Abstract: The objective of the study is to investigate the effects of geometrical and physical parameters on failure loads unidirectional composite laminates by finite element analysis. The failure load of for a single pin hole, parallel pin hole and multi-pin holes. Three different distance variables were investigated during analysis the ratio of free edge distance to the outer holes/pin diameter (E/D = 2, 3, 4, 5), the ratio of longitudinal distance between the holes/pin diameter (G/D = 2, 3, 4, 5), and the ratio of transverse distance between the parallel holes/pin diameter (W/D = 2,3, 4, 5) ratios. Yamada-Sun failure criterion was used for failure analysis. The results from finite element analysis showed that it is very important to consider the effect of E/D, G/D and W/D ratios in design of single, double and multiple joints. The results showed that the pin hole farthest from the free edge is subjected to the highest stress.
When fiber-reinforced composite materials occur a crack, phenomenon of bridging fiber pull-out will often occur ahead of the crack tips and off x-axis on occasion, and analyzing crack problems in this situation is more diffi- cult. Composite materials are often referred to as ortho- tropic aniostropic body in virtue of the direction of their fibers, while bridging fibers play an important role in their strength, consequently queries on bridging fiber pull-out are one of the most complex advancing tasks in mechanics of composite materials. When a crack moves with high speed, bridging fiber pull-out phenomenon of composite materials is still likely to exist. Because the problems of bridging fibers are more complicated and cockamamie, there is a lot of difficulty in mathematical calculations. In order to resolve dynamic fracture queries of bridging fiber pull-out of unidirectional composite materials, it is indispensable to establish a suitable sym- metrical dynamic model of bridging fiber pull-out, hence fracture dynamics problems of bridging fiber pull-out of composite materials are effectively solved.
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both the matrix and the ﬁber are homogeneous and isotropic, (c) the thermal contact resistance between the ﬁber and matrix is negligible, (d) the problem is two-dimensional, and (e) the ﬁbers are arranged in a square periodic array, i.e. they are uniformly distributed in the matrix. The model shown in Fig. 3(a) is a unit cell which represents one-cycle of the periodic structure, so the transverse thermal conductivity of unidirectional composite of circular cylinders was estimated by using this unit cell. The unit cell was divided into 4-node ﬁxed size square elements as shown in Fig. 3(b), so that the FE model obtained from the unit cell became equivalent to that obtained from the microstructure of composites. Under the conditions described above, the microstructure is re- stricted to the model size in the direction of estimation even though it is assumed to spread inﬁnitely in other directions. So, the models which consist of several unit cells as shown in Fig. 4 are considered in this work for evaluating the eﬀect of boundary conditions. When the model consists of several unit cells, multiplying the number of elements per unit cell by the number of unit cells gives the total number of elements in the model. Thus, the number of unit cells represents the size of the model in this study. The analysis conditions are shown in Table 1.
The determination of the elastic constants of unidirectional carbon ﬁbre composite via immersion based ultrasound is an established area with much literature. Existing literature reviews in this area discuss the extant literature but do not o ﬀ er a deep review of the seminal publications during this period, but instead focus on reporting the contributions of the published literature. Thus, a gap in knowledge exists for a comprehensive literature review charting the evolution of how the elastic constants of uni-directional carbon ﬁ bre composite are determined via immersion based ultrasonic through transmission. This work addresses this. Building on previous literature, this paper reviews seminal publications in chronological order, with the bene ﬁ ts, drawbacks and contributions to knowledge of each reviewed publication identi ﬁ ed within this work. This review is bounded from 1970 to 2015, (some 45 years of literature), and maps the progression of technological and scienti ﬁ c advancement of the through transmission technique; that is, seminal literature during this period is both identi ﬁ ed and reviewed in chronological order thus de- monstrating how each paper builds on previous work. This paper also documents two novel information tables, which for the ﬁ rst time allow the signi ﬁ cant contributions to knowledge during this period to be quickly identi ﬁ ed.
