Damage analysis of composites reinforced with Alfa fibers: Viscoelastic behavior and debonding at the fiber/matrix interface

Abstract

In this article, we first review state‐of‐the‐art experimental techniques and measurements to characterize the mechanical properties of anisotropic vegetal alfa fibers, epoxy‐resin, and the behavior of the interphase between the matrix and alfa fibers. Second, we conduct experimental tests to determine the mechanical properties of fibers, resin, and the interphase. Third, we carry out a series of finite element simulations to predict damage initiation and to estimate crack propagation in alfa‐fiber/epoxy‐resin (AFER) composites. Different tests to determine the longitudinal Young's modulus of alfa fibers and epoxy resin as well as nanoindentation tests to obtain the transverse stiffness of the fibers are presented. Experimental results from the characterization are introduced in a micromechanical model to estimate, using the concept of the energy release rate (ERR), the matrix crack, and its interaction with interfacial debonding. The wettability problems in the preparation of vegetable composites and their effect on fiber‐matrix interfacial debonding are also addressed. The analysis of the damage behavior of AFER composites demonstrates that under load transverse to the fiber axis, a crack initiated in the matrix is propagated perpendicular to the direction of the load. Near the interface, the ERR decreases and this energy is higher in the presence of interfacial debonding areas generated by problems of fiber wettability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43760.

Towards the design of high-performance plant fibre composites

“…These investigations are possible by nanoindentation and were studied by Gindl and co-workers [381] on a large range of cellulose fibres; by comparing transverse nanoindentation modulus with tensile longitudinal ones, the authors observed a high and pronounced degree of mechanical anisotropy for these fibres. The same approach was used by Bourmaud and Baley on sisal and hemp fibres [69] and Khaldi et al [382] on alfa fibres. Despite the difficulty in sample preparation, this characterisation interestingly opens a window to an alternate, inverse method [383] to experimentally estimate the transverse stiffness of plant fibres.…”

“…Nanoindentation can be used to determine the longitudinal or transverse mechanical properties of natural fibres. The determination of the transverse modulus of plant fibres gives their stiffness anisotropy values as described previously [69,382]. Wei and Bhushan [385,386] performed nanoindentation tests on human hairs to point out the influence of structure, damage, treatments or soaking.…”

About the influence of temperature and environmental relative humidity on the longitudinal and transverse mechanical properties of elementary alfa fibers

“…In our study, the fibers were harvested in the region of El Bayed in western Algeria. The alfa fibers are extracted from the raw alfa stalks (Figure ) by various processes such as mechanical, chemical, and steam explosion methods . They are used, in the raw state for the artisanal manufacture of objects and in the extracted state in the paper industry.…”

Plant-Based Natural Fibre Reinforced Composites: A Review on Fabrication, Properties and Applications

“…Light weight but greater mechanical strength; lower manufacturing costs; resistance to fatigue and corrosion; and greater availability, renewability and biodegradability than synthetic fibres, are some of the major reasons for this increased demand of NFRCs [279][280][281][282]. The potential application areas have been increasing dramatically over the last few decades, including but not limited to the automobile, packaging, military, sports, medical, building and constructions sectors [279][280][281]. Among these, the applications of NFRCs are the most prevalent in the automobile industry, due to the requirements for eco-friendly lightweight materials and associated costs [9,13,55].…”