2010 Project Progress Report
Program Name: 3-D FRP Sandwich Panels with Corrugated
Sheets for Bridge Decks
Program Manager / PI: Dr. Sami Rizkalla
Company / Sponsor: Martin Marietta Composites, Inc.
Project Number: NCSU - 2
Overview: The project will study the behavior of innovative three-dimensional glass fiber reinforced
polymer (3-D GFRP) sandwich panels under various loading conditions. The study will also examine the
two-way bending behavior under concentrated wheel load and one-way flexural fatigue characteristics
of the panels.
Experimental Plan: The project involves parametric testing program to study the structural
performance of new 3-D FRP sandwich panels in presence of core corrugation. The first phase of
experiment studied influence of corrugated sheets on the shear modulus in comparison to panels
without corrugated sheets. A total of six specimens have been tested as per ASTM C273 standards for
sandwich panels, with set of three in two principle directions. The size of specimens measured at two
opposite ends were nominally 9 in x 12 in. selected intentionally to include one complete repeating
pattern of corrugation.
The next phase of testing program studied influence of the corrugated sheets on the elastic stiffness of
the new 3-D FRP sandwich panel. A panel of size 72 in x 46 in was tested in three-point bending
configuration using simple support conditions under a line load. The panel was tested three times within
the elastic range on three different spans of 36 in, 48 in and 60 in respectively to determine the elastic
stiffness. Finally, it was loaded to failure at 60 in span. The subsequent portion of testing program
involved evaluation of two-way bending behavior of the new sandwich panels with core corrugations
under concentrated wheel load. A panel of size 72 in x 46 in was tested to failure under simply
supported conditions with a single patch load applied at the centre.
The remaining phase of the testing program will focus on parametric study of new sandwich panels in
shear and flexural fatigue behavior. For shear test, a panel of size 48 in x 46 in will be tested under
double line loads placed closed to each supports. For flexural fatigue behavior, two specimens of size
72 in x 19 in will be tested under three-point bending configuration with a maximum load based on the
shear stress corresponding to a 1% core shear strain proportional limit . The panels will be subjected to
a maximum of 2,000,000 cycles with a frequency of 2 Hz.
Goals and Motivation: Previous research at North Carolina State University`s Construction Facilities
Laboratory demonstrated distinctiveness of an innovative 3-D GFRP sandwich panels (Reis, 2005) and
behavior under two-way bending as well as fatigue load (Taylor, 2009). Since the main advantage of a
sandwich structure is its exceptionally high flexural stiffness-to-weight ratio, the core material
configurations such as thickness and lateral through thickness fiber density has previously shown a
significant effect on increasing compressive strength and shear stiffness of the panel. Also, increase in
shear stiffness has helped to resist out-of-plane deflection associated with buckling failure mode and
hence enhanced ultimate capacity of the panel. The new Transonite 3-D GFRP sandwich panels are the
product of relatively new technology with additional core corrugation and therefore further research is
required to determine the behavior of these panels under various loading conditions for future use for
civil engineering infrastructure and transportation applications. The experimental results will be used to
calibrate specific analytical approach based on Sandwich Panel theory and/or Finite element analysis.
The analysis is expected to simplify and propose a straightforward tool to determine the structural
properties of new Transonite panels with corrugated sheets and through thickness fibers.
Previously Reported Findings: N/A
Budget Update: $50,000
Findings Since Last Report: N/A (New Project)
Potential Member Company Benefits: The work will characterize the structural performance of new
3-D FRP sandwich panels with corrugations sheets under various loading conditions. Due to their high
strength-to-weight ratio and durability, these panels have many potential applications in civil
engineering infrastructure, including pedestrian bridges and bridge decks. As they are a relatively new
technology, wide-ranging tests and analytic modeling will assist to study more about the behavior of
these panels. Engineers and designers will have more confidence in using them for a wider range of
applications as the behavior of new sandwich panels will be put forward. The success of this particular
type of panel will also increase confidence and expand the use of other composite technologies
throughout the civil infrastructure.
Next Steps:
1. Complete experimental program
2. Analyze experimental results
3. Introduce analytical model to be calibrated by experimental results