Residual Compression Research Articles

Light weight non-metallic lightning strike protection film for CFRP

To reduce the weight of state-of-the-art aeronautical lightning protection material, a non-metallic lightning strike protection film was prepared. The new film consisted of 2 functional layers, which were capable of dispersing lightning current and blocking heat propagation from lightning plasma, respectively. Graphene and conductive polymer veil were adopted as electrical conductivity modifier; expandable graphite was adopted as thermal insulator. By integrating these functions, the new film featured by light weight, good bonding strength and lightning protection effectiveness, the lightning damage depth reduced by 79 % and the residual compression strength was increased by 21 %. This paper proposed and verified that establishing synergistic system which respond to electrical and thermal induced lightning damage simultaneously could remarkably increase the lightning protection effectiveness of CFRP, the prospect of this new technique was also discussed.

Mapping the residual strain of carbon nanotubes in DWCNT/epoxy nanocomposites after tensile load using Raman microscopy

The toughness mechanisms of epoxy-based nanocomposites reinforced by double-walled carbon nanotubes (DWCNT) are investigated using Raman microscopy mapping. Maps of the residual strain of the carbon nanotubes were generated for the fracture surfaces obtained after tensile loading. By imaging through different microscope objectives, Raman mapping allowed to determine the distribution of the nanotube residual strain, indicating tension or compression, in different sampling volumes near the fracture surface. The G′ band with its high sensitivity to nanotube diameter variations, and not overlapping with the characteristic epoxy Raman lines, was selected for the mapping. Results provide a quantitative analysis of the nanotube bridging and pull-out mechanisms identified by scanning electron microscopy (SEM) inspection of the fracture surfaces.

Investigation of crack propagation in the surface white layer of rail steel

Introduction . The paper is devoted to the evaluation of cracking of white layers formed on the surface of the rail while in operation. Cracks are detected in the white layer of rail steel after one thousand test cycles. This is due to tensile and shear stresses on the surface of the wheel-rail contact spot. The paper presents the study results of the morphological characteristics of the white layer on the rail surface. Materials and Methods . The object of study (rail surface after operation) was examined under a microscope. Then, a two-dimensional model of finite elements of the plane deformation was developed to simulate the dynamic characteristics of the white layer cracking. Mathematical models describing crack propagation are proposed. For this, we applied the criterion of the elastic plastic fracture mechanics, the J -integral method. The SYSWELD program performed numerical modeling of the formation of a white layer and the distribution of residual stresses. Results . Optical images of the microstructure of the cross section of a white layer on the rail surface after operation are presented. Two different types of cracks were fixed at the trailing edge of the white layer of the samples studied. The SYSWELD program visualized fragments of simulating the mechanism of the white layer formation with the distribution of residual stresses, compression, and tension. The calculation results show that the values of the J -integral for all three cracks slightly decrease if the crack length reaches 10-50 gm. Discussion and Conclusions . The results obtained are applicable to assess the wear resistance of rail steels and predict the direction of crack growth. Comparisons of J -integral maxima have shown that under identical load conditions, crack no. 1 is likely to grow faster than cracks nos. 2 and 3. With an increase in the length of the crack, the maxima of the J -integral of all three cracks decreased.

Real-time monitoring the growth of strained off-stoichiometric NixFe3−xO4 ultrathin films on MgO(001)

Ni x Fe 3 − x O4 thin films with varying Ni amount (0 ≤ x ≤ 1.5) were deposited on MgO(001) via reactive molecular beam epitaxy. The growth process was monitored during film deposition by means of X-ray diffraction. All prepared films exhibit a well-ordered structure with complete vertical crystallinity throughout the whole film growth and flat surfaces of the final films independent of the Ni amount. An enhancement of the vertical compression in the initial growth continuously decreases up to a film thickness of 8 nm. During further growth, all films exhibit residual and constant vertical compression with lateral adaption of the final films to the substrate lattice, as observed by high energy surface X-ray diffraction experiments. Hard X-ray photoelectron spectroscopy measurements of the final films reveal increasing Fe3+:Fe2+ ratios for higher Ni content and point to additional NiO agglomerations within the films exceeding the stoichiometric Ni amount of x = 1.

