Composites Part C Open Access最新文献

Individual Layer Fabrication (ILF) is a novel additive manufacturing process that was developed to create objects with high wood content and high mechanical strength. Here, thin and individually contoured wood composite panels are created via Binder Jetting and subsequent mechanical pressing. Like in Sheet Lamination, these panels are then laminated onto each other to create a three-dimensional object. With wood contents (more than 85 mass percent) and mechanical properties (more than 30 MPa flexural strength) on par with other engineered wood products like particle boards and plywood, the produced objects are well suited for the construction and furniture industry. To gain a deeper understanding of the process, the influence of processing parameters on the geometric and mechanical properties of the finished objects were investigated. As process parameters the amounts of adhesive and the pressing forces for both panel production and lamination were selected. It was discovered that the interaction between the amount of adhesive and the pressure used to produce the panels is highly relevant for the geometric properties. The three core mechanisms that are responsible for the mechanical properties of produced parts were identified and can be ranked in the following order: 1) the amount of adhesive in the panels binding the particles, 2) the density of the panels, 3) the amount of adhesive for laminating the panels.

There is a global emphasis on recycling and reuse of plastic waste. Despite constituting over one-third of the world's annual plastic production, only 10 % of polyethylene is recycled. This study explores the use of fused deposition modeling (FDM) to enable the recycling of industrial waste of low-density polyethylene (LDPE) blended with expanded polystyrene (EPS). Two LDPE/EPS ratios (50/50 and 70/30) were investigated, and two types of styrene-ethylene-butylene-styrene (SEBS) rubber were incorporated as compatibilizers. The mechanical, rheological, thermal, and morphological properties of these blends were analyzed to assess their printability. Results indicate that the use of SEBS enhances the mechanical properties, thermal stability, and morphological uniformity of the blends. Particularly, malleated SEBS exhibited superior compatibilizing ability, fostering strong interactions at the LDPE/EPS interface. The best blend, based on printability assessments, was the 50/50 LDPE/EPS ratio with a 5 wt% malleated SEBS. Consequently, this blend was extruded into feedstock filaments, and it was successfully printed via FDM. The proposed blends are anticipated to perform effectively in various applications and serve as a foundation for future development of wear-resistant materials. The outcomes of this study present a novel approach for upcycling LDPE waste while promoting sustainable FDM practices.

We propose and demonstrate a computational framework to obtain data-driven surrogate constitutive models capturing the mechanical response of anisotropic brittle solids displaying progressive anisotropic damage. We train the constitutive models on data obtained from the analysis of a volume element of a material of interest; the data is generated by a constitutive model for braided composites, displaying a complex anisotropic damage evolution progressively transitioning from transversely isotropic to orthotropic. Training involves imposing six-dimensional random strain histories on the physical model and recording the histories of stress, strain and homogenised stiffness matrix of the material, obtained by a set of linear perturbation analyses. Supervised machine learning and dimensionality reduction are applied to the data and a structure for a surrogate model is proposed. The surrogate predicts the evolution of the stiffness of the solid consequent to an arbitrary imposed six-dimensional strain increment, thereby calculating the corresponding increment in stress. The model displays high accuracy and is able to reproduce the homogenised material's response via simple neural networks.

With the rapid advancement in the manufacturing industry, there has been a massive rise in the demand for products made of fiber reinforced polymer composites as they have high stiffness and strength to weight ratios. They are widely used in the manufacturing of parts in aerospace and automobile industry. The manual draping process of prepreg on the mold is time intensive and requires a highly skilled worker to perform the task. Various techniques have been designed to automate the process of composite parts manufacturing using automated fiber placement (AFP), automated tape laying (ATL) and automated plies layup. These methods use robots equipped with an end effector designed to drape the prepreg. The system utilizes both single and multi-robot cells for the process of composites manufacturing. The aim of this paper is to review the techniques and strategies employed for conforming and grasping of prepreg. The paper will also delve into the process parameters that influence the composites manufacturing process and investigate the impact of correct and inaccurate selection of process parameters on the final product. The paper will also discuss the limitations, challenges and future prospects for automated composite part manufacturing.

