Design Of Composite Components Research Articles

Finite element modelling of continuous fiber–reinforced composites produced by automated manufacturing

Abstract With the advent of automated, continuous filament placement technologies, the possibilities for reinforcement placement in composite manufacturing have been further expanded, as the reinforcement path can be continuously varied within the layer. This allows far more efficient structures to be created, resulting in a further reduction in the weight of the structure compared to conventional composites. At the same time, this manufacturing freedom also poses a major challenge for the structural design of composite components, as simulation methods based on meso-level homogenization are mostly not usable due to the lack of periodicity of the reinforcement structure. In our paper, we have established a structural modelling method using finite element analysis (FEA) for fused filament fabrication-based additive manufacturing of continuous fiber–reinforced composites. For modelling the reinforcement structure properly, we used the base-coordinate sweep (BCS) modelling method and for capturing progressive failure mechanisms we used Ansys LS-Dyna with the MAT54 material card. Based on the simulations and tests performed, we demonstrated that the method we present is suitable for the engineering modelling of continuous fiber–reinforced 3D printed composites.

On the use of double‐double design philosophy in the redesign of composite fuselage barrel frame components

AbstractThe use of optimization procedures can provide a valuable contribution in optimizing the laminate design of composite components for mass minimization and mechanical performance maximization. Design for weight and strength requirements of composite structures can be efficiently provided with the newly developed double‐double laminates concept, which allows to overcome the conventional 0, 90, and ±45° ply orientations and symmetry requirements in laminates. In the double‐double designed components, composite laminates are made up stacking thin sub‐laminates with four [±Φ, ±Ψ] oriented plies without symmetry requirements. In the present paper, the lay‐up and thickness profile of the composite frames in a fuselage section have been redesigned according to the double‐double design concept taking into account the operating loads. The starting quad configuration has been replaced by an optimized double‐double configuration with suitable lay‐up and thickness profile for each of the frames, while achieving a reduction in the total components mass.Highlights Double‐double laminates offer a novel approach to composite laminate design. Double‐doubles aim to simplify design with composites as with metals. Laminate optimization performed varying plies orientations and number. Double‐double design of components optimized with respect to the acting loads. In aviation double‐doubles allow lightening of composite laminate components.

Analytical stress analysis of the furan epoxy composite coatings subjected to tensile test

The presence of reliable techniques for predicting the stress state in composite materials is one of the most important requirements in the design of composite components and structures. An analytical model has been developed to evaluate the shear stresses at the substrate-coating interface in tensile testing of a flat specimen. The developed model has been verified by numerical simulation. The strength and mechanisms of the fracture of furan epoxy composite coatings with polyvinyl chloride and zinc oxide fillers with various concentrations were studied. The adhesion strength of furan epoxy composite coatings with metal substrate was determined by the pull-off test of cylindrical specimens and the tensile test of flat-coated specimens. The correlation between the measured values of fracture stresses for two types of tests of composite coatings was determined. It is concluded that for qualitative comparison of fracture stress in composite coatings it is possible to neglect stress concentration in the specimens. The analyzed methods of stress evaluation have the same trends in the change of the measured values for different composite coatings. However, considering the stress concentration in the specimens provides more accurate results in determining the strength characteristics.

Investigation on damage evolution of open-hole plain woven composites under tensile load by acoustic emission signal analysis

The open-hole structure has been concerned in the design of composite components, which inevitably brings about local damage and stress concentration with a substantial reduction in structural stability and strength of the resulting composites. In this paper, damage mode identification, damage initiation detection, and damage evolution analysis of open-hole plain woven composites (OHPWCs) under tensile load were investigated by acoustic emission (AE) signal analysis. The effect of the open-hole diameter on mechanical properties and failure mechanisms was assessed. The peak frequency ranges of typical failure modes were identified by k-means++ cluster analysis: matrix cracking [0-160 kHz], fiber/matrix debonding [160-220 kHz], fiber pull-out [220-300 kHz], and fiber breakage [300-450 kHz], respectively. Moreover, a novel concept of damage participation rate (DPR) was proposed based on AE count to characterize the contribution of different damage modes to the overall failure of the plain woven composites. The results showed that matrix cracking was the major proportion of damage modes in the damage evolution process of OHPWCs under tensile load and the DPR of the fiber breakage increases with the increase in the diameter of the OHPWCs.