TECHNOLOGY OF COMBINED ELECTROMECHANICAL TREATMENT WITH PROFILE ROLLING

The technology of combined electromechanical treatment with profile rolling is presented, which is a combination of electromechanical treatment and surface plastic deformation, which allows to create on the surface directed regular microrelief. The proposed technology is tested during processing of parts of multipurpose tracked and wheeled machines operating under difficult loading conditions, signalternating dynamic loads, often with limited lubricant or presence of abrasive in its composition. Reasonable selection of relief (pattern) of treated surface makes it possible to maximize retention of lubricating material in zone of tribocontact, as well as to increase wear resistance of parts and to create residual compression stresses in surface layer. The mechanical properties of the surface layer of the sample with a strengthened geometric pattern by changing the microhardness of the smoothed surface and oil pockets (channels) obtained by surface plastic deformation were examined. Electromechanical treatment by rolling the profile makes it possible to create on the surface a strengthened surface layer with naturally varying parameters with the specified regular micro-relief including oil pockets (channels) and reinforced tracks, at the same time considerable increase of wear resistance of triboscreating is provided.

Cracking evolution of atmospheric plasma-sprayed YSZ thermal barrier coatings subjected to isothermal heat treatment

It is known that residual stress is the main factor causing the final failure of thermal barrier coatings (TBCs). However, it is still unclear how the stress governs the cracking sequence. In this paper, atmospheric plasma-sprayed (APS) 8 wt% yttria-stabilized zirconia (YSZ) TBCs were subjected to isothermal heat treatment at 1050 °C for different time. The cracking evolution and the underlying mechanical mechanisms for cracking were investigated. Residual stress distribution through the YSZ thickness was evaluated using Raman spectroscopy. It is found that, after thermal exposure, the in-plane residual compression in the top-coat (TC) near the TC/thermally grown oxide (TGO) interface increases as the TGO thickens, inducing tensile stresses normal to the interface in the TC close to the undulation crests. A spherical analytical model is used to evaluate this tensile stress, and the result shows that it rises with the TGO growth. This normal tensile stress is the driving force for cracking of TBCs. Cracking parallel to the TGO/TC interface first initiates in the TC near the interface, and then coalesces with the cracks within the TGO and at the bond-coat (BC)/TGO interface, leading to the final delamination. Because TC has a relatively low fracture toughness, the delamination trajectory is primarily in the TC near the TGO/TC interface and along the pathway that contains inter-splat cracks, pores and weak splat boundaries. The results indicate that the large in-plane compressions play a significant role in the cracking evolution of TBCs because they induce normal tensile stress in the TC or at the TGO/BC interface. A cracking pattern dominated by the stress evolution is established in this work and it will provide an informed basis for improving the durability of APS-TBCs.

Respiratory consequences of intra-abdominal hypertension.

Intra-abdominal hypertension (IAH) is a common complication in critically ill patients that may lead to multiorgan failure and is associated to worse outcome. Respiratory failure is among the most important consequences of IAH and it is originated by different mechanisms, such as chest wall elastance increase, functional residual capacity reduction, compression atelectasis and lung edema formation through reduction in lymphatic drainage. Many experimental studies showed that total lung capacity and functional residual capacity can be decreased by 40% during abdominal hypertension, while respiratory system and chest wall pressure-volume curves can be significantly shifted downward and to the right. Moreover, the relationship between intra-abdominal volume and airway pressure has been found to be exponential, meaning that small increases in volume can translate in dramatic increases in pressure. Clinical studies confirmed relevant atelectasis in dependent lung regions during IAH, with significant reductions in functional residual capacity and compromised oxygenation. Moreover, sepsis-related capillary leak and fluid overload may aggravate IAH and respiratory failure, thus establishing a dangerous vicious circle. Respiratory management of patients with IAH is challenging and there is no univocal answer. The measurement of intra-abdominal pressure and esophageal pressure (as a surrogate of pleural pressure) may be useful in assessing the condition and guiding mechanical ventilation. Positive end-expiratory pressure (PEEP) must be carefully selected to counteract IAH-related diaphragm displacement, but too high PEEP levels are associated with hemodynamic failure. Continuous negative extra-abdominal pressure is a promising approach, but its clinical application needs more investigation.

