The lead crack concept applied to defect growth in aircraft composite structures

Molent, L.; Forrester, Crystal

doi:10.1016/j.compstruct.2016.12.076

Cited by 25 publications

(11 citation statements)

References 18 publications

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“…Here it should be noted that, as first shown in [71], growth of the lead damage in the composites was again exponential.…”

Section: Impact Damagementioning

confidence: 95%

“…However, the lead damage growth history, which [71] defines as the growth history associated with the fastest growing damage, shows little apparent retardation. Further, as first shown in [71] for the growth of impact damage, the lead damage growth history is often nearly exponential in character. It will be shown that these observations for the FCG rate histories associated with the fastest growing (i.e.…”

Section: Aims Of the Present Papermentioning

confidence: 99%

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Delamination growth in polymer-matrix fibre composites and the use of fracture mechanics data for material characterisation and life prediction

Jones

Kinloch

Michopoulos

et al. 2017

Composite Structures

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The growth of delaminations in polymer-matrix fibre composites under cyclic-fatigue loading in operational aircraft structures has always been a very important factor which has the potential to significantly affect the service-life of such structures. The recent introduction by the Federal Aviation Administration (FAA) of a 'slow growth' approach to the certification of composites has further focused attention on the experimental data and the analytical tools needed to assess the growth of delaminations under fatigue loads. Specific attention is given to the test and data-reduction procedures required to determine a 'valid' rate of fatigue crack growth (FCG), da/dN, versus the range of the energy release-rate, ΔG, (or the maximum energy release-rate, G max , in a cycle) relationship (a) to characterise and compare different types of composites, and (b) for designing and lifing in-service composite structures. Now, fibre-bridging may occur behind the tip of the advancing delamination and may cause very significant retardation of the FCG rate. Such retardation effects cannot usually be avoided when using the Mode I double-cantilever beam test to ascertain experimentally the fatigue behaviour of composites, so that a means of estimating a valid (i.e. ideally a 'retardation-free' or, at least, a very low-retardation) relationship is needed. The present paper presents a novel methodology, that is based on a variant of the Hartman-Schijve equation, to ascertain a valid, 'retardation-free', upper-bound FCG rate curves.

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“…Here it should be noted that, as first shown in [71], growth of the lead damage in the composites was again exponential.…”

Section: Impact Damagementioning

confidence: 95%

Section: Aims Of the Present Papermentioning

confidence: 99%

Delamination growth in polymer-matrix fibre composites and the use of fracture mechanics data for material characterisation and life prediction

Jones

Kinloch

Michopoulos

et al. 2017

Composite Structures

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“…in [2,[40][41][42][43][44] it has been shown that the fastest growing, i.e. lead, delaminations that arise under the cyclic-fatigue loading of aircraft components with mis-drilled holes, ply drop-offs, impact damage, manufacturing defects, etc.…”

Section: Introductionmentioning

confidence: 99%

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

Yao

Alderliesten

Jones

et al. 2018

Composite Structures

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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 composite components and structures reveal that no, or only little, retardation of the fatigue crack growth (FCG) rate occurs as delamination/impact damage grows. Therefore, of course, the FCG data that are ascertained in laboratory tests, and then employed as a material-allowable property to design and life the structure, as well as for the development, characterisation and comparison of composite materials, must also exhibit no, or only minimal, retardation. Now, in laboratory tests the double-cantilever beam (DCB) test, using a typical carbon-fibre reinforced-plastic (CFRP) aerospace composite, is usually employed to obtain fracture-mechanics data under cyclic-fatigue Mode I loading. However, it is extremely difficult to perform such DCB fatigue tests without extensive fibre-bridging developing across the crack faces. This fibre-bridging leads to significant retardation of the FCG rate. Such fibre-bridging, and hence retardation of the FCG, is seen to arise even for the smallest values of the pre-crack extension length, a p-a 0 , that are typically employed. The results from the DCB tests also invariably exhibit a relatively large degree of inherent scatter. Thus, a methodology is proposed for predicting an 'upper-bound' FCG curve from the laboratory test data which is representative of a composite laminate exhibiting no, or only very little, retardation of the FCG rate under fatigue loading and which takes into account the inherent scatter. To achieve this we have employed a novel methodology, based on using a variant of the Hartman-Schijve equation, to access this 'upperbound' FCG rate curve, which may be thought of as a material-allowable property and which is obtained using an 'A basis' statistical approach. Therefore, a conservative 'upper-bound' FCG curve may now be calculated from the DCB laboratory test data for material development, characterision and comparative studies, and for design and lifing studies.

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“…Advanced composites are increasingly being used in many applications [1][2][3][4]. However, the prognosis of their long-term behavior is still an active area of research.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Impact Localization in Composite Plate Using Newly Developed Imaging Method

et al. 2018

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This paper focuses on impact localization of composite structures, which possess more complexity in the guided wave propagation due to the anisotropic behavior of composite materials. In this work, a composite plate was manufactured by using a compression molding process with proper pressure and temperature cycle. Eight layers of woven composite prepreg were used to manufacture the composite plate. A structural health monitoring (SHM) technique was implemented with piezoelectric wafer active sensors (PWAS) to detect and localize the impact on the plate. There were two types of impact event that were considered in this paper (a) low energy impact event (b) high energy impact event. Two clusters of sensors recorded the guided acoustic waves generated from the impact. The acoustic signals were then analyzed using a wavelet transform based time-frequency analysis. The proposed SHM technique successfully detected and localized the impact event on the plate. The experimentally measured impact locations were compared with the actual impact locations. An immersion ultrasonic scanning method was used to visualize the composite plate before and after the impact event. A high frequency 10 MHz 1-inch focused transducer was used to scan the plate in the immersion tank. Scanning results showed that there was no visible manufacturing damage in the composite plate. However, clear impact damage was observed after the high-energy impact event.

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The lead crack concept applied to defect growth in aircraft composite structures

Cited by 25 publications

References 18 publications

Delamination growth in polymer-matrix fibre composites and the use of fracture mechanics data for material characterisation and life prediction

Delamination growth in polymer-matrix fibre composites and the use of fracture mechanics data for material characterisation and life prediction

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

Experimental Investigation of Impact Localization in Composite Plate Using Newly Developed Imaging Method

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