The main goal of this study is the comparison of different reinforcement architectures on the low-velocity impact behavior of green composites. The study includes the comparison of unidirectional, basket weave, and twill weave flax/PLA composites, they are subjected to unidirectional tensile tests, drop-weight impact tests, and after-impact compression tests. Results show that the unidirectional composite demonstrates superior tensile strength and initial modulus due to reduced fiber crimp, while basket weave exhibits the highest energy absorption capability and strain capacity attributed to its higher fiber-weight ratio and fiber crimp. Unidirectional composite also shows a larger impacted damage area compared to basket weave and twill weave, attributed to its internal architecture. Residual compressive strength across all composites decreased by 40% compared to the reference sample. However, the reduction in stiffness after impact was different, UD/PLA composite stiffness was reduced by 30% while the reduction in BW/PLA and T/PLA composites was about 20%.
The interaction properties between natural fiber and matrix play an important role in the mechanical performance of composite materials. The adhesion properties and the mechanical interaction between an Ichu fiber (Stipa obtusa) treated with sodium hydroxide and a cementitious matrix were studied by conducting experimental, numerical, and analytical pull-out tests. Through the experimental tests, the force–displacement curve for a fiber length embedded 5 mm deep in the cementitious matrix, maximum force, cohesive parameters, and the type of interface failure were determined. The results were used to calibrate the numerical and analytical models for different lengths of fiber (3, 5, 7, 9, and 11 mm) embedded in the cementitious matrix. The numerical model was implemented in the finite element software Abaqus CAE, and the analytical formulation considered the fiber embedded in a half-space continuous medium. From the experimental test, the force–displacement curve, interfacial shear strength of 0.124 MPa, and the softening type slip were obtained, despite obtaining the hardening-type slip in certain tests. The numerical and analytical results of the load–displacement curve closely approximate the experimental results. This study provides a numerical and analytical model to simulate the alkali-treated Ichu fiber–cementitous matrix interface.
The durability of structural components under fatigue loading is a huge concern, especially in laminated composites. During the last few years, flax fibers have also gained an outstanding position as a reinforcement of biopolymeric matrices as polylactic acid (PLA). However, there is limited reported information regarding the fatigue behavior of unidirectional flax/PLA composites. Therefore, fatigue properties of unidirectional flax/PLA composites are evaluated in this work; tools such as infrared thermography and dissipated energy were used in order to establish the fatigue limit, and fracture surface was analyzed. Results show consistent and reliable tensile properties (σut = 234.4 MPa, E = 20.56 GPa, and εf = 0.0181). The fatigue stress-cycle curve was established and fitted to the Basquin and Weibull fatigue models and the fatigue limit (σ∞) was obtained as 0.4343 and 0.426 using the thermography and dissipated energy, respectively. Furthermore, the fatigue fracture surface presents a striation on the matrix due to the progressive crack propagation.
The aim of this study was to understand the role of the processing in determining the mechanical properties of glass fibre reinforced polybutylene terephth
Ichu and Cabuya were characterized and the effect of alkali treatment on the chemical and physical properties of these fibers was studied. This treatment was carried out to remove non-cellulosic components in order to improve the adhesion of these fibers to be used as reinforcing composites since they are currently being tested in polymer matrix composites. The chemical properties were investigated through TAPPI Standards and FTIR spectroscopy. The physical properties (microfibrillar angle and density) were analyzed through polarized light microscopy and a gas pycnometer, respectively. The results show that with this chemical treatment, it is possible to remove 53.9% of lignin and 22.7% of hemicellulose for Ichu fiber and 50.7% and 91.7%, respectively, for Cabuya. Besides, it was found that the microfibrillar angle is not affected by this chemical treatment since its effect is only superficial. In addition, SEM images show that Ichu fiber has amorphous silica particles in its surface, in which it becomes a potential fiber for cement composites.