Transverse impact behavior and residual axial compression characteristics of braided composite tubes: Experimental and numerical study

In this study, transverse low-velocity impact response and residual axial compression behavior of braided composite tube with different ply number was investigated by experimental and numerical methods. The transverse low-velocity impact tests with 5.6 J energy were conducted on the composite tubes. The quasi-static axial compression performance of intact and pre-impacted tubes was compared to evaluate the effect of impact damage. A two-step finite element (FE) model was also established to reveal damage mechanisms of braided tube under impact loading and following axial compression. It was found that the wall thickness had a significant influence on the impact response. Obvious structural deformation occurred in 2-ply tube when subjected to impact loading, resulting in a large projected delamination area. In following axial compression process, the delamination failure significantly reduced the local compression stiffness and caused a structural instability, which led to a buckling failure mode. In contrast, increasing bending stiffness of 3 or 4-ply tube suppressed its structural deformation during impact, leading to a confined projected delamination area and therefore the buckling of tube wall was prevented effectively when subjected to axial compression. For all impacted tubes, the transition of failure mode from progressive folding mode in intact tube led to a lower energy absorption capacity per composite ply, especially for 2-ply tube.

Effect of decompression range on decompression limit of cervical laminoplasty.

BackgroundsCervical posterior decompression surgery is used to relieve ventral compression indirectly by incorporating a backward shift of the spinal cord, and this indirect decompression is bound to be limited. This study aimed to determine the decompression limit of posterior surgery and the effect of the decompression range.MethodsWe retrospectively reviewed the data of 129 patients who underwent cervical open-door laminoplasty through 2008 to 2012 and were grouped as follows: C4–C7 (n = 11), C3–C6 (n = 61), C3–C7 (n = 32), and C2–C7 (n = 25). According to the relative location of spinal levels within a decompression range, the type of decompression at a given level was categorized as external decompression (ED; achieved at the levels located immediately external to the decompression range margin), internal decompression (ID; achieved at the levels located immediately internal to the decompression range margin), and central decompression (CD; achieved at the levels located in the center, far from the decompression range margin). The vertebral–cord distance (VCD) was used to evaluate the decompression limit. The C2–C7 angle and VCD on post-operative magnetic resonance images were analyzed and compared between groups. The relationship between VCD and decompression type was analyzed. Moreover, the relationship between the magnitude of the ventral compressive factor and the probability of post-operative residual compression at each level for different decompression ranges was studied.ResultsThere was no significant kyphosis in cervical curvature (> −5°), and there was no significant difference among the groups (F = 2.091, P = 0.105). The VCD of a specific level depended on the decompression type of the level and followed this pattern: ED < ID < CD (P < 0.05). The decompression type of a level was sometimes affected by the decompression range. For a given magnitude of the ventral compressive factor, the probability of residual compression was lower for the group with the larger VCD at this level.ConclusionsOur study suggests that the decompression range affected the decompression limit by changing the decompression type of a particular level. For a given cervical spinal level, the decompression limit significantly varied with decompression type as follows: ED < ID < CD. CD provided maximal decompression limit for a given level. A reasonable range of decompression could be determined based on the relationship between the magnitude of the ventral compressive factor and the decompression limits achieved by different decompression ranges.

Residual stress in struck and cast coins

It has been shown that the metal on struck coin surfaces demonstrates residual elastic compression while the metal on cast coin surfaces demonstrates no stress at all or, sometimes, elastic tension. Non-destructive X-ray diffraction (XRD) (the so-called 'sin 2 Ψ method') is applied in this work for residual elastic stress analysis. It is quite an effective tool in the authentication of coins by establishing the production method of such objects (struck or cast).

Effect of Velocity and Duration of Residual Compression in a Rat Dislocation Spinal Cord Injury Model.

