Carbon Fiber Plate Research Articles

Effect of the Construction of Carbon Fiber Plate Insert to Midsole on Running Performance.

In this paper, to investigate the independent effect of the construction of the forefoot carbon-fiber plate inserted to the midsole on running biomechanics and finite element simulation, fifteen male marathon runners were arranged to run across a runway with embedded force plates at two specific running speeds (fast-speed: 4.81 ± 0.32 m/s, slow-speed: 3.97 ± 0.19 m/s) with two different experimental shoes (a segmented forefoot plate construction (SFC), and a full forefoot plate construction (FFC)), simulating the different pressure distributions, energy return, and stiffness during bending in the forefoot region between the SFC and FFC inserted to midsole. Kinetics and joint mechanics were analyzed. The results showed that the footwear with SFC significantly increased the peak metatarsophalangeal joint (MTPJ) plantarflexion velocity and positive work at the knee joint compared to the footwear with FFC. The results about finite element simulation showed a reduced maximum pressure on the midsole; meanwhile, not significantly affected was the longitudinal bending stiffness and energy return with the SFC compared to the FFC. The results can be used for the design of marathon running shoes, because changing the full carbon fiber plate to segment carbon fiber plate induced some biomechanical transformation but did not significantly affect the running performance, what is more, reducing the peak pressure of the carbon plate to the midsole by cutting the forefoot area of the carbon fiber plate could be beneficial from a long-distance running perspective for manufacturers.

Deformable foot orthoses redistribute power from the ankle to the distal foot during walking

Recently, carbon fiber plates, or orthoses, have been incorporated into footwear to improve running performance, presumably through improved energy storage and return. However, few studies have explored the energetic effects these orthoses have on the distal foot, have utilized such orthoses in walking, and none have sought to specifically harness metatarsophalangeal joint deformation to store and return energy to the ankle–foot complex. To address these gaps, we developed and tested a deformable carbon fiber foot orthosis aiming to harness foot energetics and quantify the resulting effects on ankle energetics during walking in healthy adults. Eight subjects walked under three conditions: barefoot (BF), with minimalist shoes (SH), and with bilateral, deformable foot orthoses in the minimalist shoes (ORTH). Ankle and distal foot energetics, foot-to-floor and ankle angle, stance time, step length, and max center of pressure (COP) position were calculated. When walking with the orthoses, subjects showed 263.6% increase in positive distal foot work along with a 31.9% decrease in ankle work and little to no change in the overall ankle–foot complex work. Step length, stance time, and max anterior COP position significantly increased with orthosis use. No statistical or visual differences were found between BF and SH conditions indicating that our findings were due to the foot orthoses. These results suggest this foot orthosis redistributes power from the ankle to the distal foot for healthy adults, reducing the energetic demand on the ankle. These results lay the foundation for designing orthotics and footwear to improve ankle–foot energetics for clinical populations.

Longitudinal bending stiffness does not affect running economy in Nike Vaporfly Shoes

PurposeThis study aimed to determine the independent effect of the curved carbon-fiber plate in the Nike Vaporfly 4% shoe on running economy and running biomechanics. MethodsFifteen healthy male runners completed a metabolic protocol and a biomechanics protocol. In both protocols participants wore 2 different shoes, an intact Nike Vaporfly 4% (VFintact) and a cut Nike Vaporfly 4% (VFcut). The VFcut had 6 medio-lateral cuts through the carbon-fiber plate in the forefoot to reduce the effectiveness of the plate. In the metabolic protocol, participants ran at 14 km/h for 5 min, twice with each shoe, on a force-measuring treadmill while we measured metabolic rate. In the biomechanics protocol, participants ran across a runway with embedded force plates at 14 km/h. We calculated running economy, kinetics, and lower limb joint mechanics. ResultsRunning economy did not significantly differ between shoe conditions (on average, 0.55% ± 1.77% (mean ± SD)) worse in the VFcut compared to the VFintact; 95% confidence interval (–1.44% to 0.40%). Biomechanical differences were only found in the metatarsophalangeal (MTP) joint with increased MTP dorsiflexion angle, angular velocity, and negative power in the VFcut. Contact time was 1% longer in the VFintact. ConclusionCutting the carbon-fiber plate and reducing the longitudinal bending stiffness did not have a significant effect on the energy savings in the Nike Vaporfly 4%. This suggests that the plate's stiffening effect on the MTP joint plays a limited role in the reported energy savings, and instead savings are likely from a combination and interaction of the foam, geometry, and plate.

