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Use of unbalanced laminates as a screening method for microcracking
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Bowles, Kenneth J. Papadopoulos, Demetrios S. |
| Copyright Year | 1990 |
| Description | State-of-the-art, high temperature polyimide matrix composites, reinforced with continuous graphite fibers are known to be susceptible to intraply cracking when thermally cycled over their useful service temperature range. It is believed that the transply cracking, in part, results from residual stresses caused by differences in coefficients of thermal expansion (CTE) between the polymer matrix and the reinforcement. Thermal cycling tests to investigate this phenomenon involve expensive time and energy consuming programs which are not economically feasible for use as a part of a materials screening process. As an alternative to thermal cycling studies, a study of unbalanced crossply graphite fiber reinforcement composites was conducted to assess the effect of the composite ply layup and surface condition on the residual stresses that remain after the processing of these materials. The residual stresses were assessed by measuring the radii of curvature of the types of laminates that were studied. The temperature at which stress-free conditions existed were determined and a dye penetrant method was used to observe surface damage resulting from excessive residual stress buildup. These results are compared with some published results of thermal cycling tests that were previously conducted on balanced polyimide composites. |
| File Size | 838248 |
| Page Count | 18 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19900011808 |
| Archival Resource Key | ark:/13960/t52g2mx6t |
| Language | English |
| Publisher Date | 1990-01-01 |
| Access Restriction | Open |
| Subject Keyword | Composite Materials Microcracks Polymer Matrix Composites Dyes Fracture Mechanics Radii Penetrants Fiber Composites Thermal Cycling Tests High Temperature Laminates Coefficients Thermal Expansion Graphite Lay-up Damage Curvature Residual Stress Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
