Visualization and Quantification of Stresses at the Ends of Short Fibers Embedded in Epoxy Resin

Abstract:

The photoelastic effect was used to visualize and quantify stresses at the end of fibers embedded in birefringent epoxy resin. A method was proposed allowing not to only quantify the differences in main principal stress for a single loading state, but to allow monitoring the evolution of local stress throughout the micro-mechanical experiment. It was found that the ends of fibers foster the formation of shear stresses which influence the principal stress distribution. Typically, star-shaped principal stress distributions were found at the ends of fibers. Finite Element simulations of the tests were in good agreement with the experimental evidence.

• Periodical: Key Engineering Materials (Volume 858)
• Pages: 66-71
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.858.66
• Online since: August 2020
• Authors: Michael May*, Holger Mohrmann, Hartwig Nahme
• Keywords: Carbon Fiber, Optical Microscopy, Photoelasticity, Polymer-Matrix Composites, Stress Concentration

References

[1] P. Pecas, H. S. H. Carvalho and M. Leite, Natural Fibre Composites and Their Applications: A Review, J Compos Sci, (2018).

[2] S. Joshi, L. Drzal, A. Mohanty and S. Arora, Are natural fiber composites environmentally superior to glass fiberreinforced composites?, Compos Part A - Appl S, pp.371-376, (2004).

DOI: 10.1016/j.compositesa.2003.09.016

[3] M. Sanjay, P. Madhu, M. Jawaid, P. Senthamaraikannan and S. P. S. Senthil, Characterization and properties of natural fiber polymer composites: A comprehensive review,, Journal of Cleaner production, pp.566-581, (2018).

DOI: 10.1016/j.jclepro.2017.10.101

[4] S. Kundalwal, Review on micromechanics of nano‐ and micro‐fiber reinforced composites,, Polymer composites, pp.4243-4274, (2018).

DOI: 10.1002/pc.24569

[5] M. May and D. Mohrmann, Micromechanical Modeling of Bio-Based Composites,, in Bio-Based Composites for High-Performance Materials - From Strategy to Industrial Application, W. Smitthiping, R. Chollakup and M. Nardin, Eds., Boca Raton, Fl, USA, CRC Press, 2015, pp.273-290.

DOI: 10.1201/b17601

[6] V. Bulsara, R. Talreja and J. Qu, Damage initiation under transverse loading of unidirectional composites with arbitrarily distributed fibers,, Compos Sci Technol, pp.673-682, (1999).

DOI: 10.1016/s0266-3538(98)00122-5

[7] C. Gonzalez and J. Llorca, Mechanical behavior of unidirectional fiber-reinforced polymers under transverse compression: microscopic mechanisms and modeling,, Compos Sci Technol, pp.2795-2806, (2007).

DOI: 10.1016/j.compscitech.2007.02.001

[8] M. May, M. Nossek, N. Petrinic, S. Hiermaier and K. Thoma, Adaptive multi-scale modeling of high velocity impact on composite panels,, Compos Part A - Appl S, pp.56-64, (2014).

DOI: 10.1016/j.compositesa.2013.11.015

[9] C. Sun and Vaidya, Prediction of composite properties from a representative volume element, Compos Sci Technol, pp.171-179, (1996).

[10] M. May, S. Kilchert and S. Hiermaier, 3D modeling of fracture in brittle isotropic materials using a novel algorithm for the determination of the fracture plane orientation and crack surface area,, Finite Elements in Analysis and Design, pp.32-40, (2012).

DOI: 10.1016/j.finel.2012.03.001

[11] R. Piggott, The Effect of the Interface/Interphase on Fiber Composite Properties,, Polymer Composites, vol. 8, no. 5, pp.291-297, (1987).

DOI: 10.1002/pc.750080503

[12] D. Brewster, Experiments on the depolarization of light as exhibited by various mineral, animal and vegetable bodies with a reference of the phenomena to the general principle of polarization,, Phils Trans, pp.29-53, 1815.

[13] D. Brewster, On the communication of the structure of doubly-refracting crystals to glass, murite of soda, flour spar, and other substances by mechanical compression and dilation,, Phil Trans, pp.156-178, 1816.

DOI: 10.1098/rstl.1816.0011

[14] F. Zhao, S. Hayes, E. Patterson, R. Young and F. Jones, Measurement of micro stress fields in epoxy matrix around a fibre using phase-stepping automated photoelasticity,, Compos Sci Technol, pp.1783-1787, (2003).

DOI: 10.1016/s0266-3538(03)00131-3

[15] F. Zhao, R. Martin, S. Hayes, E. Patterson, R. Young and F. Jones, Photoelastic analysis of matrix stresses around a high modulus saphire fibre by means of phase-stepping automated polariscope,, Compos Part A - Appl S, pp.229-244, (2005).

DOI: 10.1016/s1359-835x(04)00172-1

[16] F. Zhao, E. Patterson and F. Jones, Phase-stepping photoelasticity for quantifying the interfacial response in fibre composites at fibre-breaks,, Mat Sci Eng A - Struct, pp.83-87, (2005).

DOI: 10.1016/j.msea.2005.08.039

[17] F. Zhao, S. Hayes, E. Patterson and F. Jones, Phase-stepping photoelasticity for the measurement of interfacial shear stress in single fibre composites,, Compos Part A - Appl S, pp.216-221, (2006).

DOI: 10.1016/j.compositesa.2005.09.021

[18] Z. Liu, F. Zhao and F. Jones, Six image phased stepped photoelasticity for the quantification of the stress field around 25 µm reinforcing fibres,, Compos Sci Technol, pp.2039-2044, (2010).

DOI: 10.1016/j.compscitech.2010.07.011

[19] W. Tyson and G. Davies, A photoelastic study of the shear stresses associated with the transfer of stress during fibre reinforcement,, Brit J Appl Phys, pp.199-205, (1965).

DOI: 10.1088/0508-3443/16/2/313

[20] T. MacLaughlin, A Photoelastic Analysis of Fiber Discontinuities in Composite Materials,, J Composite Materials, pp.44-55, (1968).

DOI: 10.1177/002199836800200104

[21] F. Zhao and F. Jones, Thermal loading of short fibre composites and the induction of residual shear stresses, Compos Part A - Appl S, pp.2374-2381, (2007).

DOI: 10.1016/j.compositesa.2007.06.012

[22] B. Fiedler and K. Schulte, Photo-elastic analysis of fibre-reinforced model composite materials, Compos Sci Technol, pp.859-867, (1997).

DOI: 10.1016/s0266-3538(96)00177-7

[23] E. Andrews and M. Garnich, Stresses around fiber ends at free and embedded ply edges,, Compos Sci Technol, pp.3352-3357, (2008).

DOI: 10.1016/j.compscitech.2008.09.001

[24] H. Gross, F. Blechinger and B. Achtner, Handbook of Optical Systems - Volume 4: Survey of Optical Instruments, Weinheim: Wiley, (2008).

DOI: 10.1002/9783527699247

[25] I. Daniel and O. Ishai, Engineering of Composite Materials - second edition, New York: Oxford University Press, (2006).