An algorithm based on logarithm of wavenumber amplitude for detection of delamination in carbon fiber composite

Delamination is one of the most common types of damage/defect in carbon/glass fiber reinforced composites and many researchers use frequency-wavenumber analysis to detect delamination. There are large fluctuations in amplitudes when Lamb wave propagates in composite plate, so that it is hard to precisely identify the boundary of delamination simply from the change of wavenumber. This paper has presented an algorithm based on logarithm of wavenumber amplitude to detect the delamination in carbon fiber plate with high precision. In wavenumber spectra after logarithm processing, the wavenumber amplitudes at delamination boundary can be significantly amplified and the resulting curve of sum of amplitudes can be used to effectively identify the boundary. In this paper, the principle of the logarithm of amplitude algorithm has been introduced and the effectiveness of the algorithm in delamination identification has been validated by finite element simulations and physical experiments. Compared with conventional algorithms, the proposed algorithm can effectively identify the boundary with better accuracy (less than 5%) and has decent identification stability under different depths of delamination. Our research has great potential for solving the challenge in precise identification of delamination boundary.

Exploring the teeter-totter effect in shoes with curved carbon fibre plates

In recent times, the Nike Vaporfly 4% marathon shoe has been one of the most exciting shoes designed for competitive runners. It has been shown to lower the energetic cost of running on average by ...

Evaluating longitudinal bending stiffness testing for performance footwear

Longitudinal bending stiffness (LBS) is a critical factor in performance running shoe design. Moreover, the recent appearance of carbon-fiber plates in running shoes has created increased interest ...

Anti-pronator components are essential to effectively alter lower-limb kinematics and kinetics in individuals with flexible flatfeet

BackgroundFoot orthoses are commonly used to correct for foot alterations and especially address excessive foot pronation in individuals with flatfeet. In recent years, 3D printing has taken a key place in orthotic manufacturing processes as it offers more options and can be patient specific. Hence, the purpose of this study was to evaluate whether stiffness of 3D printed foot orthoses and a newly designed rearfoot posting have an effect on lower limb kinematics and kinetics in individuals with flatfeet. MethodsNineteen patients with flexible flatfeet were provided two pairs of customized 3D printed ¾ length orthotics. Foot orthoses were of different stiffness and could feature a rearfoot posting, consisting of 2-mm carbon fiber plate. Lower limb kinematics and kinetics were computed using a multi-segment foot model. One-way ANOVAs using statistical non-parametric mapping, refined by effect sizes, were performed to determine the magnitude of the effect between conditions. FindingsFoot orthoses stiffness had little effect on midfoot and forefoot biomechanics. Reductions in midfoot eversion and forefoot abduction were observed during short periods of stance with rigid foot orthoses. Adding the posting had notable effects on rearfoot kinematics and on the ankle and knee kinetics in the frontal plane; it significantly reduced the eversion angle and inversion moment at the ankle, and increased the knee abduction moment. InterpretationUsing an anti-pronator component is more effective than increasing foot orthoses stiffness to observe a beneficial impact of foot orthoses on the control of excessive foot pronation in individuals with flatfeet.

