Compression behavior of materials: Part I. Glassy polymers
- PDF / 1,956,106 Bytes
- 10 Pages / 576 x 792 pts Page_size
- 37 Downloads / 229 Views
Compression behavior of materials: Part I. Glassy polymers Victor V. Kozey and Satish Kumar School of Textile & Fiber Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0295 (Received 24 January 1994; accepted 3 June 1994)
In this three-part series the compressive behavior of (i) glassy polymers, (ii) high performance polymeric and carbon fibers, and (iii) polymeric matrix composites has been addressed. The glassy polymers exhibit plastic yielding in compression. The dependence of compressive yield strength on factors such as tensile modulus, glass transition temperature, density, and free volume has been examined. Failure theories for yielding in glassy polymers have been reviewed. Compression behavior of high performance fibers and that of the composites is discussed in Parts II and III, respectively.
I. INTRODUCTION
II. COMPRESSIVE YIELD BEHAVIOR
Recent research efforts on compressive strength have been mostly due to the poor axial compressive strength of the high performance polymeric and pitch-based carbon fibers as well as their composites. Despite the continuing interest, compressive behavior of the materials in general and of high performance fibers in particular still remains a much misunderstood subject. Compressive failure in modern composites is affected by compressive failure of fibers, yielding of polymer matrix, or failure at the fiber-matrix interface. Therefore, it is important to recognize compressive failure mechanisms in polymer matrices, high-performance fibers, and in polymeric matrix composites. This series of papers consists of three parts. In Part I compression behavior of glassy polymers and its dependence on structural and mechanical parameters has been discussed. Compression test methods for single fibers, dependence of compressive strength on various structural parameters, and failure modes of high performance polymeric and carbon fibers have been discussed in Part II. Various issues involved in compression failure of polymeric matrix composites containing polymeric, carbon, and glass fibers have been addressed in Part III.
A. Stress-strain behavior
Many aspects of compressive failure observed in bulk polymers, fibers, and composites are also observed in other materials. For example, the kinking failure mechanism discussed in Parts II and III of this series is observed not only in anisotropic fibers and fibrous composites, but also in metallic crystals, wood, and rocks. From this point of view, significant discussion on failure mechanism is of a general nature. Table I compares typical compressive strength values for various structural materials. J. Mater. Res., Vol. 9, No. 10, Oct 1994
http://journals.cambridge.org
Downloaded: 24 Mar 2015
Bulk polymers generally exhibit plastic yielding in compression. Typical compressive stress-strain curves for different thermosetting epoxy resins and thermoplastic PVC are given in Fig. 1. This figure indicates that thermosetting epoxy resins, which generally have brittle failure under tension, undergo considerable plastic
Data Loading...
