Title: Robust Out-of-Autoclave Prepreg Processing Using a Semi-Permeable Membrane to Maintain Resin Pressure

Authors: Daniel Zebrine, Mark Anders, Steven Nutt

DOI: 10.33599/nasampe/c.22.0047

Abstract: Out-of-autoclave processing of carbon fiber-reinforced polymer composites offers certain advantages compared to autoclave cure, but limited compaction pressure often causes inconsistent part quality. To aid in removing entrapped air, OoA prepregs can be semi-impregnated to leave dry fiber tows and increase in-plane or through-thickness air evacuation. Porosity due to volatile evolution can arise if resin pressure decreases during the cure cycle, which can occur when resin bleeds out of the laminate. In this work, we investigate the use of a discontinuous resin film combined with a semi-permeable (air-permeable, resin-impermeable) release film to allow through-thickness air evacuation while simultaneously restricting resin loss. In situ measurements of resin pressure were deployed to test the hypothesis that resin pressure was maintained during cure when using a semi-permeable release film. Concurrently, visualization of the tool-side surface during cure revealed efficient evacuation of entrapped air. Porosity in laminates formed at high temperatures when using resin-permeable consumables, but did not form when using resin-impermeable (semi-permeable) consumables. To confirm that the observed void growth behavior was due to a loss in resin pressure, experiments were conducted to measure resin pressure during cure with both resin-permeable and resin-impermeable (semi-permeable) consumables. In both cases, resin pressure peaked before decreasing, a finding attributed to resin flowing to fill dry regions in the fabric, present by design. The drop in resin pressure, however, was greater in magnitude and longer in duration when using resin-permeable boundaries, indicating that the observed void growth at elevated temperature was caused by a loss in resin pressure. Use of a semi-permeable membrane was effective in retaining resin content and mitigating such porosity.

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Conference: CAMX 2022

Publication Date: 2022/10/17

SKU: TP22-0000000047

Pages: 16

Price: $32.00