Auxetic composite laminates, i.e. laminates with a NPR (Negative Poisson’s Ratio), are regarded as a promising solution to combat LVI (Low-velocity impact) delamination BVID (Barely visible internal damage) and ensuing property degradation, a cause for concern in aerospace components, mainly inflicted by fortuitous accidents during handling operations. In order to potentiate the auxetic effect through the minimization of the Poisson’s ratio, a thorough analysis of material properties and stacking sequences is required, as only a restricted domain of combinations can generate the desired effect, either in an IP (In-plane) or TTT (Through-the-thickness) configuration. This paper focuses on a MATLAB program developed for IP and TTT auxetic laminate design, based on the CLT (Classical Lamination Theory). Cases studies on NPR domain definition of C/E (Carbon/epoxy), G/E (Glass/epoxy) and hybrid C-G/E (Carbon-Glass/epoxy) laminates are presented. Moreover, the influence of fibre volume fraction on C/E and G/E laminates is analysed.

The selection of materials in the construction industry plays a pivotal role in advancing sustainability goals. Traditional materials derived from natural resources face inherent constraints linked to geographic limitation, growth time, and geometric inconsistency and therefore recent attention has shifted towards developing novel bio-based materials. Composites, offering varying properties and geometries, are becoming increasingly popular for customising materials for specific applications. Pultrusion, a technology for manufacturing linear fibre-reinforced composites, is a well-established and reliable method. This study delves into optimising pultrusion technology, which traditionally relies on synthetic fibres, by exploring the potential of natural alternatives, specifically hemp bast fibres. Additionally, it presents a customised formulation based on a plant-based resin and additives. This formulation is tailored for pultrusion to produce high-performance biocomposites for use as load-bearing components in structural applications, with an initial focus on bending structures. The study elaborates on the material composition and performance of these newly developed natural fibre pultruded profiles, showcasing their mechanical capabilities through rigorous experimentation and testing. The results demonstrate the material's mechanical capabilities showcasing a flexural strength of 260 MPa with a bending modulus of 21 GPa and a bending radius reaching 0.5 m. While this study focuses on the material formulation tested on laboratory-scale pultrusion, the findings will be later applied in an upscaled production at an industrial level, aiming to enhance overall sustainability in the construction industry.

In this study, lignin underwent chemical modification via acetylation of hydroxyl groups to enhance its interfacial connection with poly (lactic acid) (PLA). Further enhancement of the blend was attained by adding an impact modifier, Biomax Strong. Incorporating Biomax Strong into PLA-lignin blends resulted in improvements in material characteristics, particularly in impact strength and thermal stability. This blend exhibited a unique set of mechanical properties, characterized by a reduction in tensile modulus as well as an increase in ductility. This will allow a more versatile use of PLA in various applications. The observed improved impact strength highlights the synergistic effect of stress redistribution within the PLA matrix contributing to widespread applications of PLA based composites. This can clearly be observed for the compound containing PLA and 15 wt.% lignin, where the impact strength was approximately 15 kJ/m². With the addition of 5 wt.% impact modifier, the impact strength increased by 60 %, reaching approximately 25 kJ/m². This synergy effect reinforces the overall structure, improving the impact toughness behavior. The combination of Biomax Strong and lignin not only address the limitations of PLA but also introduces new opportunities for applications requiring a balance of impact strength, ductility, and thermal stability. These advancements indicate a promising future for composite materials in various applications.

