Understanding limitations of through thickness test methods

Through thickness properties are increasingly important for the derailed an alysis of complex composite structures. Recent papers and research have pro posed a variety of test method solutions for the determination of through t hickness properties. A comprehensive experimental evaluation has led to the drafting of standards for through thickness tension, compression, and shea r test methods. A detailed comparison of the mechanical test methods, data and failure modes is presented. An assessment is made of their utility, app licability, and limitations, highlighting sensible test precautions. In sel ected cases, comparisons with elastic constant data obtained using ultrason ic techniques are provided. Despite a number of difficulties, tension and compression specimens are rel atively easy to design, provided the test material is of sufficient thickne ss (e.g. 20 mm). Shear test methods are not so easily defined, such that no ne is applicable to all materials or all directions, and failure modes may be neither initiated nor dominated by shear. PRC/1524 (C) 1999 IoM Communic ations Ltd.