Early decompression of the traumatically injured and persistently compressed spinal cord is intuitively beneficial for neurological outcome. Despite considerable pre-clinical evidence of a neurological benefit to early decompression, the effect of early surgical decompression in clinical spinal cord injury (SCI) remains less clear. The discrepancy between pre-clinical and clinical results may be due to differences between the biomechanical variables used in pre-clinical animal models and the biomechanical conditions occurring in clinical injuries. These pre-clinical variables include region of spinal cord, velocity of impact, and injury mechanism. In this study, the effect of velocity and duration of residual compression on injury severity were evaluated using a novel, rodent model of cervical dislocation SCI. Fifty-two male Sprague-Dawley rats were included in five groups: two timings of decompression (24 min, 240 min), two velocities (10 mm/sec, 500 mm/sec), and a sham group. All injuries involved a 1.45-mm dorsal dislocation of the C6 vertebra relative to C5 with subsequent residual compression of 0.8 mm. Animals were evaluated for motor function using the Martinez open field, grip strength, and grooming tests for 6 weeks post-injury. Immunohistochemistry and histology following sacrifice were conducted with counts for NeuN- and choline acetyltransferase (ChAT)-positive neurons, and length of cavitation. Behavioral testing and histological analysis revealed that injuries induced by the high velocity were consistently more severe than those induced by the low velocity, with behavioral correlations ranging between 0.46 and 0.58 (p < 0.05). Longer duration of residual compression did not produce significantly more severe injuries as measured by functional tests and histology. These findings demonstrate that the velocity of the initial traumatic impact may be a more important factor than duration of residual compression in determining SCI severity in a dislocation model of SCI.

Increasing fatigue life of gte compressor disks made of titanium alloys by discs treatment in fluidized abrasive layer

Purpose. Increasing fatigue life of GTE compressor disks made of titanium alloys by discs treatment in the fluidized abrasive bed.Investigation methods and equipment. The investigations were carried out using LPC stage I discs of ВТ3-1 alloy and HPC stages IV and V discs made of ВТ-9 titanium alloy of Д-36 aircraft engine.In the process of discs manufacture the following manufacturing methods were used: ultrasonic hardening and treatment in the fluidized abrasive bed.The ultrasonic hardening was carried out using Motor Sich serial installation and the fluidized abrasive bed treatment – using the АПС-600А installation.The discs were tested before and after the treatment on a special electrohydraulic test bench with a multi-axis loading system using a fixture reproducing radial and circumferential stresses at the base of an inter-slot projection.The testing was carried out at specimens temperature of 390 °С and 430 °С.For measuring the length of cracks and the time of their occurrence in the slots, the discs were inspected by ЛЮМ-1-ОВ method ant using the МПБ-2 microscope and КМ-8 cathetometer.Obtained results. It has been established that for LPC stage I discs made of ВТ3-1 alloy the increased fillet radius combined with subsequent treatment in the fluidized abrasive bed increases fatigue life of the discs by 6 times before crack occurrence, and increases durability of the disc with a crack by 5.5 times.Durability of a disc is within 41 % to 77.8 % of their total fatigue life .Treatment of the compressor dics made of ВТ-9 titanium alloy in the fluidized abrasive bed creates residual compression strain up to 300 MPa in the surface layer.Testing of the LPC stage 1 discs showed that frequency and shape of the discs effect both fatigue life prior to a crack occurrence and durability prior to discs destruction within the entire investigated loading frequency range of 0.01 Hz to 1.0 Hz.Testing of HPC stages IV and V discs of ВТ-9 titanium alloy showed that temperature variation within 390 °С to 430 °С did not contribute significantly to the fatigue life change. Introduction of endurance into the loading cycle has a considerable effect on the low-endurance fatigue of the compressor discs.Increase of the soak time up to 60 seconds under the same loading conditions decreased fatigue life of the full-scale specimens by 10 times.Scientific novelty. It was demonstrated that treatment of the compressor disks made of titanium alloys in the fluidized abrasive bed increases their cyclic life by 5 to 6 times in comparison with their treatment in accordance with serial technology.Practical effect. A process sheet was proposed and the modes of compressor discs treatment in the fluidized abrasive layer were developed that provide increase of the fatigue life by 5 to 6 times as compared with a serial technology.

