HexPly 8552 — toughened 180 °C epoxy prepreg for primary aircraft structures

Country: · Model: HexPly 8552

HexPly 8552 is a toughened epoxy prepreg that cures at 180 °C (350 °F) and is designed as a low-flow material for service up to 121 °C (250 °F). It is selected for primary aircraft structures where stiffness and damage tolerance are needed, and is supplied as tapes and fabrics of carbon, glass and other fibers.

Matrix: amine-cured toughened epoxy resin, cure 180 °C (350 °F), low flow
Service temperature: up to 121 °C (250 °F)
Tg dry / wet: 200 °C (392 °F) / 154 °C (309 °F)
Neat resin: density 1.30 g/cm³; tensile strength 121 MPa (17.5 ksi); K1C 1.475 ksi·√in

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Technical specifications

Matrix	amine-cured toughened epoxy resin, cure 180 °C (350 °F), low flow
Service temperature	up to 121 °C (250 °F)
Tg dry / wet	200 °C (392 °F) / 154 °C (309 °F)
Neat resin	density 1.30 g/cm³; tensile strength 121 MPa (17.5 ksi); K1C 1.475 ksi·√in
Gel time at 177 °C	13 min
Versions	8552 (standard), 8552ATL (reduced tack for automated lay-up), 8552S
Reinforcement	carbon tapes and fabrics (AS4, IM7), glass, aramid, quartz, tow prepreg
Resin content	tapes 33–38 %, fabrics 32–42 %; volatiles ≤ 1.0–1.5 %
0° tension (AS4/IM7, −55 °C)	300 / 373 ksi

Specifications are taken from the manufacturer’s technical documentation. Updated 11/06/2026.

Description

The matrix is amine-cured and toughened for damage tolerance. The glass transition temperature of the neat resin is 200 °C dry and 154 °C wet, tensile strength is 121 MPa, elongation 1.7 %, and fracture toughness K1C 1.475 ksi·√in. Gelation at 177 °C takes 13 min. Carbon tapes contain 33–38 % resin, fabrics 32–42 %, and volatiles do not exceed 1.0–1.5 %. The TDS gives laminate properties from −55 to +90 °C dry and wet, including compression after impact (CAI). For 0° tension at −55 °C, tapes on AS4 and IM7 have 300 and 373 ksi. The material is supplied in rolls and stored in a freezer. Shelf life is 12 months at −18 °C, tack lasts 10 days, and outside the freezer the prepreg can sit for up to 30 days at 23 °C. Before opening, the package is warmed to room temperature, otherwise condensation will settle on the fiber.

How to choose

First determine the lay-up method. For hand lay-up the standard 8552 is taken, for automated tape laying (ATL) the 8552ATL version with reduced tack, and 8552S is another version of this matrix. If the part will operate for long periods above 121 °C, see the bismaleimide M65 and F655 up to 204 °C, and for repairing structures without an autoclave there is M20 with a cure at 130 °C.