Assessing and quantifying variability across vacuum‐assisted resin infusion variants for aerospace‐grade composite manufacturing

Conventional vacuum-assisted resin transfer molding (C-VARTM) is recognized as a cost-effective resin infusion technique for manufacturing large-scale composite structures. However, C-VARTM suffers from inherent limitations, notably non-uniform resin flow, uncontrolled vacuum levels that generate unstable pressure gradients, and variability in fiber compaction. These factors collectively reduce process repeatability and dimensional precision, posing a major constraint to qualifying C-VARTM laminates for aerospace applications. Therefore, identifying, understanding, and justifying the dominant sources of process variability is essential to enable reliable production of aerospace-grade composite structures at quality levels comparable to autoclave processing. In this study, C-VARTM, employing flow distribution media, vacuum bagging, and passive impregnation without auxiliary compaction, was used as the baseline. Several vacuum infusion variants, including pressure-driven vacuum infusion (PD-VARTM), vibration-assisted vacuum infusion (VAVI), controlled atmospheric pressure resin infusion (CAPRI), and the membrane-assisted vacuum infusion process (MAVIP), were evaluated in terms of laminate density, fiber volume fraction (FVF), void content, and thickness uniformity, quantified at the resin inlet and vacuum outlet. Flexural testing was conducted on all laminates to evaluate their structural performance against panels produced by the aerospace-qualified, Bombardier-patented resin transfer infusion (RTI) process, whose first successful laboratory scale implementation based on soft-stiff compaction concept is reported here, thereby addressing a key gap in the literature.

Highlights

C-VARTM has FVF Δ = 6.7% and flexural strength varied by 13% across the part.

VAVI has FVF Δ = 10.3% and peak flexural strength 803 MPa at the vacuum outlet.

MAVIP has FVF Δ = 0.44% and flexural strength 671–631 MPa as inlet and outlet

PD-VARTM has FVF Δ = 1% and flexural strength 714–747 MPa as inlet and outlet.

RTI has FVF > 55% and Δ = 0.2% flexural strength, 768 MPa and modulus > 54 GPa.