Analysis of nonlinear deformations and damage in CFRP textile laminates (original) (raw)
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Analysis of nonlinear deformations and damage in CFRP textile laminates-JPCS DAMAS 2011
Carbon fibre-reinforced polymer (CFRP) textile composites are widely used in aerospace, automotive and construction components and structures thanks to their relatively low production costs, higher delamination and impact strength. They can also be used in various products in sports industry. These products are usually exposed to different in-service conditions such as large bending deformation and multiple impacts. Composite materials usually demonstrate multiple modes of damage and fracture due to their heterogeneity and microstructure, in contrast to more traditional homogeneous structural materials like metals and alloys. Damage evolution affects both their in-service properties and performance that can deteriorate with time.
Applied Composite Materials, 2012
Textile-reinforced composites such as glass fibre-reinforced polymer (GFRP) used in sports products can be exposed to different in-service conditions such as large bending deformation and multiple impacts. Such loading conditions cause high local stresses and strains, which result in multiple modes of damage and fracture in composite laminates due to their inherent heterogeneity and non-trivial microstructure. In this paper, various damage modes in GFRP laminates are studied using experimental material characterisation, non-destructive micro-structural damage evaluation and numerical simulations. Experimental tests are carried out to characterise the behaviour of these materials under large-deflection bending. To obtain inplane shear properties of laminates, tensile tests are performed using a full-field strainmeasurement digital image correlation technique. X-ray micro computed tomography (Micro CT) is used to investigate internal material damage modesdelamination and cracking. Twodimensional finite element (FE) models are implemented in the commercial code Abaqus to study the deformation behaviour and damage in GFRP. In these models, multiple layers of bilinear cohesive-zone elements are employed to study the onset and progression of inter-ply delamination and intra-ply fabric fracture of composite laminate, based on the X-ray Micro CT study. The developed numerical models are capable to simulate these features with their mechanisms as well as subsequent mode coupling observed in tests and Micro CT scanning. The obtained results of simulations are in agreement with experimental data.
Damage in woven CFRP laminates subjected to low velocity impacts
Carbon fabric-reinforced polymer (CFRP) composites used in sports products can be exposed to different in-service conditions such as large dynamic bending deformations caused by impact loading. Composite materials subjected to such loads demonstrate various damage modes such as matrix cracking, delamination and, ultimately, fabric fracture. Damage evolution in these materials affects both their in-service properties and performance that can deteriorate with time. These processes need adequate means of analysis and investigation, the major approaches being experimental characterisation and non-destructive examination of internal damage in composite laminates. This research deals with a deformation behaviour and damage in woven composite laminates due to low-velocity dynamic out-of-plane bending. Experimental tests are carried out to characterise the behaviour of such laminates under large-deflection dynamic bending in un-notched specimens in Izod tests using a Resil Impactor. A series of low-velocity impact tests is carried out at various levels of impact energy to assess the energy absorbed and force-time response of CFRP laminates. X-ray micro computed tomography (micro-CT) is used to investigate material damage modes in the impacted specimens. X-ray tomographs revealed that through-thickness matrix cracking, inter-ply delamination and intra-ply delamination, such as tow debonding and fabric fracture, were the prominent damage modes.
Composites Science and Technology, 1999
The relationship between the mechanical behaviour (i.e. Young's modulus, Poisson's ratio and residual strain) of CFRP woven fabric laminates and the damage sustained during quasi-static loading has been investigated in two, four-and six-layer laminates. The laminate thickness is found to be an important parameter in determining the eect of matrix cracking and delaminations on the mechanical properties. The laminate behaviour has been modelled by a shear-lag analysis which takes into account delaminations at the crimp regions in the laminate where appropriate. Reasonable agreement is found between experiment and theory for the change in laminate properties as a function of damage accumulation. #
Damage and fracture in fabric-reinforced composites under quasi-static and dynamic bending
Fabric-reinforced polymer composites used in sports products can be exposed to different in-service conditions such as large deformations caused by quasi-static and dynamic loading. Composite materials subjected to such bending loads can demonstrate various damage modes - matrix cracking, delamination and, ultimately, fabric fracture. Damage evolution in composites affects both their in-service properties and performance that can deteriorate with time. Such behaviour needs adequate means of analysis and investigation, the main approaches being experimental characterisation and non-destructive examination of internal damage in composite laminates. This research deals with a deformation behaviour and damage in carbon fabric-reinforced polymer (CFRP) laminates caused by quasi-static and dynamic bending. Experimental tests were carried out to characterise the behaviour of a CFRP material under large-deflection bending, first in quasi-static and then in dynamic conditions. Izod-type impact bending tests were performed on un-notched specimens of CFRP using a Resil impactor to assess the transient response and energy absorbing capability of the material. X-ray micro computed tomography (micro-CT) was used to analyse various damage modes in the tested specimens. X-ray tomographs revealed that through-thickness matrix cracking, inter-ply and intra-ply delamination such as tow debonding, and fabric fracture were the prominent damage modes both in quasi-static and dynamic test specimens. However, the inter-ply damage was localised at impact location in dynamically tested specimens, whereas in the quasi-static specimens, it spread almost over the entire interface.
