Structures and Materials Laboratory

The Structures and Materials Laboratory in the School of Aero Engineering consists of a number of separate facilities that are spread over several labs with a total floor space of almost 5000 sq. ft. An extensive range of equipment for investigating problems of stress and strain distribution in a variety of materials and under many environments is available. There are several testing machines and computer driven data acquisition systems along with equipment for photo-elasticity, Moire fringe analysis, brittle lacquer, strain transfer, digital image processing and a range of transducers for measuring force, displacement, velocity, acceleration and strain. There are excellent capabilities for dynamic testing as well, including impact, fatigue and vibration. All test work can be recorded using video cameras and VHS recorders. Specific equipment and capabilities are as follows.

Load frames and testing machines
The Structures Lab is equipped with a state-of-the-art 55,000 lb MTS 800 series electro-hydraulic testing machine and a smaller 22,000 lb Instron electro-hydraulic testing system, both equipped with full real-time digital controls including stepless mode and control channel switching. These machines represent the best technology available today and can be used for complex static, quasi-static and dynamic testing of material samples and small structural components. Other testing machines include a Baldwin screw-jack universal testing machine of 120,000 lbs. capacity, an Instron screw-jack test machine of 20,000 lbs. capacity, a Riehle universal hydraulic test machine with 40,000 lbs. capacity and capability to accommodate specimens up to 12 ft. in length, an Applied Test Systems 20,000 lb creep testing machine, and a range of MTS multi-channel hydraulic servo-controllers with actuators, load cells, fixtures and hydraulic control elements. All testing machines include standard fixtures like tension grips, compression plattens and bend test fixtures (three point and four point). Two environmental chambers are available and can be used with several of the test machines. The MTS machine also has a Gilmore torsion fixture with a 10 inch arm. The Lab is equipped with a multipoint hydraulic distribution system with a 3000 psi, 10 gpm capacity pump.

Data acquisition systems
All data acquisition systems are independent of the testing machines to allow any system to operate with any test machine. The systems include a 30 channel HP-IB and PC based quasi-static data logger, a 200 channel strain/temperature/voltage PC-based data acquisition system, a Kiethley Instruments - PC based system, a LeCroy 6 channel 32 million samples/sec system with an HP 9000 series controller , a Nicolet digital storage oscilloscope with PC interface, an HP 8 channel portable FM tape recorder, and a selection of flat bed and strip chart recorders.

Specimen Fabrication and Conditioning
Composite laminated specimens can be fabricated in a small special-purpose autoclave equipped with interchangeable plattens to allow manufacture of flat and contoured laminated sections. In addition to the standard material and specimen storage facilities, environmental conditioning facilities include several humidity - temperature chambers and a constant temperature water bath. NDE tools include a Fokker bond tester, a Unitron microscope, acoustic emission equipment and a pulse propagation type ultrasonic inspection system. In addition, the Structures Lab has access to shared composites manufacturing facilities located in the School of Textile and Fiber Engineering. Dynamic Testing: Each of the servo-controlled electro-hydraulic test machines described above is capable of developing low-cycle dynamic loading using either periodic or quasi-random loading histories. Such capabilities are ideally suited for fatigue and fracture studies. In addition, other facilities exist for impact and vibration testing. The impact test facility is a tube-guided drop weight type system with a 50 lb (maximum) drop mass and a 15 ft (maximum) drop height. The facility is instrumented with photo-electric timers, a reaction load cell, and an accelerometer instrumented stationary impact head (signal is integrated to obtain displacement history). Extensive vibration testing equipment includes a range of structural electrodynamic shakers, instrumented hammers, accelerometers and associated signal processing electronics for swept sine, random and impact excitation. Analysis equipment includes a Tektronix 2630 structural dynamics analyzer and a GENRAD 2515 computer aided test system, both with extensive data acquisition, modal analysis, and parameter estimation software. A selection of piezoelectric sensors, drivers and control electronics is available for investigation of smart structures and active damping concepts. Three large structural "hard backs" are also available for mounting models or full scale specimen for testing. Current full scale test articles under study include an F-15 aft fuselage and tail section and an UH-1 helicopter tail boom.

Stress and Strain Analysis
Equipment for measurement of stress and strain includes Brittle lacquer coating, Moire fringe equipment, transmission and reflection polariscopes with digital compensators, Mullard - Hickson type strain transfer equipment and numerous load cells, displacement transducers and extensiometers, strain gage mounting and inspection stations, BLH and Vishay strain indicators.

For more information, please contact:
E. A. Armanios, S. C. Bailey, J. I. Craig, K. Gramoll, S. V. Hanagud, G. Kardomateas, and R. Talreja