A combined XFEM and cohesive zone model for composite laminate microcracking and permeability

Damage and permeability in tape-laid thermoplastic composite cryogenic tanks

“…8). The general XFEM-SCZM approach is implemented within an adapted form of the general purpose, non-linear finite element code, Abaqus v6.14, as is described in detail in previous work [35,36].…”

“…However, due to the complex thermo-mechanical load state present in the cryo-tank, the original method [36] has been improved here to incorporate a more sophisticated mixed-mode compression-shear matrix failure criterion. Oblique fracture planes aligned with the fibre angle are now permitted, along with the usual transverse microcracking perpendicular to the ply interface.…”

“…Two distinct methods of simulating random microcrack initiation within the cryo-tank, based on methods outlined in [36], are used. These methods have been adapted for use with the tapelaid CF/PEEK material described in Section 2.…”

“…Due to the lack of experimental data in the literature on the material, an inverse identification procedure was adopted to estimate the Weibull modulus of the material. Based on the tensile test geometry described in [36], successive tensile test simulations were performed, iteratively adjusting the Weibull modulus for a prescribed strength distribution until the predicted average bulk transverse stress at failure matched the measured value of 41 MPa. Fig.…”

“…Note that a limited distribution is used in simulations in order to prevent the material from having a transverse stren above 100 MPa, taken as the upper limit of physically realistic values. The second approach is based on a general elemental representation of defects whereby voids are represented via reduced element stiffness throughout the finite element mesh [36]. The purpose of this is to simulate the local inhomogeneity in stiffness within the composite material due to the presence of randomly distributed defects.…”