Composite resin richness in areas with sharp contours
Composite resin richness in areas with sharp contours
(OP)
Hi all,
We are experiencing an issue with one of our composite molded products. We are use a bag mold process to form a composite helmet. The layup process is wet on a headform/bladder that is then transferred to a hot mold and cured. In areas where the contour bends sharply we are experiencing resin richness. The Kevlar material is not conforming to the contour in these areas. We have tried numerous combinations of hard pushers, initial curing at low temperatures, etc. with no positive result. We are using a single layer of peel ply on the outside of the layup that appears to act a sieve and does help considerably to remove the resin - the lack of definition of the Kevlar is the biggest current issue. We do not currently have any bleedout/vents anywhere on this particular tool and we are considering their addition as we generally do have them in other tools.
This tool is not dedicated to one particular use - it is a base/insert combination and makes several sizes of product. Bleedout install can be a bit tricky and production volume is low for this item.
Any suggestions?
We are experiencing an issue with one of our composite molded products. We are use a bag mold process to form a composite helmet. The layup process is wet on a headform/bladder that is then transferred to a hot mold and cured. In areas where the contour bends sharply we are experiencing resin richness. The Kevlar material is not conforming to the contour in these areas. We have tried numerous combinations of hard pushers, initial curing at low temperatures, etc. with no positive result. We are using a single layer of peel ply on the outside of the layup that appears to act a sieve and does help considerably to remove the resin - the lack of definition of the Kevlar is the biggest current issue. We do not currently have any bleedout/vents anywhere on this particular tool and we are considering their addition as we generally do have them in other tools.
This tool is not dedicated to one particular use - it is a base/insert combination and makes several sizes of product. Bleedout install can be a bit tricky and production volume is low for this item.
Any suggestions?





RE: Composite resin richness in areas with sharp contours
RE: Composite resin richness in areas with sharp contours
RE: Composite resin richness in areas with sharp contours
This is a bag molding process not an Autoclave process. We do a wet layup on a rubber bladder (we call it a saddle) and then transfer the saddle and layup into a two piece mold. The mold opens and closes horizontally with hydraulics. Once the layup/saddle is in position we close the mold halves around it. Then the top plate on which we have a water bag (or bladder) is lowered into the layup saddle that is open on the bottom end. We then then fill and pressurize the bag with water. The bag applies pressure to the saddle and the actual composite material is between the saddle and the steel mold. Cure take place under heat and pressure.
Sorry for the confusion - we refer to this process as bag molding, there is no vacuum involved, just heat and pressure.
RE: Composite resin richness in areas with sharp contours
Airtech has a product called Airpad which is an uncured rubber sheet used to fill these low pressure areas.
RE: Composite resin richness in areas with sharp contours
Yes, we have tried hard plastic pushers integrated into the saddle. We've also tried a harder rubber inside the saddle in the trouble area. We have seen slight improvement but not quite what we need. We also saw a greater incidence of blisters in the finished product that may be related to the harder materials.
I have been trying to get samples of product from Airtech for about a month and half. I may just have to buy some of the Airpad product.