A new test methodology based on structural resonance for mode I fatigue delamination growth in an unidirectional composite

Abstract

a b s t r a c tA specific device has been set up to test by vibration resonance the mode I fatigue delamination growth onset of composite laminates. This test system, based on the DCB test specimen, is a mass-spring-specimen dynamic system designed to resonate. The defined operating conditions allow performing delamination propagation tests under imposed load and stopping the test under reproducible conditions, identical to the ones recommended in the ASTM-D6115 standard. This system allows fatigue tests to be driven up to 100 Hz, reducing the time taken by a factor of ten without detrimental heat being generated in the material. The effect of frequency on the fatigue delamination growth on mode I has been investigated through a comparison with standard tests performed at 10 Hz. A decrease in resistance to the propagation of delamination is observed with the increase in frequency for the composite studied. This frequency effect seems to be a strain rate effect and was taken in consideration by using dynamical critical energy restitution rate for the G-N curve plotting.⇑ Corresponding author. Tel.: +33 (0) 561339195; fax: +33 (0) 561339095. ⇑⇑ Principal corresponding author. Tel.: +33 (0) 561339141; fax: +33 (0) 561339095.

Intralaminar fatigue crack growth properties of conventional and interlayer toughened CFRP laminate under mode I loading

“…Therefore fracture toughness for intralaminar crack growth must be lower than the interlaminar delamination crack growth. Many researchers have actively discussed interlaminar delamination static crack growth characteristics [24][25][26][27][28] and interlaminar delamination fatigue crack growth characteristics [29][30][31] of interlayer toughened CFRP laminates under mode I loading. Their results demonstrate the static and fatigue crack growth resistances which decrease with increasing crack length when the location of the crack path progresses from the toughened interlayer region to a non-toughened intralaminar fibre-rich region during crack growth [24,25,29].…”

Nondestructive Testing of Polymers and Polymer–Matrix Composites

“…61-64. On the other hand, resonance methods have been shown to propagate delaminations in PMC in high frequency cyclic fatigue tests (65). There is, therefore, the risk of initiating or propagating defects in PMC by resonance testing.…”

Onset-of-growth behavior of mode II delamination in a carbon fiber composite under spectrum fatigue loads

“…(4) Intersection of line given in Eqs. (4) and (7) gives the position of current cycle on the COLD diagram. Equating Eqs.…”

“…Maillet et al [4] studied the effect of frequency on the delamination onset behavior and observed that increasing the frequency from 10 Hz to 100 Hz decreases the onset life at stress ratio, R of 0.1, by over an order of magnitude. Arguelles et al [5] studied the effect of stress ratio and observed that increasing the R from 0.2 to 0.5 increases the onset life and also increases the onset threshold.…”