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In the present article, the above cohesive crack model- ing approach is applied to 3D domains and used for pre- dicting mode I fracture behaviour of unidirectional lami- nates. To this end, an ABAQUS user-element subroutine has been developed to model the nonlinear behaviour of composite samples (T300/977-2 carbon fiber reinforced epoxy and AS4/PEEK carbon fiber reinforced polyether ether ketone) under the standard double cantilever beam (DCB) test. Cohesive zone was added to enrich elements in the crack front under a bilinear traction-separation law. In addition, a technique is introduced for simple imple- mentation of the cohesive zone by avoiding material sof- tening due to the application of large process zone. Name- ly, to decrease the computational time and to avoid insta- bility during simulations, a critical length of cohesive zone in vicinity of the crack tip is defined such that the user-defined XFEM elements are only assigned inside this region. It is shown that the new technique avoids predefining a complete delamination path along the spe- cimen length, and leads to more realistic prediction of experimental data. Finally, a set of sensitivity analyses have been performed to identify effects of different mod- eling parameters, while comparing the results to conven- tional FEM, the mesh free method, and the interface element approaches.
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DOI: 10.4236/ojcm.2018.81001 2 Open Journal of Composite Materials portation equipment such as aircrafts and automobiles results in the improve- ment of its fuel efficiency, the performance improvement of lightweight struc- tural materials with high strength is required. In particular, the application of carbon fiber reinforced plastics (CFRP) with lightweight and high strength in- creases in composite materials utilized in the aerospace industry  . One of the major molding methods of CFRP is the vacuum assisted resin transfer molding (VaRTM) method, and it is a reliable low-cost manufacturing process. Since the method does not require the use of prepregs and autoclaves, it can save on a lot of expanse for intermediate materials and manufacturing equipment. Additionally, large-size structural components can be integrally molded by the method, leading to a reduction in the number of parts . However, the method using thermoset resin needs an oven or another simple heating method to cure resin impregnated with fibers. In the previous study, the influences of external and internal heating in the curing process to the mechanical properties of fiber reinforced plastics (FRP) were investigated using the same materials and mold- ing process . While external heating was defined as heating the base material by hot air generated in an oven, internal heating indicated that the base material was heated by self-generated heat of fibers. The study revealed that external heating improved the tensile strength of FRP laminates in the transverse (90˚) direction . The studies on the heating methods using microwaves and near infrared waves in the curing process have been conducted  . However, the relationship between a molding process and the mechanical properties of molded products is not investigated and assessed in the studies. Also, there are no precedent reports on mechanical properties of FRP laminates processed by a conventional FRP molding process in applying of ultrasonic waves. In this study, the effects of ultrasonic waves using an ultrasonic generator during resin im- pregnation on the mechanical properties of FRP laminates were investigated in the VaRTM process. The laminates were processed using ultrasonic waves and not using them. The mechanical strength testing of the laminates was performed to discuss the effectivity and advantages of ultrasonic waves in the curing process of the VaRTM method.
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Figure 14 shows the obtained results compared to with the previous shear lag results (Khennane and Melchers, 2003), the experimental results on S-glass fibres compiled by Phoenix (2000), as well as the experimental results on a unidirectional composite (UD), a chopped strand mat (CSM) and a woven roving/ chopped strand mat (WR/CSM) compiled by Clarke (1996). Interestingly, the finite element simulations are very close to the experimental results compiled by Carter on composite materials. Most importantly, it appears that the decrease in strength of the composite (fibre plus matrix) is less pronounced than that of fibres alone as shown by the slope of the curves. Without doubt, this is due to the matrix carrying some stress and reducing stress concentration on the fibres. This is well reproduced by the finite element model. It also appears that matrix cracking has no effect on the life of the sample when subject to stress corrosion in a saturated environment. This not surprising, since, as demonstrated previously, the matrix only takes a very small amount of the total stress. However, in practice where moisture profiles are common place, this is certainly not the case as matrix cracking would allow fore more environment ingress into the composite therefore thus causing more deleterious effects. This current area is currently under investigation.
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The aim of this work is to evaluate fatigue behavior of centrifugal compressor impeller with different materials. To identify this, FV520B and Nickel base alloy are considered as the common materials of the impeller. The carbon/epoxy laminated composite is considered as new material to study impeller behavior. Stress analysis has done under only centrifugal and aerodynamic loads. Fatigue damage and life is predicted by using FEM.
