Assessment of cumulative damage by using ultrasonic C-scan on carbon fiber/epoxy composites under thermal cycling

Abstract

In recent years, structural composites manufactured by carbon fiber/epoxy laminates have been employed in large scale in aircraft industries. These structures require high strength under severe temperature changes of -56° until 80 °C. Regarding this scenario, the aim of this research was to reproduce thermal stress in the laminate plate developed by temperature changes and tracking possible cumulative damages on the laminate using ultrasonic C-scan inspection. The evaluation was based on attenuation signals and the C-scan map of the composite plate. The carbon fiber/epoxy plain weave laminate underwent temperatures of -60° to 80 °C, kept during 10 minutes and repeated for 1000, 2000, 3000 and 4000 times. After 1000 cycles, the specimens were inspected by C-scanning. A few changes in the laminate were observed using the inspection methodology only in specimens cycled 3000 times, or so. According to the found results, the used temperature range did not present enough conditions to cumulative damage in this type of laminate, which is in agreement with the macro -and micromechanical theory.

Porosity Characterization of Carbon Fiber/Epoxy Composite Using Hg Porosimetry and Other Techniques

“…3, the white arrow indicates the injection direction, and legend color indicates the percentage of wave returned, which is associated to defects detection. The variation in the impregnation is in agreement with reports in the literature for advanced composites [22,23], in which the wave return is established in the range of 20%-40%. Near the inlet gate, a higher wave return occurs due to the resin-rich region.…”

“…Near the inlet gate, a higher wave return occurs due to the resin-rich region. According to other studies [18,23], defects along the material, especially at the laminate end, alter the wave return, and thus defects, such as resin-poor or resin-rich regions, porosity, and fiber misalignment, can be detected on the map.…”

Anti‐symmetrical curved composite laminate subject to delamination induced by thermal cycling

“…The effect of thermal variation in composite laminates is considered deleterious at the interface because of differences in coefficient of thermal expansion (CTE) of fiber and matrix. These differences may induce thermal stresses which cause microcracking and fiber/matrix debonding . Other processes of matrix degradation occur as, for example, a combination of oxygen and high temperature that breaks covalent bonds which accelerate the damage progression …”

“…These differences may induce thermal stresses which cause microcracking and fiber/matrix debonding. 8,9 Other processes of matrix degradation occur as, for example, a combination of oxygen and high temperature that breaks covalent bonds which accelerate the damage progression. 8,10 The combined mechanisms of cyclic mechanical load with temperature change will result in delamination process.…”

Nondestructive evaluation of wood decayed by xylophagous organisms

“…NDT is the science for identification of the physical and mechanical properties of a material in order to make decisions without modifying the final uses 3,4 . The advantages of NDT's are security, low cost, versatility 5,6 , considerable reduction in the test time, standard laboratory equipment are not required 7,8 , estimation of defects in the material 7,9,10 and easy transport of the equipment in comparison to destructive techniques.…”