scholarly journals Manufacturing and Shear Response Characterization of Carbon Nanofiber Modified CFRP Using the Out-of-Autoclave-Vacuum-Bag-Only Cure Process

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Erin E. McDonald ◽  
Landon F. Wallace ◽  
Gregory J. S. Hickman ◽  
Kuang-Ting Hsiao

The interlaminar shear response is studied for carbon nanofiber (CNF) modified out-of-autoclave-vacuum-bag-only (OOA-VBO) carbon fiber reinforced plastic (CFRP). Commercial OOA-VBO prepregs were coated with a CNF modified epoxy solution and a control epoxy solution without CNF to make CNF modified samples and control samples, respectively. Tensile testingwas used to study the in-plane shear performance of [±45°]4scomposite laminates. Significant difference in failure modes between the control and CNF modified CFRPs was identified. The control samples experienced half-plane interlaminar delamination, whereas the CNF modified samples experienced a localized failure in the intralaminar region. Digital image correlation (DIC) surface strain results of the control sample showed no further surface strain increase along the delaminated section when the sample was further elongated prior to sample failure. On the other hand, the DIC results of the CNF modified sample showed that the surface strain increased relatively and uniformly across the CFRP as the sample was further elongated until sample failure. The failure mode evidence along with microscope pictures indicated that the CNF modification acted as a beneficial reinforcement inhibiting interlaminar delamination.

2016 ◽  
Vol 50 (30) ◽  
pp. 4251-4268 ◽  
Author(s):  
Rahul P Mohan ◽  
Hassan Alshahrani ◽  
Mehdi Hojjati

The successful formation of composite parts without defects remains a challenging issue due to the complexity of the forming process. A better understanding of the factors that cause these flaws is necessary to optimize the operation. The present work investigates the in-plane shear behavior of out-of-autoclave carbon epoxy thermoset prepregs OOA and its effect on wrinkling using the picture frame test. The deformability of OOA at the real processing conditions helps to understand the applicability of such material for forming processes such as the double-diaphragm forming technique with aims to minimize overall manufacturing time and cost. Tests were performed at varying temperatures and displacement rates in order to determine their contribution to the fabric deformability. Digital image correlation was used to take sequential images at various stages of deformation and capture the onset of wrinkling. It was found that the processing temperature (resin viscosity), displacement rate, and layer counts (layer interactions) are the three most important parameters that influence the wrinkling. Presence of resin between the layers makes them interact with each other and therefore has an impact on the each layer shear angle. These parameters were then analyzed using the Taguchi and analysis of variance techniques to determine which factor has the most significant influence on the wrinkling.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Rudwan Kazwini ◽  
Tarek Kasem ◽  
Noor Ewaz Ali Alhuda ◽  
Marwah Albarshah ◽  
Dania Subeh ◽  
...  

Abstract Background War on Syria extended for a long time and resulted in significant impacts on various aspects, one of these aspects was displaced people crisis, and thus its impact on complete neglecting of oral health despite of its importance and impacts on the general health. This study aims to assess the oral health of the displaced Syria sample as a result of the war on Syria. Methods The sample included 118 patients of displaced families from different regions and cities to shelters in Damascus city, and the study included 118 control samples from the Faculty of Dentistry, Damascus University. The non-profit initiative team included 20 dentists of all dental specialties. Oral health was assessed using DMFT index. Data were analyzed using SPSS V.22 in comparison with the gender of the patients, age groups, and socioeconomic status. Finally, the number of the treatment provided by the non-profit initiative was collected and presented in the study. Results No significant differences found in the DMFT index between children and adults (P = 0.750), DMFT value ranged between (0 and 11) with a mean value (2.4). The total DMFT value for adults was (2.77), while for children (2.12). Also, no statistical difference was found between males and females (P = 0.688). While the control group had an average DMFT value of (2.37), the difference between the displaced and control samples was not significant. Over 200 dental treatments were provided by the team. Conclusion This study concluded that the DMFT value is high among the displaced people as one of the consequences of the war on Syria, however, no significant difference was found when the results of the displaced sample was compared to a control sample.


