Longitudinally jointed edge-wise compression honeycomb composite sandwich coupon testing and FE analysis: three methods of strain measurement, and comparison
In this work, all three methods of strain sensing, described above, were used to monitor strain during Edge-Wise Compression testing of a composite jointed panel: resistive strain gages, fiber optic strain sensing, and three-dimensional DIC. The strain from each technique is compared to the FEA model in order to correlate data between these three measurement methodologies.
In accordance with ASTM C364, three distinct strain measurement methods (i.e. foil resistance strain gages, fiber optic strain sensors, and a three-dimensional digital image photogrammetry that gives full field strain and displacement measurements) were implemented to measure strains on the back and front surfaces of a longitudinally jointed curved test article subjected to edge-wise compression testing, at NASA Goddard Space Flight Center. The pre-test finite element analysis (FEA) was conducted to assess ultimate failure load and predict strain distribution pattern throughout the test coupon. The predicted strain pattern contours were then utilized as guidelines for installing the strain measurement instrumentations. The foil resistance strain gages and fiber optic strain sensors were bonded on the specimen at locations with nearly the same analytically predicted strain values, and as close as possible to each other, so that, comparisons between the measured strains by strain gages and fiber optic sensors, as well as the three-dimensional digital image photogrammetric system are relevant. The test article was loaded to failure (at ~167 kN), at the compressive strain value of ~10,000 μɛ. As a part of this study, the validity of the measured strains by fiber optic sensors is examined against the foil resistance strain gages and the three-dimensional digital image photogrammetric data, and comprehensive comparisons are made with FEA predictions.
B. Farrokh, N.A. Abdul Rahim, K. Segal, T. Fan, J. Jones, K. Hodges, N. Mashni, N. Garg, A. Sang. Longitudinally jointed edge-wise compression honeycomb composite sandwich coupon testing and FE analysis: three methods of strain measurement, and comparison. SAMPE 2013