The most advanced of these processes can produce high-tech net shape
aircraft components.
Introduction

3. Overview
Resin transfer molding (RTM) is an increasingly common form of molding, using liquid composites.
It is primarily used to mold components with large surface areas, complex shapes and smooth
finishes. RTM is unlike reaction injection molding and structural reaction injection molding processes
(SRIM), in which the chemical reaction is induced by the mixture of reactants.
Instead, the chemical reaction for resins used in RTM are thermally activated from the fiber mat or
preform and mold wall. The reaction speed of RTM is much slower than that in SRIM, allowing for a
longer fill time at lower injection pressure.
Final RTM products will be light in weight and high in strength. However, RTM uses heavy structured
tooling to withstand the hydraulic pressure, and hence it has high tooling cost.
Resin Transfer Molding (RTM) is the process of producing composite components within a
mechanically-clamped, rigid, normally two-part (male-female) mold.

4. RTM is a closed-mold, vacuum-assisted process that employs a flexible solid counter tool used for the B-side surface
compression. This process yields excellent strength-to-weight characteristics, high glass-to-resin ratios and increased
laminate compression.
In this process, fiber preform or dry fiber reinforcement is packed into a mold cavity that has the shape of the desired
part. The mold is then closed and clamped.
Catalyzed, low viscosity resin is then pumped into the mold under pressure, displacing the air at the edges, until the
mold is filled.
After the fill cycle, the cure cycle starts during which the mold is heated, and the resin polymerizes to become rigid
plastic. Gel coats may be used to provide a high-quality, durable finished product.
This process is well-suited for mass production of 100 to 10,000 units/year of high-quality composite fiberglass or
fiber-reinforced plastic parts. It is recommended for products that require high strength-to-weight requirements.
Tooling used in this process can be made from various materials including aluminum, nickel shell, mild steel and
polyester.
The light RTM (LRTM) process, on the other hand, is similar to that of RTM, but differs in the method of closing the
mold. The closure of the mold is done mechanically or by applying vacuum between two seals in the mold peripheral
flange.
Resin Transfer Molding Process

5. A video to demonstrate the RTM process…
RTM Process

7. Companies Involved in Resin Transfer Molding
The following is a list of various composite/fiber glass
producers, specializing in RTM:
1. Composite Integration Ltd
2. JHM Technologies
3. Owens Corning
4. Apogee Products
5. FormaShape
This photograph shows aluminum RTM tooling being operated in a hydraulic
press to produce composite door skin panels.

8. Benefits
The key benefits of resin transfer molding include the following:
Good surface quality
Wide range of reinforcements
Large, complex shapes
Dimensional tolerances
Low capital investment
Less material wastage
Tooling flexibility
Low environmental impact
Labor savings
Ability to add inserts and reinforcements at a point of infusion for greater strength
Zero air entrapment within the product.

9. Applications
RTM is of major interest for various molding applications as it promises
performance improvements and cost savings over traditional methods.
Some of the major applications of the RTM process include:
Truck panels
Boat hulls
Wind turbine blades
Aerospace and automobile parts
Medical composites
Bathroom fixtures, car body, helmet, etc.
Airbus A340 carbon composite spoiler made with RTM

10. • http://www.azom.com/article.aspx?ArticleID=8620
• http://www.nuplex.com/Composites/processes/resin-transfer-moulding
• http://en.wikipedia.org/wiki/Resin_transfer_molding#Vacuum_assisted_RTM_.28VARTM.29
• http://www.compositesworld.com/articles/airbus-a340-carbon-composite-spoiler-made-with-rtm
• http://www.composite-integration.co.uk/about-rtm.php
References