Today we’ll be demonstrating the advantages of fabricating a RTM infusion foil and strut for the ORPC RivGen® Power System.

We will be showing the fabrication of a foil using the Hawthorn Composites Advantage that includes using custom, dry carbon fiber and resin transfer molding (RTM) with industrial grade epoxy resin.

First the carbon fabric is cut to precise ply shapes using an automated table cutter and the plies are kitted. We are using A&P Technology’s braided carbon fabrics for the foil that include unidirectional zero, +/- 45° BiMax, and 0°+/-60° Qiso.

Now the technician lays up the kitted plies into the upper clamshell and lower clamshell molds. The plies are held in place using a tackifier spray.

After a tube bag is applied onto the laminate on the lower clamshell mold, the upper clamshell mold is flipped and lowered into position on the lower clamshell mold. Once in position, the mold halves are bolted together to compress the O-ring.

Next we attach intermediate seal plates and once secured, the tubular vacuum bag is sealed out to the intermediate seal plates using vacuum tape.

Then, we secure pressurization plates to each end of the mold.

The pressurization plates allow us to create a reverse autoclave effect in an oven. We are able to apply pressure to the vacuum bag during and after resin infusion to ensure we eliminate voids and fully compact the laminate.

After infusion hardware is fastened to the mold and a positive vacuum leak check is preformed on the system, the mold is staged onto the infusion stand and plumed inside the oven. This is where the infusion mold in wetted out by infusing the part with epoxy.

Disassembly is performed in reverse order of assembly and once the clamshell mold is unbolted, the upper mold is lifted away.

Next the composite foil is removed from the lower clamshell mold and is transferred to a hand finishing work station.

Here the foil is deburred and sanded per part specifications

Now epoxy foam is poured inside the hollow foil and expands to fill the cavity.

A trim and drill fixture is used to drill precise holes.

Next metallic backing plates are bonded onto the foil in 3 locations, which allow the foil to be attached to the struts at ORPC.

The foils are painted with a clear coat epoxy paint to protect them from UV Light.

The foil was made at a 35% reduction in cost and a 70% reduction in fabrication time.

Next, we show the fabrication of a strut using the Hawthorn Composites Advantage that includes using dry fiberglass fabric and resin transfer molding of industrial grade resin.

First 36 plied of A&P Technology’s braided QISO fiberglass are cut into precise ply shapes with an automated fabric cutter and the plies are kitted.

Now the plies of kited fiberglass are laid up by a technician into their respective clamshell mold halves. Then the upper clamshell mold is flipped and assembled to the lower clamshell mold.

The molds are bolted together and infusion hardware is installed and a vacuum leak check is performed on the mold. Once passed, the mold is installed into the infusion stand, placed into the oven and plumbed for infusion.

An Infusion Vessel is used to prep the epoxy resin, including elevating the temperature, de-gassing and mixing. The infusion vessel allows us to perform an RTM process and to apply pressure during infusion and cure to fully wet out the laminate and ensure full compaction.

The part is infused and cured following the resin manufacturers recommendations.

After cure is complete, the mold is removed from the oven and the demolding process begins.

Once the demolding process is complete, the composite strut is removed and prepped for the trim and drill operation.

Now the strut is placed onto a high-speed CNC router bed and is drilled and trimmed to the customers specifications. Once this step is completed, the part is complete and ready to be inspected and sent out to the customer.

The strut was made at a 20% reduction in cost.

Using the Hawthorn Composites manufacturing methods allow us to fabricate complex composite parts that are equal in performance and quality to baseline manufacturing methods at significantly lower cost and fabrication time.

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