Assessing capacity of corroded angle members in steel structures based on experiment and simulation

The residual bearing capacity of corroded angle members is critical for safety assessment of on-service steel tower structures. In this study, a total of 90 angle members were evaluated, among which 6 angle members were un-corroded and 84 angle members, with three sizes of cross sections (L50 × 4, L56 × 4 and L70 × 5) and three slenderness ratios (L0/r = 60, 90 and 120), were corroded using an accelerated laboratory testing method. Four corrosion levels, with a mass loss ranging from 10% to 40%, were considered. The compressive capacity of these corroded angle members was evaluated. Finite element simulations were conducted to analyze the failure modes and the residual capacities of corroded angle members using the ABAQUS computer program, under the assumption of uniform corrosion of angle steel members. The test results revealed that there is a strong linear relationship between the thickness and mass losses (in percentage, %) of the corroded angle members. When the mass loss is below 43%, the residual capacity of the corroded members decreased linearly with the increasing mass loss, and the slenderness and cross section area have little influences on the residual capacity. According to the data obtained from all tests and simulations, the residual compression capacity of the angle steel members approximates to a quadratic function of their corrosion levels, as the corrosion levels ranged from 0% to 100%. The GB50017-2017 model provides a more rational prediction of the residual capacity than the ASCE10-97, DL/T5154-2012 and AISC360-05 models.

Technical notes and clinical efficacy analysis of full-endoscopic thoracic discectomy via transforaminal approach

Objective: To study the technical notes and clinical efficacy of full-endoscopic thoracic intervertebral discectomy via transforaminal approach. Methods: We included 16 patients with thoracic disc herniation treated by full-endoscopic thoracic discectomy via transforaminal approach between January 2017 and September 2018 in ours department of orthopedics. The average age is 53.7 years. The compressionare classified by nature: 5 cases of soft thoracic disc herniation, 7 cases of calcified or ossified thoracic disc herniation, and 4 cases of osteophyte protrusion of the posterior edge of the adjacent vertebral body of the diseased disc. All patients had symptoms of thoracic myelopathy before operation, and 7 of them had radiculopathy. Via transforaminal approach under local anesthesia, enlarged foraminoplasty and full-endoscopic thoracic discectomy were used for treatment. Observe the changes of postoperative imaging, pain symptoms and recovery of spinal cord function at 1 week, 3 months, 6 months and 1 year after operation. Back pain and radicular pain were scored with VAS, neurological function was assessed with Nurick score and mJOA score, and thoracic spine function was assessed with Oswestry disability index (ODI). Results: All operations were successfully completed, and no intraoperative conversion of surgical methods occurred. Postoperative thoracic MRI and CT examinations of all patients showed that the spinal cord was fully decompressed without any residual compression. Back pain and radicular pain were all relieved obviously in all patients, and spinal cord function was obviously restored. Transient intercostal neuralgia occurred in 2 cases after operation, and no other surgical complications occurred. Conclusions: Full-endoscopic or fluoroscopic foraminoplasty and full-endoscopic thoracic discectomyvia transforaminal approach under local anesthesia is a safe and effective treatment for soft and hard thoracic disc herniation located on the ventral side of the spinal cord.

Analysis of Low-Velocity Impact Resistance of Carbon Fiber Reinforced Polymer Composites Based on the Content of Incorporated Graphite Fluoride

