Effects of waviness on fiber-length distribution and interfacial shear strength of natural fibers reinforced composites

Abstract Natural fibers are not as rigid as glass or carbon fibers. During composites extrusion and injection molding, they tend to bend and twist in the polymeric matrix, thus resulting in fiber waviness and decreased mechanical properties of natural fiber composites. The most widely used models for the estimation of interfacial shear strength (IFSS) and elastic modulus, which consider the fiber aspect ratio and mechanical properties of the fiber and matrix, do not consider these important features. In order to account for fiber waviness, an effective fiber length is proposed in this paper. The undulation of the fibers is approximated with a sinusoidal arc along with a calculated new length. The proposed correction factor depends on the wavelength and amplitude of the wave approximating the fiber. To verify this method, blends of polylactic acid (PLA) and polycarbonate (PC) (prepared with and without an interchange reactions catalyst) with addition to various percentages of cellulosic fibers (5 wt%, 10 wt% and 15 wt%) have been prepared and characterized. It has been demonstrated that by considering the corrected length values, it is possible to predict the mechanical properties and the effective reinforcement attained in the composites by using the most widely used models. In particular, the prediction of the elastic modulus is slightly affected by this correction, whereas the calculation of IFSS is strongly dependent on it.

[1]  Norman A. Fleck,et al.  Compressive strength of fibre composites with random fibre waviness , 2004 .

[2]  F. Vilaseca,et al.  Determination of corn stalk fibers' strength through modeling of the mechanical properties of its composites , 2010, BioResources.

[3]  M. Misra,et al.  Sustainable Bio-Composites from Renewable Resources: Opportunities and Challenges in the Green Materials World , 2002, Renewable Energy.

[4]  M. Taya,et al.  A comparison between a shear lag type model and an eshelby type model in predicting the mechanical properties of a short fiber composite , 1987 .

[5]  Rodney Hill,et al.  Theory of mechanical properties of fibre-strengthened materials—III. self-consistent model , 1965 .

[6]  M Raspanti,et al.  Hierarchical structures in fibrillar collagens. , 2002, Micron.

[7]  J. C. H. Affdl,et al.  The Halpin-Tsai Equations: A Review , 1976 .

[8]  T. W. Clyne,et al.  A simple development of the shear lag theory appropriate for composites with a relatively small modulus mismatch , 1989 .

[9]  Isaac M Daniel,et al.  Elastic properties of composites with fiber waviness , 1996 .

[10]  Mpf Sutcliffe,et al.  Measurement of fibre waviness in industrial composite components , 2012 .

[11]  James Thomason,et al.  Interfacial strength in thermoplastic composites - at last an industry friendly measurement method? , 2002 .

[12]  M. Piggott,et al.  The effect of fibre waviness on the mechanical properties of unidirectional fibre composites: A review , 1995 .

[13]  James Thomason,et al.  Micromechanical parameters from macromechanical measurements on glass reinforced polypropylene , 2001 .

[14]  József Karger-Kocsis,et al.  Single-polymer composites (SPCs): Status and future trends , 2014 .

[15]  J. Thomason.  The influence of fibre length and concentration on the properties of glass fibre reinforced polypropylene: 5. Injection moulded long and short fibre PP , 2002 .

[16]  I. LeGrice,et al.  3‐Dimensional configuration of perimysial collagen fibres in rat cardiac muscle at resting and extended sarcomere lengths , 1999, The Journal of physiology.

[17]  H. L. Cox.  The elasticity and strength of paper and other fibrous materials , 1952 .

[18]  J. Wood,et al.  Measuring polymer composite interfacial strength , 2014 .

[19]  Andrzej K. Bledzki,et al.  Properties and modification methods for vegetable fibers for natural fiber composites , 1996 .

[20]  P. Fratzl,et al.  Fibrillar structure and mechanical properties of collagen. , 1998, Journal of structural biology.

[21]  Inderdeep Singh,et al.  Development and characterization of PLA-based green composites , 2014 .

