scholarly journals Modelling the development of defects during composite reinforcements and prepreg forming

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150269 ◽  
Author(s):  
P. Boisse ◽  
N. Hamila ◽  
A. Madeo
Keyword(s):  
Composite Materials ◽  
Structural Integrity ◽  
Fibrous Composite ◽  
Bending Stiffness ◽  
Textile Composite ◽  
Forming Process ◽  
Transition Zones ◽  
Process Simulations ◽  
Composite Reinforcement ◽  
Composite Reinforcements

Defects in composite materials are created during manufacture to a large extent. To avoid them as much as possible, it is important that process simulations model the onset and the development of these defects. It is then possible to determine the manufacturing conditions that lead to the absence or to the controlled presence of such defects. Three types of defects that may appear during textile composite reinforcement or prepreg forming are analysed and modelled in this paper. Wrinkling is one of the most common flaws that occur during textile composite reinforcement forming processes. The influence of the different rigidities of the textile reinforcement is studied. The concept of ‘locking angle’ is questioned. A second type of unusual behaviour of fibrous composite reinforcements that can be seen as a flaw during their forming process is the onset of peculiar ‘transition zones’ that are directly related to the bending stiffness of the fibres. The ‘transition zones’ are due to the bending stiffness of fibres. The standard continuum mechanics of Cauchy is not sufficient to model these defects. A second gradient approach is presented that allows one to account for such unusual behaviours and to master their onset and development during forming process simulations. Finally, the large slippages that may occur during a preform forming are discussed and simulated with meso finite-element models used for macroscopic forming. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

Damage Mechanisms in Loaded Aramid Composites by Means of Embedded PVDF Acoustic Emission Sensors

2006 ◽  
Vol 13-14 ◽  
pp. 337-342 ◽  
Author(s):  
Claudio Caneva ◽  
I.M. De Rosa ◽  
F. Sarasini
Keyword(s):  
Acoustic Emission ◽  
Composite Materials ◽  
Polyvinylidene Fluoride ◽  
Structural Integrity ◽  
Fibrous Composite ◽  
Failure Mechanisms ◽  
In Situ Monitoring ◽  
Epoxy Composites ◽  
Pvdf Film ◽  
Emission Data

Cost-effective and reliable damage detection is critical for the utilization of composite materials due to the relatively localised nature of damage formation and the resultant reduction in structural integrity. Of the methods available, Acoustic Emission (AE) is considered as one potential technology for on-line and in situ monitoring of structural degradation of composite materials. Purpose of this work was to study the interaction between embedded PVDF (polyvinylidene fluoride) transducers and composite samples as well as detect and characterize the failure mechanisms in aramid/epoxy flexural test specimens using acoustic emission data obtained by embedded PVDF film sensors. Furthermore, it has been realized a comparison with surface mounted PVDF data. Results of our previous works (Caneva et al., 2005) dealing with monitoring tensile and flexural behaviour of glass/epoxy composites enabled to extend this methodology to aramid/epoxy composites. The use of Acoustic Emission and Scanning Electron Microscopy (SEM) observations enabled to identify and understand the failure mechanisms of the composites tested. Furthermore, satisfactory results of this work highlighted that the application of PVDF shows promise as a suitable acoustic emission transducer for fibrous composite materials.

Ecological Aspects of Producing Fibrous Composite Materials for Plant Cultivation

2021 ◽  
Author(s):  
A. A. Lysenko ◽  
N. I. Sverdlova ◽  
L. E. Vinogradova ◽  
L. M. Shtyagina
Keyword(s):  
Composite Materials ◽  
Fibrous Composite ◽  
Plant Cultivation ◽  
Ecological Aspects

scholarly journals Design of Center Pillar with Composite Reinforcements Using Hybrid Molding Method

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2047
Author(s):  
Ji-Heon Kang ◽  
Jae-Wook Lee ◽  
Jae-Hong Kim ◽  
Tae-Min Ahn ◽  
Dae-Cheol Ko
Keyword(s):  
Composite Materials ◽  
Weight Reduction ◽  
Fuel Efficiency ◽  
Vehicle Body ◽  
Process Time ◽  
Fiber Reinforced ◽  
Fiber Reinforced Plastic ◽  
Molding Method ◽  
Reinforced Plastic ◽  
Composite Reinforcements

