Progressive failure simulation in laminated composites under fatigue loading by using discrete damage modeling

Abstract

The discrete damage modeling method is extended for progressive failure analysis in laminated composites under fatigue loading. Discrete damage modeling uses the regularized extended finite element method for the simulation of matrix cracking at initially unknown locations and directions independent of the mesh orientation. A material history variable in each integration point is introduced and updated after each loading increment, corresponding to certain load amplitude and number of cycles. The accumulation of the material history variable is governed by Palmgren-Miner’s rule. Cohesive zones associated with mesh-independent cracks are inserted when the material history parameter reaches the value of 1. Cohesive zone model consistently describing crack initiation and propagation under fatigue loading without any assumption of initial crack size is proposed. The fatigue properties required for matrix failure prediction include shear and tensile S-N curves as well as Mode I and II Paris law parameters. Tensile fiber failure is assumed unaffected by fatigue. All input data required for model application are directly measured by ASTM tests except tensile fiber scaling parameter and compression fiber failure fracture toughness, which were taken from literature sources. The model contains no internal calibration parameters. Fatigue damage extent, stiffness degradation and residual tensile and compressive strength of IM7/977-3 laminates have been evaluated. Three different layups, [0/45/90/-45]2S, [30/60/90/-60/-30]2S and [60/0/-60]3S, were modeled and tested. The predictions captured most experimental trends and showed good agreement with X-ray CT damage assessment; however, significant further work is required to develop reliable methodology for quantitative composite durability prediction.

A cohesive XFEM model for simulating fatigue crack growth under mixed‐mode loading and overloading

“…For both models, this is solved through forcing the physical crack tip forward by setting the damage of the process zone element that is adjacent to the current physical crack tip equal to one . As a result, the FPZ decreases in size, as is shown in Figure .…”

“…In the first approach, the crack tip is forced forward and the amount of cycles required for this jump is computed by means of the Paris equation. In these models, the energy release rate (ERR) is computed by the J‐integral around the zero thickness interface elements or by using the local ERR extracted from the cohesive law of the most damaged point in the FPZ . Since the bulk material is not considered in this J‐integral, it can also be used to compute the ERR as a local driving force for propagation of a crack embedded in an elastic‐plastic bulk material.…”

An improved delamination fatigue cohesive interface model for complex three-dimensional multi-interface cases

“…For fatigue initiation, a stress based initiation model similar to the one proposed by Iarve et.al. [32] is modified and incorporated here. The initiation is applied only to elements that are in the linear elastic region.…”

Composites fatigue delamination prediction using double load envelopes and twin cohesive models

“…2b. Under fatigue loading, damage initiation is usually predicted by a failure criterion devised based on experimental S-N curves [16,19,20]; when the initiation criterion is satisfied, the mode I/II strength pair is scaled or reduced to zero [16,20]. Good agreement has been achieved in some cases, however, building up a thoroughly validated fatigue damage initiation approach is still a challenge, which becomes even more difficult due to the generally large scatter in experimental results [21,22].…”