2017 ◽  
Vol 65 (2) ◽  
Author(s):  
Bleydis Paola Gutierrez Rapalino ◽  
Yamileth Del Carmen Domínguez Haydar

Seed dispersal is a key process in the re-establishment of vegetation on reclaimed lands. The aim of this study was to determine the contributions of the ant species Ectatomma ruidum and Pheidole fallax to seed dispersal and germination on reclaimed lands in the Cerrejón coal mine, Colombia. Four 6 x 40 m plots were installed in each area, in which the number of nests by species was counted and distances between closest nests of each species were measured. Five of the nests counted were chosen for seed extraction, and a nearby control sample was taken from each nest. In total, 295 nests were counted: 59 nests during the dry season and 236 nests during the rainy season, of which 84 belonged to P. fallax and 211 belonged to E. ruidum. A total of 21 304 seeds were found in nests and control samples, of which 19 349 were obtained from P. fallax nest refuse, and 318 were obtained from E. ruidum nests; 597 seeds were found in control samples. The number of seeds extracted from nests was significantly higher than the number of seeds removed from control samples. There was a significant difference between the number of seeds removed by P. fallax and the number of seeds removed by E. ruidum. The seed germination percentage from nests was higher than the percentage from seeds in control samples. In the case of P. fallax, the germination percentage was lower in control samples and higher in nests and refuse. The results suggest that the ant species E. ruidum and P. fallax may contribute to seed dispersal and re-establishment of vegetation in areas where they were found. These ants may thus significantly contribute to restoration processes in areas degraded by mining.


2022 ◽  
Vol 58 (4) ◽  
pp. 179-186
Author(s):  
Constantin Stochioiu ◽  
Anca Deca ◽  
Anton Hadar ◽  
Horia Gheorghiu

The present paper is aimed at studying the in-plane shear response of a flax fiber - epoxy resin composite laminate. Rectangular specimens, with �45� laminate orientation with respect to loading direction were used for the experimental procedure. Tensile testing up to failure allowed to extract the shear strain-shear stress curve, which have shown a linear domain, up to approximately 25 MPa, where a shear modulus was calculated, of 1.67 GPa and a Poisson ratio of 0.7, value which is typical for off axis laminates. Strain measurement during these tests, using Digital Image Correlation, have shown that, at high stress levels, concentrators occur in the specimen in the region of failure. Repeated loading tests have shown that the material stiffens approximately 9% when increasing loading speed, leading to conclude that a viscoelastic component of the deformation is present during loading. Repeated creep-recovery tests showed that, for longer periods of time, viscoplastic deformations appear as well, with an exponential evolution with respect to the creep duration.


2016 ◽  
Vol 697 ◽  
pp. 629-632
Author(s):  
Li Xian Zhang ◽  
Rui Li ◽  
Yu Niu ◽  
Yu Xiao Liu

To explore the effect of thickness on the fracture strength and failure modes of zirconia crowns, four crown models with different thickness (1.2 mm, 1.0 mm, 0.8 mm, 0.6 mm) with the same shape were designed by Dental Designer software in CAD/CAM system. They were manufactured to 40 zirconia crowns by CAM carving machine. The fracture strength and the failure modes of each crown was measured, while porcelain fused to metal (PFM) crowns as control. The average fracture strength of different zirconia crowns were recorded as below: 1308.38 ± 111.38 N (Group 0.6 mm), 1841.60 ± 68.21 N (Group 0.8 mm), 2429.88 ± 315.03 N (Group 1.0 mm), 3068.31 ± 233.88 N (Group 1.2 mm). There was no significant difference between Group 1.0 mm and Group 1.2 mm (P > 0.05), and statistical significance was obtained among every other two groups (P < 0.05). The failure modes of different thickness zirconium crowns are similar. There are more broken pieces from thicker crowns compared to thinner ones. It is concluded that the thickness can influence the fracture strength of zirconia crown. With the increase of the thickness, the fracture strength of the zirconium crowns also increases. We recommend zirconia crowns thicker than or at least 1.0 mm in dental practice.


