A testing time for composite seating

| Environmental Testing

Performing single axis carbon fibre seat tests

Andy Pye examines a Moog developed portable three-channel electromechanical test system to simulate loads on vehicle seat backs and benches for in-vehicle tests.

The system comprises three electric actuators (Moog’s electric linear actuators incorporate a brushless servomotor and ballscrew), a portable test controller with three channels, three servo drives and test software. Three servomotors move the actuators vertically to compensate for vertical displacement of the seats. An angle sensor placed on the seat provides information concerning seat displacement in order to determine the correct height of the actuators.

Recently released software gives access to the controller’s embedded user interface. This can be accessed directly through the display or via a mobile device. Software features, such as station configuration, calibration and tuning, sequence building, playing, editing and recording sequences, are available through the PC, and multiple stations can be run simultaneously.

“Our seat test system provides the advantages of an electric system: easy to setup, versatile, and compact, but more importantly it allows seats to be tested in-house, which saves time and allows for greater flexibility in the research and development of new seats”, said Marie-Laure Gelin, marketing manager, Test and Simulation at Moog.

The system has already been installed at a car seat manufacturer in Asia that manufactures complete seating systems and interior components. Other applications can be tested including car doors and panels, gear levers, pedals and seat belts.

More widely, this digital servo controller can run hydraulic, pneumatic or electric test actuators and 6-DOF hydraulic simulation tables. It can control up to six servo-control channels.

Carbon fibre components

Carbon fibre-reinforced plastic (CFRP) is attractive for automotive applications, but the material and manufacturing costs can exceed that of steel by a factor of 10. $5 additional cost per saved kg of vehicle weight is currently considered to be the guideline. Several development programmes are underway to challenge this problem.

One such is CAMISMA (Carbon fibre/Amid/Metal Interior Structure using Multi-material System Approach). Within this mouthful, Amid is short for polyamide. It is funded by the German Federal Ministry of Education and Research (BMBF, Bonn and Berlin).

The aim is to develop an automobile seat design that reduces weight by 40% compared to conventional metallic constructions, while meeting front and rear impact safety requirements.

Moog car seat test systemCAMISMA exploits three recently developed technologies:

* a new type of unidirectional polyamide pre-preg tape
* nylon 12 powder impregnated non-woven mats made from recycled carbon fibre
* a hybrid injection moulding/thermoforming process developed during another BMBF-funded project (Spriform), which enables forming of the PA12 tapes and mats, overmoulding of plastic features and incorporation of metal inserts in one step; in CAMISMA the SpriForm process is the same, but the materials are new.

A key to the SpriForm development is understanding the strain-rate-dependent material properties of both short-fibre-reinforced and continuous-fibre-reinforced plastics, so that process tooling and parameters could be optimised, both for the hybrid materials and hybrid moulding. The computer models were validated by materials testing.

CFRP testing

As the increased need for using lightweight materials has accelerated the amount and type of tests performed on composite materials, the Composite Materials Laboratory at the Inholland University of Applied Sciences in Delft is using the Moog Portable Test Controller for single-axis testing of fibre-reinforced composites.

Initially, the lab used the system to perform material tests related to aerospace, and has since extended its scope to cover automotive and sports equipment.

The characteristics of a composite material depend on the quantity of carbon fibre in a resin, as well as how the two are combined.

“The Moog Portable Test Controller and software interface provide us with an increase in testing efficiency,” says Bob Brocken, an Inholland University engineer and teacher. “We can now integrate more I/O devices than before and we can obtain real-time and realistic measurements from our climate chamber.”

“We can also change the force we apply to a part during a testing sequence. When we run a tension fatigue test, the objective is not to tear the material apart, but to measure the fatigue characteristics within the break limits. A composite material can consist of multiple layers, and we are trying to find out how strong the adhesion is between the layers. We prepare samples according to ASTM criteria.”

Latest posts by Andy Pye (see all)

About Andy Pye

Andy Pye is a graduate of Cambridge University and has had a high profile career in the technical press as well as being a pioneer in web publishing.

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