Effective anisotropic stiffness of inclusions with debonded interface for Eshelby-based models

International Journal of Fatigue

Paepegem

Verpoest

et al. 2016

Self Cite

Short fiber reinforced composite (SFRC) materials have a different fiber orientation distribution (FOD) at every point. The fatigue properties of SFRC are known to depend on the FOD.The Master SN curve (MSNC) method for predicting an SN curve for a given FOD based on the known SN curve for the reference FOD is used to predict the local SN curve of a SFRC component by relating the damage at the microscopic level to the macroscopic fatigue properties. A simplified version of MSNC method, which needs even less experimental input, uses an assumption of constant SN curve slope is also presented in this paper. The paper validates both variants of the MSNC method on three sets of experimental data on fatigue of short fiber composites and analyses their accuracy. It is demonstrated that the MSNC approach needs only one SN curve as input with no specific requirements to the fiber orientation of the test coupon. Test coupons could have either uniform fiber orientation in the thickness or a "skin core" orientation variation. Highlights: A method for generating local SN curves for short fiber composites is presented  Method is based on combination of manufacturing studies, tests and micromechanics  Slope of SN curve is found to be independent of fiber orientation distribution(FOD)  Only one SN curve is needed as input with no restriction on FOD of reference coupon

Section: Micromechanical Modellingmentioning

confidence: 99%

“…While for the other types of loading, simple stress redistribution rules have been developed. Expressions for the stress distribution for an inclusion with debonded interface scheme are presented in table 1, detailed derivations and FE validation of the proposed "EqBI" can be found in [32].…”

Section: Micromechanical Modellingmentioning

confidence: 99%

A feasibility study of the Master SN curve approach for short fiber reinforced composites

International Journal of Fatigue

Paepegem

Verpoest

et al. 2016

Self Cite

“…Using a combination of the Mori-Tanaka formulation [16] and an algorithm for treating fiber matrix debonding [17], this method predicts the local SN curve with only one SN curve as input. The approach was named the Master SN curve approach, in short the MSNC approach.…”

Section: *Manuscript Click Here To View Linked Referencesmentioning

confidence: 99%

A statistical treatment of the loss of stiffness during cyclic loading for short fiber reinforced injection molded composites

Composites Part B: Engineering

Paepegem

Verpoest

et al. 2016

Self Cite

Injection molded short fiber reinforced composites (SFRC) have different local fiber orientation distribution (FOD) at every point. SN curves of short fiber reinforced composites are known to depend on the fiber orientation distribution. Such materials also suffer from continuous loss of stiffness during cyclic loading. It is not known whether the loss of stiffness is different for SFRC with different FOD. A statistical analysis of the loss of stiffness curves is presented in this paper. Tension-tension fatigue experiments are performed and loss of stiffness is collected for every data point in the SN curve. A systematic method for comparing the loss of stiffness is developed. It is concluded that the difference in loss of stiffness curves for coupons of SFRC with different FOD is not statistically significant. Dear Editor,We, hereby submit revised version of article "A statistical treatment of the loss of stiffness during cyclic loading for short fiber reinforced injection molded composites" by the authors Atul Jain, Wim Van Paepegem, Ignaas Verpoest, Stepan V. Lomov to journal Composites Part B: EngineeringIn this paper, a new method to statistically compare the loss of stiffness curves is developed and sufficiently high number of experiments are performed to compare the loss of stiffness curves of short fiber reinforced composites. It is seen that the loss of stiffness curves are independent of the fiber orientation distribution in the short fiber reinforced composites.All the comments by all the referee have been addressed and described in the "answer to reviewer document".We declare that the content is not duplicated and not submitted to any other journal We thank the Referee for his continued interest in our work and for helpful comments that will greatly improve the manuscript and we have tried to do our best to respond to the points raised. The Referee has brought up some useful points and we appreciate the opportunity to clarify our research objectives and methods.As indicated below we have checked all the comments provided by the Referees and have made necessary changes accordingly to their indications. At the end of reply, wherever possible, we have indicated in bold the page number in text where change has been made.New text in the paper has been typed in red. Point 1: Influence of specimen extraction position (pag. 4)Profiles of the orientation tensor components over the thickness form process simulation are reported. An indication of the positions chosen for the plots of Fig.3a and Fig. 3b would be helpful for the reader. However, experimental evidence of FOD over the thickness is missing. Further, the influence of extraction position on mechanical properties is still not directly addressed. In view of this facts, it should be stated in the paper that "the FOD is uniform over the plate" is actually an assumption (supported by simulation) and that "extraction of specimens from different positions on the plate is a possible source of the scatter of quasistatic as well as fatigue strength". ...

“…It is known that the first mode of damage in SFRCs is fiber matrix debonding. There are multiple methods to calculate the onset of debonding, for example the Modified Coulomb criteria [22]. It can be shown that the stress at which onset of debonding occurs is much lower than the expected stress to failure for a SFRCs after a million cycles of loading.…”

Section: Theory and Formulation Of The Master Sn Curve Approachmentioning

confidence: 99%

“…In the proposed MSNC approach, the first cycle of loading is modelled by using the full MT formulation, which is chosen based on its predictive abilities for stresses in individual inclusions [24] and the degree of asymmetry in the predicted stiffness tensor is also rather limited when the MT formulation is applied to SFRCs [25]. Non-linear stress strain behavior of SFRCs during the first cycle of loading is modelled by accounting for fiber-matrix debonding and matrix non-linearity, which is described below.…”

Section: Theory and Formulation Of The Master Sn Curve Approachmentioning

confidence: 99%

The Master SN curve approach – A hybrid multi-scale fatigue simulation of short fiber reinforced composites

Composites Part A: Applied Science and Manufacturing

Veas

Straesser

et al. 2016

Self Cite