Mode I fatigue delamination growth in composite laminates with fibre bridging

Advanced composite materials have been commonly used in aerospace engineering, because of their good mechanical properties and attractive potential for creating lightweight structures. Susceptibility to delamination is one of the most important issues in the applications of these materials. This disadvantage can prohibit the application of...

Fatigue crack propagation and delamination growth in Glare

Fibre Metal Laminate Glare consists of thin aluminium layers bonded together with pre-impregnated glass fibre layers and shows an excellent fatigue crack growth behaviour compared to monolithic aluminium. The fibres are insensitive to the occurring fatigue loads and remain intact while the fatigue cracks occur in the aluminium layers. As a...

Fatigue life prediction and strength degradation of wind turbine rotor blade composites

Wind turbine rotor blades are subjected to a large number of highly variable loads, but life predictions are typically based on constant amplitude fatigue behaviour. Therefore, it is important to determine how service life under variable amplitude fatigue can be estimated from constant amplitude fatigue behaviour. A life prediction contains...

Mixed-Mode Fatigue Disbond on Metallic Bonded Joints

Aerospace structures have been long dealing with the safety versus weight issue. Lighter airplanes are cheaper to operate, however, they may face a safety issue because of the reduced fatigue life. Consequently, a heavier/safer structure is designed. Adhesive bonding is a joining technique that offers potential for improvement in the fatigue...

An experimental and analytical investigatin on the fatigue behaviour of fuselage riveted lap joints

Subsurface fatigue crack growth in Glare fibre metal laminates

The investigation of the present thesis is concerned with the fatigue crack growth behaviour of part through the thickness cracks in Glare™ fibre metal laminate (FML) subjected to combined tension and bending. An experimental program was executed which required the development of a novel fatigue specimen, the Milled Open Hole Tension Bending ...

Stress analysis of fatigue cracks in mechanically fastened joints: An analytical and experimental investigation

The two historical fuselage failures, Comet in 1954 and Aloha in 1988, illustrate that similar accidents must be avoided which requires a profound understanding of the fatigue mechanisms involved, including analytical models to predict the fatigue behavior of riveted joints of a fuselage structure. The scope of the research project covers a...

On the relationship between disbond growth and the release of strain energy

Current prediction methods for growth of disbonds under fatigue loading are generally based on a correlation with either the maximum strain energy release rate (SERR) or the SERR range. This paper highlights some issues with this approach. In particular, it is argued that the maximum SERR or the SERR range alone do not give sufficient...

Towards Understanding Fatigue Disbond Growth via Cyclic Strain Energy

The concept of relating fatigue disbond growth to the strain energy release rate (SERR) is critically examined. It is highlighted that the common practise of using only the maximum SERR or only the SERR range is insufficient to correctly characterize a load cycle. As crack growth requires energy, it is argued that growth should be related to the...

Methods for the prediction of fatigue delamination growth in composites and adhesive bonds: A critical review

An overview is given of the development of methods for the prediction of fatigue driven delamination growth over the past 40 years. Four categories of methods are identified: stress/strain-based models, fracture mechanics based models, cohesive-zone models, and models using the extended finite element method. It is highlighted that most models...

Increased Energy Yield using the Smart Rotor: Sizing and Control of Trailing Edge Flaps on a Smart Rotor for Maximum Power Generation in Low Fatigue Wind Regimes

Design of a lightweight FRP T-boom for an offshore gangway, and development of a fatigue model for prediction of its service life

The high stiffness to weight ratio of fibre reinforced composites have been utilized in improving the performance of various structures conventionally designed using metals. One such application is the gangway of the Ampelmann system used to transfer personnel safely from and to the offshore platform in sea. In the current work, a preliminary...

Preliminary fatigue analysis of anionic polyamide-6 composites

Thermoplastic blades offer a variety of advantages to the wind energy industry, but also a few major drawbacks. One of these is the weak fiber to matrix bond in traditional melt processed thermoplastic composites. Because fatigue is dependent on a strong interface, and it is a driving requirement for wind turbine blades, research has been...

Fatigue disbond growth in primary aerospace structures

A parametric finite element model incorporating virtual crack closure technique was developed in order to determine the critical disbond size and location for disbond growth in an adhesively bonded skin stiffened structure, subjected to uniaxial compression loading. The model was validated using static experimental tests on both pristine and...

Effect of fiber sizing on the fatigue properties of heavy tow carbon fiber composites

The carbon fiber industry is nowadays developing new grades of fibers that combine the high mechanical performance of carbon fibers in composites with more attractive cost structure. These developments are in the direction of heavy tow carbon fibers with tow values ranging from 50 to 60K. Using heavy tow carbon fibers reduces the cost structure...

Predicting fatigue crack initiation and propagation in Glare reinforced frames

The most highly loaded frames of the newly developed Airbus A400M transport aircraft have glass reinforced aluminium laminate (Glare) straps attached to them to increase their resistance to fatigue damage. These straps were designed using static strength requirements for the frame. Basic justification was done in two steps. Firstly, the frame...

Crack closure in Glare

The fatigue life of an aircraft is dependent on the loads of the aircraft service spectrum. Due to the variable nature of the load spectrum, fatigue crack growth is accelerated and decelerated by interaction effects. Interaction effects, like crack closure, make an accurate prediction of the fatigue life challenging. The material GLARE, a...

Delamination of Bonded Repairs: A Damage Tolerance Approach

A model was developed for delamination growth in bonded repair patches under constant amplitude fatigue loading. The model used the finite element method, employing the virtual crack closure technique, to determine the strain energy release rate (SERR) as a function of delamination length. Interaction effects between multiple delaminations, and...