Effects of thickness and fiber volume fraction variations on strain field inhomogeneity

Jensen, Eric M.; Leonhardt, David; Fertig, Ray S.

doi:10.1016/j.compositesa.2014.11.019

Cited by 25 publications

(11 citation statements)

References 14 publications

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“…Previously, it has been shown that thickness variation exists in laminates such as the ones used for this study. 19 This thickness variation leads to stress and strain inhomogeneity in the composite. This strain inhomogeneity is exacerbated by creep deformation as illustrated by the two dimensional strain field measurements in Figure 6 scenario as steps were taken to minimize this in future samples used for the open hole tests.…”

Section: Resultsmentioning

confidence: 99%

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Combined Multiscale Creep Strain and Creep Rupture Modeling for Composite Materials

Jensen

Fertig

2015

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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In this study, a novel multiscale combined creep strain and creep rupture model is proposed. By comparing to experimental data it was shown that the model provides accurate creep rupture predictions for unidirectional off-axis specimens. The creep strain model provides accurate predictions within the confines of the linear elastic restrictions used in its development. This creep strain and creep rupture model was incorporated into a progressive failure finite element simulation so that the effects of load redistribution could be considered, which tended to increase the life of the part. The finite element implementation also allowed for the consideration of realistic geometries resulting in complex stress states. By considering a perfectly flat specimen and one containing worst case thickness variation the experimental open hole creep rupture data was bounded. This suggests that by quantifying material defects realistic lifetime predictions can be made and an estimate of scatter can be acquired.

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Section: Resultsmentioning

confidence: 99%

“…Strain was measured using foil resistance strain gages and an in house digital image correlation (DIC) system. 19 The DIC technique also allows for the measurement of two dimensional strain fields on the surface of the specimens. Tension and compressions tests were performed according to ASTM D3039 and ASTM D3410.…”

Section: Model Calibrationmentioning

confidence: 99%

Combined Multiscale Creep Strain and Creep Rupture Modeling for Composite Materials

Jensen

Fertig

2015

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

Self Cite

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“…This is mainly due to ply waviness induced into the plies surrounding the defect ply. A study on the effect of thickness and fiber volume fraction variations on strain field inhomogeneity under transverse load was done in [4]. In this study it was found that a strain inhomogeneity of up to 10 % is possible for fiber volume fraction variations in a flat part.…”

Section: Introductionmentioning

confidence: 94%

The effect of ply folds as manufacturing defect on the fatigue life of CFRP materials

Hörrmann¹,

Adumitroaie²,

Schagerl³

2016

Frattura Ed Integrità Strutturale

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ABSTRACT. Manufacturing defects are inherent to any manufacturing process. However, in composite materials they might be unavoidable, e.g. ply waviness or even folds of plies are present in complex shaped parts during high pressure resin transfer molding of carbon fiber reinforced polymers. In this work, the effect of the ply folds on the fatigue life of the composite material is investigated. Folds along fiber direction (as they commonly appear during manufacturing) were artificially introduced in unidirectional non crimp fabric plies. The target of this study is the prediction of damage initiation due to this particular type of manufacturing defect. The folds locally increase the fiber volume fraction and also introduce resin rich areas. Fatigue tests in fiber direction and transverse to fiber direction are performed at different load ratios under constant amplitude loading. The influence of the defect geometry on damage initiation and progression is investigated at different scales by non-destructive methods before testing, continuous strain measurement and monitoring the damage progression during testing and fractography analysis after final failure. Most of the time, the first damage was observed at the location of the introduced fold for all considered load cases. However, it was also found, that the folds lead to no significant reduction in fatigue life. KEYWORDS. Manufacturing defects; CFRP; Fatigue damage, Fold.Citation: Hörrmann, S., Adumitroaie, A., Schagerl, M., The effect of ply folds as manufacturing defect on the fatigue life of CFRP materials, Frattura ed Integrità Strutturale, 38 (2016) 76-81.

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“…Whereas the aforementioned publications mainly concentrate on coupling effects, the influence of ply level uncertainties on reliability and failure is investigated in [16] and [19]. The different considered mechanisms of ply thickness variations in [16] show how complex the concentration on one scale Table 1 Exemplary parameters subject to uncertainties classified to the containing scale in accordance with [7,9,[11][12][13][14][15][16][17] is. The variation of thickness can be subdivided to fibre dominated or matrix dominated variation.…”

Section: Uncertainty Quantification In Endless Fibre Reinforced Plasticsmentioning

confidence: 99%

Tolerance management during the design of composite structures considering variations in design parameters

Franz¹,

Schleich²,

Wartzack³

2021

Int J Adv Manuf Technol

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Composite structures play an important role in realising resource-efficient products. Their high lightweight potential and improved manufacturing technologies lead to an increased use in high-volume products. However, especially during the design and development of high-volume products, the consideration of uncertainties is essential to guarantee the final product quality. In this context, the use of modern lightweight materials, such as fibre reinforced plastics (FRP), leads to new challenges. This is due to their high number of design parameters, which are subject to deviations from their nominal values. Deviating parameters, e.g. ply angles and thicknesses, influence the manufacturing process as well as the structural behaviour of a composite part. To consider the deviating design parameters during the design process, a new tolerance optimisation approach is presented, defining tolerance values for laminate design parameters, while ensuring the functionality of the composite structure. To reduce the computational effort, metamodels are used during this optimisation to replace finite element simulations. The proposed approach is applied to a use case with different key functions to show its applicability and benefits.

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Effects of thickness and fiber volume fraction variations on strain field inhomogeneity

Cited by 25 publications

References 14 publications

Combined Multiscale Creep Strain and Creep Rupture Modeling for Composite Materials

Combined Multiscale Creep Strain and Creep Rupture Modeling for Composite Materials

The effect of ply folds as manufacturing defect on the fatigue life of CFRP materials

Tolerance management during the design of composite structures considering variations in design parameters

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