Mode-II fracture of nanostitched para-aramid/phenolic nanoprepreg composites by end-notched flexure

2020 ◽  
Vol 54 (24) ◽  
pp. 3537-3557
Author(s):  
Kadir Bilisik ◽  
Gulhan Erdogan ◽  
Erdal Sapanci ◽  
Sila Gungor
Keyword(s):  
Fracture Toughness ◽  
Composite Structures ◽  
Phenolic Resin ◽  
Mode Ii ◽  
Stick Slip ◽  
Blunt Crack ◽  
Pristine Sample ◽  
Pull Out ◽  
Filament Bundles ◽  
Phenolic Composite

The mode-II interlaminar fracture toughness considering the end-notched flexure method of nanostitched para-aramid/phenolic composite structures was investigated. The fracture toughness (GIIC) of the nanostitched and stitched composites exhibited a slight increase as compared to the pristine sample. Hence, the nanostitching enhanced the fracture toughness of the para-aramid/phenolic composite structures. Although the type of stitch fiber was not effective, the fabric interlacement frequency, notably prepreg Twaron nanostitched yarn and basket nanoprepreg biaxial interlaced fabric was of critical importance. The principle mechanism for raising the GIIC in the nanostitched composite structure was the interlayer resin fracture particularly as a form of slight shear hackle marks. Cracks grew around the inter- and intrayarn boundaries where the resin was fractured half way around each yarn cross-section. This is called a “zigzag crack path,” and microcracks moved to the through-the-thickness of the composite where nanostitching arrested the crack growth and suppressed delamination in the stitching zone. At the blunt crack tip, carbon nanotubes in the phenolic resin and multiple filament bundles probably diminished the stress clustering via friction/debonding/pull-out/sliding or stick-slip. Thus, nanostitched para-aramid/phenolic composite structures demonstrated better damage tolerance behavior considering the neat structure.

Mode-II toughness of nanostitched carbon/epoxy multiwall carbon nanotubes prepreg composites: Experimental investigation by using end notched flexure

2019 ◽  
Vol 53 (28-30) ◽  
pp. 4249-4271 ◽  
Author(s):  
Kadir Bilisik ◽  
Gulhan Erdogan ◽  
Erdal Sapanci ◽  
Sila Gungor
Keyword(s):  
Carbon Nanotubes ◽  
Fracture Toughness ◽  
Multiwall Carbon Nanotubes ◽  
Fold Increase ◽  
Woven Fabric ◽  
Woven Composites ◽  
Mode Ii ◽  
Stick Slip ◽  
Pull Out ◽  
Multiwall Carbon

The mode-II interlaminar fracture toughness properties following the end notched flexure method of nanostitched carbon/epoxy nanoprepreg composites were studied. The fracture toughness (GIIC) of the nanostitched and stitched composites showed 3.4 fold and 2.7 fold increase compared to the control, respectively. Thus, the nanostitching improved the mode-II toughness of all the carbon/epoxy composites with regard to the nano, and base composites. It was assumed that the type of stitch fiber as well as fabric pattern, in particular prepreg carbon stitching fiber and satin prepreg woven fabric, was effective. The basic mechanism for the enhancement of the GIIC toughness in the nanostitched composite was the interlaminar resin layer failure especially as a form of shear hackle marks where nanostitching arrested the delamination in the stitching zone during crack propagations. Multiwall carbon nanotubes in the matrix and filament also mitigated the stress concentration probably as an outline of debonding/pull-out/stick-slip/friction. Therefore, nanostitched as well as stitched carbon/epoxy woven composites exhibited improved damage tolerance performance with regard to the base composites.

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.

scholarly journals Moisture Absorption Effects on Mode II Delamination of Carbon/Epoxy Composites

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2162
Author(s):  
King Jye Wong ◽  
Mahzan Johar ◽  
Seyed Saeid Rahimian Koloor ◽  
Michal Petrů ◽  
Mohd Nasir Tamin
Keyword(s):  
Fracture Toughness ◽  
Moisture Content ◽  
Composite Structures ◽  
Moisture Absorption ◽  
Peak Load ◽  
Epoxy Composites ◽  
Mode Ii ◽  
Damage Initiation ◽  
Residual Properties ◽  
Mode Ii Fracture Toughness

It is necessary to consider the influence of moisture damage on the interlaminar fracture toughness for composite structures that are used for outdoor applications. However, the studies on the progressive variation of the fracture toughness as a function of moisture content M (%) is rather limited. In this regard, this study focuses on the characterization of mode II delamination of carbon/epoxy composites conditioned at 70 °C/85% relative humidity (RH). End-notched flexure test is conducted for specimens aged at various moisture absorption levels. Experimental results reveal that mode II fracture toughness degrades with the moisture content, with a maximum of 23% decrement. A residual property model is used to predict the variation of the fracture toughness with the moisture content. Through numerical simulations, it is found that the approaches used to estimate the lamina and cohesive properties are suitable to obtain reliable simulation results. In addition, the damage initiation is noticed during the early loading stage; however, the complete damage is only observed when the numerical peak load is achieved. Results from the present research could serve as guidelines to predict the residual properties and simulate the mode II delamination behavior under moisture attack.

Fracture Properties and Characteristics of Sisal Textile Reinforced Epoxy Composites

2006 ◽  
Vol 312 ◽  
pp. 167-172
Author(s):  
Yan Li ◽  
Yiu Wing Mai ◽  
Lin Ye
Keyword(s):  
Fracture Toughness ◽  
Surface Treatment ◽  
Fiber Surface ◽  
Epoxy Composites ◽  
Mode I ◽  
Mode Ii ◽  
Fracture Properties ◽  
Pull Out ◽  
Mode Ii Fracture Toughness ◽  
Fiber Surface Treatment

In this paper, double cantilever beam (DCB) and end notch flexural (ENF) tests were performed to study mode I and mode II interlaminar fracture toughness of sisal textile reinforced epoxy composites. Two kinds of fiber surface treatment methods were used to improve the interfacial bonding properties between sisal fiber and the epoxy resin. Effect of fiber surface treatments on mode I and mode II fracture toughness was analyzed with the aid of microobservation and single fiber pull-out test. It was concluded that proper fiber surface treatment could improve the fracture properties of this kind of Eco-composite.

