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

Abstract

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". ...

Prediction of elastic anisotropic thermo-dependent properties of discontinuous fiber-reinforced composites

“…It can also be seen that there is a clear distinction of the stress levels, without any overlapping of the curves. This validates the proposed cutting pattern and leads to a high reproducibility for each configuration, higher than results in literature (21,22). Each configuration corresponds to a different average orientation tensor, with a particularly obvious difference for L1.…”

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

“…Increasing error in the low cycles (high loads) could be due to two reasons: the cumulative error during the micromechanics modelling increases as the applied load increases and second, it is possible that the assumptions made during the MSNC formulation are not valid in the low cycle fatigue region. This second possibility was confirmed by a statistical study of loss of stiffness curves presented in [29]. Finally the predictions of the ss-MSNC are compared and presented in Table 5.…”

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