Using PXI for Portable Composite Material Repare Equipment for Material Structures

Author(s):
Manuela Valero - TEMAI Ingenieros and COMPOSYSTEMS

Industry:
Government/Defense

Products:
PXI/CompactPCI, LabWindows/CVI, LabVIEW

The Challenge:
Designing a portable repair system for composite materials.

The Solution:
Using a PXI controller, DAQ cards, GPIB, vacuum system, thermal control, and LabWindows/CVI to repair composite material structures.

Ensuring Flexibility
During the entire repair process, the portable repair system controls variables in temperature, vacuum, and time. On the structure of a wing, once a hole or crack is detected, a new layer of carbon fiber is added. In order to melt this layer with the structure, we have to subject the current layer to a vacuum and temperature cycle process. We applied a heat blanket and plastic cover over the carbon fiber layer.

A pump creates a vacuum to the plastic cover, and the heating blanket melts the layer. The resins and adhesives polymerize, causing the elements to cure, harden, and compact during the cure cycle.

With the equipment, we can configure principal control parameters and ensure flexibility, including the repair of:

• Heating velocity
• Heating time
• Stabilization of temperature
• Stabilization time
• Vacuum
• Cooling speed

The equipment operates both automatically and manually. The automatic mode permits repairs from an automatic form. If any of the temperature or vacuum limits exceed the maximum or minimum, or if a thermocouple or any other component fails, the equipment notifies the user graphically and acoustically.

The system saves all temperature and vacuum data on file for processing later. When the repairs are complete, the user can print a report of the data cycle.

Strength in a Small Format
We selected a four-slot National Instruments PXI-1002 chassis as a control platform because of its small size and strength. The NI PXI-8156-B has a Windows NT operating system. This device has two serial ports, one for the printer, GPIB, VGA, Ethernet, USB, mouse, and keyboard.

For data acquisition cards, we used:

• NI PXI-4351 -- The temperature recorder with up to 14 thermocouples type J, with cold junction compensation held at 0 ˚C
• NI PXI-6040E -- An analog card registers the values of the vacuum sensor during the repairs
• NI PXI-6527 -- A relay digital card that controls the temperature of the heater blanket in the repairs that controls the siren in case of an alarm

For the development of the vacuum system, electrovalves, and vacustats, we used standard market elements including a user-friendly touch flat screen monitor and membrane keyboard. The equipment has RS-232, GPIB, and Ethernet for transferring data.

Application Versatility
We chose LabWindows/CVI 5.5 as the software program because of its demonstrated application versatility in the world of industrial automation.

With the software, we designed a simple and interesting configuration for the user. Some of the many options include:

• User management -- The software permits establishment of a user level hierarchy - administrator, technician, and operator managing the different levels of access, depending on the login and password.
• Cure cycles configuration -- The user can configure the cure cycle parameters, heating speed, stabilization temperature and time, and cooling speed. The user can also configure complex cycles up to 15 segments.
• Printing configuration -- Users can choose the different parameters to print on the report at completion.
• Communications -- From this utility file, users can carry out transfers with external equipment via RS-232 or via GPIB
• Sensor calibration -- The user can carry out software calibration of the measurements coming from the vacuum and temperature sensors (thermocouples type J)
• Operations manual -- From this option, the user can test the correct functioning of the system before the repairs
• Users can view measurements in a graphic window in degrees Celsius for each of the thermocouples connected to the reparation and the measurement in (bares) of the vacuum sensors
• The user can manually apply more heat, controlling the power supply to the heater blanket directly from the software
• Automatic mode -- In this option, the software requests that the user selects the cure cycle that they wish to carry out. Above is a table that contains the following data: operator's name, repair zone, and aircraft identifier.

Finally, the software prompts the user to choose a file name to save the data acquired during the cycle. The system carries out the user-configured cycle graphically informing the evolution of this cycle, measurements of each of the connected thermocouples, vacuum measurements, and more.

If the temperature or vacuum limits exceed the user-established limits, the equipment halts the repairs and informs the user acoustically and with an onscreen message about the cause.

• Presentation of results: The equipment prints a graphic report of the ideal and real evolution of the cycle carried out with the main data of this cycle.

Users can see all the numerical data obtained during the reparation for temperature, vacuum, date, and time from any text-processing application or spreadsheet application.

Adaptable, Compatible, and Practical
Users can adapt the system to the needs of any enterprise dedicated to repairing composite materials and constitutes a practical and economic tool to carry out small repairs.

The benefits of equipment include a color screen, membrane keyboard, small size, durability, mobility, and watertightness.

The equipment satisfies the requirements of Eurofighter, military, and standard specifications. Users can adapt the software package for the repair equipment, allowing for the personalization of the application.

For more information, contact:
COMPOSYSTEM Ctra. Madrid -- Toledo
Km 32,4 Señorío de Illescas -- Toledo
Tel: 925 51 26 01
Fax: 925 51 18 56com
E-mail: composyst@composystem.com
www.composystem.com

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