Journal Published Online: 02 March 1992
Volume 14, Issue 1

Redesign of the Mixed-Mode Bending Delamination Test to Reduce Nonlinear Effects



The mixed-mode bending (MMB) test uses a lever to apply simultaneously Mode I and Mode II loading to a split-beam specimen. An iterative analysis that accounts for the geometric non-linearity of the MMB test was developed. The analysis accurately predicted the measured load-displacement response and the strain energy release rate, G, of an MMB test specimen made of APC22 (AS4/PEEK). The errors in G when calculated using linear theory were found to be as large as 30% in some cases. Because it would be inconvenient to use a nonlinear analysis to analyze MMB data, the MMB apparatus was redesigned to minimize the nonlinearity. The nonlinear analysis was used as a guide in redesigning the MMB apparatus. With the improved apparatus, loads are applied just above the midplane of the test specimen through a roller attached to the lever. This apparatus was demonstrated by measuring the mixed-mode delamination fracture toughness of APC2. The nonlinearity errors associated with testing this tough composite material were less than ±3%. The data from the improved MMB apparatus analyzed with a linear analysis were similar to those found with the original apparatus and the nonlinear analysis.

Author Information

Reeder, JR
NASA Langley Research Center, Hampton, VA
Crews, JH
NASA Langley Research Center, Hampton, VA
Pages: 8
Price: $25.00
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Stock #: CTR10078J
ISSN: 0884-6804
DOI: 10.1520/CTR10078J