Modeling fatigue-driving delamination using a thick level set interface model

This paper presents a new discontinuous damage model for simulating fatigue-driven delamination in composites. Fatigue models commonly describe crack growth using the Paris law which provides the link between the energy released due to delamination and the crack growth rate. A core issue in implementing the Paris law is to accurately compute the...

Cohesive zone and level set method for simulation of high cycle fatigue delamination in composite materials

This paper deals with high cycle fatigue delamination in composite materials. The cohesive zone approach along with the level set method is used to simulate fatigue-driven delamination growth. The cohesive zone method is used for calculation of the energy release rate at the crack front because of its superiority over the virtual crack...

Mode I fatigue delamination growth with fibre bridging in multidirectional composite laminates

Fatigue delamination in multidirectional composite laminates was experimentally investigated in present study. Both the Paris relation and a modified Paris relation (with a new similitude parameter) were employed to interpret fatigue delamination with significant fibre bridging. The results clearly demonstrated that fatigue delamination was...

Acoustic Emission-Based Methodology to Evaluate Delamination Crack Growth Under Quasi-static and Fatigue Loading Conditions

The aim of this study was to investigate the applicability of acoustic emission (AE) technique to evaluate delamination crack in glass/epoxy composite laminates under quasi-static and fatigue loading. To this aim, double cantilever beam specimens were subjected to mode I quasi-static and fatigue loading conditions and the generated AE signals...

Fatigue crack propagation in composite laminates by a novel approach based on the S-N diagrams

This paper focuses on a novel numerical formulation based on cohesive elements and S-N diagram to simulate fatigue-driven delamination in composite laminates. The constitutive model adopts a two-parameters heuristic equation, which coefficients are evaluated using an idealization of the S-N diagram rather than the more commonly used Paris law....

Scrutinizing interlaminar fatigue loading cycle in composites using acoustic emission technique: Stress ratio influence on damage formation

Current models for delamination propagation prediction in fiber-reinforced polymer (FRP) composites exhibit limitations to explain the physics underlying the mechanisms of damage formation in fatigue. In order to contribute in this field, this research focuses on the study of damage development within a single loading cycle of FRP double...

Fatigue analysis of a post-buckled composite single-stringer specimen taking into account the local stress ratio

The fatigue life prediction of post-buckled composite structures represents still an unresolved issue due to the complexity of the phenomenon and the high costs of experimental testing. In this paper, a novel numerical approach, called “Min-Max Load Approach”, is used to analyze the behavior of a composite single-stringer specimen with an...

An adaptive floating node based formulation for the analysis of multiple delaminations under high cycle fatigue loading

A novel efficient numerical formulation for the analysis of multiple fatigue-driven delamination cracks is presented. A cohesive zone model is used in combination with an Adaptive Refinement Scheme (ARS) and an Adaptive Floating Node Method (A-FNM) element that refine the model effectively during the analysis. Novel techniques are proposed to...

Unfolding the Early Fatigue Damage Accumulation for Cross-ply Laminates

Fatigue damage of composite laminates has attracted considerable attention from research community and industry, in view that laminated structures are inevitable to suffer from fatigue loading during their service life. It is rather complicated to understand and explain, what governs the initiation, accumulation, interaction (synergy or...

Towards understanding residual strength and damage evolution in damaged composite laminates

Fibre reinforced polymer composites have found increasing use in aircraft structures. This means that fleet managers need damage assessment tools for such materials, in order to decide on appropriate sustainment strategies. Developing such tools is hindered by the difficulty of generalising from lab tests to predict the behaviour of full-scale...

Compression after impact fatigue damage growth in CFRP – what does no-growth really mean?

Impacts on carbon fiber reinforced composites (CFRP) can produce a complex internal damage comprising multiple delaminations, which is hard to detect from visual inspection. This situation is known as barely visible impact damage (BVID). Considering that every airplane faces several impacts during its operational life, and that the majority of...

Investigating apparent plateau phases in fatigue after impact damage growth in CFRP with ultrasound scan and acoustic emissions

In previous literature, a plateau phase in fatigue growth of impact delamination projected area in CFRP was found. Explaining this plateau phase still represents a knowledge gap. In the present work, echo-pulse and through thickness transmission ultrasonic scan inspections were combined with acoustic emission monitoring to explain this...

Experimental study of post-buckled single-stringer composite specimens under fatigue loads with different load levels and load ratios

This study aims at better understanding the damage tolerance of stiffened composite panels subjected to fatigue loads in the post-buckling regime. Ten single-stringer hat-stiffened specimens with an initial delamination between the skin and the stringer foot were manufactured, and then tested under quasi-static and fatigue loads in post...

Methods for the exclusion of the fibre bridging effect in composite structures under cyclic Mode I loading

In composite structures, delamination damage is typically the most common failure mechanism. Accurately characterizing the delamination behaviour of composite laminates is therefore crucial for predicting the fatigue safe-life of such structures. To this end, double-cantilever beam (DCB) composite specimens are used to measure the interlaminar...

Hygrothermal effects on fatigue delamination behavior in composite laminates

Fatigue delamination growth (FDG) is an important failure in composite structures during their long-term operations. Hygrothermal aging can have significant effects on interlaminar resistance. It is therefore really necessary to explore FDG behavior in composite laminates with hygrothermal aging. Dynamic mechanical thermal analysis (DMTA),...