Karakteristik Tegangan dan Regangan Tarik Pada Komposit CFRP Yang Berlubang

In the industrial world, the development of material technology is growing rapidly. There is an increasing demand for materials with certain properties such as perforated composites. The consideration of perforated composites is an important parameter in the design of composite components. The purpose of this study was to determine the tensile stress and strain characteristics of hollow CFRP composites. The research method used is to analyze the tensile test using abaqus software, the tensile test analysis is carried out with 3 variations in the diameter of the hole (2 mm, 4 mm, and 6 mm). From the tensile test simulation results, it is found that the highest stress occurs in the 6 mm diameter composite with a maximum stress value of 180.4 N/mm², and the lowest stress occurs in the 2 mm diameter composite with a maximum stress value of 102.6 N/mm². The highest stress and strain that occurs in each specimen is located on the edge of the hole perpendicular to the direction of the force, the stress and strain increase based on the diameter of the hole in the composite, the larger the diameter in the composite, the greater the stress that occurs..Keywords: Tensile test, CFRP composite, abaqus software

Elastic properties and multi-scale design of long carbon fiber nonwoven reinforced plane-based isotropic composite

Carbon fiber reinforced composite is considered as a potential substitutes used in the lightweight of automotive engineering. Nevertheless, the high price and complicated manufacturing process remain challenges for the large-scale application of conventional carbon fibers. In this study, a novel plane isotropic composite reinforced by long carbon fiber non-woven is introduced, which overcomes the obstacles in the application of carbon fiber at present. A multi-scale optimization method is proposed to realize the performance optimization and lightweight design of composite components. The linear elastic properties of long carbon fiber non-woven composite (LCFNC) were studied experimentally and analytically. The predictions of homogenization theory were found to be very similar to the experimental results within an interval of volume fraction. Then the relationship between microstructure and material performance was evaluated in detail. The results showed that there is a critical point for the influence of aspect ratio to the material properties. Thirdly, thickness of LCFNC at macro scales and the fiber parameters at micro scales were simultaneously optimized by Non-dominated sorting genetic algorithm-II (NSGA- II) to enforce multi-objective optimization design. Finally, the lightweight design of automobile hood was performed by the LCFNC and the proposed method. The results showed that the weight of automobile hood was reduced by 37%, while exhibiting better stiffness and strength performance compared with the conventional steel.

Optimization of Structures Made From Composites With Elliptical Inclusions

This paper seeks to determine the relationship between the parameters that define microstructures composed of a matrix with periodic elliptical inclusions and the effectiveness of structural optimization through the application of existing methods. Stiffness properties for a range of microstructures were obtained computationally through homogenization, and these properties were used to conduct separate homogeneous topology optimization and heterogeneous microstructural optimization on two canonical structural problems. Effectiveness was evaluated on the basis of final total strain energy when compared to a reference configuration. Local minima were found for the two structural problems and various microstructure configurations, indicating that the microstructure of composites with elliptical inclusions can be fine-tuned for optimization. For example, when applying topology optimization to a cantilever beam made from a material with soft, horizontal inclusions, ensuring that the aspect ratio of the inclusions is 2.25 will yield the stiffest structure. In the case of heterogeneous microstructural optimization, one of the results obtained from this analysis was that optimizing the aspect ratio of the inclusion is much more impactful in terms of increasing the stiffness than optimizing the inclusion orientation. The existence of these optimal designs have important implications in composite component design.

