Yiming Yao

Mechanical characterization of the tensile properties of glass fiber and its reinforced polymer (GFRP) composite under varying strain rates and temperatures

Unidirectional glass fiber reinforced polymer (GFRP) is tested at four initial strain rates (25, 50, 100 and 200 s−1) and six temperatures (−25, 0, 25, 50, 75 and 100 °C) on a servo-hydraulic high-rate testing system to investigate any possible effects on their mechanical properties and failure patterns. Meanwhile, for the sake of illuminating strain rate and temperature effect mechanisms, glass yarn samples were complementally tested at four different strain rates (40, 80, 120 and 160 s−1) and varying temperatures (25, 50, 75 and 100 °C) utilizing an Instron drop-weight impact system. In addition, quasi-static properties of GFRP and glass yarn are supplemented as references. The stress–strain responses at varying strain rates and elevated temperatures are discussed. A Weibull statistics model is used to quantify the degree of variability in tensile strength and to obtain Weibull parameters for engineering applications.

Sequential Cracking and Their Openings in Steel-Fiber-Reinforced Joint-Free Concrete Slabs

AbstractNumerical and empirical models addressing the drying shrinkage cracking behavior of joint-free steel-fiber-reinforced concrete (SFRC) slabs are presented. Effect of water–cement ratio, admixtures, and free shrinkage are considered. Mechanical restrictions including base friction, fiber dosage, and interfacial bond properties restrain the growth of microcracks into main cracks and also reduce crack opening. A model based on a finite-difference equilibrium solution of a one-dimensional (1D) slab on frictional ground simulates the formation and subsequent opening of cracks in the slab. Results are compared with an empirical predictive tool for crack opening. A sensitivity study shows that correlation of predicted crack opening reduced by increasing fiber volume, base friction, and interfacial bond strength. Case studies are conducted on three slabs in service at different occasions and both models are used to predict the crack opening. While these models are developed based on different methodologies...

Failure Localization and Correlation of High-Speed Tension and Impact Tests of Strain-Hardening Cement-Based Composites

AbstractMechanical properties of strain-hardening cement-based composites (SHCC) subjected to impact and high-speed tensile loading were studied. The impact test setup was based on a free-fall drop...

Analysis and Design Procedures for Strain Hardening Flexural Beam and Panel

This paper presents design procedures for 1-D and 2-D strain hardening cement composites (SHCC) members based on analytical models. Closed-form solutions of moment-curvature responses of SHCC are derived based on elastic perfectly plastic compressive model and trilinear strain hardening tension model. Tension stiffening behavior of SHCC due to fiber toughening and distributed cracking are considered and incorporated in the cross-sectional analysis. Load-deflection responses for beam and panel members are obtained using several different methods including moment-area, direct integration and Yield Line Theory. The proposed models provide insights in the design of SHCC to utilize the hardening properties after cracking. Using proper parameters, generalized materials model are applicable to both SHCC and strain softening cement composites such as steel fiber reinforced concrete (SFRC), textile reinforced concrete (TRC) and ultra-high performance concrete (UHPC).

Experimental study of tensile behaviour of AFRP under different strain rates and temperatures

Abstract This paper focuses on the tensile behaviours of Kevlar 29 and 49 fabrics reinforced polymers (AFRP-K29 and -K49) at four strain rates (25, 50, 100 and 200 s−1) and five temperatures (−25, 0, 25, 50 and 100 °C). The experimental results show that the tensile mechanical properties of two types of aramid fibre-reinforced polymer (AFRP) are strain-rate dependent in terms of Young’s modulus, tensile strength and toughness at 25 °C. While the changes of mechanical properties except for the Young’s modulus of both AFRPs and the tensile strength of AFRP-K29 under different temperatures (−25, 0, 25, 50 and 100 °C) are not significant at the strain rate of 25 s−1. The failure patterns of AFRP samples are similar at the strain rates and temperatures investigated. Non-uniform strain fields on AFRP specimens were identified by digital image correlation (DIC) technique.