As a graphite derivative, graphite fluoride (GrF) has a remarkable fracture toughness improvement effect on epoxy materials. The fracture toughness variation of the epoxy could exert an influence on the low velocity impact resistance of the corresponding carbon fiber reinforced polymer (CFRP) composite. Therefore, the dependence of the low velocity impact resistance of the incorporated CFRP on the GrF content is worth analyzing. Here, different contents of GrF were applied to incorporate CFRP laminates and planned to find the optimal GrF content, in turn leading to the best impact resistance. Using a drop-weight impact test, the load vs. time curves and load vs. displacement curves were obtained. The incipient damage loads and maximum loads of various GrF contents of the samples were compared carefully. The absorbed energies during the impact process were calculated. The trend of absorbed energy decreased up to the 1 wt% sample, then increased significantly with the rise of GrF content. This deflection behavior can be explained by the combination of crack pinning, crack deflection and crack propagation, due to the rise in GrF content. Through the ultrasonic C-scan evaluation, the delamination areas of different GrF content of samples were measured. The trend of delamination area variation was accordant with the trend of absorbed energy variation. This presents a demonstration of the correlation between the absorbed energy and the damage level. The SEM images of the fracture surfaces were analyzed for the deflection behavior of the fracture toughness with various GrF contents. The plot of residual compression strength versus GrF content further indicated the 1 wt% was the optimal content at which the incorporated GrF endowed the most impact-resistant property to the CFRP laminates.

Behaviour and residual compression resistances of circular high strength concrete-filled stainless steel tube (HCFSST) stub columns after exposure to fire

The structural behaviour and residual compression resistances of circular high strength concrete-filled stainless steel tube (HCFSST) stub columns after exposure to fire were experimentally and numerically investigated in this paper. The experimental study was performed on 12 circular HCFSST stub column specimens after exposure to the ISO-834 standard fire for three levels of heating durations (15 min, 30 min and 45 min) as well as 4 unheated circular HCFSST stub column specimens (i.e. reference specimens). The experimental study was supplemented by a numerical modelling study, where two types of finite element (FE) models, namely heat transfer and mechanical FE models, were firstly developed to simulate the thermal and mechanical responses of the circular HCFSST stub column specimens, and then used to perform parametric studies to derive additional numerical results. Due to the lack of existing design codes for concrete-filled stainless steel tube members and concrete-filled carbon steel tube members after exposure to fire, the corresponding codified design provisions for circular concrete-filled carbon steel tube members at room temperature, as established in Europe, Australia and America, were evaluated for their suitability to circular HCFSST stub columns after exposure to fire, based on the test and numerical parametric study results. It was generally found that both the European and Australian codes yield a high level of accuracy and consistency in predicting the residual compression resistances of circular HCFSST stub columns after exposure to fire, while the American specification leads to rather conservative and scattered design residual compression resistances.

Research on Data Fusion Scheme for Wireless Sensor Networks with Combined Improved LEACH and Compressed Sensing.

There are a lot of redundant data in wireless sensor networks (WSNs). If these redundant data are processed and transmitted, the node energy consumption will be too fast and will affect the overall lifetime of the network. Data fusion technology compresses the sampled data to eliminate redundancy, which can effectively reduce the amount of data sent by the node and prolong the lifetime of the network. Due to the dynamic nature of WSNs, traditional data fusion techniques still have many problems. Compressed sensing (CS) theory has introduced new ideas to solve these problems for WSNs. Therefore, in this study we analyze the data fusion scheme and propose an algorithm that combines improved clustered (ICL) algorithm low energy adaptive clustering hierarchy (LEACH) and CS (ICL-LEACH-CS). First, we consider the factors of residual energy, distance, and compression ratio and use the improved clustered LEACH algorithm (ICL-LEACH) to elect the cluster head (CH) nodes. Second, the CH uses a Gaussian random observation matrix to perform linear compressed projection (LCP) on the cluster common (CM) node signal and compresses the N-dimensional signal into M-dimensional information. Then, the CH node compresses the data by using a CS algorithm to obtain a measured value and sends the measured value to the sink node. Finally, the sink node reconstructs the signal using a convex optimization method and uses a least squares algorithm to fuse the signal. The signal reconstruction optimization problem is modeled as an equivalent -norm problem. The simulation results show that, compared with other data fusion algorithms, the ICL-LEACH-CS algorithm effectively reduces the node’s transmission while balancing the load between the nodes.

Is Modified K-line a Powerful Tool of Surgical Decision Making for Patients With Cervical Spondylotic Myelopathy?

