Abstract
In this work, we present a multimodal approach to three-dimensionally quantify and visualize fiber orientation and resin-rich areas in carbon-fiber-reinforced polymers manufactured by vacuum infusion. Three complementary image modalities were acquired by Talbot–Lau grating interferometer (TLGI) X-ray microcomputed tomography (XCT). Compared to absorption contrast (AC), TLGI-XCT provides enhanced contrast between polymer matrix and carbon fibers at lower spatial resolutions in the form of differential phase contrast (DPC) and dark-field contrast (DFC). Consequently, relatively thin layers of resin, effectively indiscernible from image noise in AC data, are distinguishable. In addition to the assessment of fiber orientation, the combination of DPC and DFC facilitates the quantification of resin-rich areas, e.g., in gaps between fiber layers or at binder yarn collimation sites. We found that resin-rich areas between fiber layers are predominantly developed in regions characterized by a pronounced curvature. In contrast, in-layer resin-rich areas are mainly caused by the collimation of fibers by binder yarn. Furthermore, void volume around two adjacent 90°-oriented fiber layers is increased by roughly 20% compared to a random distribution over the whole specimen.
Highlights
The high strength at moderate weight in combination with superior corrosion and fatigue properties [1, 2] makes carbon-fiber-reinforced polymer (CFRP) an attractive material for lightweight applications in aerospace
We present a multimodal approach to three-dimensionally quantify and visualize fiber orientation and resin-rich areas in carbon-fiber-reinforced polymers manufactured by vacuum infusion
Using Talbot–Lau grating interferometer (TLGI) X-ray microcomputed tomography (XCT), this study explores three different X-ray contrast mechanisms to characterize internal features and defects in vacuuminfused aerospace-grade CFRP parts
Summary
The high strength at moderate weight in combination with superior corrosion and fatigue properties [1, 2] makes carbon-fiber-reinforced polymer (CFRP) an attractive material for lightweight applications in aerospace. CFRP parts are often characterized by the presence of deeply enclosed porosity, resin-rich areas and deviations from the desired fiber layup. These internal features and part-to-part variations can pose a serious threat to the mechanical integrity of a component. Carbon fibers are too small to be visualized at reasonable specimen dimensions, making the combined investigation with resin-rich areas inefficient, as these are typically a multitude larger in size
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