Fractographic Observation of Various Loading Modes of Fibre Reinforced Laminates

2012 ◽  
Vol 730-732 ◽  
pp. 337-342 ◽  
Author(s):  
Rosa Marat-Mendes ◽  
Manuel de Freitas
Keyword(s):  
Mixed Mode ◽  
Mode I ◽  
Mode Ii ◽  
Scanning Electron Micrographs ◽  
Mode Iii ◽  
Fibre Breakage ◽  
Pull Out ◽  
Fractographic Features ◽  
Static Conditions ◽  
Scanning Electron

One of the major disadvantages of laminated composites is their tendency to delaminate. Unidirectional glass/epoxy laminates have been tested under static conditions by the use of fracture mechanics. Mode I, mode II, mixed mode I-II, mode III and mixed mode II-III tests were performed. Double cantilever beam (DCB), end-notched flexure (ENF), mixed-mode bending (MMB) and edge crack torsion (ECT) specimens were used. Scanning electron microscopy technique was used to identify distinguishing fractographic features and to establish the differences between the various modes of fracture after specimens testing. The propagated orientation of the delamination could be specified from the patterns of fracture surface. Scanning electron micrographs of fractured surfaces showed that the most predominant fractographic features in mode I and mode II are the large amount of fibre pull-out and the cusps markings respectively. In the MMB specimen the fracture surfaces are characterized by fibre breakage under shearing with fractures localized in the resin with cusps having an orientation of 90º (mode II) and also fractures localized in the resin and along the resin/fibre interface (mode I). Mode III characterization concluded that some limited mixed mode II-III seems to be present for ECT specimen on delamination initiation and growth, but a large majority of mode III delamination is present.

scholarly journals Cementitious Composites Reinforced with Polypropylene, Nylon and Polyacrylonitile Fibres

2012 ◽  
Vol 730-732 ◽  
pp. 271-276
Author(s):  
H.R. Pakravan ◽  
M. Jamshidi ◽  
M. Latifi ◽  
F. Pacheco-Torgal
Keyword(s):  
Absorption Capacity ◽  
Cement Matrix ◽  
Cementitious Composites ◽  
Scanning Electron Micrographs ◽  
Energy Absorption Capacity ◽  
Cement Ratio ◽  
Pull Out ◽  
Water To Cement Ratio ◽  
Before And After ◽  
Scanning Electron

This paper compares the adhesion strength between three polymeric fibres (polypropylene (PP), nylon66 (N66) and polyacrylonitrile (PAN)) embedded in a cement paste. The specimens were prepared at a water to cement ratio (w/c) of 0.5 and tested after 7, 14 and 28 curing days. It was found that although the adhesion between the polymeric fibres to the cement matrix is an important factor, the energy absorption capacity or energy dissipation ability of the fibres, plays a more important role in the improvement of the cementitious composites fracture toughness. Scanning electron micrographs were used to characterize the fibres surface before and after the Pull-out tests.

scholarly journals Mixed-Mode Interlaminar Fracture Toughness of Glass and Carbon Fibre Powder Epoxy Composites—For Design of Wind and Tidal Turbine Blades

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2103
Author(s):  
Christophe Floreani ◽  
Colin Robert ◽  
Parvez Alam ◽  
Peter Davies ◽  
Conchúr M. Ó. Brádaigh
Keyword(s):  
Fracture Toughness ◽  
Carbon Fibre ◽  
Composite Structures ◽  
Mixed Mode ◽  
Epoxy Composites ◽  
Mode I ◽  
Mode Ii ◽  
Pure Mode ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture

