Ultrasonic Influence of Porosity Level on CFRP Composite Laminates Using Rayleigh Probe Waves

Abstract

It was found that a pitch-catch signal was more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composites (damages, fiber orientation, low level porosity, ply waviness, and cracks). Both the strength and stiffness depend on the fiber orientation and porosity volume in the composites. The porosity content of a composite structure is critical to the strength and performance of the structure in general. The depth of the sampling volume where the pitch-catch signal came from was relatively shallow with the headto-head miniature Rayleigh probes, but the depth can be increased by increasing the separation distance of the transmitting and receiving probes. Also, a method was utilized to determine the porosity content of a composite lay-up by processing micrograph images of the laminate. A free software package was utilized to process micrograph images of the test sample. The results from the image processing method were compared with existing data. Beam profile was characterized in unidirectional CFRP(carbon fiber reinforced plastics) using pitch-catch Rayleigh probes and the one-sided pitch-catch technique was utilized to produce C-scan images with the aid of the automatic scanner.

Porosity Distribution in Composite Structures with Infrared Thermography

“…More exactly, from the nondestructively obtained thermal diffusivity map, it is possible to gain information on the porosity distribution over the whole sample; whereas, on the contrary, the measure of density through the destructive volumetric method is just a local action regarding only a very small part of the sample. For a quantitative analysis, by calling Δ and Δ the variation of porosity and thermal diffusivity, respectively, we can introduce a parameter defined as = Δ Δ (7) which can also be regarded as a resolution measure of the employed method. It is possible to see that attains first a value of 5 until a porosity level of 4%, while it drops below 2 as the porosity increases towards 8%.…”

“…Many techniques have been investigated for estimation of porosity in fiber reinforced composites [5][6][7][8][9][10][11][12][13]. Some are destructive like the acid digestion [5,10], which can supply information only by statistical inference and so has to be regarded as a reference rather than a quality assessment method.…”

“…Some are destructive like the acid digestion [5,10], which can supply information only by statistical inference and so has to be regarded as a reference rather than a quality assessment method. The most commonly accepted method is the ultrasonic (US) one for which the porosity percentage is linearly correlated to the attenuation of ultrasonic waves [5][6][7][8][9][10]; however, such an attenuation is affected by size, shape, and orientation of the pores leading to significant errors in quantitative data.…”

Evaluation of hygrothermal ageing in CFRP composite material using a non-destructive approach

“…7,8 Several NDE methods that include radiography, acoustic techniques and infrared thermography are being used extensively for detection and evaluation of defects and damage in a composite material. [9][10][11][12][13][14][15][16][17][18] These techniques have shown versatility in evaluating the type and extent of defects/damages in a composite material. Perhaps less attention is dedicated to developing these techniques for assessing the environmental degradation of composite material that has its own set of challenges.…”

Ultrasonic wave propagation in the corner section of composite laminate structure: Numerical simulations and experiments

“…While delamination-type defects are explicitly visualized by ultrasonic echoes [1][2][3][4], distributions of minute pores, called porosity, need to be evaluated via overall changes in ultrasonic wave propagation characteristics. Foregoing studies have revealed that the porosity content of composites can be evaluated by measuring the attenuation of ultrasonic waves [5][6][7][8][9][10][11][12]. In practice, some threshold levels are preset for the height of ultrasonic echoes for each composite component to judge the porosity level on an empirical basis.…”