Effect of temperature on the dynamic fracture and shock performance of graded materials
The effect of thermal loading on the performance of the graded materials has been studied. In this study, two types of graded materials have been considered: 1) continuous graded materials 2) sandwich graded materials. For the first part, a transient analysis of a mixed mode dynamic crack in continuous graded materials under thermo-mechanical loading was performed. Later, the effect of low and high temperature on the blast performance of sandwich graded materials was investigated.
Asymptotic analysis in conjunction with displacement potentials are used to develop thermo-mechanical stress fields for a mixed mode propagating crack in a continuous graded material. The crack is assumed to propagate at an angle with respect to the gradation direction. Asymptotic temperature field equations are derived for exponentially varying thermal properties, and these equations were then used to develop various temperature fields around the crack-tip. Later, these temperature fields were used in deriving thermo-mechanical stress fields. Using asymptotic thermo-mechanical stress fields, the effect of temperature field and transient parameters (loading rate, crack-tip acceleration, temperature change) on the contours of maximum principal stress and circumferential stress is discussed. Also, the effect of different temperature fields on the crack extension angle was studied.
High strain rate constitutive behavior of E-glass Vinyl ester composites and Corecell™ M100 foam at different temperatures has been studied using SHPB apparatus. Eight different target temperatures were chosen: -40ºC, -20ºC, 0ºC, 22ºC, 40ºC, 60ºC, 80ºC and 100ºC. The sandwich composites were maintained at the target temperature before being subjected to shock-wave loading using a shock-tube. A high-speed photography system utilizing Digital Image Correlation (DIC) was used to record the real time deformation of the specimen. The results show a significant decrease in flow stress with the increase in the temperature of the core material. Significant fiber-matrix delamination was observed in face-sheets at elevated temperatures with little change in the value of compression modulus. For the low temperature environment, the core material shows brittle behavior resulting in core-cracking of the sandwich specimen under blast loading.