Fiber-Matrix Interface Strength Facility |
|
| NIST has three machines used to measure and assess the interfacial shear properties between fibers and polymeric matrices. The first is an automated single fiber fragmentation testing (sfft) machine. Resin samples containing a single fiber are put into the machine and the testing cycle is conducted by the machine. The load vs. time curve is captured automatically, along with images at each strain level. From these images we can determine the strains and fragment distributions and, ultimately, the interfacial shear properties. The second is a manual sfft machine. |  |
| With this machine, the load vs. time data is captured automatically, but each straining increment must be made by hand, and strains and fragment distributions must be made during the test. The third is a microdrop shear apparatus. For this machine, a droplet of resin is bonded onto a fiber and then the droplet is sheared off mechanically. Interfacial shear properties are then made by dividing the load to debond the droplet by the area of bonding. | |
Description |
|
|
An important aspect that needs to be addressed for the growth of polymeric composites is understanding their long-term properties. Chief among these properties are those of the interface between the polymeric matrix and the fiber. Although tests on bulk composites such as the short beam shear test can give useful comparative properties, the results are confounded due to the complex nature of the specimen geometry. Single fiber test methods were developed to reduce the complexity of events at the interface and to understand more fully the nature of the interface. To that end, the Polymer Composites Group at NIST has three machines to conduct tests on single fiber composites. The first is an automated single fiber fragmentation testing (sfft) machine. Resin samples containing a single fiber are put into the machine and the testing cycle is conducted by the machine. The operator would mount the specimen in the machine and then specify the loading program. Once the test starts, the load vs. time curve is captured automatically, along with images at each strain level. From these images we can determine the strains and fragment distributions and, ultimately, the interfacial shear properties. The advantage of this machine is in the reproducibility of each test and the labor savings by having most of the test done automatically. The second is a manual sfft machine. With this machine, the load vs. time data is captured automatically, but each straining increment must be made by hand, and strains and fragment distributions must be made during the test. The results are reproducible, but, do to the manual nature of the machine, requires a significant amount of operator time. The third is a microdrop shear apparatus. For this machine, a droplet of resin is bonded onto a fiber and then the droplet is sheared off mechanically. Interfacial shear properties are then made by dividing the load to debond the droplet by the area of bonding. |
|
Research Activity |
|
| Ballistic Resistance of Polymeric Materials | |
| This project is developing metrologies and predictive models to test and predict the long-term reliability of polymers used in ballistic resistant armor. Use of these metrologies and models will enable us to provide methods for monitoring the performance of polymeric materials while in use, elucidate how environmental and mechanical factors influence performance, and provide a basis for estimating durability and establishing care procedures. | |
Contact Information |
|
|
|
|
| Walter McDonough (301) 975-3661 Email: walter.mcdonough@nist.gov |
|
| NIST Materials Science & Engineering Laboratory - Polymers Division | |
