Accession Number : ADA255548


Title :   Determination of Stresses on Laminated Aircraft Transparencies by the Strain Gage-Hole Drilling and Sectioning Method


Descriptive Note : Final rept. Jan 1989-Sep 1990


Corporate Author : DAYTON UNIV OH RESEARCH INST


Personal Author(s) : Whitney, Thomas J ; Stenger, Gregory J


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a255548.pdf


Report Date : Apr 1992


Pagination or Media Count : 205


Abstract : Reducing the incidence of transparency changeouts due to craze of the outer acrylic ply requires knowledge of stress levels in in-service aircraft transparencies. Laboratory and field craze data may then be correlated to predict craze onset. Experiments conducted during the first phase of this study verified that the strain gage-hole drilling method, with calibration modification, can measure biaxial stress states in laminated transparencies with an error of less than 10% for stresses over 500 psi. A device to apply this method to full-scale transparencies was then designed and fabricated. In the second phase, stresses due to three mechanisms (residual stress, installation, and cabin pressurizing) in full-scale transparencies were measured. For comparison purposes and to identify the contribution of particular mechanisms to the total stress state, the sectioning method was also used. The measurements made on full-scale transparencies removed from service due to craze indicate residual stresses are too low to cause crazing in a 'uniform' environment (one free from wide temperature variation and extended contact with crazing agents). Stresses due to transparency installation and cabin pressurizing were also low relative to the maximum principal stress criteria used in this study. Recommendations include examination of other craze criteria, examination of other stress inducing mechanisms such as moisture desorption from the surface, and examination of cyclic loading and chemical exposure on craze.


Descriptors :   *FIGHTER AIRCRAFT , *STRESS ANALYSIS , *LAMINATES , *CRAZING , *TRANSPARENCIES , STRESSES , MACHINING , SURFACES , RESIDUAL STRESS , AIRCRAFT CANOPIES , MOISTURE , DRILLS , DRILLING , CYCLIC LOADS , DESORPTION , CALIBRATION , STRAIN GAGES , ERRORS , MODIFICATION , CHEMICALS , TEMPERATURE , AIRCRAFT


Subject Categories : Attack and Fighter Aircraft
      Laminates and Composite Materials
      Machinery and Tools


Distribution Statement : APPROVED FOR PUBLIC RELEASE