Solid epoxy prepregs with patterned resin distribution: Influence of pattern and process parameters on part quality in vacuum‐bag‐only processing

Abstract

Solid resins (SR) are fully reactive resin systems that are solid at room temperature. Up to a critical temperature they can be quasi‐infinitely molten and solidified without any relevant curing reaction. This study deals with novel SR‐based prepregs where a dry textile is covered with a regular SR (uncured) pattern, allowing for storage and draping at room temperature. The manufacturing of SR prepregs with accurate pattern geometries and the processing of the same into laminates with a pore volume content <1% using a vacuum bag only process is demonstrated for four pattern types and two curing cycles. The study furthermore shows that the pattern design has an influence on the mandatory drying phases as well as on fiber undulations. With sufficiently long drying phases, equivalent pore volume contents and interlaminar shear strength could be obtained with different pattern types.Highlights Manufacturing of carbon fiber (CF) solid epoxy prepregs with patterned resin distribution Epoxy powder processing Out‐of‐Autoclave manufacturing with vacuum‐bag‐only prepregs Interlaminar shear strength of carbon fiber reinforced plastics (CFRP) made of woven CFs Analysis of pore volume content and fiber undulation

Hygroscopicity in Epoxy Powder Composites

“…In the context of advanced composite materials, powder-based systems occupy several niches within the market: powder binder for preforming [5][6][7][8][9], powder towpregging [10][11][12][13][14], and powder semi-pregging [15][16][17][18][19]; each of which is shown in Figure 1. In the context of advanced composite materials, powder-based systems occup eral niches within the market: powder binder for preforming [5][6][7][8][9], powder towpre [10][11][12][13][14], and powder semi-pregging [15][16][17][18][19]; each of which is shown in Figure 1. In the case of powder binders, typically, only 3-9 wt% of polymer powder is a to dry reinforcing fabric.…”

“…Reprocessing is a poss for these epoxy powders because they contain latent, heat-activated curing agent have a glass transition temperature above 40 °C. This means that they require no ref ated storage to prevent curing, i.e., the epoxy powder is stable at ambient conditio several months, unlike conventional liquid epoxy systems which undergo ageing [2 Likewise, epoxy powders have undergone significant development for powder pregs; a form of vacuum-bag-only (VB ) prepreg developed for low-cost out-of-auto ( oA) processing [16,17,19,26,27]. Vacuum-bag-only (VB ) prepregs differ from co tional prepregs in that the fibre bed is only partially impregnated with resin.…”

“…Likewise, epoxy powders have undergone significant development for powder semipregs; a form of vacuum-bag-only (VBO) prepreg developed for low-cost out-of-autoclave (OoA) processing [16,17,19,26,27]. Vacuum-bag-only (VBO) prepregs differ from conventional prepregs in that the fibre bed is only partially impregnated with resin.…”

“…Through-thickness permeability is particularly desirable for evacuation as the through-thickness flow paths tend to be significantly shorter than the in-plane flow paths [31]. As such, several recent studies have been dedicated to studying how resin deposition can improve through-thickness gas evacuation [19,[32][33][34]. Powder semi-pregs have inherent three-dimensional gas permeability, assuming the powder is left unsintered.…”

Hygroscopicity in Epoxy Powder Composites

“…In the context of advanced composite materials, powder-based systems occupy several niches within the market: powder binder for preforming [5][6][7][8][9], powder towpregging [10][11][12][13][14], and powder semi-pregging [15][16][17][18][19]; each of which is shown in Figure 1.…”