Influence of Loading Frequency and Force Level on the Cyclic Performance of Strain-Hardening Cement-Based Composites (SHCC)

Abstract

Structures are exposed to a variety of quasi-static and dynamic/cyclic loads. For a safe, material-minimized structural design, a comprehensive knowledge of the material behavior under various loading conditions is required. Previous studies showed that Strain-Hardening Cement-based Composites (SHCC), in literature also often called Engineered Cementitious Composites (ECC) are a promising class of materials that exhibits an outstanding mechanical resistance under both quasi-static and cyclic loading regimes. However, a profound understanding of the mechanisms leading to the specific behaviors under cyclic loads is missing.

The article at hand presents experimental results from cyclic tension-swelling and alternating tension-compression tests performed on uniaxially loaded, notched dogbone-shaped specimens made of high-strength SHCC with a polyethylene fiber content of 2% by volume. The samples were exposed to harmonic loads with different frequencies, i.e., 1 Hz and 20 Hz for a certain number of load cycles. The chosen stress level in the tension-swelling tests corresponded to 80% of the first crack strength while for the alternating cyclic loading tests 25% of the compressive strength and 80% of the first crack strength were defined as reversal points. In addition, morphological analysis of the fracture surfaces and crack patterns were carried out by means of microscopy in order to determine the degradation condition of each phase, i.e., polyethylene fiber and matrix. Finally, the results were discussed referring to the physical phenomena causing the observed behavior.