Effect of multiple matrix cracking on crack bridging of fiber reinforced engineered cementitious composite

2020 ◽  
Vol 54 (26) ◽  
pp. 3949-3965 ◽  
Author(s):  
Xuan Zheng ◽  
Jun Zhang ◽  
Zhenbo Wang

In the present paper, a modified micromechanics based model that describes the crack bridging stress in randomly oriented discontinuous fiber reinforced engineered cementitious composite is developed. In the model, effect of multiple matrix cracking on fiber embedded length, which in turn influencing fiber bridging in the composite, is taken into consideration. First, crack spacing of high strength-low shrinkage engineered cementitious composite was experimentally determined by photographing the specimen surface at some given loading points during uniaxial tensile test. The diagram of average cracking spacing and loading time of each composite is obtained based on above data. Then, fiber bridging model is modified by introducing a revised fiber embedment length as a function of crack spacing. The model is verified with uniaxial tensile test on both tensile strength and crack opening. Good agreement between model and test results is obtained. The modified model can be used in design and prediction of tensile properties of fiber reinforced cementitious composites with characteristics of multiple matrix cracking.

2012 ◽  
Vol 256-259 ◽  
pp. 796-800
Author(s):  
Chun Hong Hu ◽  
Yan E Gao ◽  
Wan Cong Ding

Based on the previous test, SHCC (Strain Hardening Cementitious Composite) with the best fluidity was got through flow test, the different stress-strain full curves of SHCC were obtained by uniaxial tensile test on three dumbbell-shape specimens of SHCC with each group according to different diameter sand and different ages; and crack development was observed during test. The experimental results show that: The finer the sand sizes, the better the strain-hardening performance and more microcrack of SHCC that can be obtained; obvious strain-hardening characteristics of the specimens at different ages are all occured and the ultimate tensile strain can reach or even more than 3%. The crack spacing of various specimens are different, that is to say, there is difference in cracking characteristics among specimens at different ages. The experimental and analytical conclusion can provide a lot of theoretical bases for the research on performances of SHCC.


2020 ◽  
Vol 22 (2) ◽  
pp. 59-67
Author(s):  
Benny Suryanto ◽  
Joshua Kiyoshi Suryanto

The four-point flexural test is now making headway as an alternative laboratory investigative technique for determining the tensile properties of Engineered Cementitious Composite (ECC) to the more traditional, direct/uniaxial tensile test. As the fundamental mechanics of ECC specimens tested in four-point flexure are well understood, it is possible to develop a simple relationship between flexural test results and the tensile properties of this cement composite. This paper extends this development and aims to provide accessible and quick calculation of the tensile properties of ECC via a virtual test environment. To this end, attention is directed towards the test configurations developed earlier at Heriot-Watt University, the University of Michigan, and Sepuluh Nopember Institute of Technology. In this paper, the technical background employed in creating the virtual environment and the computer implementation using the JavaScript programming language are presented. The prototype virtual environment is freely available via the Internet at https://ecc-calculator.netlify.app/.


Author(s):  
R Pramod ◽  
N Siva Shanmugam ◽  
C K Krishnadasan ◽  
G Radhakrishnan ◽  
Manu Thomas

This work mainly focuses on designing a novel aluminum alloy 6061-T6 pressure vessel liner intended for use in launch vehicles. Fabrication of custom-made welding fixtures for the assembly of liner parts, namely two hemispherical domes and end boss, is illustrated. The parts of the liner are joined using the cold metal transfer welding process, and the welding trials are performed to arrive at an optimized parametric range. The metallurgical characterization of weld joint reveals the existence of dendritic structures (equiaxed and columnar). Microhardness of base and weld metal was 70 and 65 HV, respectively. The tensile strength of base and weld metal was 290 and 197 MPa, respectively, yielding a joint efficiency of 68%. Finite-element analysis of a uniaxial tensile test was performed to predict the tensile strength and location of the fracture in base and weld metal. The experimental and predicted tensile test results were found to be in good agreement.


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