Surface Irregularity Factor as a Parameter to Evaluate the Fatigue Damage State of CFRP.

Pablo Zuluaga-Ramírez,Tomás Belenguer,Malte Frövel,Félix Salazar

doi:10.3390/ma8115407

Pablo Zuluaga-Ramírez, Tomás Belenguer + Show 2 more

Open Access

https://doi.org/10.3390/ma8115407

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Abstract

This work presents an optical non-contact technique to evaluate the fatigue damage state of CFRP structures measuring the irregularity factor of the surface. This factor includes information about surface topology and can be measured easily on field, by techniques such as optical perfilometers. The surface irregularity factor has been correlated with stiffness degradation, which is a well-accepted parameter for the evaluation of the fatigue damage state of composite materials. Constant amplitude fatigue loads (CAL) and realistic variable amplitude loads (VAL), representative of real in- flight conditions, have been applied to “dog bone” shaped tensile specimens. It has been shown that the measurement of the surface irregularity parameters can be applied to evaluate the damage state of a structure, and that it is independent of the type of fatigue load that has caused the damage. As a result, this measurement technique is applicable for a wide range of inspections of composite material structures, from pressurized tanks with constant amplitude loads, to variable amplitude loaded aeronautical structures such as wings and empennages, up to automotive and other industrial applications.

Highlights

The knowledge of the fatigue damage state of structures made of composite material such as carbon fiber reinforced polymer (CFRP) is essential to make the step in the optimization of composite structures in the aeronautic industry and in general industrial applications
Experimental studies show that this rule leads to inaccurate and non-conservative predictions for composite materials under realistic variable amplitude loads [2,3,4]
Results of previous works by the authors with specimens cycled with constant amplitude loads (CAL) show that the changes of the surface roughness are correlated with the stiffness degradation [14,15], which is a classical metric of fatigue damage

Summary

Introduction

The knowledge of the fatigue damage state of structures made of composite material such as carbon fiber reinforced polymer (CFRP) is essential to make the step in the optimization of composite structures in the aeronautic industry and in general industrial applications. There are models developed for fatigue damage accumulation of composite materials, including strength and stiffness degradation. Results of previous works by the authors with specimens cycled with constant amplitude loads (CAL) show that the changes of the surface roughness are correlated with the stiffness degradation [14,15], which is a classical metric of fatigue damage.

Results

Conclusion