Thermoset prepregs meet lightning strike protection specifications

Panel 1 testing (left) and panel 2 testing (right) results. Source | A.P.C.M.

Adhesive Prepregs for Composite Manufacturers (A.P.C.M., Plainsfield, Conn., U.S.) has been developing thermoset epoxy prepregs for the manufacturers, designers and hobbyists of composite parts since 1992. A.P.C.M. highlights how its standard epoxy prepreg systems and substrates are available for lightning strike testing review. To achieve this, the company develops the panels and sends them for testing by the Elements Testing Group (Pittsfield Mass., U.S.).

A.P.C.M. breaks down this process. To create the test panels, the company lays up 22 plies of material, the top ply being the lightning strike carbon fiber prepreg. Complete panels are 27" × 27" and 0.20-0.22 thousands thick. Debulking, curing and paint parameters are per Boeing specifications.

Panels testing shows two panels — differentiated by the thickness and the weight of the needle punched copper foil used to make the lightning strike prepreg — prior to and after strike tests. Testing is called zone 1 and zone 2, which equates to the power of the electricity used to strike the panel. One panel had a 0.029 Ib/²ft of copper and the other 0.040 Ib/²ft of copper. Each panel experienced surface damage but maintained their structural strength and protected against lightning strikes. which can result in the shorting out any of an aircraft’s electrical components.

At its booth, A.P.C.M. is showing a high-speed video of the test being performed, as well as all of its other standard thermoset epoxy prepreg products, from 180-375°F curing systems, including specialty woven and standard woven substrates from glass to carbon fiber to Kevlar. This includes hybrid carbon fiber/colored glass, carbon fiber/Kevlar, spread tow carbon, flax and hemp. Cured and uncured samples, as well as substrates are available for attendees to view.