kf Evaluation in GFRP Composites by Thermography

Abstract

Since the presence of a notch in a mechanical component causes a reduction in the fatigue strength, it is important to know the kf value for a given notch geometry and material. This parameter is fundamental in the fatigue design of aeronautical components that are mainly made of composites. kf is available in the literature for numerous types of notch but only for traditional materials such as metals. This paper presents a new practice, based on thermographic data, for the determination of the fatigue notch coefficient kf in composite notched specimens. The innovative aspect of this study is therefore to propose the application on composite materials of a new thermographic procedure to determine kf for several notch geometries: circular, U and V soft and severe notches. It was calculated, for each type of notch, as the ratio between the fatigue limits obtained on the cold and hot zone corresponding to the smooth and notched specimen, respectively. Consequently, this research activity provides, for the first time, a little database of kf for two particular typologies of composite materials showing a fast way to collect further values for different laminates and notch geometries.

Structural integrity evaluation of cyclic loading Glass Fibre Reinforced Polymer composite by acoustic emission and heat transfer

“…The thermal signature of fatigue-loaded (R= 0.1) CFRP samples due to notch-induced stress concentration have been captured and on mapping the temperature rise of hot zones offers a quicker way to determine the fatigue limit by NDT [31]. A similar trend of rising in temperature was recorded with in-situ impact-loaded composite thus substantiating the occurrence of damage on the structure [32] [33].…”

“…32 Such thermal signatures have been captured and mapped with various zones of the specimen to facilitate easy identification of fatigue limit and the corresponding damage. 30,33,34…”

Failure Prediction and Surface Characterization of GFRP Laminates: A Study of Stepwise Loading

“…An edge notch was applied to both edges of the sample to initiate the stress concentration. The results concluded that the technique can be efficiently used and improved by considering temperature adjustment [ 21 ]. Another study by Colombo et al [ 22 ] incorporated simulation analysis using delamination crack propagation using cohesive elements to strengthen the data during the GFRP laminate testing that used thermographic equipment.…”