Prediction of Long-Term Compression Strength for Quasi-Isotropic CFRP Laminates

Long-term strength prediction method is developed based on three theories: accelerated testing methodology (ATM), strain invariant failure theory (SIFT) and progressive damage analysis (PDA). It can predict the strength and damage at a given failure time. Net resin 5228A was experimented by dynamic mechanical analysis and static tensile loading under various temperatures to determine the time-temperature shift factors and master curve of Young’s modulus. Unidirectional laminates of CCF300/5228A were tested under different temperatures to calculate the SIFT/ATM critical parameters. Long-term strength of quasi-isotropic composite laminates (QIL) was predicted. Good agreement between numerical results and experiments is observed, which demonstrates the applicability of this method.

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Evaluating Long-Term Strength and Time to Failure of Sandstone with Different Initial Damage

Advances in Civil Engineering ◽

10.1155/2020/7149148 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Rongbin Hou ◽

Yanke Shi ◽

Leige Xu ◽

Jinwei Fu ◽

Kai Zhang

Keyword(s):

Failure Time ◽

Term Strength ◽

Steady Creep ◽

Creep Failure ◽

Damage State ◽

Term Stability ◽

Long Term Stability ◽

Creep Stress ◽

Initial Damage

Long-term strength (LTS) of rock materials is important for the long-term stability analysis and the failure prediction of structures in rock engineering. Numerous studies have been carried out on the LTS for various kinds of rock; however, the effects of initial damage on the LTS and creep failure time of rock have not been conducted. In the present study, the creep experiment with controllable initial damage state of rock was designed. Then, the LTS of rock specimens with different initial damage was determined by four methods (i.e., the isochronous stress-strain curve method, the steady creep discriminated method, the volumetric strain inflexion point determined method, and the intersection of the steady creep rate method). The results show that, with the increase in the initial damage, the LTS of rock decreases and the relationship between the initial damage and the LTS of rock can be described as a linear function. Finally, an evaluation method for predicting the creep failure time of rock under a single stress level was proposed. In addition, the creep failure time of rock with different initial damage under different creep stress levels was obtained by the method. The results indicate that both the initial damage and the creep stress levels have a great influence on creep failure time, i.e., greater initial damage or creep stress leads to a shorter period for rock failure. Thus, for analyzing the long-term stability of rock mass structure, not only the influence of in situ stress but also the initial damage state of the surrounding rock should be considered.

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Accelerated testing for long-term strength of innovative CFRP laminates for marine use

Composites Part B Engineering ◽

10.1016/j.compositesb.2007.02.009 ◽

2008 ◽

Vol 39 (1) ◽

pp. 5-12 ◽

Cited By ~ 29

Author(s):

Yasushi Miyano ◽

Masayuki Nakada ◽

Jun Ichimura ◽

Eiji Hayakawa

Keyword(s):

Accelerated Testing ◽

Term Strength ◽

Cfrp Laminates

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S0406-3-3 Prediction of Long-term Strength of CFRP Laminates by MMF/ATM

The proceedings of the JSME annual meeting ◽

10.1299/jsmemecjo.2009.1.0_343 ◽

2009 ◽

Vol 2009.1 (0) ◽

pp. 343-344

Author(s):

Masahiro NAKAMURA ◽

Mikiya HIRAOKA ◽

Hongneng CAI ◽

Masayuki NAKADA ◽

Yasushi MIYANO

Keyword(s):

Term Strength ◽

Cfrp Laminates

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An Experimental Study on the Creep Characteristics of Sandstone in the Interval of Different Critical Stresses

Shock and Vibration ◽

10.1155/2021/4604027 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Chao Yang ◽

Xingchen Dong ◽

Xuan Xu ◽

Qiancheng Sun

Keyword(s):

Failure Time ◽

Strain Curve ◽

Creep Model ◽

Creep Process ◽

Term Strength ◽

Creep Tests ◽

Critical Stresses ◽

Brittle Sandstone ◽

Time Required

Creep tests on brittle sandstone specimens were performed to investigate the time-dependent characteristics in the interval of different critical stresses. The results showed that failure will not occur when the loaded stress σ1 is less than the critical stress of dilation σcd, while all specimens were destroyed when σ1 is larger than σcd. In addition, the value of σcd was very close to the long-term strength obtained by the method of the isochronous stress-strain curve. Therefore, σcd can be regarded as the long-term strength of the sandstone specimens. When σ1 is larger than σcd, the time required for the failure of specimen tf decreases with the increase of σ1; the creep rate dε/dt increases with time t, and the specimen will be destroyed when it reaches a maximum value (dε/dt)max. Both relationships tf and σ1 and (dε/dt)max and σ1 can be described by the exponential function. Then, a nonlinear damage creep model considering the deformation damage and strength damage in the interval of different critical stresses was established, which can describe the whole creep process and predict the failure time of sandstone specimens.

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Method to Realize the Tilt Monitoring and Instability Prediction of Hazardous Rock on Slopes

Advances in Civil Engineering ◽

10.1155/2021/9965113 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Zheng He ◽

Mowen Xie ◽

Zhengjun Huang ◽

Guang Lu ◽

Bo Yan ◽

...

Keyword(s):

Tilt Angle ◽

Failure Time ◽

Prediction Method ◽

Correlation Equation ◽

Physical Model Test ◽

Sensitive Material ◽

Monitoring Method ◽

Accelerated Evolution ◽

Separation Degree

Hazardous rock refers to an unstable rock block that is cut by weak structural planes and gradually separates from the slope. Hazardous rock generally collapses rapidly, and at present, it is challenging to effectively identify the separation degree of the rock and accurately predict its sudden failure. In this study, focusing on a hazardous rock with tilt behavior, a microelectromechanical system (MEMS) acceleration sensor is used in combination with the calculation principle of the included angle of the space vector to establish a microtilt angle monitoring method. A physical model test is designed, in which a thermally sensitive material (with heat-sensitive strength) is adopted as the weak structural plane of the hazardous block, and the change in the tilt angle during the process of block instability is monitored at a sampling frequency of 1000 Hz. The test results show that the accelerated evolution of the tilt angle is a precursor to hazardous rock failure. In the rapid acceleration stage, the reciprocal of the tilt angle rate is approximately linear with time, and a correlation equation is obtained. Assuming that the change rate of the tilt angle is approximately infinite, the failure time of hazardous rock can be predicted using the correlation equation. In addition, the effectiveness of the instability prediction method based on microtilt angle monitoring is verified by analyzing the long-term monitoring data of hazardous rock.

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