Damage characterization of stiffened glass-epoxy laminates under tensile loading with acoustic emission monitoring

Abstract The design of composite components in the aerospace industry often includes structural discontinuities, such as cutouts, for functional requirements like ventilation, tunnel passage, maintenance and repair. The presence of cutout holes leads to complicated stress concentrations with a substantial reduction in structural stability and strength of the resulting composites. It is known that reinforcing with additional material at the cutout zones can extend the damage tolerance of a structure, therefore maintaining structural integrity and load carrying capacity. This study focuses on the experimental investigation of the tensile behavior and failure characteristics of stiffened glass/epoxy composite laminates, with cutouts, under acoustic emission monitoring. The progressive failure mechanisms of laminates with cutouts and the potential benefits of additionally dropped reinforcements are evaluated under tensile loading. The additional reinforcements were provided in either a step-like or as a simultaneous drop-off sequence between adjacent continuous plies. Results showed that adding ply drop reinforcements at the location of the cutout hole improves the stiffness, strength, and also prolongs the life of the composite laminates. It is also observed that step-like ply drop arrangements performed more effectively than simultaneously dropped configurations. The location and extent of damage identified by microscopic images correlated well with the acoustic emission results.

Design and Optimization of Composite Automotive Hatchback Using Integrated Material-Structure-Process-Performance Method

The application of polymer composites as a substitution of metal is an effective approach to reduce vehicle weight. However, the final performance of composite structures is determined not only by the material types, structural designs and manufacturing process, but also by their mutual restrict. Hence, an integrated “material-structure-process-performance” method is proposed for the conceptual and detail design of composite components. The material selection is based on the principle of composite mechanics such as rule of mixture for laminate. The design of component geometry, dimension and stacking sequence is determined by parametric modeling and size optimization. The selection of process parameters are based on multi-physical field simulation. The stiffness and modal constraint conditions were obtained from the numerical analysis of metal benchmark under typical load conditions. The optimal design was found by multi-discipline optimization. Finally, the proposed method was validated by an application case of automotive hatchback using carbon fiber reinforced polymer. Compared with the metal benchmark, the weight of composite one reduces 38.8%, simultaneously, its torsion and bending stiffness increases 3.75% and 33.23%, respectively, and the first frequency also increases 44.78%.

Bending fatigue behavior of twill fabric E-glass/epoxy composite

Twill E-glass/epoxy composite was considered for its bending fatigue behavior. Displacement controlled bending fatigue tests with stress ratio R of 0.1 were conducted on standard specimens and damage development in the composite was continuously monitored through the decrease of bending moment during cycling. The specimens were subjected to different fatigue loadings with the maximum loading level up to 75% of the material ultimate flexural strength. Early damage was observed after hundreds of loading cycles causing degradation of material stiffness with cycling. The amount of stiffness reduction was observed to be a function of the magnitude of the fatigue loading applied to the specimen. For some selected specimens, after 1 million cycles, fatigue tests were stopped and residual properties were measured. Different levels of reduction on material strength and elastic modulus were found to depend on the level of fatigue loading. Finally detailed discussion is made to correlate the found fatigue data and obtain general description of the material fatigue behavior useful for composite component design.

Damage progression and defect sensitivity: An experimental study of representative wrinkles in tension

This paper presents an experimental study on the effect of localised wrinkling defects on the strength of glass reinforced epoxy laminates. A method for generating wrinkles based on the ‘natural’ mechanism of formation was developed and used to make larger scale laminates, with the aim of being representative of industrial components. Wrinkle severity was characterised using optical microscopy and correlated to the results obtained from tensile testing, which showed that the most serious misalignment can cause a 40% strength knock-down. Two optical systems – Digital Image Correlation and Video Extensometry were used to visualise the strain distribution, which showed highly localised concentrations surrounding the wrinkle. The role of the strain distribution in causing the initiation and progression of damage is explored, and finally some implications for the design of composite components are considered.

