Effect of fatigue loading on stiffness degradation, energy dissipation, and matrix cracking damage of CFRP [±45]_3Scomposite laminate

Abstract

In this study, a concept of using experimental matrix crack density, residual stiffness, and energy dissipation as a comparative life monitoring tool for any arbitrary stacking sequence is proposed. First, IMA/M21 [±45]3S carbon fibre‐reinforced polymer (CFRP) multidirectional (MD) laminates were fabricated by autoclaving technique. The static tension and compression tests were conducted to determine the fatigue stress levels. Then, constant amplitude tension–tension fatigue tests were carried out at two stress ratios (R = σmin/σmax) of 0.1 and 0.5. Three stress levels on the basis of cycles to failure (Nf) were chosen, ie, lower stress run‐out (LSR), lower stress fractured (LSF), and higher stress fractured (HSF). The LSF and LSR specimens primarily degraded due to matrix cracking that caused higher stiffness degradation and lower energy parameter, whereas HSF specimens having the least possibility of matrix crack growth showed lower stiffness degradation and higher energy parameter in a fibre‐dominated failure.

Prediction and evaluation of fatigue life via modified energy method considering surface processing

“…Fatigue was a complex damage accumulation process Yue et al, 2020), which was characterized by microstructure evolution, strain localization, crack nucleation and growth at different length scales. And it can be considered as a continuous process of energy dissipation from an energetic perspective (Behera et al, 2019).…”

Estimation of the Dissipative Heat Sources Related to the Total Energy Input of a CFRP Composite by Using the Second Amplitude Harmonic of the Thermal Signal

“…The total energy input can be also evaluated by means of experimental approaches. In effect, several experimental techniques [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] were used in the last decades capable of assessing the evolution of the total energy input and studying the damage. Behera [21] used optical microscopy coupled with the measurements of the load-displacement area under the hysteresis loop that was provided by an automatic data acquisition system to study stiffness degradation and material energy dissipations.…”

“…In effect, several experimental techniques [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] were used in the last decades capable of assessing the evolution of the total energy input and studying the damage. Behera [21] used optical microscopy coupled with the measurements of the load-displacement area under the hysteresis loop that was provided by an automatic data acquisition system to study stiffness degradation and material energy dissipations. The approach is useful for structural health monitoring assessment, but, to perform quantitative microscopy analysis, the sample has to be removed from the loading machine grips.…”

Fatigue characterization study of CFRP under hygrothermal environment based on continuum damage mechanics model

“…17 As a result, to make full utilization of the entire performance of CFRP, detailed knowledge about the failure behaviour and the failure mechanisms of CFRP are required. 18 At present, the research of hygrothermal effects on the mechanical properties of CFRP are limited to the tensile, bending and compression properties under static loads. There are few studies on the fatigue behaviour and the corresponding failure mechanisms of CFRP under hygrothermal environment, 19 which do not correspond to the actual flight of the aircraft.…”

“…Furthermore, current CFRP structures in aircrafts are subjected to cyclic loading with more than 10 8 cycles while the range of more than 10 7 cycles is called very high cycle fatigue (VHCF) regime 17 . As a result, to make full utilization of the entire performance of CFRP, detailed knowledge about the failure behaviour and the failure mechanisms of CFRP are required 18 …”