Optimization and mechanical response of modular infusion compaction and normalization

Abstract

Modular infusion (MI) is utilized to eliminate dry spot defects within complex multi-architecture composites by segregating and controlling flow fronts in-process. Compaction, employed to arrest in-plane flow, results in a crimp witness, which can be eliminated through MI fiber bed normalization. However, the MI normalization techniques generate voids within the cured components. To study the mechanisms that control the MI fiber bed normalization process, an in-process X-ray computed tomography (XCT) approach is developed to provide a visualization of fiber bed thickness and void distribution. Inner bag regulation during normalization is identified as the primary cause of the void generation. C-scans on a cured panel corroborate XCT findings, as well as validating the quality of the panel produced for subsequent mechanical test samples. Hence, it is demonstrated that the approach enables the optimization of a MI manufacturing process, which is supported by the findings of the mechanical characterization campaign. Flexural tests were carried out in three and four-point bend testing using samples cut from the panel, with Digital Image Correlation (DIC) providing comparative measurements for a baseline and MI case. Flexural testing of MI samples showed that a comparable mean strength and stiffness to that of the baseline material was achieved, demonstrating complete restoration of material thickness and mechanical properties during the optimised MI process.