Research on Knowledge-based System for Typical Aircraft Composite Component Design

Considering the characteristic of composite component design, a knowledge-based system for the design of aircraft composite component is developed. The system design adopts client/application/server (C/A/S) three-layer structure. The implementation method and theory of the knowledge-based system is introduced in detail. Firstly, the system architecture of the developed knowledge-based system is presented. Then, the system framework of the case design base is also described. Case design of a composite component includes question description and solving scheme of this component. By comparing the question description and calculating the similarity of the components, new case design can be obtained from the existed case design. This knowledge-base system is integrated with CATIA software. The process of data exchange between CATIA and knowledge-base system is presented. The 3D model of composite component created in knowledge-base system can be modified by parameter driving. By implementing the proposed knowledge-based system, the design efficiency of composite component can be increased.

Stress intensity factors for an arbitrarily oriented crack near a hole in longeron web

Damage-tolerant design of composite components in aerospace structures requires computationally effective stress and failure analysis methods. This study introduces an analytical/numerical method to determine the stress field and the stress intensity factors in a composite longeron web with an arbitrarily oriented straight crack near a hole. Typical of webs in wing longerons with massive belts, the tapered web is loaded in bending and shear. The solution method makes use of the complex potentials in conjunction with the boundary collocation technique. The present results are in close agreement with those obtained by finite element.

Composite technology in load-bearing orthopaedic implants

Composite materials have been widely promoted as possible orthopaedic biomaterials but to date have found few successful commercial applications, due to the many challenging problems presented by their design, fabrication and testing. The range of possible composite biomaterials is reviewed, together with the possible methods of fabrication and the limitations that these place on the design of composite components. The use of composite materials allows many new design possibilities, but this freedom of design requires a clearer understanding of the objectives and constraints on the design process. The testing of composite components also presents many challenging problems, which are not adequately addressed by existing standards developed for testing conventional monolithic materials. The interaction of composite materials with the body is more complex than that of the component materials, and the prediction of their long-term mechanical performance also presents many intractable difficulties. However, despite these challenges composite materials are likely to prove invaluable in the future development of orthopaedics.

Automating the manufacture of composite broadgoods

This paper describes the work completed under a three year European Commission research and development contract, entitled ‘Integrating automatic handling of flexible materials, composite component design and quality assurance procedures’. The paper describes the reasons for conducting the work, the main drivers that shaped the final outcome, the key areas of study and the technical solution adopted, with a description of the systems, tests conducted and a discussion of the achievements and future options. A machine was built that took prepreg material from a standard roll, through removal of the backing sheets, visual inspection, cutting, handling, lay-up and consolidation to form a multi-layer doubly curved component. The system demonstrated that the engineering problems are not insurmountable, and with the right products in mind, a semi-automated system could provide the necessary quality and productivity for an acceptable price.

Role of Crack Wake Toughening on Elevated Temperature Crack Growth in a Fiber Reinforced Ceramic Composite

Theoretical models were developed to predict the nature of the elevated temperature failure behavior in composites containing bridged cracks both for the case where crack front creep is absent (brittle regime) and for the case where a frontal creep process zone is present (ductile regime). The nature of the thermally activated time-dependent bridging of matrix cracks was first briefly reviewed from an earlier study and then applied to the case where crack front creep was present. Stable crack growth was predicted both in the presence and absence of crack front creep after an initial delay period, or initiation, which depends on crack size and wake parameters, such as, fiber diameter, volume fraction and interface properties. The dependence of the initiation time and crack growth rates on flaw size and wake parameters as well as on composite microstructure was derived both for the presence and absence of crack front creep. The implications of the results for elevated temperature composite component design are discussed.

Design methodology for automotive components using continuous fibre-reinforced composite materials

A design methodology is described which outlines the concepts used in designing automotive components in continous fibre composite materials. The description includes overall conceptual development of the design procedures. In addition, this report highlights the specific techniques for laminate design and stress analysis in composite component design. These are the core features which differentiate composite design from design in more conventional materials. Complete mastering of the design procedure in composites will also require “hands-on” experience because of the sophistication of the analytical process.