Permeability measurements of engineering textiles exhibit large variability as no standardization method currently exists; numerical permeability prediction is thus an attractive alternative. It has all advantages of virtual material characterization, including the possibility to study the impact of material variability and small-scale parameters. This paper presents the results of an international virtual permeability benchmark, which is a first contribution to permeability predictions for fibrous reinforcements based on real images. In this first stage, the focus was on the microscale computation of fiber bundle permeability. In total 16 participants provided 50 results using different numerical methods, boundary conditions, permeability identification techniques. The scatter of the predicted axial permeability after the elimination of inconsistent results was found to be smaller (14%) than that of the transverse permeability (∼24%). Dominant effects on the permeability were found to be the boundary conditions in tangential direction, number of sub-domains used in the renormalization approach, and the permeability identification technique. 

This work focuses on developing a seamlessly integrated modeling platform for manufacturing, designing, and analyzing fiber-reinforced composite structures. The manufacturing method is vacuum assisted resin transfer molding, and the analysis method is the finite element method. The unique integration of two commercial software (Moldex3D and ABAQUS) with additional interfaces and physics-based micromechanics enables variabilities during the manufacturing to be directly embedded into the structural analysis. The manufacturing output is the resin pressure which is used to predict the compaction pressure and calculate local fiber volume fractions. The predicted non-uniform volume fractions provide local mechanical properties allowing seamless transfer of process effects and properties variability to the final structural analysis. Three demonstrators are presented as examples for simulation and validation against experiments, both in manufacturing and structural performance. The results show very good agreement between simulations and experiments regarding resin flow times and measurements (within 17%) and demonstrators’ structural stiffness (within 15%). © The Author(s) 2022.

The production of large-scale products is currently undergoing a considerable shift in the manufacturing sector in favor of additive manufacturing (AM). Complex structures and elaborate designs that were previously impossible to produce using conventional manufacturing techniques are now possible thanks to the usage of additive printing technology. At the same time, using recycled materials in the production process has also risen to the top of the industry’s priority list as a result of a growing focus on sustainability. In this context, the use of recycled polymer composites in large-scale additive manufacturing (LSAM) is beginning to attract attention from both industry and research. Indeed, recycled polymer composites offer several benefits, including not only lower costs but also significantly reduced environmental impact and improved mechanical properties compared to virgin polymer materials. However, several challenges are still associated with using recycled materials in AM, including issues with material properties and compatibility with the AM process. Perhaps the most difficult polymer for AM is nylon where different grades pose different printing properties and challenges, thus printing large-scale objects in recycled nylon is a challenge that few have taken on. One objective of our project is to improve the properties of recycled polymers for LSAM by investigating how different additives, such as mineral wastes and/or recycled short fibers, influence the LSAM process and the properties of the resulting printed object. One way to achieve this objective is by simulating the AM process where we use ABAQUS AM capabilities that enable us to optimize the process and material parameters. Thermal and mechanical analyses using the element activation technique in ABAQUS AM allow us to implement multi-scale multi-physical models for material and process simulation and ensure that the final product meets the desired mechanical and structural properties. To truly reach a circular economy, a systems-level transformation of manufacturing must be achieved [1]. Our vision is to digitally transform manufacturing by turning recycled polymers and other industrial wastes into secondary raw materials and composites for LSAM of final products. However, further research on different industrial use cases and applications is needed to address the remaining challenges associated with this approach and to fully realize its potential in the manufacturing industry. 

Hybrid bolted joints between composite materials and metals are an example of composites’ sensitivity to notches. The current research paper presents an experimental test setup on single-lap shear bolted joints of a unidirectional (UD) composite laminate with steel plate exposed to a tensile load. A 3D explicit finite element (FE) simulation is developed using ABAQUS/Explicit and a 3D physically-based progressive damage model in the VUMAT subroutine. The model can identify the locations of delamination represented by the fully damaged plies among other degrading properties. Then “damage and cohesive” contact surfaces are defined in the respected damaged plies, for the material interface, to simulate interlaminar damage and delamination. The predicted failure load was significantly influenced by the combination of a 3D physically-based progressive damage model and damage and cohesive surfaces. The combined model can reproduce with accuracy the experimental load–displacement test curves up to the point where bearing damage occurs. Experimental results using DIC measurement are presented to demonstrate the feasibility of the methodology. The study shows that numerical models can be used to help in the stiffness and strength design of the bolted joints of composites and metals, but further improvements are necessary to predict the energy absorption. 

