ELSEVIER PII: S1359-835X(97)00009-2 Composites Part A 28A (1997) 587-594 0 1997 Elsevier Science Limited Printed in Great Britain. All rights reserved 1359-835X/97/$17.00 Comparison of the short beam shear (SBS) and interlaminar shear device (ISD) tests F. Rosselli and M. H. Santare* Department of Mechanical Engineering, University of Delaware, 126 Spencer Laboratory, Newark, DE 19716-3140, USA (Received 12 April 1996; accepted 12 December 1996) The Short Beam Shear (SBS) and Interlaminar Shear Device (LSD) tests are compared as methods for determining interlaminar shear strength of thermoplastic composite rings. The rings were manufactured using laser-assisted on-line consolidation and the interlaminar shear strength is taken as a measure of the quality of parts subjected to various processing conditions. Although a number of shear test methods have been developed for use with composite materials over the years, none provide pure uniform shear, or provide the entire stress-strain response to failure from a single specimen [Adams, D.F. and Lewis, E.Q., Current status of composite material shear test methods. SAMPE 31, 1994,6,32-401. Hence, a testing technique is required to provide efficient interlaminar shear strength results. Through the test results, it can be seen that a different mode of failure is acting in each of the tests. Finite Element Analyses (EEA) of the test procedures show that the stress state at the failure site for SBS is not interlaminar shear whereas it is the stress state in the failure zone of the ISD. Therefore, it is concluded that the ISD provides a better measure of the interlaminar shear strength of these specimens. 0 1997 Elsevier Science Limited (Keywords: short beam shear; interiaminar shear device; interlaminar strength) INTRODUCTION AND OBJECTIVES Interlaminar shear strength of a composite laminate is often the limiting design characteristic, therefore a number of tests have been developed to evaluate this parameter. Although interlaminar tension is also an important para- meter, the purpose of this study is to compare shear strength measurement techniques. In addition, these tests can be used to assess the quality of manufacturing for a specific component. Two such tests, the Short-Beam-Shear2 and the recently developed Interlaminar Shear Device test’, were used to assess the consolidation quality of a series of thermoplastic rings manufactured using a laser assisted on- line consolidation process. APC-2/IM7 preimpregnated tape was used to manufacture rings representative of tape wound structures. The prepreg tape had a volume fraction of 60% with a width of 5.9 mm (0.23 in) and a thickness of 0.15 mm (0.006 in). The rings were manufactured using varying laser power, keeping winding speed, laser beam alignment and all other processing parameters constant. The on-line consolidation technique is of great interest in the manufacture of composite parts due to it’s high production speed, manufacturing flexibility, high energy concentration and quick response. The rings used in the present study were manufactured by winding the successive plies of prepreg *To whom correspondence should be addressed tape while consolidating onto previously laid material on the mandrel. Laser energy was used to melt the surfaces of the prepreg tape and consolidated material just before they came into contact. A compaction roller was then applied to the outer surface to provide contact pressure during bonding. After leaving the consolidation zone, the matrix cooled and solidified. On the next pass. the outer surface of the previously added ply was consolidated with another layer, thus building up the material to the desired thickness. Ring specimens of 40-plies were manufactured with an inner diameter of 146 mm (5.75 in). Having manufactured a variety of rings at different laser powers, interlaminar strength tests were used to investigate the quality of consolidation4. Both tests were conducted on a number of adjacent specimens cut from the rings. The interlaminar shear strengths, as well as the failure modes, differed between the two tests. In an attempt to reconcile these differences, FE models of typical specimens were generated in each testing configuration. The testing and subsequent modeling is discussed in the following. INTERLAMINAR STRENGTH TESTING The interlaminar shear strength and the fracture toughness in mode I and II loading are sensitive quantities for evaluating fabrication quality, especially the consolidation, of the composite’. The aim of this work is to choose an 587