2021 ◽  
Author(s):  
Ali Mirzazade ◽  
Cosmin Popescu ◽  
Thomas Blanksvärd ◽  
Björn Täljsten

<p>This study is carried out to assess the applicability of using a digital image correlation (DIC) system in structural inspection, leading to deploy innovative instruments for strain/stress estimation along embedded rebars. A semi-empirical equation is proposed to predict the strain in embedded rebars as a function of surface strain in RC members. The proposed equation is validated by monitoring the surface strain in ten concrete tensile members, which are instrumented by strain gauges along the internal steel rebar. One advantage with this proposed model is the possibility to predict the local strain along the rebar, unlike previous models that only monitored average strain on the rebar. The results show the feasibility of strain prediction in embedded reinforcement using surface strain obtained by DIC.</p>


Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Arjun Angral ◽  
Mandar Kulkarni ◽  
Jeff Suhling

Relative damage-index based on the leadfree interconnect transient strain history from digital image correlation, explicit finite-elements, cohesive-zone elements, and component’s survivability envelope has been developed for life-prediction of two-leadfree electronic alloy systems. Life prediction of pristine and thermally-aged assemblies, have been investigated. Solder alloy system studied include Sn1Ag0.5Cu, and 96.5Sn3.5Ag. Transient strains during the shock-impact have been measured using digital image correlation in conjunction with high-speed cameras operating at 50,000 fps. Both the board strains and the package strains have been measured in a variety of drop orientations including JEDEC horizontal drop orientation, vertical drop orientation and intermediate drop orientations. In addition the effect of sequential stresses of thermal aging and shock-impact on the failure mechanisms has also been studied. The thermal aging condition used for the study includes 125°C for 100 hrs. The presented methodology addresses the need for life prediction of new lead-free alloy-systems under shock and vibration, which is largely beyond the state of art. Three failure modes have been predicted including interfacial failure at the copper-solder interface, solder-PCB interface, and the solder joint failure. Explicit non-linear finite element models with cohesive-zone elements have been developed and correlated with experimental results. Velocity data from digital image correlation has been used to drive the attachment degrees of freedom of the submodel and extract transient interconnect strain histories. Explicit finite-element sub-modeling has been correlated with the full-field strain in various locations, orientations, on both the package and the board-side. The survivability of the leadfree interconnections under sequential loading (thermal aging and shock-impact) from simulation has been compared with pristine circuit assemblies subjected to shock-impact. Sequential loading changes the failure modes and decreases the drop reliability as compared to the room temperature experimental results. Damage index based survivability envelope is intended for component integration to ensure reliability in harsh environments.


2018 ◽  
Vol 28 (0) ◽  
Author(s):  
Grazia Attili ◽  
Lorenza Di Pentima ◽  
Alessandro Toni ◽  
Antonio Roazzi

Abstract Research on eating disorders (ED) has shown in patients a prevalence of insecure attachment working models (IWMs). Nevertheless, the issue of a prevalence, in patients, of high anxiety IWMs (HAIWMs) has rarely been addressed. This study aimed to investigate the prevalence in ED patients of high anxiety IWMs and their transmission by parents. The Separation Anxiety Test was administered to 55 patients with an ED, a control sample (n = 80), their mothers and fathers. The two groups differed significantly, with a prevalence of HAIWMs in the patients and their parents compared to the controls; in ED no significant difference appeared in mother-patient versus father-patient matching for HAIWMs. The implication is that patients with an ED might benefit more from individual attachment-based therapy and/or a family therapy than from other types of psychotherapeutic approaches.


2013 ◽  
Vol 26 (05) ◽  
pp. 356-365 ◽  
Author(s):  
K. L. Wendelburg ◽  
S. Tepic ◽  
S. M. Stover ◽  
T. Garcia-Nolen ◽  
P. B. Stearns ◽  
...  