Reducing vehicle weight is crucial for enhancing fuel efficiency and reducing emissions in transportation. Traditional composite materials offer improved energy absorption over metals yet are limited by brittleness. This study introduces an innovative approach, inspired by the mantis shrimp's natural defense mechanisms, to enhance the crashworthiness and energy absorption of composite structures, optimizing safety and performance. Utilizing a bio-inspired design, we developed corrugated Carbon Fiber Reinforced Polymer (CFRP) crash box structures, aiming to optimize their energy absorption capabilities and crash force efficiency (CFE) for potential applications in transportation safety. Through a series of quasi-static axial compression tests, the corrugated structures' performance was evaluated against traditional crash box designs. The experimental results demonstrate that the bio-inspired configurations improved crashworthiness characteristics. Strategic manipulation of layer numbers and corrugations led to superior CFE values, indicative of safer, more controlled collision behavior. The “7N-6L” configuration featuring seven corrugations with six layers of CFRP demonstrated the highest efficacy, achieving an optimal CFE of 1.08. This configuration demonstrated a Specific Energy Absorption (SEA) of 1.56 J/g and an Energy Absorption (E_a) of 42.56 J. Furthermore, compared to conventional steel crash boxes, the CFRP crash box with 7N-6L corrugated structure showcased competitive energy absorption capabilities with significantly reduced mass, absorbing 2850 J with a CFE of 0.91, nearly matching the ideal CFE and highlighting its superior lightweight performance. These results underline the potential of integrating bio-inspired designs to develop robust, lightweight structures for improved crashworthiness, paving the way for safer and more sustainable transportation solutions.

In this study, we examine to derive the solutions of effective elastic moduli and thermal expansion coefficient for composite materials containing ellipsoidal fillers oriented randomly in the material using homogenization theories, which are the self-consistent method and the Mori–Tanaka method. This analysis is carried out by micromechanics combining Eshelby’s equivalent inclusion method for each theory. The solutions for effective elastic moduli and thermal expansion coefficient obtained on each theory are expressed by common coefficients composed of both the physical properties of the constituents of the composite material and geometrical factors depending upon the shape of the fillers. Moreover, these solutions enable us to calculate effective elastic moduli and thermal expansion coefficient for composite materials that contain randomly oriented fillers of various shapes and physical properties. By taking the limit of eliminating the existence of the matrix for these solutions, we can derive effective physical properties of polycrystalline materials. Using the obtained solutions, we investigate the effects of the shape of the fillers on the effective elastic moduli and thermal expansion coefficient. As a result, we confirm that these effective properties fall within the lower and upper bounds, and find that a characteristic result appears when the shape of the fillers is flake or oblate. Through comparisons between the analytical and experimental results, we confirm the practical usability of the solutions obtained in this analysis. Furthermore, we determine originally the shape factor for the filler and can show that this factor has the potential to provide guidelines for the optimal design of filler shape to improve the effective elastic properties of materials.

This article deals with a detailed experimental study dedicated to the evaluation of the overall mechanical behaviour of a bio-based composite structure used in transportation industries. The sandwich structure is designed to increase the lightening, vibration damping, and composite recyclability. The considered materials consist of a Flax/Elium® laminate composite for skins associated with a balsa core. The sandwich structure was obtained using a one-shot liquid resin infusion process. Low-velocity impact tests were carried out on different sandwich configurations with the aim of characterizing the effects of the stacking sequence and the density and thickness of the core. Furthermore, an experimental comparative analysis was conducted involving two composite laminate types: Glass/Elium and Flax/Elium to enhance the specific behaviour of flax fibre composite to be used as skins in the sandwich structures. The impact tests were carried out at low velocities and at different levels of impact energy using a drop-weight test bench. Notable damage mechanisms have been identified, and a chronological sequence of their development has been suggested. Ultrasonic analyses using C-Scan imaging were applied to the opposite side of the impacted specimen. The research proves the efficient energy-absorbing capability of the biobased sandwich structure during impact. Finally, this study enables a deeper understanding of various parameters that influence the behaviour of sandwiches during low-velocity impacts, thereby facilitating more informed material selection for practical applications.