Mode II Behavior of High-Strength Concrete under Monotonic, Cyclic and Fatigue Loading

An economically efficient yet safe design of concrete structures under high-cycle fatigue loading is a rather complex task. One of the main reasons is the insufficient understanding of the fatigue damage phenomenology of concrete. A promising hypothesis states that the evolution of fatigue damage in concrete at subcritical load levels is governed by a cumulative measure of shear sliding. To evaluate this hypothesis, an experimental program was developed which systematically investigates the fatigue behavior of high-strength concrete under mode II loading using newly adapted punch through shear tests (PTST). This paper presents the results of monotonic, cyclic, and fatigue shear tests and discusses the effect of shear-compression-interaction and load level with regard to displacement and damage evolution, fracture behavior, and fatigue life. Both, monotonic shear strength and fatigue life under mode II loading strongly depend on the concurrent confinement (compressive) stress in the ligament. However, it appears that the fatigue life is more sensitive to a variation of shear stress range than to a variation of compressive stress in the ligament.

Study of mode II interlaminar fracture toughness of laminated composites of glass and jute fibres in epoxy for structural applications

Composites are being used in the place of metals in many industries as they have a lower density and are cheaper than metals. In aerospace industries there is requirement for light weight together with strength, and reinforced fibre composites are superior in some critical properties compared with metals. In this study, laminated composites were fabricated with woven E-glass and jute fibres in an epoxy matrix by a hand layup method. The samples were prepared as per the relevant the America Society for Testing ad Materials (ASTM) standard and tested for mode II interlaminar fracture toughness to investigate delamination resistance. Mode II interlaminar fracture toughness was evaluated by an end-notched flexure test using three-point bending. The fracture toughness G IIC was calculated for a curing temperature range from 40 °C to 70 °C at intervals of 5 °C for different sets of laminated composites. The investigations revealed that when the curing temperature of laminated composites was increased from 40 °C to 70 °C, the interlaminar fracture toughness G IIC was increased in neat woven E-glass laminated composites, decreased in neat jute laminated composites, significantly increased in laminated composites with woven E-glass fibres in compression and jute fibres in tension and slightly increased when woven E-glass fibres were kept in tension and jute fibres in compression.