Model and Maximal Pull-Out Force of Helicoidal Fiber Structure in the Underpinnings of Tumblebug Cuticle

2011 ◽  
Vol 686 ◽  
pp. 427-431 ◽  
Author(s):  
Bin Chen ◽  
Da Gang Yin ◽  
Quan Yuan ◽  
Ji Luo ◽  
Jing Hong Fan
Keyword(s):  
Fracture Toughness ◽  
Composite Structures ◽  
High Performance ◽  
Parallel Fiber ◽  
Fiber Structure ◽  
Protein Matrix ◽  
The Core ◽  
Pull Out ◽  
Collagen Protein ◽  
Scanning Electron

The observation of scanning electron microscope (SEM) on the cuticle of Tumblebug shows that the cuticle is a kind of biocomposite consisting of chitin-fibers and collagen protein matrix. The observation also shows that there are many underpinnings in the cuticle. The underpinnings are also a kind of biological composite consisting of chitin-fiber layers and collagen protein matrixes. More careful observation indicates that the chitin-fiber layers enwrap the core of the underpinnings forming a kind of helicoidal fiber structure. The maximal pull-out force of the helicoidal fiber structure, related to the fracture toughness of the underpinnings, is theoretically and experimentally investigated and compared with that of parallel fiber structure. It shows that the maximal pull-out force of the helicoidal fiber structure is larger than that of the parallel fiber structure, which gives profitable information for the design of man-made high-performance composites and composite structures.

Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

1989 ◽  
Vol 47 ◽  
pp. 556-557
Author(s):  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Frictional Stress ◽  
Fiber Reinforced ◽  
Pull Out ◽  
Carbon Coated ◽  
Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

scholarly journals Environmental effects on mode II fracture toughness of unidirectional E-glass/vinyl ester laminated composites

2021 ◽  
Vol 28 (1) ◽  
pp. 382-393
Author(s):  
Mazaher Salamt-Talab ◽  
Fatemeh Delzendehrooy ◽  
Alireza Akhavan-Safar ◽  
Mahdi Safari ◽  
Hossein Bahrami-Manesh ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Sulfuric Acid ◽  
Vinyl Ester ◽  
Cohesive Zone Model ◽  
Flexural Modulus ◽  
Mode Ii ◽  
Zone Model ◽  
Sharp Drop ◽  
Mode Ii Fracture ◽  
Mode Ii Fracture Toughness

Abstract In this article, mode II fracture toughness ( G IIc {G}_{\text{IIc}} ) of unidirectional E-glass/vinyl ester composites subjected to sulfuric acid aging is studied at two different temperatures (25 and 90°C). Specimens were manufactured using the hand lay-up method with the [ 0 ] 20 {{[}0]}_{20} stacking sequence. To study the effects of environmental conditions, samples were exposed to 30 wt% sulfuric acid at room temperature (25°C) for 0, 1, 2, 4, and 8 weeks. Some samples were also placed in the same solution but at 90°C and for 3, 6, 9, and 12 days to determine the interlaminar fracture toughness at different aging conditions. Fracture tests were conducted using end notched flexure (ENF) specimens according to ASTM D7905. The results obtained at 25°C showed that mode II fracture toughness increases for the first 2 weeks of aging and then it decreases for the last 8 weeks. It was also found that the flexural modulus changes with the same trend. Based on the results of the specimens aged at 90°C, a sharp drop in fracture toughness and flexural modulus with a significant decrease in maximum load have been observed due to the aging. Finite element simulations were performed using the cohesive zone model (CZM) to predict the global response of the tested beams.

scholarly journals Displacement Rate Effects on the Mode II Shear Delamination Behavior of Carbon Fiber/Epoxy Composites

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1881
Author(s):  
Kean Ong Low ◽  
Mahzan Johar ◽  
Haris Ahmad Israr ◽  
Khong Wui Gan ◽  
Seyed Saeid Rahimian Koloor ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Peak Load ◽  
Epoxy Composites ◽  
Displacement Rate ◽  
Interface Debonding ◽  
Mode Ii ◽  
Scanning Electron Micrographs ◽  
Unstable Crack ◽  
Mode Ii Fracture ◽  
Mode Ii Fracture Toughness

This paper studies the influence of displacement rate on mode II delamination of unidirectional carbon/epoxy composites. End-notched flexure test is performed at displacement rates of 1, 10, 100 and 500 mm/min. Experimental results reveal that the mode II fracture toughness GIIC increases with the displacement, with a maximum increment of 45% at 100 mm/min. In addition, scanning electron micrographs depict that fiber/matrix interface debonding is the major damage mechanism at 1 mm/min. At higher speeds, significant matrix-dominated shear cusps are observed contributing to higher GIIC. Besides, it is demonstrated that the proposed rate-dependent model is able to fit the experimental data from the current study and the open literature generally well. The mode II fracture toughness measured from the experiment or deduced from the proposed model can be used in the cohesive element model to predict failure. Good agreement is found between the experimental and numerical results, with a maximum difference of 10%. The numerical analyses indicate crack jump occurs suddenly after the peak load is attained, which leads to the unstable crack propagation seen in the experiment.

Sign in / Sign up

Export Citation Format

Share Document