SummaryElbow dysplasia, primarily affecting the medial compartment, is the most common cause of lameness in the thoracic limb. Elbow arthroplasty is an option for end stage or severely affected patients. The purpose of this study was to compare ex vivo axial load to failure of an implanted novel elbow arthroplasty system to control limbs. The partial arthroplasty is a medial compartmental, unconstrained system, intended to allow conversion to total arthroplasty. We hypothesized that there would not be any significant difference between implanted and controlled limbs when loaded to failure. Six pairs of medium mixed breed canine cadaveric thoracic limbs were prepared for comparison of failure loading of control and implanted limbs. Axial compression was performed using a mechanical testing system. Failure loads were normalized to bodyweight. The mean normalized failure load (N/kg) for the implanted limbs and control limbs were 2.47 (range: 1.62-3.38) and 2.68 (range: 2.25-3.25), respectively. An implanted to control ratio of 0.93 ± 0.19 was calculated. The difference between paired control and implanted limbs in normalized failure loading was not significant (p = 0.38). There were not any differences noted in the yield load (p = 0.30), stiffness (p = 0.62), or energy (0.58). Failure modes were recorded. We concluded that the differences between implanted and control limbs in supra-physiologic axial load to failure were not significant.


2019 ◽  
Vol 3 (2) ◽  
Author(s):  
S. Huang ◽  
B. M. Bohrer

ObjectivesNovel, non-allergenic ingredients with properties that improve the quality of processed meat products are needed for the meat industry. The objectives of this study were to investigate the effect of breadfruit (Artocarpus altilis) flour on color of comminuted beef compared with other flour sources.Materials and MethodsFlour sources included breadfruit, corn, soy, tapioca, and wheat. All flours were obtained commercially and were unmodified. Lean beef (from the same commercially sourced batch targeted to 90% lean and 10% fat), 10% ice, 1.5% salt, and flour sources at two inclusion levels (2.5% and 5%) were mixed using a bowl chopper to prepare beef patties for evaluation. The ground beef was manufactured into 115 g patties that were placed on a retail display shelf under continuous LED lighting at 4°C for 7 d. Lighting was measured periodically during the study and LUX was ensured to be between 1612.5 lux and 2152.0 lux. Objective CIE L* (lightness), a* (redness), and b* (yellowness), chroma, and hue scores were collected with a Minolta CR-400 Chroma meter (Konica Minolta Sensing, Inc., Osaka, Japan) utilizing a D65 light source and a 0° observer with an aperture size of 8 mm on each day of the simulated retail display. This study was conducted in three independent replicates for each treatment. Statistical analyses for parameters (L*, a*, b*, chroma, and hue) were conducted using the MIXED procedure of SAS with fixed effects of flour source*inclusion level, day, and their interaction. Least square means were separated using the PDIFF option with a Tukey-Kramer adjustment. Differences were considered statistically different at P < 0.05.ResultsThe interaction of storage day and treatment significantly (P ≤ 0.001) affected a*, b*, chroma, and hue. There was not an interaction of storage day and treatment for L*. Both the main effect of storage day and the main effect of treatment significantly (P < 0.01) affected all the attributes measured in this study. Mean L* over the display period of beef patties prepared with 2.5% breadfruit flour were not different (P = 0.95) compared with control samples. There was no significant difference between the mean hue over the 7-d display period of the beef patties prepared with 2.5% breadfruit flour compared with control samples. a* decreased at different rates for each treatment throughout the display period. Beef patties prepared with 2.5% and 5% breadfruit flour were redder (greater a*; (P < 0.05)) compared with other treatments and control samples over the 7-d display period. To the contrary, a* values of beef patties prepared with soy flour were less than (P < 0.05) other treatments and the control samples on Day 0 and Day 1 and remained constant at lower values as the display period increased.ConclusionBreadfruit flour improved the redness of comminuted beef products immediately and prevented discoloration for a longer period. The results indicate that breadfruit flour can effectively improve initial color and stability of color in processed beef products. More research is warranted to further investigate the mechanism of action of breadfruit flour in governing the color properties of comminuted beef products.


Sign in / Sign up

Export Citation Format

Share Document