Experimental Investigation of the Controlled Atmospheric Pressure Resin Infusion (CAPRI) Process

Abstract

Controlled atmospheric pressure resin infusion (CAPRI) is a variation of the vacuum-assisted resin transfer molding (VARTM) process. The CAPRI process increases the fiber volume fraction of the preform prior to infusion via debulking and applies a reduced pressure gradient during infusion to minimize thickness gradients during processing. This study experimentally investigates the effect of debulking and reduced pressure gradient on the incoming material parameters, process behavior and final dimensional tolerances. The effect of debulking on fabric permeability and compaction behavior has been investigated and shows a significant impact on the infusion time and final fiber volume fraction. Several E-glass plain weave preforms have been infused and flow, pressure and thickness data has been recorded and compared to traditional VARTM processing. A previously developed model uses the experimentally obtained permeability data and good agreement of the flow behavior is observed, the CAPRI process decreases thickness gradients to less than 1% while increasing fiber volume fraction by 5% in the composite part.

Experimental investigation into the post-filling stage of the resin infusion process

“…Different techniques have been devised to improve process control and laminate quality by adding more consumables or more complexity to the equipment and process. The controlled atmospheric pressure RI (CAPRI) process 10 includes a debulking phase during pre-filling, where the vacuum is applied cyclically hundreds of times in order to improve the compressibility of the reinforcement. During the filling stage the inlet is also maintained at a pressure lower than atmospheric in order to reduce the laminate thickness gradient formed during infiltration.…”

Improvement of the impact and crack resistance of epoxy thermosets and thermoset-based composites with the use of thermoplastics as modifiers

“…In [89], a number of nonwoven reinforcing fillers of various organizations (spanbond, veil) and chemical natures (polyamide, thermoplastic polyurethane) were studied as secondary reinforcing fillers for the CAPRI (Controlled Atmospheric Pressure Resin Infusion) technology [125]. It was shown that, depending on the chemical nature of the filler, both improvement and worsening of compression strength after impact may be observed.…”

Permeability characterization of stitched carbon fiber preforms by fiber optic sensors

“…The whole system was sealed by the vacuum bag. A partial vacuum has been applied also to the resin container to reduce the local pressure variations and, hence, to minimize the thickness changes during the resin flow according with the study of Niggemann et al [34] that have demonstrated the positive effect of this procedure for un-debulked preforms. Figure 5 shows two pictures of the beginning and the end of the infusion tests.…”