A Review on the Mechanical Modeling of Composite Manufacturing Processes

© 2016, The Author(s). The increased usage of fiber reinforced polymer composites in load bearing applications requires a detailed understanding of the process induced residual stresses and their effect on the shape distortions. This is utmost necessary in order to have more reliable composite manufacturing since the residual stresses alter the internal stress level of the composite part during the service life and the residual shape distortions may lead to not meeting the desired geometrical tolerances. The occurrence of residual stresses during the manufacturing process inherently contains diverse interactions between the involved physical phenomena mainly related to material flow, heat transfer and polymerization or crystallization. Development of numerical process models is required for virtual design and optimization of the composite manufacturing process which avoids the expensive trial-and-error based approaches. The process models as well as applications focusing on the prediction of residual stresses and shape distortions taking place in composite manufacturing are discussed in this study. The applications on both thermoset and thermoplastic based composites are reviewed in detail

Thermo-mechanical properties of 5-harness satin fabric composites

The use of woven textile reinforcements in composite structures increased significantly in the past decades due to their interesting properties over unidirectional fibres. Therefore, the prediction of the thermo-mechanical properties of woven fabric composites is essential from a design and manufacturing standpoint. A micromechanical approach based on finite element method that utilizes three-dimensional unit cell was applied to predict the effective properties of a periodic woven fabric composite material. Using the resin processing properties models such as cure kinetics, shrinkage, glass transition temperature and elastic modulus models, the development of the periodic woven fabric composite material thermo-mechanical properties, as the cure progresses was predicted. The residual strains and stresses generated in the composite unit cell during the cure were also predicted and linked with the development of the material properties. The effective properties of the cured woven fabric composite material were compared to the one of an equivalent cross-ply composite material to verify the validity of neglecting the fibre waviness while modelling woven fabric composite. \ua9 The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.Peer reviewed: YesNRC publication: Ye

Relation between volumetric changes of unsaturated polyester resin and surface finish quality of fiberglass/unsaturated polyester composite panels

Resin dimensional changes, including cure shrinkage and thermal expansion, highly influence the surface finish quality of composite parts. Low profile additives (LPA) are commonly incorporated in unsaturated polyester (UP) resins to compensate for resin shrinkage and obtain a high quality surface finish. In this study, the dimensional change of an UP resin with different LPA contents was characterized. Both resin cure shrinkage and resin thermal expansion were measured. A simple methodology was then developed to estimate the surface finish quality of panels, manufactured by resin transfer molding (RTM), based on the prediction of part thickness variation during the process. Results show good agreement with the experimental investigations. \ua9 2011 Society of Plastics Engineers.Peer reviewed: YesNRC publication: Ye

Investigation of process-induced strains development by fibre Bragg grating sensors in resin transfer moulded composites

A comprehensive understanding of the development of residual strains in composite processing is essential to manufacture high quality composite parts. In this paper, the use of fibre Bragg grating (FBG) optical sensors was investigated to measure in situ the build-up of the process-induced strains in composite panels manufactured by resin transfer moulding. The FBG sensors, embedded in the composite laminate, successfully measured the evolution of the composite in-plane strains due to the temperature history. The sensors also captured a strain discontinuity during the cool-down related to the debonding of the composite from the mould. Finite element models were then proposed to simulate the strain development measured by the FBG sensors. Three different contact interactions between the tool and the laminate were investigated: no bonding, perfect bonding and frictional contact. The model using the frictional contact interaction described well the evolution of the measured strains. © 2010 Elsevier Ltd. All rights reserved

Modelling of the thermo-mechanical properties of woven composites during the cure

Woven fabrics are used more widely in composite materials as reinforcements to manufacture complex structures due to their high drapability and good impact resistance compared to unidirectional fibres. Understanding the properties of woven composites and their evolution during the cure is therefore important in terms of design and manufacturig of complex composite structures using woven fabrics.NRC publication: Ye

Carded recycled carbon fiber mats for the production of thermoset composites via infusion/compression molding

The use of carbon fiber reinforced thermoset composites has doubled in the last decade raising questions about the waste generated from manufacturing and at end-of-life, especially in the aircraft industry. In this study, 2.5 cm long carbon fibers were recovered from thermoset composite waste using a commercial scale pyrolysis process. Scanning electron microscopy, density measurements, single filament tensile testing as well as micro-droplet testing were performed to characterize the morphology, mechanical properties, and surface adhesion of the fibers. The recycled fibers appeared to be mostly undamaged and clean, exhibiting comparable mechanical properties to virgin carbon fibers. A carding process followed by an ultrasound treatment produced randomly aligned recycled fiber mats. These mats were used to fabricate composite plates, with fiber volume fractions up to 40 %, by infusion / compression molding. The mechanical properties of the plates were evaluated by tensile and flexural testing, and were found to be comparable to an equivalent containing virgin carbon fibers. Copyright \ua9 2013 SAE International.Peer reviewed: YesNRC publication: Ye

Processing Variability in Low-Cost VARTM Aeronautical Structures

Peer reviewed: YesNRC publication: Ye

Influence of the reaction stoichiometry on the mechanical and thermal properties of SWCNT-modified epoxy composites

Previous studies suggest that carbon nanotubes (CNTs) have a considerable influence on the curing behavior and crosslink density of epoxy resins. This invariably has an important effect on different thermal and mechanical properties of the epoxy network. This work focuses on the important role of the epoxy/hardener mixing ratio on the mechanical and thermal properties of a high temperature aerospace-grade epoxy (MY0510 Araldite as an epoxy and 4,4\u2032-diaminodiphenylsulfone as an aromatic hardener) modified with single-walled carbon nanotubes (SWCNTs). The effects of three different stoichiometries (stoichiometric and off-stoichiometric) on various mechanical and thermal properties (fracture toughness, tensile properties, glass transition temperature) of the epoxy resin and its SWCNT-modified composites were obtained. The results were also supported by Raman spectroscopy and scanning electron microscopy (SEM). For the neat resin, it was found that an epoxy/hardener molar ratio of 1:0.8 provides the best overall properties. In contrast, the pattern in property changes with the reaction stoichiometry was considerably different for composites reinforced with unfunctionalized SWCNTs and reduced SWCNTs. A comparison among composites suggests that a 1:1 molar ratio considerably outperforms the other two ratios examined in this work (1:0.8 and 1:1.1). This composition at 0.2 wt% SWCNT loading provides the highest overall mechanical properties by improving fracture toughness, ultimate tensile strength and ultimate tensile strain of the epoxy resin by 40%, 34%, 54%, respectively. \ua9 2013 IOP Publishing Ltd.Peer reviewed: YesNRC publication: Ye

Compression moulding of discontinuous-fibre carbon/PEEK composites: Study of mechanical properties

A new multi-disciplinary study is being conducted to systematically evaluate, characterize and model the moulding process and mechanical properties of composites manufactured fro mrandomly-oriented carbon/PEEK chopped strips. The heterogeneous meso-structure of this material is expected to give rise to unique material behaviour, which is not entirely accounted for in the current ASTM standards for mechanical testing. This paper presents results of a sensitivity study aimed to evaluate the dependence of measured properties on the size of the coupon gauge section. Coupons of different widths (12.5 - 50 mm) were cut from compression moulded flat panels of randomly oriented chopped strips 25 mm in length and were subjected to quasi-static tensile loading. Results did not show any noticeable effect of the coupon width on the measured properties. Tensile strength and stiffness were found to be substantially lower than those of quasi-isotropic continuous fiber laminates, 59 % and 26 % lower, respectively.Peer reviewed: YesNRC publication: Ye