Adhesion failure analyses of laminated FRP composite made bonded tubular T-joints with axially compressed brace

摘要

Laminated FRP composite bonded tubular T-joints with constrained chord-ends and compressively loaded brace has been considered in the present research for detailed adhesion failure analysis of the non-planar T-joint region. Computational fracture mechanics based APDL codes have been developed and validated with respect to literature. Three-dimensional stress analyses revealed that Saddle points corresponding to Bottom Toe Line (BTL)/Middle Fillet Line (MFL) in joint regions are predominantly vulnerable towards adhesion/cohesion failures, respectively. Adhesion failure predicted to be the cardinal factor behind joint fracture (over cohesion failure) using Tsai-Wu/Parabolic yield criteria. Strain Energy Release Rate (SERR) estimated through Virtual Crack Closure Technique (VCCT) has been used for quantifying fracture growth. Pre-embedded through-the-circumference adhesion failure (2 phi = 360 degrees) is primarily susceptible towards mode-I fracture about saddle points with saddle-crown-mid-points and crown points predisposed towards mode-III and mode-II fractures, respectively. Adhesion failures (2 phi = 180 degrees) are predominantly susceptible towards mode-I radial fracture growth (than circumferential fracture), leading to enhanced chances of adhesion and cohesion failures at Top Toe Line (TTL) and MFL, respectively. Quasi-isotropic ([90/ + 30/ -30/90](2s)), and cross-ply ([0/90](4s)) are the suggested optimum chord stacking sequences improving fracture resistance of joint against micro (a/f(b) = 0.3) and macro (a/f(b) 0.3) failure ranges.