NEWS | Sept. 5, 2011

NRL Robotic Loader System Achieves Composite Material Testing Milestone

By Daniel Parry

The Naval Research Laboratory robotic materials testing system, NRL66.3, has achieved, to date, the highest industrial rates of fully-automated production mode functionality known to NRL researchers, yielding a total of 216 specimen tests at a rate of 26 per hour under six-degrees of freedom (6-DoF - three translations and three rotations) multiaxiality conditions.

The Computational Multiphysics Systems Laboratory of the Center of Computational Materials Science in the Materials Science Division completed the final construction phase of the NRL66.3, April 21, as well as its functional verification.

This system is designed to generate all the necessary material response data that enable the characterization of the constitutive behavior of complex, anisotropic materials in general and composite materials in particular.

In addition to providing constitutive characterization data for establishing material properties, it is anticipated that the use of such systems can influence drastically the composite material design, certification and qualification methodologies used for sea and aerospace platforms built from high performance composite materials, says Dr. John Michopoulos, head, Computational Multiphysics Systems Laboratory.

The loader consists of six recursive instances of a parallel linkage hexapod configuration (with six base and six moving platform spherical joints connected by six linkages), as well as custom-developed stereoscopic machine vision for three dimensional (3D) full-field remote displacement and strain measurements and sensor subsystems for measuring the response of the tested materials.

This capability represents a dramatic improvement in terms of kinematic freedom, speed, efficiency and accuracy compared to traditional uniaxial systems as well as its multiaxial predecessors also developed at NRL. The specimens tested were machined with water-jet cutting out of standard autoclave-produced balanced layup composite plates.

These recent tests have been funded through Naval Research Laboratory core funding and the Office of Naval Research-International Field Office (ONR-IFO) and ONR through a Naval International Cooperative Opportunities in Science and Technology Program (NICOP) program. The collaborating members of this effort in addition to NRL were the USDA Forest Products Laboratory, a consortium of research institutions and organizations in Australia led by the Cooperative Research Centre for Advanced Composite Structures (CRC-ACS), Virginia Tech and Massachusetts Institute of Technology (MIT).