A Novel Approach to Modeling Arbitrary Damage in Composite Structures through a Discontinuous Galerkin Cohesive Zone Model

Finite Element Methods (FEMs) are widely employed for damage simulation in composites, with the Cohesive Zone Model (CZM) being particularly favored for its robustness and scalability. Despite the CZM's mesh-dependent nature, the Discontinuous Galerkin Cohesive Zone Model (DG/CZM) formulation allows for relatively arbitrary crack propagation...

Modelling fatigue transition behaviour of FRP in mode I block loading

According to experiments the fatigue damage behaviour of fibre reinforced polymers (FRP) experiences a load sequence effect. In this report the ability of the cohesive fatigue damage model of Dávila (2020) to simulate the behaviour after a load amplitude change is investigated. For this a double cantilever beam (DCB) with fictitious material...

Surface Crack Growth in Metallic Pipes Reinforced with Composite Repair System

Surface cracks are serious threats to the structural integrity of offshore metallic pipes. This dissertation proposes a protocol of composite reinforcement on surface cracked metallic pipes subjected to cyclic loads, aiming to decrease the crack growth rate and prolong the residual fatigue life. The main objective of this dissertation is to...

Blunt Notch Behaviour of Stainless-Steel-CFRP Fiber Metal Laminates

Joining of aerospace structures has been accomplished using mechanical fasteners since the advent of flight. With the growing application of lightweight composite structures in aircrafts, joining methods involving fasteners have been under scrutiny. The lack of material plasticity and high notch sensitivity of composites in the presence of...

Fatigue life of post-buckled composite structures

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 adopted to analyze the behavior of a single-stringer composite specimen with an...

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....

Durability of stiffened CFRP panels with initial delaminations

A numerical fatigue delamination model is validated by means of experimental tests. Delamination is initiated on the skin-stiffener interface which, under cyclic compressive loading and in the post-buckling regime, grows at a decreasing rate. A cohesive zone formulation is used to model the static and fatigue delamination growth, good agreement...

High Order Adaptively Integrated Cohesive Elements: Development, implementation and testing on composite delamination

Composite delamination represents one of the most critical failure mechanisms occurring in composite structures. In case complex structures are being designed, numerical methods need to be employed. One of the methods to numerically simulate delamination in a Finite Element environment is through the employment of the Cohesive Elements, which...

Application of fracture mechanics in a blended numerical framework for progressive damage analysis of CFRPs in FEM

Composite structures are increasingly applied for their unique set of properties. However, their behavior is not yet fully understood, amongst others, due to complex interactions of failure modes. This research implemented a blended stress-strain and fracture mechanics based progressive damage analysis model, based on a Continuum Damage Model ...

Progressive damage modelling of FRPs using a blended stress-strain and fracture mechanics approach in FEM

Despite great strides made in understanding and modelling Fiber-Reinforced Polymers (FRPs), their full potential is held back by the inability to accurately predict failure. Contrary to past attempts focused on isolated application of stress-strain and fracture mechanics based failure theories, this research builds upon the existing framework by...

Numerical modelling of dowelled connections in Laminated Veneer Lumber

The complex mechanical behaviour of timber makes it hard to predict the failure modes in connections made of timber in Finite Element Models (FEM). The combination of various failure modes (brittle and ductile) , anisotropic behaviour, contact of steel elements and large deformations that can occur in a timber joint challenges the use of FEM. To...