[22]  Isaac M Daniel,et al.  Effects of material and geometric nonlinearities on the tensile and compressive behavior of composite materials with fiber waviness , 2001 .

[23]  John F. Mandell,et al.  Compression Strength of Carbon Fiber Laminates Containing Flaws with Fiber Waviness , 2004 .

[24]  F. Espinach,et al.  Estimation of the interfacial shears strength, orientation factor and mean equivalent intrinsic tensile strength in old newspaper fiber/polypropylene composites , 2013 .

[25]  G. Karami,et al.  Micromechanical study of thermoelastic behavior of composites with periodic fiber waviness , 2005 .

[26]  Kevin W Eliceiri,et al.  NIH Image to ImageJ: 25 years of image analysis , 2012, Nature Methods.

[27]  Isaac M Daniel,et al.  EFFECT OF FIBER WAVINESS ON STIFFNESS AND STRENGTH REDUCTION OF UNIDIRECTIONAL COMPOSITES UNDER COMPRESSIVE LOADING , 1996 .

[28]  P. Cinelli,et al.  Compatibilization and property enhancement of poly(lactic acid)/polycarbonate blends through triacetin-mediated interchange reactions in the melt , 2014 .

[29]  Yan Li,et al.  Determination of interfacial shear strength of white rot fungi treated hemp fibre reinforced polypropylene , 2009 .

[30]  Frank T. Fisher,et al.  Fiber waviness in nanotube-reinforced polymer composites-I: Modulus predictions using effective nanotube properties , 2003 .

[31]  R. Joffe,et al.  Evaluation of the apparent interfacial shear strength in short-flax-fiber/PP composites , 2012, Mechanics of Composite Materials.

[32]  Andrea Lazzeri,et al.  Reactively extruded ecocomposites based on poly(lactic acid)/bisphenol A polycarbonate blends reinforced with regenerated cellulose microfibers , 2017 .

[33]  Lin Yang,et al.  Molecular orientation of collagen in intact planar connective tissues under biaxial stretch. , 2005, Acta biomaterialia.

[34]  Balbir Singh Kaith,et al.  Cellulose-Based Bio- and Nanocomposites: A Review , 2011 .

[35]  M.J.A. van den Oever,et al.  Mechanical properties of short-flax-fibre reinforced compounds , 2006 .

[36]  M. G. Bader,et al.  On the re-inforcement of thermoplastics by imperfectly aligned discontinuous fibres , 1972 .

[37]  Eric Baer,et al.  Fibre-buckling in composite systems: a model for the ultrastructure of uncalcified collagen tissues , 1974 .

[38]  Michael R Wisnom,et al.  Variability, fibre waviness and misalignment in the determination of the properties of composite materials and structures , 2008 .

[39]  A. Kelly,et al.  Tensile properties of fibre-reinforced metals: Copper/tungsten and copper/molybdenum , 1965 .

[40]  F. Vilaseca,et al.  Mean intrinsic tensile properties of stone groundwood fibers from softwood , 2011, BioResources.

[41]  Long Yu,et al.  Polymer blends and composites from renewable resources , 2006 .

[42]  L. Lim,et al.  Processing technologies for poly(lactic acid) , 2008 .

[43]  Ghodrat Karami,et al.  Effective moduli and failure considerations for composites with periodic fiber waviness , 2005 .

[44]  Youssef Habibi,et al.  Polylactide (PLA)-based nanocomposites , 2013 .

[45]  F. Avilés,et al.  Fibre waviness and misalignment measurement of unidirectional glass/LPET commingled composites – Effect on mechanical properties , 2013 .

[46]  S. Ji,et al.  Refinements of shear-lag model and its applications , 1997 .

[47]  L. Kwac,et al.  Evaluation of elastic modulus for unidirectionally aligned short fiber composites , 2009 .

[48]  M. Starink,et al.  Shear lag models for discontinuous composites : fibre end stresses and weak interface layers , 1999 .