(the company also does process development and worksta- tion design). “We’ve been doing this long enough that some of our customers are doing it on their own,” said Coughlin, refer- ring to the technology that enables near net shape assem- blies. “Where we stay in the game is providing the work cells.”
The principle behind SQRTM (pronounced “squirt ’em”) is that it uses the same resin that’s pre-impregnated in the ma- jority of the composite materials aircraft manufacturers have spent a few million dollars to qualify. “We wanted to be able to use those materials because they’re important to them [the manufacturers who are Radius’ clients],” said Coughlin. The resin injected during the SQRTM process isn’t used to wet the composite material. Instead, it’s used to maintain steady hydrostatic pressure within the mold to prevent voids, much the same as an autoclave. There are other advantages to SQRTM, including no need for an autoclave. Also, SQRTM-manufactured pieces don’t have to be ma- chined to net. “Machining is incredibly expensive,” Coughlin said.
Thin is in Another advance in composites for aerospace is spread
tow, aka thin ply. While regular tow might be 5/1000" (127-µm) thick and 20 fibers deep, spread tow is 1/1000" (25.4-µm) thick and made of only four or five fibers though the thickness, said the Institute for Advanced Composites Manufacturing Innovation’s Pipes. “The thinner we make the tow, the stronger they are,” said
Pipes. “We don’t know why, but there are several theories. “If you can figure that out, you can perhaps learn how to make it even stronger.” Thin ply is also less prone to cracking and delamination. “The tendency to delaminate is inverse to thickness,” he said.
Squirt ’em?
In the time since Radius Engineering (Salt Lake City, UT) developed same qualified resin transfer molding, a major- ity of the large aircraft manufacturers around the world have conducted their own development programs on the method, said Tom Coughlin, business developer for Radius, a closed mold tooling and injection systems manufacturer
The manufacturing process is streamlined, with no need to catalog, inspect and inventory multiple parts that typically make up primary structures (the parts of an aircraft whose failure would seriously compromise safety, such as fuselages and wings).
It allows manufacturers to “cellularize” their manufactur- ing: in other words, instead of making one part of an as- sembly, a work team makes the entire assembly. “I’m making the whole thing,” said Coughlin of the cellularized workers’ mindset. “You’d be surprised how important that is.” Even if an aircraft manufacturer can’t make an entire primary structure using SQRTM, he can significantly cut down on the number of parts. For example, if a manufacturer needs to incorporate de-icers in a wing flap, he can make the part minus one skin (the upper or lower skin). After the de-icers are added, he can attach the skin. Determinate as- sembly is the result of net shaped composite manufacturing process.
“This allows us to create an entire assembly and it’s the same way every time,” Coughlin said of the SQRTM method. Abaris’ Dorworth said: “It’s taking the assembly and all of the inspection related to that into the layup room.”
107 — Aerospace & Defense Manufacturing 2016
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