Development of an electromechanical triaxial test facility for composite materials

An experimental facility has been developed that is capable of generating a ny combination of tensile and/or compressive forces on three mutually ortho gonal axes of a cruciform-shaped composite specimen. Using this computer-co ntrolled test facility, any stress ratio in biaxial (sigma(1)-sigma(2)) or triaxial (sigma(1)-sigma(2)-sigma(3)) stress space can be evaluated. A desc ription of this electromechanical testing facility, including the reaction frame, test fixture, computer control system and instrumentation is include d. Once fully assembled, uniaxial, biaxial and triaxial tests were performe d on aluminum and on a carbon/epoxy composite laminate to evaluate the perf ormance of the test facility. Using the data generated from these tests, th e performance of many aspects of the triaxial testing facility, including t he intra-axis alignment, automated computer testing algorithms, data acquis ition algorithms, calibration values and machine compliance, was evaluated. The overall very acceptable performance of the triaxial testing facility i s believed to have been demonstrated.