2014
In this paper, an experimental study is performed to characterise the behaviour of fabric-reinforced composites used in sports products under large-deflection bending in Izod-type impact tests. X-ray micro computed tomography (micro-CT) is used to investigate various damage modes in the impacted CFRP specimens. It revealed that matrix cracking, delaminations, tow debonding, and fibre fracture were the prominent damage modes. Three-dimensional finite-element models are developed to study the onset, progression and interaction of some damage modes such as delamination and fabric fracture observed with micro-CT. A damage modelling technique based on a cohesive-zone method, which is more efficient than continuum damage mechanics approach, is proposed for analysis of interaction of damage modes. The developed numerical models are capable to simulate the damage mechanisms and their interaction observed in the tests. In this study, the pattern of damage formation observed in specimens was front-toback, unlike bottom-to-top one in drop weight impact tests. The effect of boundary conditions on the dynamic response and damage evolution of composite laminates is also investigated.
2018
Fabric-reinforced polymer (FRP) composites are increasingly employed in aerospace structures and sports products. In these applications, they are usually subjected to large-deflection quasi-static and dynamic bending deformations. Such loading conditions induce damage within the material at various scale levels affecting their strength, stiffness and energy-absorbing capability. For this purpose, mechanical behaviour of woven carbon and glass fabric-reinforced polymers (C/GFRPs) composites in onand off-axis orientations is first quantified by carrying out large-deflection quasi-static bending tests followed by dynamic ones employing an Izod type impact tester. The obtained stress-strain and force-deflection plots showed CFRP laminates fractured due to brittle carbon fibres. The off-axis CFRP and both the onand off-axis GFRP samples showed damage and nonlinearity at low impact energy with residual load carrying capability. Further, off-axis laminates of both materials and on-axis GFR...
Characterisation of mechanical behaviour and damage analysis of 2D woven composites under bending
Composites Part B-engineering, 2015
In this paper, flexural loading of woven carbon fabric-reinforced polymer laminates is studied using a combination of experimental material characterisation, microscopic damage analysis and numerical simulations. Mechanical behaviour of these materials was quantified by carrying out tensile and largedeflection bending tests. A substantial difference was found between the materials' tensile and flexural properties due to a size effect and stress stiffening of thin laminates. A digital image-correlation technique capable of full-field strain-measurement was used to determine in-plane shear properties of the studied materials. Optical microscopy and micro-computed tomography were employed to investigate deformation and damage mechanisms in the specimens fractured in bending. Various damage modes such as matrix cracking, delaminations, tow debonding and fibre fracture were observed in these microstructural studies. A two-dimensional finite-element (FE) model was developed to analyse the onset and propagation of inter-ply delamination and intra-ply fabric fracture as well as their coupling in the fractured specimen. The developed FE model provided a correct prediction of the material's flexural response and successfully simulated the sequence and interaction of damage modes observed experimentally.
2017
Woven composites such as carbon and glass fabric-reinforced polymers (C/GFRPs) laminates are increasingly employed in aerospace structures and sports products. In these applications, they are usually subjected to large-deflection quasi-static and dynamic bending deformations during service. Such loading conditions induce damage within the material at various scale levels affecting their strength, stiffness and energy-absorbing capability. Further, FRPs especially made of carbon fibres are inherently brittle, proven to sudden and catastrophic failure without yielding like ductile materials. For this purpose, mechanical behaviour of woven CFRP and GFRP composites in onand off-axis orientations is first quantified by carrying out large-deflection quasi-static bending tests followed by dynamic ones employing an Izod type impact tester. Both types of laminates of various orientations were tested at loads increasing up to failure to determine their energy-absorbing capability. The obtaine...
Damage in Fibre-Reinforced Composite Laminates Subjected to Dynamic Loading
Fibre-reinforced polymers (FRPs) became one of the most important structural materials in various industries due to a combination of characteristics such as excellent stiffness, high strength-to-weight ratio, and ease to manufacture shapes tailored for application. Hence, they are now broadly used in aerospace and naval structures as well as in automotive, construction and energy industry; there is an increasing use of them in sports products. In service, composite structures can be exposed to different loading conditions including multiple impacts. Such loading is called impact fatigue (IF) and can cause deterioration of structural integrity and load-bearing capacity due to induced damage. Composite laminates usually demonstrate multiple modes of damage and fracture due to their heterogeneity and microstructure, in contrast to more traditional homogeneous structural materials such as metals and alloys. The most prominent damage mechanisms in them are fibre breaking, transverse matrix cracking, delamination and debonding between fibres. Such events can take place without leaving evidence of the damage on the surface of the component, therefore, non-destructive techniques (NDT), such as X-ray microcomputer tomography (MCT), are required for characterisation of internal flaws. Advanced FE models were developed in Abaqus/Explicit to characterise the response of CFRP laminates to impact loading conditions in order to elucidate their dynamical mechanical behaviour. A 3d finite-element model for uniaxial tensional impact loading of tested samples of CFRP cross-ply laminates is presented. A hammerspecimen interaction is simulated directly to obtain detailed information about impact conditions. The developed fully-transient explicit model serves as the first step in modelling damage in CFRP laminates under conditions of impact loading. To analyse initiation and evolution of multiple delamination in specimens of CFRP laminates, a cohesive-element approach is used.