Prepreg design and fabrication for robust composite processing
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Abstract:
Prepreg design plays a key role in part quality for composites produced using out-of-autoclave vacuum bag only (VBO) techniques. To date, however, VBO prepregs have been produced, essentially, as modified versions of autoclave prepregs. Traditional prepreg fabrication consists of coating thin films of resin onto backing papers. These films are then sandwiched on either side of dry fabric and compacted through rollers to impregnate the fiber. VBO prepregs rely on partial impregnation of resin into the fiber bed to create in-plane pathways for air transport. These in-plane channels facilitate air removal via edge breathing mechanisms. Through-thickness permeability in commercially supplied VBO prepregs, however, is negligible and inconsistent, leading to issues of surface pitting and void formation when edge breathing of each ply is insufficient or not feasible (e.g., with embedded ply drops or corners). This presentation will address ongoing efforts in the fabrication of prepreg with discontinues resin distributions. These novel prepreg formats result in through-thickness pathways for air transport leading to near-zero internal porosity and excellent surface finish in parts cured out-of-autoclave under vacuum-bag-only (VBO) conditions.
Prepreg design plays a key role in part quality for composites produced using out-of-autoclave vacuum bag only (VBO) techniques. To date, however, VBO prepregs have been produced, essentially, as modified versions of autoclave prepregs. Traditional prepreg fabrication consists of coating thin films of resin onto backing papers. These films are then sandwiched on either side of dry fabric and compacted through rollers to impregnate the fiber. VBO prepregs rely on partial impregnation of resin into the fiber bed to create in-plane pathways for air transport. These in-plane channels facilitate air removal via edge breathing mechanisms. Through-thickness permeability in commercially supplied VBO prepregs, however, is negligible and inconsistent, leading to issues of surface pitting and void formation when edge breathing of each ply is insufficient or not feasible (e.g., with embedded ply drops or corners). This presentation will address ongoing efforts in the fabrication of prepreg with discontinues resin distributions. These novel prepreg formats result in through-thickness pathways for air transport leading to near-zero internal porosity and excellent surface finish in parts cured out-of-autoclave under vacuum-bag-only (VBO) conditions.
Biography:
Lessa Grunenfelder has a B.S. in astronautical engineering and a MS and PhD in materials science, all from USC. In 2015 she joined the Mork Family Department as teaching faculty. She teaches both undergraduate and graduate courses on material properties, processing, selection, and design. Her research interest is in efficient manufacturing of high-performance composites. She is an active member of the Society for the Advancement of Material and Process Engineers (SAMPE) and remains engaged in research through collaboration with the M.C Gill Composites Center at USC.
Lessa Grunenfelder has a B.S. in astronautical engineering and a MS and PhD in materials science, all from USC. In 2015 she joined the Mork Family Department as teaching faculty. She teaches both undergraduate and graduate courses on material properties, processing, selection, and design. Her research interest is in efficient manufacturing of high-performance composites. She is an active member of the Society for the Advancement of Material and Process Engineers (SAMPE) and remains engaged in research through collaboration with the M.C Gill Composites Center at USC.
