2-11 Interfacial shear stresses in uniaxial graphite/epoxy laminate system at
A T = 4 0 5 K ................................ ............. .... ....................................3 0
2-12 Maximum principal stress distribution in the LH2 Graphite/Epoxy composite
tank. Tank pressure = 10 KPa and temperature = 50 K (AT= -405 K). .................31
3-1 (a) Geometry of interfacial fracture specimens, (b) A crack normal to laminate
interface with different stacking sequence. ............. ......................... ...............35
3-2 Deformed geometry in the vicinity of a crack and interfacial fracture finite
elem ent m odel. ..................................................... ................. 37
3-3 Contour plots of stress distribution for a [0/90/O]T composite model at a
crack-tip under tensile and bending loads. ..................................... ............... 37
3-4 Stress distribution under (a) tensile loads; (b) bending loads. ................................38
3-5 Four-point bending test to determine the fracture load........................................40
3-6 Load-displacement curves of four-point bending tests at room temperature
for the Specim en 1 .....................................................................4 1
3-7 Load-displacement curves of four-point bending tests at room temperature
for the Specim en 2 ....................... .................... ..................... .. ......4 1
3-8 Load-displacement curves of four-point bending tests at room temperature
for the Specimen 3........................................... ........... 41
3-9 Stress distribution for the 4-Pt bending simulation at (a) room temperature;
(b) cryogenic tem perature. ............................................. .............................. 43
3-10 Variation of K = -r^ with the distance from the crack tip at room temperature.......43
3-11 Logarithmic plot of the stresses as a function of distance from the crack-tip..........44
3-12 Cryogenic experimental setup of the four-point bending test................................45
3-13 Crack propagation in the 900 layer of a graphite/epoxy laminate at cryogenic
tem perature................................... ................................ ........... 45
3-14 Contour plot of stresses normal to ply direction near the free-edge in a
graphite/epoxy laminate at cryogenic temperature. ............................................46
3-15 Load-displacement curves from four-point bending tests at cryogenic
temperature. The mid-ply thickness and hence the specimen thickness varied
from specimen to specimen ............... ....................... .. ... ............... 46