P. Ganeshan et al., Experimental investigation of interfacial fracture parameters and crack initiation under mechanical and thermomechanical loading, J THERM STR, 22(6), 1999, pp. 615-634
Mechanically, and thermomechanically stressed interface cracks in adhesivel
y bonded bimaterials (PMMA-aluminum) with a large elastic and thermal prope
rty mismatch are experimentally studied The elasto-optic effects are mapped
as (sigma(x) + sigma(y)) contours in the PMAA halves and interfacial fract
ure parameters are estimated. Crack initiation under mechanical and thermom
echanical loading conditions are shown to be controlled by different microm
echanical processes. The results suggest that the micromechanical unlocking
of microcavities and microprotrusions along the interface is primarily res
ponsible for failure initiation under thermomechanical loading conditions.
This is unlike the mechanical loading situations wherein fracture toughness
is derived primarily from the breakage of interlocking microentanglements.
The measured values of the fracture parameter Delta Im(Ka(i epsilon))(T) d
ue to a temperature rise is a constant and much higher than its real counte
rpart (Delta psi(T)(a) approximate to 76 - 82 degrees). The Delta(Ka(i epsi
lon))(T)\(cr) thus obtained are much lower than the mechanical counterparts
.