Abstract Scope |
In manufacturing of carbon-fiber reinforced (CFR) composite aircraft structures, resin infusion offers a repeatable process for manufacturing low-porosity structural components with resin content control, low labor requirements, and complex curvatures. To further understand the structural capabilities of resin infused composites (RIC) in aircraft manufacturing, this study – as part of the NASA-led Hi-Rate Composite Aircraft Manufacturing (HiCAM) project efforts – performed open hole tension (OHT) and open hole compression (OHC) mechanical tests of resin-infused non-crimp fabric (NCF) laminates. This testing is important in that it provides information on the damage morphology and growth characteristics of RICs, which fuels the development and evaluation of analysis tools for progressive damage growth and failure responses.
A quasi-isotropic layup (24 plies) was used for this paper. Prior to OHC/OHT testing, mechanical properties of the panels were evaluated; axial and transverse tension and compression to obtain the relevant Young’s moduli and Poisson’s ratios, and V-notched rail shear for obtaining shear modulus. Select OHT/OHC specimens of each layup and test method were loaded monotonically to a predefined failure condition and the remaining specimens of each layup and test method were loaded incrementally to the same failure condition. For the incrementally loaded specimens, each incremental load point was predefined and, upon being met, the specimen was unloaded, and X-ray Computed Tomography (XCT) was used to assess damage propagation due to loading. The OHT tests were performed with bonded strain gages, extensometers, and digital image correlation (DIC) systems. The OHC tests did not include strain gages or DIC systems. From the data obtained in this study, damage mechanisms leading to failure were identified, damage morphology was assessed, and damage initiation and failure loads were measured, feeding RIC-specific design requirements, and allowing for the development of RIC damage and failure analysis tools. |