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This study investigates the hygrothermal aging effect on the tensile and impact behavior of flax/PLA biocomposites. Specimens underwent up to four weeks of conditioning at 40°C in a climate chamber with water. Analysis covered porosity, moisture diffusibility, and transversal microstructure, enabling assessment of tensile strength, tensile modulus, and impact performance in relation to moisture uptake and fiber orientation. The study of tensile properties revealed that at approximately 12% moisture content, stiffness and yield stress decrease, while strength remains constant. Moisture diffusivity is higher in warp and weft yarn directions than the out‐of‐plane direction. Tensile testing at environmental equilibrium moisture reveals greater stiffness in the weft direction, correlated with lower crimp percentage and yarn angle. The main contribution of the paper is the study of the influence of moisture on the impact behavior, the results show that energy absorption capability of flax/PLA biocomposite increases with moisture content. Highlights: Fully biodegradable composite material by heat‐compression molding subjected to hygrothermal aging conditions for up to four weeks.The moisture diffusivity in both the warp and weft yarn directions registered higher values in comparison to the out‐of‐plane direction.Tensile testing at environmental equilibrium moisture revealed that the stiffness in the weft direction presented higher values.At 12% of moisture uptake, the stiffness and yield stress reached their lowest values, while strength remained constant.However, the low‐velocity impact properties of the composites exhibited improvement with moisture. [ABSTRACT FROM AUTHOR]

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%. [ABSTRACT FROM AUTHOR]

The objective of this work is to analyze the influence of the cross-section of a bumper beam made of fully biodegradable composites. Flax/PLA bumper beams were manufactured with four types of cross-sections with different degree of roundness. Specimens were subjected to low velocity impacts and the post-impact behavior is evaluated under three-point bending tests. Results indicate that different cross-sections can be selected if the objective is to maximize the impact performance or the post-impact residual properties. The bumper beam with the higher roundness exhibits the best impact performance, while an intermediate section exhibits the best after impact residual mechanical properties. [ABSTRACT FROM AUTHOR]

This work analyses the buckling behaviour of cracked Euler–Bernoulli columns immersed in a Winkler elastic medium, obtaining their buckling loads. For this purpose, the beam is modelled as two segments connected in the cracked section by a mass-less rotational spring. Its rotation is proportional to the bending moment transmitted through the cracked section, considering the discontinuity of the rotation due to bending. The differential equations for the buckling behaviour are solved by applying the corresponding boundary conditions, as well as the compatibility and jump conditions of the cracked section. The proposed methodology allows calculating the buckling load as a function of the type of support, the parameter defining the elastic soil, the crack position and the initial length of the crack. The results obtained are compared with those published by other authors in works that deal with the problem in a partial way, showing the interaction and importance of the parameters considered in the buckling loads of the system. [ABSTRACT FROM AUTHOR]

This paper focuses on the analysis of drilling induced damage on biocomposites (woven fibers of cotton, flax and jute combined with polylactic acid, PLA, as the matrix). The main contribution of this work is the analysis of the influence of cutting parameters and drill geometry on fully biodegradable composites based on two different types of PLA and different fibers types. The damaged area was studied both at the hole entry and exit. Contrary to the behavior commonly observed when drilling conventional composites, delamination was negligible. The hole entry and exit damage were analyzed and quantified in terms of the fraying extension being the dominant. The damage extension was found to be dependent on the matrix, fiber type and drill geometry. The combination between cotton fiber and the small drill point angle showed the lowest level of damage. On the other hand, composite reinforced with flax fibers (those that exhibited the highest tensile strength) presented the greatest damage extension, increasing with the number of layers of the composite. The matrix based on polymer 10361D PLA, recommended for natural fibers because of the better interface cohesion, resulted in reduced fraying. Concerning the influence of cutting parameters, damage decreased when increasing the cutting speed and feed rate. [ABSTRACT FROM AUTHOR]

This paper focuses on the numerical analysis of the ballistic performance of Kevlar®-29 under impact of different double-nosed stepped cylindrical projectiles. Numerical modelling based on finite element method was carried out in order to predict the failure mode of the target as well as the ballistic limit. A detailed analysis of the ballistic limit, failure mode and deformation of the targets due to impact of double-nosed projectiles was developed, discussed and compared with those involved in penetration of single-nosed flat and conical projectiles. Significant influence of the projectile geometry was demonstrated: the lowest ballistic limit was obtained with the conical–conical nose shape projectiles. [ABSTRACT FROM AUTHOR]

This study focuses on the analysis of influence of temperature and bolt torque on aeronautical joint behavior. A single-lap joint, according to ASTM D5961, with a titanium bolt and composite plates was considered. A numerical model based on FEM was developed to evaluate the stress in both bolt and composite plates. Load—displacement curves, stress fields, and induced damage showed, significantly, the influence of temperature combined with torque level on the joint. It was found that in the plate, both maximum and minimum levels of torque considered produced damage above critical threshold. This fact should be accounted for, during the design process of the joint. [ABSTRACT FROM AUTHOR]