Prospective observational single-center study. To evaluate anterior decompression and fusion (ADF) or posterior surgery (PS) for patients with cervical spondylotic myelopathy (CSM) using the modified K-line (mK-line) and to compare clinical and radiologic outcomes between these 2 techniques. The authors have previously reported that insufficient posterior decompression is often seen after laminoplasty for CSM in patients with preoperative anterior clearance of the spinal cord <4 mm on the basis of the mK-line. However, to our knowledge, no study has investigated the role, if any, of the mK-line in surgical decision making for patients with CSM. A total of 87 patients were enrolled who underwent surgery for treatment of CSM between 2011 and 2015 at our hospital and who could be followed up for at least 2 years. ADF was selected as a more favorable procedure than PS in patients with anterior spinal clearance of <4 mm on preoperative midsagittal magnetic resonance imaging. On the basis of the Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy, the rate of recovery of the JOA scores at 2 years after surgery was investigated as a clinical outcome to compare these 2 groups. Mean age was 65.1 (±12.9) years in the ADF group (n=26) and 70.5 (±8.6) years in the PS group (n=61). In the PS group, 10 patients underwent posterior decompression with fusion. Mean preoperative and postoperative JOA scores were 10.5 and 14.1 points in the ADF group and 9.8 and 13.1 points in the PS group, respectively, showing no significant difference in recovery rate of JOA score between the ADF (58.9%) and PS (47.1%) groups. However, patients with a minimum interval between the mK-line and the anterior compression factor on the midsagittal image (minimum interval of the spinal cord) <4 mm tended to have unsatisfactory outcomes (recovery rate 29.6%) compared with patients with minimum interval of the spinal cord >4 mm (53.6%, P=0.07) in the PS group. Preoperative intervention using the mK-line is useful to predict residual cord compression and might homogenize postoperative clinical outcomes in both anterior surgery and PS.

Compression after Impact Behaviour and Failure Analysis of Nanosilica-Toughened Thin Epoxy/GFRP Composite Laminates.

Nanosilica particles were utilized as secondary reinforcement to enhance the strength of the epoxy resin matrix. Thin glass fibre reinforced polymer (GFRP) composite laminates of 3 ± 0.25 mm were developed with E-Glass mats of 610 GSM and LY556 epoxy resin. Nanosilica fillers were mixed with epoxy resin in the order of 0.25, 0.5, 0.75 and 1 wt% through mechanical stirring followed by an ultrasonication method. Thereafter, the damage was induced on toughened laminates through low-velocity drop weight impact tests and the induced damage was assessed through an image analysis tool. The residual compression strength of the impacted laminates was assessed through compression after impact (CAI) experiments. Laminates with nanosilica as secondary reinforcement exhibited enhanced compression strength, stiffness, and damage suppression. Results of Fourier-transform infrared spectroscopy revealed that physical toughening mechanisms enhanced the strength of the nanoparticle-reinforced composite. Failure analysis of the damaged area through scanning electron microscopy (SEM) evidenced the presence of key toughening mechanisms like damage containment through micro-cracks, enhanced fiber-matrix bonding, and load transfer.

On the damage mechanism of high-speed ballast impact and compression after impact for CFRP laminates

Single and multiple track-ballast impacts are investigated for the CFRP laminates used in train carbodies. Numerical simulations have been performed to study the damage behaviors of CFRP laminates during ballast impacts and compressions after ballast impact (CABI). Intralaminar and interlaminar damages are successfully predicted using continuum damage mechanics and cohesive zone model, respectively. It reveals that, for a high-speed ballast impact, delamination occurs during the damage initiation and appears at several interfaces nearby the impacted side of the specimen. After that, fiber breakage and matrix cracking appear, while delamination continuously extends until the failure. Repeated ballast impacts on the same site and different sites of specimens show significant increase of delamination while indicating less intralaminar damage. Furthermore, CABI simulations show that, the residual compression strength decreases in a nonlinear manner with the increase of impact energy. To bear the same impact energy, less detrimental effect is caused when one impact is replaced by two or more impacts.