Non contact inspection of the fatigue damage state of carbon fiber reinforced polymer by optical surface roughness measurements

This work presents the evaluation of a new non-contact technique to assess the fatigue damage state of CFRP structures by measuring surface roughness parameters. Surface roughness and stiffness degradation have been measured in CFRP coupons cycled with constant amplitude loads, and a Pearson?s correlation of 0.79 was obtained between both variables. Results suggest that changes on the surface roughness measured in strategic zones of components made of the evaluated CFRP, could be indicative of the level of damage due to fatigue loads. This methodology could be useful for other FRP due to similarities in the fatigue damage process.

Optical sensing of the fatigue damage state of CFRP under realistic aeronautical load sequences

We present an optical sensing methodology to estimate the fatigue damage state of structures made of carbon fiber reinforced polymer (CFRP), by measuring variations on the surface roughness. Variable amplitude loads (VAL), which represent realistic loads during aeronautical missions of fighter aircraft (FALSTAFF) have been applied to coupons until failure. Stiffness degradation and surface roughness variations have been measured during the life of the coupons obtaining a Pearson correlation of 0.75 between both variables. The data were compared with a previous study for Constant Amplitude Load (CAL) obtaining similar results. Conclusions suggest that the surface roughness measured in strategic zones is a useful technique for structural health monitoring of CFRP structures, and that it is independent of the type of load applied. Surface roughness can be measured in the field by optical techniques such as speckle, confocal perfilometers and interferometry, among others.

Fatigue and efficiency: a study in industry

by Josephine Goldmark ; introduction by Frederic S. Lee ...

One year after the Youth Guarantee: Policy fatigue or signs of action? EPC Policy Brief, 27 May 2015

In April 2013, the EU Council called on EU member states to establish Youth Guarantee (YG) schemes, ensuring that “all young people under the age of 25 years receive a good-quality offer of employment, continued education, apprenticeship or traineeship within a period of four months of becoming unemployed or leaving formal education”. Implementation was meant to start more than a year ago, but political interest seems to have waned a bit. Is a ‘policy fatigue’ contaminating youth employment policies across the EU? Have some timid signs of economic recovery led to youth unemployment being less urgent or are we witnessing the usual policy developments whereby grand EU statements are worn down by political realities and resistance on the ground? In this Policy Brief, Claire Dhéret and Martina Morosi assess the implementation of the Youth Guarantee and provide suggestions on how to renew a sense of enthusiasm for such an ambitious tool across Europe.

Effect of material damping and stress distribution on the resonant fatigue strength of parts /

"Materials Laboratory Contract no. AF 33(038)-20840; Project no. 7360; Task no. 73604."

Blink rate as a measure of fatigue: a review.

Federal Aviation Administration, Washington, D.C.

Mental fatigue during continuous exercise of a single function /

Also published as thesis (Ph.D.) Columbia university, 1918.

Effects of hours of service regularity of schedules, and cargo loading on truck and bus driver fatigue. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

The effects of fatigue and alcohol on highway safety. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Energy versus stress theories for combined stress; a fatigue experiment using a rotating disc,

"Department of Army Project no. 5B99-01-004, Ordnance R and D Project no. TB2-0001. Office of Ordnance Research Project no. 1348 Contract no. DA-19-020-ORD-3520."

A theory for the effect of mean stress on fatigue of metals under combined torsion and axial load or bending.

"Department of Army Project no. 5B99-01-004, Ordnance R and D Project no. TB2-0001, Office of Ordnance Research Project no. 1348, Contract no. DA-19-020-ORD-3250."

Modern installation for testing of large assemblies under static and fatigue loading. Description of installation at Fritz Engineering laboratory, Lehigh University, Bethlehem, Pennsylvania,

"Not for publication."