SAMPE Journal - July/August 2020 - 8

FEATURE / COMPOSITE WING MOVEABLES
range of the SQRTM injection/curing cycle are typically within the current process specifications of
OEMs. The injection system and press equipment
are similar to those used for RTM. SQRTM is compatible with both UD and woven reinforcements
and all qualified prepregs (ex: 8552, 977-2, M21E,
3900-2, BMI 5250-4) as long as the resin of the prepreg (or almost equivalent resin) is available in
bulk or unreinforced film form. This is the case for
the resins mentioned previously. There is no material qualification needed and the existing material
allowables (from autoclave curing) can be used.
Mechanical tests on coupons (lamina and laminate properties) have shown the material properties equivalency between autoclave and SQRTM
curing5. The only qualification needed is the part
qualification as requested for any new serial components.
Table 1 presents a comparison between the
main manufacturing processes for composite
aerostructures (Autoclave, RTM, Vacuum infusion
and SQRTM). This comparison is based on medium size parts (typically max 8 m x 1,5 m x 0,3 m),
complex structures (integrating several ribs and/or
spars) and relatively flat in the spanwise direction
(if double curvature). Wing moveables (slats, flaps,
ailerons, etc.) are parts that have these characteristics.
As shown in Table 1, SQRTM combines advantages from both prepreg and closed mold technologies.

From prepreg technologies:
- Use of qualified tough prepregs without additional costs for material
allowables establishment.
- Existence of qualified automated lay-up processes (AFP or ATL) with the
use of UD reinforcements; automation can be pushed further than
autoclave (no vacuum bag, more repeatable process).
- A large variety of qualified prepregs from different suppliers.
From closed mold technologies:
- High control on the thicknesses and the geometry (radii, plies conformity).
- High surface quality.
- Robustness, less scraps, less non conformities and repairs.
- Faster NDT inspection (due to the better surface quality) ; inspection time
is estimated to be divided by about 15% compared to autoclave
equivalent parts.
- Reduced direct and indirect costs related to inspection and
non-conformities (by about 50%).
- High level of parts integration possible, allowing for curing costs reduction.
- Lower cost of ancillary materials and significantly lower energy
consumption in comparison with autoclave.
- Reduction of assembly cost and lead-time (less shimming due to
high dimensional tolerances, potential for more integrated parts,
assembly automation easier due to close tolerances and geometry
repeatability).
- Better buy-to-fly ratio as near net shape parts are produced
(material attrition is reduced).
SQRTM is very suitable for wing components
(slats, flaps, ailerons, etc.) with respect to the size,
part complexity and aero quality requirements. For
the typical business base of a commercial aircraft
or business jet, the tools extra cost (closed mold) is
balanced by the recurrent cost savings.

Table 1. Comparison between SQRTM, autoclave, RTM and vacuum infusion.

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SAMPE Journal - July/August 2020

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