Book Review: Experimental Characterization of Composites
Most composite engineers will have to deal with coupon testing at some point in their careers. Very few composite materials have been fully characterized. Even when the data do exist, it is common practice to test at least a few samples for verification.
Experimental Characterization is an introductory textbook to the field of composite material testing. It presents the most common tests used to characterize composites in a format suitable for both students and practicing engineers.
The authors open the book with an overview of composite theory: micromechanics, laminate analysis, strength analysis and fracture theory. The only unique discussion in this chapter is a section on St. Venant's principle. Most engineers probably forget about this topic after sophomore structures classes. Numerical expressions are given for the decay lengths of edge effects, and they tend to be much longer than for isotropic materials. This is an important consideration when designing test coupons.
Tests for determining basic elastic and strength properties are covered in sufficient detail to actually perform the tests, with perhaps some reference to the appropriate ASTM or other standard. Each chapter provides a good list of references. The reference lists are short but complete, making it easy to find related material.
Discussion is limited to the most common tests. For example, the chapter on lamina shear response covers the +/-45 tension test and the Iosepescu shear test. Other shear tests, such as the torsion tube, are not mentioned. This is not a major shortcoming, because the references can be consulted for a more exhaustive listing. A comparison of the methods presented, however, would help the reader to determine the most appropriate test for a given material or program requirements.
Beyond the basic material tests, the authors also cover thermoelastic tests (thermal expansion coefficients), flexural tests, off-axis tensile tests, open hole tensile tests and delamination tests. The latter three topics are especially notable for their good but concise overview of the theories and test methods.
The only topic missing from the book is an overview of statistical methods. Reference is made to using the least squares approach to fitting lines to data, but that is all. A more thorough discussion of curve fitting, including methods to identify break points, would be appropriate. To make the book truly complete, some coverage of other statistical topics, such as Weibull parameters and generation of allowables (A- and B-basis), should be included. Even a reference to MIL-HDBK-17 would help.
For more advanced testing topics, and information on some of the practical aspects of composites testing, I recommend Mechanical Testing of Composites. That book has its flaws, but would still make a good complement to Experimental Characterization.
Details: Experimental Characterization of Advanced Composite
Materials Second Edition, by
Leif A. Carlsson and R. Byron Pipes, published by Technomic Publishing
Company, 1997, ISBN
1-56676-433-5.
1. Analysis of Composite Materials; 2. Processing of Composite
Laminates; 3. Bonding of End Tabs, Specimen Preparation, and
Measurements of Deformation; 4. Determination of Fiber Volume
Fraction; 5. Lamina Tensile Response; 6. Lamina Shear Response;
7. Lamina Compressive Response; 8. Lamina Thermoelastic Response;
9. Lamina Flexure Response; 10. Lamina Off-Axis Tensile Response;
11. Laminate Tensile Response; 12. Laminate Thermoelastic Response;
13. Open Hole Tensile Strength of Laminate; 14. Characterization of
Delamination Failure; A. Compliance and Stiffness Transformations and
Matrix Operations; B. Preparation of Test Specimens and Panels;
C. Apparent Flexural Modulus for Beam with Unequal Tension and
Compression Moduli; D. Correction Factors for Off-Axis Tension Test;
E. Unit Conversion