Delamination in Composite Materials as Observed Using an Optical Fiber Strain Gage
Abstract
Composite materials are used extensively in the air and space industries, where materials of high strength and light weight are required. Unlike metals, these materials often give little or no warning before failing-a potentially fatal characteristic for structural members in aircraft. A common mode of failure in composites is delamination, in which the layers of the material separate from each other. Delamination can be caused by impact, longitudinal shear stress between the layers, or transverse tensile stress across the layers. Optical fibers embedded in the composite material provide a means of monitoring the strains which lead to such failures. This project involves the use of an optical fiber strain gage in the configuration of a Michelson interferometer to study a composite sample that experiences transverse tensile stress resulting in delamination. The transverse tensile stress is produced by straightening out an already curved specimen of composite material. The output signal of the interferometer represents the integrated strain over the length of the optical fibers. By embedding the fibers in a composite specimen, the strain experienced in the material can be measured. This signal is recorded on an common audio tape, transferred to a computer, and analyzed quantitatively.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 17, 1993
- Accession Number
- ADA270803
Entities
People
- Glen E. Sabin
Organizations
- United States Naval Academy