In this paper a rapid method for residual cure stress analysis from composite manufacturing is presented. The method uses a high-fidelity path-dependent cure kinetics subroutine implemented in ABAQUS to calibrate a linear elastic model. The path-dependent model accounts for the tool-part interaction, forming pressure, and the changing composite modulus during the rubbery phase of matrix curing. Results are used to calculate equivalent lamina-wise coefficients of thermal expansion (CTE) in 3 directions for a linear temperature analysis. The goal is to accurately predict distortions for large complex geometries as rapidly as possible for use in an optimization framework. A carbon-epoxy system is studied. Simple coupons and complex parts are manufactured and measured with a 3 D scanner to compare the manufactured and simulated distortion. Results are presented and the accuracy and limitations of the rapid simulation method are discussed with particular focus on implementation in a numerical optimization framework. © The Author(s) 2021.

Processing of polymer fibre composites has a remarkable influence on their mechanical performance. These mechanical properties are even more influenced when using recycled reinforcement. Therefore, we place particular attention on the evaluation of micromechanical models to estimate the mechanical properties and compare them against the experimental results of the manufactured composites from recycled carbon fibre material. For the manufacturing process, an epoxy matrix and carbon fibre production cut-offs as reinforcing material are incorporated using a vacuum infusion process. In addition, continuous textile reinforcement in combination with the epoxy matrix is used as reference material to evaluate the degradation of mechanical performance of the recycled composite. The experimental results show higher degradation of the composite strength compared to the stiffness properties. Observations from the modelling also show the same trend as the deviation between the theoretical and experimental results is lower for stiffness comparisons than the strength calculations. Yet still, good mechanical performance for specific applications can be expected from these materials.

In this paper, recent shell model is advanced towards the calibration and validation of the Vacuum-assisted Resin Transfer Molding (VARTM) process in a novel way. The model solves the nonlinear and strongly coupled resin flow and preform deformation when the 3-D flow and stress problem is simplified to a corresponding 2-D problem. In this way, the computational efficiency is enhanced dramatically, which allows for simulations of the VARTM process of large scale thin-walled structures. The main novelty is that the assumptions of the neglected through-thickness flow and the restricted preform deformation along the normal of preform surface suffice well for the thin-walled VARTM process. The model shows excellent agreement with the VARTM process experiment. With good accuracy and high computational efficiency, the shell model provides an insight into the simulation-based optimization of the VARTM process. It can be applied to either determine locations of the gate and vents or optimize process parameters to reduce the deformation.

Within this paper, the authors present a rapid method for residual cure stress analysis. The method uses a high-fidelity path-dependent cure kinetics analysis subroutine implemented in Abaqus to calibrate values for a linear elastic analysis. The path dependent model accounts for the tool-part interaction, forming pressure, and the changing composite modulus during the rubbery region of matrix curing during an arbitrary cure cycle. Results are used to calculate equivalent lamina-wise coefficients of thermal expansion (CTE) in 3 directions for a linear temperature analysis. The goal is to accurately predict distortions for large complex geometries with a single linear temperature load as rapidly and accurately as possible for use in an optimization framework. A carbon-epoxy system is studied. Simple parts are manufactured using unbalanced layups and out-of-autoclave methods. The resulting distortions are scanned with a 3D scanner and compared with simulation results for the same geometries. Further, a more complicated part is studied to compare the two methods using complex geometry. Results are presented and the accuracy and limitations of the rapid simulation method are discussed with particular focus on implementation in a numerical optimization framework.

To increase the use of polymeric structural composites, a major issue is to properly account for intra-laminar failure mechanisms, such as fiber kinking which is typically induced in compression. We propose a new set of continuum damage models that are able to predict fiber kinking response under compression. A structure tensor based formulation is established at the unidirectional ply level, where the elastic material response is governed by transverse isotropy. To consider geometrical effects in conjunction with fiber kinking instability, a continuum damage formulation at finite strain is developed. The fracture area progression includes a convective and a local damage production involving a finite progression speed. In this framework, two damage evolution models are considered; one non–local model including the gradient damage effect and a local one, without the gradient enhancement. The models are implemented in a FE–code and validated for a compression loaded specimen. The models are computationally robust and can predict the localized nature of fiber kinking. A thorough sensitivity study is presented to show how the different formulations influence the predicted responses.

In process simulation of composite materials, 3D simulation of manufacturing processes is desirableconsidering the manufacturing trend where parts became more complex leading to complex3D stress-strain states. Moreover, coupling of sub-processes that are happening simultaneouslysuch as macro-scale preform processes, micro-infiltration and solid and fluid interactionrequires full 3D description of the problem.The development is exemplified considering compression moulding process of prepregs wherethe main focus of the modeling will be on the compression and compaction of directionalprepreg laminate and flow consolidation. To this end, the theory of two phase porous mediais used along with assuming hyper-elastic material response for the laminate to formulatethe problem. A finite element formulation and implementation of the two-phase problem is developedfor incompressible constituents and is implemented in a user defined element (UEL)to be used with Abaqus.