Recently, with the increase in awareness about a clean environment worldwide, fuel efficiency standards are being strengthened in accordance with exhaust gas regulations. In the automotive industry, various studies are ongoing on vehicle body weight reduction to improve fuel efficiency. This study aims to reduce vehicle weight by replacing the existing steel reinforcements in an automobile center pillar with a composite reinforcement. Composite materials are suitable for weight reduction because of their higher specific strength and stiffness compared to existing steel materials; however, one of the disadvantages is their high material cost. Therefore, a hybrid molding method that simultaneously performs compression and injection was proposed to reduce both process time and production cost. To replace existing steel reinforcements with composite materials, various reinforcement shapes were designed using a carbon fiber-reinforced plastic patch and glass fiber-reinforced plastic ribs. Structural analyses confirmed that, using these composite reinforcements, the same or a higher specific stiffness was achieved compared to the that of an existing center pillar using steel reinforcements. The composite reinforcements resulted in a 67.37% weight reduction compared to the steel reinforcements. In addition, a hybrid mold was designed and manufactured to implement the hybrid process.

Investigation of the mechanical and forming behaviour of 3D warp interlock carbon woven fabrics for complex shape of composite material

2021 ◽  
pp. 152808372098410
Author(s):  
Mehmet Korkmaz ◽  
Ayşe Okur ◽  
Ahmad Rashed Labanieh ◽  
François Boussu
Keyword(s):  
Composite Materials ◽  
Complex Shape ◽  
Impact Damage ◽  
Woven Fabrics ◽  
Forming Process ◽  
Warp Yarn ◽  
Delamination Resistance ◽  
Fabric Architecture ◽  
Weave Pattern ◽  
Carbon Fabrics

Composite materials which are reinforced with 3D warp interlock fabrics have outstanding mechanical properties such as higher delamination resistance, ballistic damage resistance and impact damage tolerance by means of their improved structural properties. Textile reinforcements are exposed to large deformations in the production stage of composite materials which have complex shape. Although good formability properties of 3D warp interlock fabrics in forming process were already proven by recent studies, further information is needed to elucidate forming behaviours of multi-layer fabrics which is produced with high stiffness yarns like carbon. In this study, 3D warp interlock carbon fabrics were produced on a prototype weaving loom and the same carbon yarn was used in two fabric directions with equal number of yarn densities. Fabrics were differentiated with regard to the presence of stuffer warp yarn, weave pattern and parameters of binding warp yarn which are angle and depth. Therefore, the effect of fabric architecture on the mechanical and formability properties of 3D warp interlock carbon fabrics could be clarified. Three different breaking behaviours of fabrics were detected and they were correlated with crimp percentages of yarn groups. In addition, the bending and shear deformations were analysed in view of parameters of fabric architectures. Two distinct forming behaviours of fabrics were determined according to the distribution of deformation areas on fabrics. Moreover, the optimal structure was identified for forming process considering the fabric architecture.

scholarly journals Physical modelling of failure in composites

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150280 ◽  
Author(s):  
Ramesh Talreja
Keyword(s):  
Composite Materials ◽  
Failure Modes ◽  
Structural Integrity ◽  
Failure Mechanisms ◽  
Local Stress ◽  
Physical Modelling ◽  
Stress Fields ◽  
Systematic Analysis ◽  
Composite Failure ◽  
Failure Theories

Structural integrity of composite materials is governed by failure mechanisms that initiate at the scale of the microstructure. The local stress fields evolve with the progression of the failure mechanisms. Within the full span from initiation to criticality of the failure mechanisms, the governing length scales in a fibre-reinforced composite change from the fibre size to the characteristic fibre-architecture sizes, and eventually to a structural size, depending on the composite configuration and structural geometry as well as the imposed loading environment. Thus, a physical modelling of failure in composites must necessarily be of multi-scale nature, although not always with the same hierarchy for each failure mode. With this background, the paper examines the currently available main composite failure theories to assess their ability to capture the essential features of failure. A case is made for an alternative in the form of physical modelling and its skeleton is constructed based on physical observations and systematic analysis of the basic failure modes and associated stress fields and energy balances. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

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