The pecan breeding and processing industry has an annual production value of 300 million dollars, yet it still depends on simple measurements such as weight, dimensions, and color to characterize different pecan varieties. Naturally such data does not directly impact the yield nor does it eliminate problems such as splitting or germinating during the maturation cycle. Our goal is to develop and conduct special experiments integrated with computational simulations to understand the material and mechanical properties of the pecan to enable better crop management as well as to minimize problems in post harvesting, including incomplete shell and meat separation.

The compressive tests we are conducting in our study utilize the full pecan to assess its strength along the three axes defined as longitudinal, transverse parallel and transverse perpendicular. The results reveal that the pecan is much stronger longitudinally, than in the transverse directions, with an average failure load of 186 pounds in the longitudinal direction. Also, the transverse parallel load at failure is almost twice as high as the transverse perpendicular with an average of 72 and 43 pounds respectively. This difference is attributed to the load path due to geometry of the surface contours. In order to better understand the pecan shell properties, samples were cut from the longitudinal and transverse directions. The ring tests revealed that the transverse modulus is 3.7 GPa and the transverse strain ratio is about 0.2. Also, longitudinal modulus, evaluated from strips cut in the longitudinal direction, is 7.6 GPa and longitudinal strain ratio is 0.5. Finite element models of the pecan shell and ring tests are created using SolidWorks and analyzed with COSMOS commercial program. Future activities include incorporating the non linearity of the material response as well as representing the interior structures of the pecan into the FE model.

• "Anisotropy in Hickory Shells: Reinforcement Architecture and Material Properties"
  R. Kulkarni, J. Brewer, O. Ochoa and M. Harris
  18th Annual Technical Conference of the American Society of Composites
  Gainesville, Florida [October 2003]