Allegany College of Maryland

The critical care nurse who cares for a patient with a myocardial infarction focuses skill and attention on the patient's immediate needs. However, by combining assessment skills and knowledge of electrocardiography the nurse also searches for possible complications of myocardial infarctions.

The adaptation of anisotropic failure criteria along with the availability of high-temperat ure material property data represents a new approach to the prediction of structural integrity in rocket nozzles. Strength, modulus, and elongation data in tension, compression and shear, and coefficient of thermal expansion data were obtained at temperatures up to 4000 F for five nozzle materials. Several failure Criteria were investigated using off-axis compression specimens in initial screening tests. Modification of one of the distortion energy criteria appears to be a promising approach for the prediction of the structural integrity of these materials at elevated temperatures and combined loading.

With the advent of the filament-wound glass fiber — resin pressure vessel, a material unlike any encountered previously was brought into the field. Metals and plastics having anisotropic structures have been commonplace, to be sure, but a two-phase system consisting of fibers of high tensile strnegth embedded in a matrix of softer plastic was a new situation. The old testing problems, such as physical property testing, thickness gaging, defect detection, and so on, were still present, but a host of new structural parameters requiring nondestructive examination were found to exist. In many instances the “tried-and-proven” non destructive test methods were ineffective for extracting needed structural information. A fortuitous exception to this was radiography, without which the entire glass fiber rocket motor case program would have been retarded.

The usefulness of a cylinder test for obtaining hoop strength design data for glass fiber composite structures is well recognized. The advantage, theoretically, is primarily in the “statistical” value of fiber strength if uniform loading can be achieved. Both the split-dee and pressurized ring testing methods are limited in this regard; in addition, in the latter schemes it is impossible to test helical windings for structural evaluation. The history of the Allegany Ballistics Laboratory (ABL) cylinder testing program is briefly reviewed. The development of a mechanical segmented cylinder test method, which provides for uniform radial expansion, is reported. Included are fundamental biaxial performance data on hoop geometries for various glass fiber — resin systems. Presented, also, is the analysis of the test fixture mechanics with confirmative experimental data. The test method and fabrication of test specimens are outlined.