Creep compaction and μCT based permeability measurement of aerospace-grade out-of-life prepregs. (December 2020)

• Record Type: Journal Article
• Authors: Umer, R; Ali, MA; Alia, RA; Khan, KA; Cantwell, WJ
• Is Part Of: Materials today communications. Volume 25(2020)
• Publication Date: 2020-12
• Subjects: Recyclability -- Prepregs -- Creep compaction -- Permeability; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2020.101419
• Languages: English
• ISSNs: 2352-4928

Abstract

Graphical abstract: Highlights: An out-of-life aerospace grade prepreg system was characterized for compaction response and permeability. The effect of number of layers and temperature on creep compaction was established. Micro CT scans were done to construct computational models for permeability computation. Air permeability through the prepreg was determined using models generated from CT scans. Abstract: This paper focuses on the experimental creep compaction behavior and μCT based permeability measurements of an "Out-of-life" aerospace-grade carbon/epoxy prepreg system. The creep compaction experiments were conducted using four different thicknesses (2, 4, 8 and 16 layers) of prepreg at three different temperatures (23, 60, and 90 °C). The effect of varying the number of prepreg layers on the creep compaction strain and fiber volume fraction at various temperatures was determined. An X-ray computed tomography (XCT) technique was carried out on all samples to observe the internal features of the compacted prepreg. It was observed that an increase in the number of layers reduced the overall creep property of the expired prepreg system. An XCT-based model was created to measure air permeability through the voids at room temperature and through-thickness reinforcement permeability at the three different temperatures using computational fluid dynamics. Several unit cells were extracted for image analysis and segmentation for subsequent modeling of the flow through the thickness of the prepreg at elevated temperatures. The flow fields and fluid velocity contours for different numbers of layers at different temperatures were also obtained. The probability of finding connected air flow paths for air permeability decreased as the number of layers increased. It was observed that creep compaction distorted the prepreg architecture at elevated temperatures, pushing the resin out and causing an increase in the through-thickness reinforcement permeability.