Compression Failure Mechanisms of Composite Structures.
Abstract
An experimental and analytical study was conducted to delineate the compression failure mechanisms of composite structures. Results on unidirectional and quasi-isotropic graphite/epoxy laminates were published previously. The present report summarizes further results on kink band formation in unidirectional composites. In order to assess the compressive strengths and failure modes of fibers themselves, a fiber bundle was embedded in epoxy casting and tested in compression. A total of six different fibers were used together with two resins of different stiffnesses. The failure of highly anisotropic fibers such as Kevlar 49 and P-75 graphite was due to kinking of fibrils. However, the remaining fibers--T3OO and T7OO graphite, E-glass, and alumina--failed by localized microbuckling. Compressive strengths of the latter group of fibers were not fully utilized in their respective composites. In addition, acoustic emission monitoring revealed that fiber-matrix debonding did not occur gradually but suddenly at final failure. The kink band formation in unidirectional composites under compression was studied analytically and through microscopy. The material combinations selected include seven graphite/epoxy composites, two graphite/thermoplastic resin composites, one Kevlar 49/epoxy composite and one S-glass/epoxy composite. The dominant mode of failure in all composites was the kink band initiation and propagation. Thus, not only microbuckling but also compressive failure of fibers could trigger kink band formation. An analytical model was developed under the assumption of plastic yielding in the matrix. (MM)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1986
- Accession Number
- ADA302024
Entities
People
- H. T. Hahn
- Mohsen Sohi
- Suresh Moon
Organizations
- University of Washington