Residual Strength and Fatigue Lifetime of ... - Solid Mechanics

arising due to the junction between the insert and the core and to a slight unintentional mismatch
between the core and the insert thicknesses, see Hayman et al. (2007). The intact panels with
PMI core failed by a combination of shear crimping and global buckling, see Figures 3.14 (b)
and 3.14 (c). Figure 3.15 shows the debond propagation load vs. the debond diameter, in each
case the mean result for two or three specimen replicates is used. It appears that the debond
propagation load decreases significantly with increasing debond diameter.
Face sheet compression
failure
Figure 3.14: (a) Compression failure of a face sheet in an intact panel with H130 core (b)
global bucking and (c) shear crimping of intact PMI panels.
Failure load (kN)
500
400
300
200
100
0
(a)
Global buckling
0 50 100 150 200 250 300
Debond Diameter (mm)
3.15: Measured propagation load vs. debond diameter. Measured failure loads for the intact
panels can be identified for a debond diameter of 0 mm.
The theoretical compressive failure loads for the intact panels, based on the material compressive
strengths in Table 3.1, are shown in Table 3.4 together with the measured values. This table also
shows the load at which wrinkling of the face sheets and shear crimping is predicted for each
case. Wrinkling load of the face sheets is determined based on a formula proposed by Hoff et al.
(1945):
52
(b)
H130
H250
PMI
Shear crimping
(c)