Samples were mounted onto sample holder and fixed with adhesive carbon tape. Fig. 3.5 and Fig. 3.6 illustrates the top surface morphology of nanoclay composite flat sheet. Voids are observed in Fig. 3.5a. Non circular bright regions shows correspond to clay agglomerates from are observed from SEM micrograph. It is observed clay particles are dispersed in the epoxy matrix and nanoclay is also distributed in the outside zone of glass fiber bundles in which epoxy resin flows.
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Finite element (FE) simulation is a powerful tool for investigating the mechanism of machining fiber‑reinforced polymer composite (FRP). However in existing FE machining simulation works, the two‑dimensional (2D) progressive damage models only describe material behavior in plane stress, while the three‑dimensional (3D) damage models always assume an instantaneous stiffness reduction pattern. So the chip formation mechanism of FRP under machin‑ ing is not fully analyzed in general stress state. A 3D macro‑mechanical based FE simulation model was developed for the machining of unidirectional glass fiber reinforced plastic. An energy based 3D progressive damage model was proposed for damage evolution and continuous stiffness degradation. The damage model was implemented for the Hashin‑type criterion and Maximum stress criterion. The influences of the failure criterion and fracture energy dissipa‑ tion on the simulation results were studied. The simulated chip shapes, cutting forces and sub‑surface damages were verified by those obtained in the reference experiment. The simulation results also show consistency with previous 2D FE models in the reference. The proposed research provides a model for simulating FRP material behavior and the machining process in 3D stress state.
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Composite materials play a significant role in satisfying the increasing demands of aerospace, automotive, high-end sports industries as well as civil engineering and leisure equipment. These applications require high stiffness and strength, enhanced chemical and corrosion resistance, good fatigue properties and most importantly weight savings. However, the incorporation of such materials is limited by their inherent brittleness as they often fail in a catastrophic manner, without preceding detectable damage or warning. To overcome this limitation and to avoid the utilization of over- conservative design envelopes and large safety margins, a new Structural Health Monitoring (SHM) concept is introduced here. While monitoring structural integrity, especially during visual inspection, damage detected in time can not only prevent catastrophic failure but it can also indicate the need for further, more thorough non-destructive testing (NDT). A UK patent application by Czél et al.  based on a unique feature of a purpose designed unidirectional (UD) hybrid composite allows for visual overload indication simply from a change in appearance as the composite is loaded over a predefined strain value. The aim of this paper is to prove this novel concept and to characterise and optimize the sensing characteristics of such technology by a simple analytical and finite element (FE) model and mechanical testing.
powders direct mixing to disperse into a mono-component epoxy resin and used as matrix for advanced composites with woven roving glass fiber reinforcements. These nano powders are added directly into the epoxy resin and uniform dispersion is to be carry out by using mechanical stirrer. In manufacturing of the hybrid nano composite with glass fiber, and epoxy polymer in the ratio of 1wt %, and 2 wt% percent of volume are to be considering. These different wt% nano- phased polymer-based nanocomposites plates are to be manufacturing by moulding in vacuum as per ASTM standards. Fatigue tests are to be conducting under constant amplitude, both under tension–tension and three points bending loadings.
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The instantaneous unidirectional probability flux from left to right at a point x 1 is defined as the probability per unit time (∆t), of Langevin trajectories that are to the left of x 1 at time t (with any velocity) and propagate to the right of x 1 at time t + ∆t (with any velocity), in the limit ∆t → 0. This can be expressed in terms of a path integral as
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ZHUANG Lin, LIU Yuan-an et al  proposed an efficient adaptive gateway discovery algorithm which successfully connects MANET having unidirectional links. AODV protocol is modified in this research. Gateway advertised message and gateway discovery messages are rebroadcasted, both are extended with the information of local connection. From global route computation, the unidirectional links can be easily removed, and the connectivity of internet is enhanced. For better coverage of gateway advertisement, an adaptive scheme was proposed which adjust the broadcast range. It sends interval of gateway advertisement messages according to network conditions. In this scheme, RREQ message will be modified to RREQ-I. In RREQ-I, neighbor’s information is appended which came from neighbor’s node list (NNL). NNL of each mobile node is maintained by sending periodic hello messages to record its set of neighbors.
