Effect of double vacuum bagging (DVB) in quickstep processing on the properties of 977‐2A carbon/epoxy composites

Abstract

An aerospace grade prepreg 977-2A carbon=epoxy composite was processed using traditional oven=autoclave and relatively new technique, Quickstep (QS). The manufacturer's recommended autoclave cure cycle was employed for oven=autoclave processing while due to greater flexibility to control the cure cycle temperature in order to manipulate the resin viscosity, several cure cycles were employed for Quickstep processing. Optimization methodology and effect of these cure schedules and their comparison with traditional oven=autoclave curing is presented in previously published article. However, in order to reduce the total cycle time of QS AD (QS-60) cure schedule, an attempt was made to facilitate the excess resin to squeeze out during QS-35 and QS-45 cure. This attempt was based on the incorporation of double vacuum bagging (DVB) technique into Quickstep processing. Statistical analysis was performed to investigate any effect of DVB in Quickstep processing and it was observed that incorporation of DVB in Quickstep processing is not found to be significantly effective, however, it is believed that small resin rich patches of QS-45 cured panels can be removed with controlled application of external pressure using DVB. POLYM. COMPOS., 34:942-952,

Effects of processing parameters for vacuum‐bag‐only method on void content and mechanical properties of laminated composites

“…The process is conducted in two phases namely degassing and compaction. Degassing phase occurs at B‐stage (low‐temperature dwell) of a cure cycle, where a full vacuum in the outer‐environment is drawn by applying a pressure of 1.01 bar whereas a partial vacuum, say 0.95 bar, is drawn in the inner‐environment, [ 28,29 ] as shown in Figures 3A and 4A. This creates a ballooning effect inside the inner‐environment, which consequently allows an easy escape for trapped volatiles.…”

Experimental comparative study of the variants of high-temperature vacuum-assisted resin transfer moulding

“…The double bag vacuum infusion (DBVI) was first developed at the Naval Air Warfare Centre in 80s for prepreg curing and previous studies have shown significant void reduction in final cured composite parts compared to single-vacuum-bag; a reduction of void content from 6-7% to 1-3% [13], [16]- [19]. The DBVI process is particularly appropriate to release volatiles such as water and solvent during curing of composite parts [17], [19]. This is still an VARTM variant (Figure .2 left side), the debulking process without compaction at vacumm conditions helps promote uniformity on the final thickness of composite parts.…”

“…VAP maintains a constant level of preform compaction during infusion since a uniform vacuum is applied across the entire panel via membrane [20]. The higher variability of thickness in DBVI can be attributed to the non-uniform distribution of perforated sheet in between the two bags, leading to a non-uniform pressure distribution over the entire laminate [17]. Unlike the satin-woven laminates, Table .5 shows that the average thickness of non-crimp laminates vary less from one variant of the vacuum infusion to another, while the variation in non-crimp laminate thicknesses is two to ten times larger than satin-woven laminates.…”

An Enhanced Vacuum-Assisted Resin Transfer Molding Process and Its Pressure Effect on Resin Infusion Behavior and Composite Material Performance

“…Various factors such as mold dimensions and structures, fiber preform design, type, layering, stacking sequence, pressure gradient distribution, and more all impact the flow of resin within the VARTM process. Therefore, improvements in the VARTM process primarily focus on these aspects and can be summarized into three main methods: (i) heating the resin to reduce its viscosity [1][2][3][4][5][6]; (ii) adjusting the pressure distribution on the mold surface [7][8][9][10][11]; and (iii) making the fiber prefabricated parts loose to increase the permeability [12][13][14][15][16][17][18][19].…”

“…This promotes in-plane resin flow through the fiber preform and achieves excellent resin impregnation into the fibers [9][10][11]. And some researchers have used the creation of a certain vacuum environment above the mold to regulate the pressure distribution on the surface of the mold, thus changing the permeability of the fiber preform and improving the infiltration of the resin [12][13][14][15][16].…”