Powder epoxy composites have several advantages for the processing of large composite structures, including low exotherm, viscosity and material cost, as well as the ability to carry out separate melting and curing operations. This work studies the mode I and mixed-mode toughness, as well as the in-plane mechanical properties of unidirectional stitched glass and carbon fibre reinforced powder epoxy composites. The interlaminar fracture toughness is studied in pure mode I by performing Double Cantilever Beam tests and at 25% mode II, 50% mode II and 75% mode II by performing Mixed Mode Bending testing according to the ASTM D5528-13 test standard. The tensile and compressive properties are comparable to that of standard epoxy composites but both the mode I and mixed-mode toughness are shown to be significantly higher than that of other epoxy composites, even when comparing to toughened epoxies. The mixed-mode critical strain energy release rate as a function of the delamination mode ratio is also provided. This paper highlights the potential for powder epoxy composites in the manufacturing of structures where there is a risk of delamination.

scholarly journals Improved Interlaminar Fracture Toughness and Electrical Conductivity of CFRPs with Non-Woven Carbon Tissue Interleaves Composed of Fibers with Different Lengths

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 803 ◽  
Author(s):  
Feng Xu ◽  
Bo Yang ◽  
Lijie Feng ◽  
Dedong Huang ◽  
Min Xia
Keyword(s):  
Electrical Conductivity ◽  
Fracture Toughness ◽  
Carbon Fibers ◽  
Mode I ◽  
Mode Ii ◽  
Thickness Direction ◽  
Interlaminar Fracture Toughness ◽  
Filtration Method ◽  
Interlaminar Fracture ◽  
Pull Out

Non-woven carbon tissue (NWCT) with different fiber lengths was prepared with a simple surfactant-assistant dispersion and filtration method and used as interleaving to enhance both delamination resistance and electrical conductivity of carbon fiber reinforced plastics (CFRPs) laminates. The toughing effect of NWCT on both Mode I and Mode II interlaminar fracture of CFRPs laminate is dependent on length of fibers, where the shorter carbon fibers (0.8 mm) perform better on Mode I interlaminar fracture toughness improvement whereas longer carbon fibers (4.3 mm) give more contribution to the Mode II interlaminar fracture toughness increase, comparing with the baseline composites, and the toughness increase was achieved without compromising of flexural mechanical properties. More interestingly, comparing with the baseline composites, the electrical conductivity of the interleaved composites exhibited a significant enhancement with in-plane and through-the-thickness direction, respectively. Microscopy analysis of the carbon tissue interleaving area in the laminate indicated that carbon fibers with shorter length can form into a 3D network with more fibers aligned along through-the-thickness direction compared with longer ones. The shorter fibers thus potentially provide more effective fiber bridges, pull-out and matrix deformation during the crack propagation and improve the electric conductivity significantly in through-the-thickness direction.

An experimental study on interfacial fracture toughness of 3-D printed ABS/CF-PLA composite under mode I, II, and mixed-mode loading

2019 ◽  
pp. 089270571987486 ◽  
Author(s):  
Abdul Samad Khan ◽  
Aaqib Ali ◽  
Ghulam Hussain ◽  
Muhammad Ilyas
Keyword(s):  
Fracture Toughness ◽  
Mixed Mode ◽  
Interfacial Fracture ◽  
Mode I ◽  
Mode Ii ◽  
Interfacial Fracture Toughness ◽  
Fused Deposition ◽  
Specimen Test ◽  
Nozzle Temperature ◽  
Printing Speed

Multimaterial structures made using fused deposition modeling (FDM) offer an attractive prospect for enhancing their mechanical properties and functionality. In this study, the interfacial fracture toughness of a unidirectional hybrid composite fabricated by FDM was studied through mechanical testing. The composite structure comprises acrylonitrile butadiene styrene and carbon fiber-reinforced polylactic acid. Since, de-adhesion or bond failure at the interface can occur under a combination of the different fracture modes, therefore, interfacial fracture toughness, in terms of the critical energy release rate, was characterized using double cantilever beam specimen test for mode I, end-notched flexural specimen test for mode II, and mixed-mode bending specimen test for mixed-mode I/II. Effects of varying process parameters, like printing speed and nozzle temperature, on the interfacial fracture toughness in mode I and II were also investigated. It was found that increasing the nozzle temperature and printing speed enhance the fracture toughness, both in mode I and II, but the effect of increasing nozzle temperature on mode II fracture toughness was quite significant.

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