Secondary aluminum swarf is a residue from the turning or drilling process that originates after the metal melting phase. It is a major problem in Peru bec
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Ichu: New Natural Fibers for Composites and its Extraction Methodology S. Mori, E. Flores, S. Charca Abstract. Natural fibers obtained from plants (vegetables) have been gaining great impulse in the last years, especially in the composites materials industry; besides, studies shows that the annual growth rate will be 10% in the coming years, which will […]
Natural fibers are a renewable resource that has become an economic alternative to replace synthetic fibers as reinforcement in composite materials. In this study, the aim was to characterize physical and thermal properties of the Andean Stipa obtusa and Jarava ichu leaves (grasses known as ichu) before and after the alkaline treatment. Energy dispersive spectrum identified external phytoliths on the surface of nontreated raw leaves. With the alkaline treatment, improvement on the thermal stability and increment in the crystalline index and size was observed. Additionally, raw leaves present a hydrophobic behavior; however, with the treatment this hydrophobicity was lost for Stipa obtusasignificantly but not for the Jarava ichu. Furthermore, low surface energy was observed for the nontreated raw leaves and increasing consistently for the treated fibers. According with these results, these grasses are quite interesting materials from which fibers can be extracted for engineering applications such as composite materials.
This study investigates the feasibility of substituting UHMWPE and steel with flax/PLA green composite in ballistic applications with the objective to increase sustainability and cost-effectiveness. Results reveal that flax/PLA composite exhibits significantly lower ballistic performance than UHMWPE due to its lower energy absorption capacity. However, hybrid panels where 33% of UHMWPE was replaced by biocomposite showed similar values of V50 than homogenous UHMWPE, suggesting potential for partial replacement without compromising ballistic performance. However, the hybrid panels of biocomposite and steel showed a ballistic limit much lower than pure steel. Analysis of scan results indicates distinct failure modes: UHMWPE exhibits viscoelastic deformation, biocomposites show local damage failure, and steel displays ductile behavior. These findings provide insights into the viability of hybridizing UHMWPE with biocomposites for eco-friendly ballistic applications.
This paper presents the fatigue limit of flax/PLA composites with different fiber reinforcement architectures. The configurations of the analyzed flax/PLA composites are [0°]8, [0°/90°]s, [+45°/−45°]s, [90°]4, stacking sequences, and basket weave laminates. The methods used to estimate the fatigue limit are the fitting of stress versus number of cycles data using Weibull and Basquin equations, the surface thermographic technique with bilinear and exponential models to analyze the evolution of temperature increment, and volumetric dissipated energy. According to the results found, superficial temperature and the maximum strain reached stabilization over 2000 cycles for σmax/σut < 0.7, which was used to determine cyclic stress–strain curves and the fatigue limit. The cyclic stress–strain shows a nonlinear behavior for all laminates, having a good correlation to the Ramberg–Osgood model. Furthermore, having the stabilized temperature and volumetric dissipated energy, the exponential model was used to evaluate the fatigue limit and compared to the values found by Basquin and bilinear models. The fatigue limit found by Basquin and bilinear models shows conservative values compared to the exponential models. The results also show that temperature measurement using infrared thermography is quite sensitive to the environmental temperature variation, especially at low stress applied, and finally, the comparison of these methods on different reinforcement configurations provides a guide to select a proper technique in each case.
Chemical Characterization for the Comparative Study of Peruvian Natural Fibers C. Tenazoa, S. Charca, M. Quintana, E. Flores Abstract. In recent years, natural fibers have acquired a fundamental role in the industry because, besides being available in great abundance, they are bio-renewable. These are mainly composed of lignin, cellulose and hemicellulose, which are natural polymers […]
Wave slamming was simulated by repeatedly slamming rectangular sandwich composite specimens mounted on a rigid wedge with constant deadrise angle onto the body of calm water at various energy levels. Under single slamming, peak pressures and strains on the specimens were consistently found near the keel, whereas the maximum damage was localized near the chine. Significant reduction in strength was observed resulting from a single slam even at a moderate slamming energy level that left no apparent/visible damage to the test panel. Similarly, a substantial reduction in strength was observed under repeated slamming at various energy levels. The results were corroborated with acoustic emission observations that indicated a substantial reduction in AE activity in slammed specimens. A methodology was developed for the quantitative assessment of remaining strength and damage accumulation in slammed specimens using AE technique. Face yielding and core crushing were found to be the dominant modes of failure.
