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The effect of contact stresses in four-point bend testing of graphite/epoxy and graphite/pmr-15 composite beams
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Roberts, Gary D. Binienda, Wieslaw K. Papadopoulos, Demetrios S. |
| Copyright Year | 1992 |
| Description | The results of in-plane four-point bend experiments on unidirectionally reinforced composite beams are presented for graphite/epoxy (T300/934) and graphite/polyimide (G30-500/PMR-15) composites. The maximum load and the location of cracks formed during failure were measured for testpieces with fibers oriented at various angles to the beam axis. Since most of the beams failed near one or more of the load points, the strength of the beams was evaluated in terms of a proposed model, for the local stress distribution. In this model, an exact solution to the problem of a localized contact force acting on a unidirectionally reinforced half plane is used to describe the local stress field. The stress singularity at the load points is treated in a manner similar to the stress singularity at a crack tip in fracture mechanisms problems. Using this approach, the effect of fiber angle and elastic material properties on the strength of the beam is described in terms of a load intensity factor. For fiber angles less than 45 deg from the beam axis, a single crack is initiated near one of the load points at a critical value of the load intensity factor. The critical load intensity factor decreases with the increasing fiber angle. For larger fiber angles, multiple cracks occur at locations both near and away from the load points, and the load intensity factor at failure increases sharply with increasing fiber angle. |
| File Size | 8846477 |
| Page Count | 25 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19930002888 |
| Archival Resource Key | ark:/13960/t91886x3d |
| Language | English |
| Publisher Date | 1992-10-01 |
| Access Restriction | Open |
| Subject Keyword | Composite Materials Crack Tips Stress Analysis Half Planes Critical Loading Graphite-polyimide Composites Cracks Stress Distribution Bend Tests Beams Supports Graphite-epoxy Composites Fiber Orientation Cracking Fracturing Elastic Properties Composite Structures Contact Loads Failure Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Technical Report |