In the present work the mechanical properties of a unidirectional (UD) carbon-epoxy composite are investigated under transverse tension and combined transverse tension / in-plane shear loading. Therefore tests at quasi-static and dynamic strain rates using transverse tension and off-axis tension specimens are performed. For the latter specimen type, the authors  have observed in a previous study that the strain rate acting in the fracture plane of the off-axis specimens is significantly higher than the applied axial strain rate and additionally depends on the off-axis angles of the specimens. Hence, in this work, the strain rate in the loading direction is adjusted to the reach same strain rate values in the fracture planes, allowing
unidirectional flux (CBF X unidirectional extraction X arterial glucose concentration) from 0.46 to 0.66 mumol/g X min during insulin infusion (plasma insulin approximately 1,500 microU/ml). The net brain uptake of glucose (CBF X arterio-venous difference for glucose) as unaltered during the investigation period of 45 min, which is too short a time for insulin to penetrate the barrier. It follows that the backflux of glucose from the brain was increased during insulin application. The effect of insulin might be a speeding up of the glucose carrier […]
because of a non-functioning high-speed camera record. In Table 2 all dynamic experimental results are listed. A mean compressive strength of 974.93 MPa with a coefficient of variance of 6.47% for the unidirectional carbon fiber reinforced polyamide-6 composite was measured. All specimens fail similar to the quasi-static specimens away from the loading surface (Fig. 9) due to the formation of kink-band followed by through thickness fiber failure. The pictures of the high speed camera show, that with maximum stress the initiation of the fiber kinking starts and subsequently the development of the kink-band. The delamination of the base-laminate in the region of the
materials (irradiated UHMWPEs and XLPEs), even if they are quite different. Due to the four-fold irradiation dose (100 kGy), XLPEs have a higher degree of cross- linking compared with UHMWPEs that are irradiated with 25 kGy. Despite this difference in the degree of crosslinking, when a unidirectional sliding motion is applied they display a similar degree of resistance. The significance of the results obtained by employing unidi- rectional motion is questionable, because wear tests us- ing this kind of motion only seem to be able to detect differences in the wear behaviour of unirradiated and irradiated UHMWPEs, while differences between dif- ferent degrees of crosslinking cannot be detected.
The propagation characteristics of the ultrasonic shear wave in unidirectional carbon-ﬁber-reinforced epoxy com- posites, with its polarization parallel to the ﬁbers, have been analyzed with the aid of the computational multiple scatter- ing simulation. The multiple scattering simulation results have been combined with the macroscopic one-dimensional theory in order to identify the phase velocity and the attenuation coeﬃcient of the composite. These character- istics have been demonstrated for diﬀerent ﬁber volume fractions and diﬀerent ﬁber arrangements. As a result, the following features have been clariﬁed.
A careful fabrication procedure was developed by Verma and Chariar [26-27] to produce laminated BFRC which combined bamboo slivers that were sliced from bamboo culms using sliver cutting machine and epoxy. Three configurations of laminated bamboo composite that were constructed using adhesives and butt joint were the unidirectional configuration, [0/0/0/0/0] (UNI), the symmetric angle-ply configuration, [0/45/0/45/0] (SAP) and the symmetric cross-ply configuration, [0/90/0/90/0] (SCP). The specimens were than tested for their tensile, compressive and flexural properties in addition to testing the screw holding capabilities. Figure- 4 (a)-(c) shows the behaviours of the BFRC under tensile, compressive and flexural testing. It was observed that in tensile test, matrix failure started first, followed by fiber fracture that propagates spontaneously until the whole layer break. Compressive failure was attributed to microbuckling surrounded by delamination while in flexural test, the tension surface failed due to matrix and fiber breakage. Compared to teak wood in terms of mechanical properties and cost , the study showed that BFRC’s properties are at par with the properties of the teak wood while fabrication cost of the BFRC is less than that of the teak wood. As such, BFRCC can be utilized as building and general purpose material for furniture, beam and column.
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