Evaluation of tabbed composite specimens for material characterization under medium loading rates: a numerical study

Abstract

Compression failure of laminated composites is a very complex mechanism involving one or more failure modes especially under high loading rates. Tabbed specimens per ASTM D695 / SACMA SRM 1R-94 are used to measure compressive responses of composites under quasi-static to low strain rates. However, untabbed cubic specimens are employed in Split-Hopkinson pressure bar (SHPB) experiments for studying the behavior under high loading rates. The compression responses and failure modes observed in SHPB experiments may not correlate well with those of tabbed specimens owing to the failure initiation mechanisms which are dominated by contact stress distributions. This study presents the results from a numerical investigation of the tabbed specimens in conjunction with D695 / SACMA SRM 1R-94 test fixture for generating material response data at medium strain rates. The issues related to dynamic testing using a traditional test fixture and the limitations of its applicability owing to wave propagation effects are characterized using finite element models. Based on this study, recommendations for force measurement, achievable strain rates and interpretation of test data are made.