SAMPE Journal - July/August 2020 - 36

FEATURE / REPAIR OF COMPOSITE STRUCTURES
Tensile Testing
UDRI performed tensile testing of all pristine and
repair specimens. Figure 15 shows the test results
compared to an expected recovery zone based on
relevant literature3,4,5. The primary conclusion that
can be drawn is that the process matters: infusion
clearly outperformed the wet layup process. Regardless of cure temperature or resin system, the
infusion specimens performed 20-60% better than
the wet layup specimens. Expectedly, the infusion
specimens yielded higher tensile strengths with
higher cure temperatures. Table 3 provides test result details.
The results can most likely be attributed to the
quality of the bondline highlighted by the fracture
surface and cross section microscopy. The infusion
specimens had less voids and better wet out in the
fiber bundles and contact surfaces. This result may
have been different with a higher viscosity infusion
resin that was not capable of wetting out the surfaces. One of the key advantages of the fast-curing
R102/H18 resin is the combination of low viscosity
at room temperature with 180°C performance.
SUMMARY
In this study, an infusion-based repair method
was performed and compared to a benchmark wet
layup repair material and process. NONA R102/
H18 resin was used for its unique combination
of properties: low viscosity at room temperature,
180°C Tg, and fast curing capability. The study
showed that the infusion process yields a higher
recovery of pristine tensile strength performance,
most likely due to the improved repair surface wetting and decreased void content.
Future work with NASA will focus on different repair configurations, including core repair,
puncture repair, and the use of qualified aerospace
resins. The existing infusion repair kit will also be
modified to improve ease of use and robustness.
ACKNOWLEDGMENTS
CRG would like to thank Jared Stonecash at UDRI
for coordinating testing and Larry Ertz and Rick
Stienecker at CRG for composite fabrication.

Figure 14. Fracture surface of infusion process
specimen. Circled areas indicate no wetting.

Figure 15. Tensile testing results.
Table 3. Tensile testing results.

3. Federal Aviation Administration, "Repair of Composite Laminates," DOT FAA AR-00
46.
4. T. D. Breitzman, "Composite Scarf Repair patch optimization under uniaxial loading

REFERENCES
1. "Composite Repair," 1 1 2014. [Online]. Available: http://
www.compositesworld.com/articles/composites-repair.
2. A. Gacoin, "Experimental and Numerical analysis on
adhesively bonded scarf joints: effects of the substrate's

conditions.," in ASME International Mechanical Engineering Congress and Exposition,
Seattle, WA, 2007.
5. T. D. Breitzman, "Optimization of a Composite Scarf Repair Patch Under Tensile Loading," Composites Part A Applied Science and Manufacturing, 2009.

material and adhesively bonded joint geometry on the

6. J. Tomblin and L. Salah, "Effects of Repair Procedures on Bonded Repairs of Compos-

damage evolution.," The Journal of Adhesion, 2008.

ite Structures.," in Joint Advanced Materials and Structures Center of Excellence, 2011.

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SAMPE Journal - July/August 2020

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