tailieunhanh - Mechanical properties of polymers and composites-Nielsen Episode 2

Tham khảo tài liệu 'mechanical properties of polymers and composites-nielsen episode 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Mechanical Tests and Polymer Transitions 3 II. MECHANICAL TESTS There are a bewildering number of mechanical tests and testing instruments. Most of these tests are very specialized and have not been officially recognized as standardized tests. Some of these tests however have been standardized and are described in the publications of the American Society for Testing and Materials 1 . Many of the important tests for plastics are given as ASTM standards in a series of volumes. The important volumes parts covering polymeric materials are listed in Table 1. Although many tests have been standardized it must be recognized that a standardized test may be no better than one that is not considered a standard. One objective of a standardized test is to bring about simplicity and uniformity to testing and such tests are not necessarily the best tor generating the most basic information or the special type of information required by a research problem. The tests may not even correlate with practical use tests in some cases. Besides the ASTM standard tests a number of general reference books have been published on testing and on the mechanical properties of polymers and viscoelastic materials 2-7 . Unfortunately a great variety of units are used in reporting values of mechanical tests. Stresses moduli of elasticity and other properties are given in such units as SI cgs and English units. A table of conversion factors is given in Appendix II. A. Creep Tests Creep tests give extremely important practical information and at the same time give useful data on those interested in the theory of the mechanical properties of materials. As illustrated in Figure 1 in creep tests one mea- Table 1 ASTM Standards Part No. Materials covered 15 Paper packaging 16 Structural sandwich constructions wood adhesives 20 Paint Materials specifications and tests 21 Paint Tests for formulated materials and applied coatings 24 Textiles Yarns and fabrics 25 Textiles Fibers 26 Plastics .