Epoxy layer shear stresses resulting from a negative 50 degree Celsius temperature change are calculated using finite element approximations and closed form methods. The analyses simulate candidate epoxy adhesive configurations that attach the silicon detector segments to the detector trays. Discrete attachment pads, line attachment segments, and total area attachments are examined with a structural finite element model. Where applicable, the finite element model results are verified by closed form expressions. Shear stress distributions as a function of attachment configuration and epoxy shear modulus are computed. The calculated results show that the shear stress increases with increasing shear modulus and that there is a tendency for the shear stress to decrease with increasing adhesive contact area. Finite element methods are used to construct finite element models (FEM) and obtain coefficient of thermal expansion (CTE) induced stresses in simulated epoxy attachment models.
The models represent the attachment of the GLAST detector segments to the underlying support trays. Three layers are simulated in the models; the first layer is a substrate, the second is the epoxy layer, and the third is the simulated silicon detector layer. Each layer is modeled using solid finite elements and isotropic material properties.
Pages : 11
Size: 224 kb
Author : Franz Biehl, Erik Swensen
GLAST Epoxy Thermal Shear Stress