Temperature effects on fatigue delamination behavior in thermoset composite laminates

Temperature can significantly affect fatigue delamination growth (FDG) behavior in composites, while fiber bridging has been frequently reported during FDG. The focus of this study was therefore on investigating temperature effects on FDG behavior with fiber bridging. Mode I fatigue delamination experiments were conducted on a thermoset...

Measurement of damage growth in ultrasonic spot welded joint

Ultrasonic spot welding is a joining technique for thermoplastic composites with great potential regarding processing speed and cost. To investigate the damage tolerance and possible inherent damage arresting behavior of multi-spot welded joints, a technique is necessary to measure damage growth in the joints under cyclic loading. Visual...

The energy dissipation during fatigue crack growth in metallic materials

An energy equation for fatigue crack growth was proposed. It equates the total external work per cycle (dW/dN) to the sum of plastic dissipation (dU_pl/dN), change in strain energy stored (dU_e/dN) and the energy dissipated in new crack surface formation (dU_a/dN). Fatigue crack growth experiment of 7075-T6 was...

The energy dissipation during fatigue crack growth in adhesive joints under Mode-I loading

An energy equation for fatigue crack growth in adhesive joints is proposed. Fatigue experiment on DCB adhesive joint specimens was used to derive the relation between fatigue crack growth rate (da/dN) and energy variables in this equation. The result shows plastic dissipation and change in stored strain energy, whose relation with da/dN both...

The relation between fatigue crack growth rate and plastic energy dissipation in 7075-T6

Plastic dissipation accompanies fatigue crack growth in ductile materials. Previous studies presented a relation between plastic dissipation (dW/dN) and the fatigue crack growth rate (da/dN), where some researchers assumed a linear relation between both to enable crack growth predictions. To study the validity of this assumption, this paper...

The effect of bond-line thickness on fatigue crack growth rate in adhesively bonded joints

The effect of adhesive thickness on fatigue crack growth in an epoxy film adhesive (FM94) was investigated, using a combination of experiments and numerical modelling. For the range of thicknesses investigated an increased thickness led to an increased crack growth rate. It was found that the energy required per unit of crack growth did not...

Fatigue in fibre metal laminates: The interplay between fatigue in metals and fatigue in composites

With the introduction of fibre metal laminates (FMLs) as a (fatigue) damage tolerant material concept in aeronautics, an interesting field emerged where fatigue damage interaction plays a dominant role. The hybrid concept effectively demands evaluating fatigue damage growth based on fracture phenomena typical for both metals and fibre...

Delamination fatigue growth in polymer-matrix fibre composites: A methodology for determining the design and lifing allowables

The introduction, originally in 2009, by the FAA of a ‘slow growth’ approach to the certification of polymer-matrix fibre composites has focused attention on the experimental data and the analytical tools needed to assess the growth of delaminations under cyclic-fatigue loads. Of direct relevance is the fact that fatigue tests on aircraft...

Using acoustic emission to understand fatigue crack growth within a single load cycle

Current methods for prediction of fatigue crack growth are based on empirical correlations which do not take the crack growth behaviour within a single cycle into account. To improve these prediction methods, more understanding of the physical mechanisms of crack growth is required. In this research the acoustic emission technique was used to...

The effect of temperature on fatigue crack growth in FM94 epoxy adhesive bonds investigated by means of energy dissipation

The effect of temperature on fatigue crack growth in epoxy adhesive bonds was investigated for a range of temperatures from -55 to 80[U+202F]°C. The fatigue crack growth behaviour was characterised using both strain energy release rate (SERR) and by measurements of energy dissipation. It was found that for a given maximum SERR, or a given...

On the physical interpretation of the R-ratio effect and the LEFM parameters used for fatigue crack growth in adhesive bonds

The available models for the prediction of fatigue crack growth in adhesive bonds rely on the similitude principle. In most cases, one of three similitude parameters based on the strain energy release rate (SERR) is used; i.e. G_max, (Δ√G)², or ΔG. In all cases it is usually observed that keeping the similitude parameter...

Characterising resistance to fatigue crack growth in adhesive bonds by measuring release of strain energy

Measurement of the energy dissipation during fatigue crack growth is used as a technique to gain more insight into the physics of the crack growth process. It is shown that the amount of energy dissipation required per unit of crack growth is determined by Gmax, whereas the total amount of energy available for crack growth in a single cycle is...

How proper similitude can improve our understanding of crack closure and plasticity in fatigue

The appropriateness of some common similitude principles with respect to describing and predicting fatigue damage propagation is discussed. Linear elastic fracture mechanics have provided a basis to describe damage growth using stress intensity factors or strain energy release rates, both related to the work of Griffith and Irwin. The fatigue...

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...

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...