• Version
• 98 Downloads
• 7.36 MB File Size
• 1 File Count
• April 21, 2016 Create Date
• April 21, 2016 Last Updated

Evaluation of Acoustic Emission SHM of PRSEUS Composite Pressure Cube Tests

A cube constructed of Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) composite
panels was pressurized pneumatically at NASA Langley Research Center (LaRC) in the
Combined Loads Test facility (COLTS) to increasing levels during a series of tests. The series
started with checkout tests to verify the proper operation of all instrumentation and finished with
the final test in which internal pressure was increased until final failure. This document describes
the investigation of the Acoustic Emission (AE) data collected during these tests.
The PRSEUS concept [1] for the composite structure improves on the state of the art as noted in
figure 1 by eliminating fasteners and providing damage arrest while incorporating integral
stiffeners for efficient strength to weight ratios. A pultruded rod in a stringer cap perpendicular to
foam-core frames is a novel way to create a dry carbon fiber stitched preform that supports itself
during vacuum bagging and resin infusion. Fabrication does not require complex interior mold
tools [2] so that point-of-fabrication customization for structural changes is easy and
inexpensive. The dry multi-ply stacks and sub-structures are stitched together using Vectran
fibers into the near final shape for incorporation into the Blended Wing Body (BWB) design.
Figure 2 illustrates a 3-D schematic of a subsection of the large scale BWB test article being
realized as the PRSEUS pressure cube test article with a bulkhead panel removed [3]. The cube
consists of six sides of PRESUS construction. There are two ribs, two bulkheads, a crown and a
floor. Each bulkhead panel is joined to the adjacent sides by bolting it to T-cross-section integral
caps. These caps on the surrounding rib, crown, and floor panels capture the panel like a picture
frame. Every panel has seven or eight rod stiffened PRSEUS stringers (rib or bulkhead panel,
respectively) spaced 6.0 inches apart. These stringers cross perpendicular to two frames spaced
24 inches apart. The spaces of unstiffened panel are called bays. At the comer of two contiguous
panels the stringers on one panel do not intersect the stringers of the other. The outside
dimensions of the pressure cube are approximately 52 in. x 48 in. x 56 in. [4]
The AE sensors applied to the crown and one of the rib panels, as well as the section of the frame
that buckled first during failure, are shown in figure 2. For purposes of illustration the bulkhead
panel indicated as “blkhd panel removed for clarity” can be considered as the panel that blew out
during failure, leaving the cube looking much as the figure illustrates, albeit, a little more ragged
and fractured.