Energetics and Biomechanics of Running Footwear with Increased Longitudinal Bending Stiffness: A Narrative Review

In the wake of the quest to break the 2-h marathon barrier, carbon-fiber plates have become commonplace in marathon racing shoes. Despite the controversy surrounding this shoe technology, studies on the effects of increased longitudinal bending stiffness on running economy report mixed results. Here, we provide a comprehensive review of the current literature on midsole bending stiffness and carbon-fiber plates in distance running shoes, focusing on how longitudinal bending stiffness affects running energetics and lower limb mechanics. The current literature reports changes in running economy with increased longitudinal bending stiffness ranging from ~ 3% deterioration to ~ 3% improvement. In some studies, larger improvements have been observed, but often those shoes varied in many aspects, not just longitudinal bending stiffness. Biomechanically, increased longitudinal bending stiffness has the largest impact on metatarsal–phalangeal (MTP) and ankle joint mechanics. Plate location [top loaded (an insole), embedded (in between midsole foam), and bottom loaded (along the bottom of the shoe)] and geometry (flat/curved) affect joint moments and angular velocities at the MTP and ankle joint differently, which partly explains the mixed running economy results. Further research investigating how carbon-fiber plates interact with other footwear features (such as foam and midsole geometry), scaling of those with shoe size, body mass, and strike pattern, and comparing various plate placements is needed to better understand how longitudinal bending stiffness affects running economy.

Experimental study of desalination and ion selection performance using electro-sorption technology with an activated carbon fiber electrode

ABSTRACT The realization of high-efficiency desalination technologies is the key to the reuse of circulating cooling sewage in power plants. Desalination experiments were carried out on an electro-sorption device with an activated carbon fiber (ACF) plate as an electrode, using the mixed salt solution to simulate actual circulating cooling sewage. The effects of flow rate and voltage on desalination and ion selection performance were investigated in the paper. Experimental results show that different ions can be effectively removed using activated carbon fiber electrodes. Under the same adsorption conditions, the adsorption rate of ions is inversely proportional to the mass-to-charge ratio; the smaller the hydration radius of ions, the larger the ion removal rate; the ion selection performance is related to the pore size distribution of the selected electrode material. The experimental results can provide basic data and reference for the treatment of circulating cooling water using electro-sorption technology.

Experimental Study on Anchoring Performance of CFRP Anchor

Prestressing carbon fiber plate (CFRP) has been gradually used in the field of bridge reinforcement, but the anchorage of CFRP is various and the anchorage performance is different. This paper studies the anchorage performance, failure form, and tension control stress of two kinds of common anchors through experiments, which provides reference for the anchorage selection and construction guidance in the future.

Shear strengthening of plate girders using carbon-fibre-reinforced polymer composites

New methods for strengthening steel structures using fibre-reinforced polymer composites have been the subject of much recent research. Few studies have been carried out on shear strengthening of plate girders using carbon-fibre composites. In the study reported in this paper, the impact of carbon-fibre composite plates on end-zone shear capacity of steel-plate girders is investigated. A section of plate girder with a length and height of 300 mm was chosen for numerical modelling. All specimens were modelled using finite-element software. Initially, the software was verified using experimental data available in the literature. Eleven specimens with different arrangements of composite strips on the web of the plate girders were then investigated. Different ratios of composites were pasted on one side or both sides of the web. Static non-linear methods were used to analyse the specimens. The results indicated that fully strengthening the plate girders on both sides of the web significantly increased bearing capacity.

Recent Improvements in Marathon Run Times Are Likely Technological, Not Physiological.

Every women’s and men’s world records from 5 km to the marathon has been broken since the introduction of carbon fibre plate (CFP) shoes in 2016. This step-wise increase in performance coincides with recent advancements in shoe technology that increase the elastic properties of the shoe thereby reducing the energy cost of running. The latest CFP shoes are acknowledged to increase running economy by more than 4%, corresponding to a greater than 2% improvement in performance/run time. The recently modified rules governing competition shoes for elite athletes, announced by World Athletics, that includes sole thickness must not exceed 40 mm and must not contain more than one rigid embedded plate, appear contrary to the true essence and credibility of sport as access to this performance-defining technology becomes the primary differentiator of sporting performance in elite athletes. This is a particular problem in sports such as athletics where the primary sponsor of the athlete is very often a footwear manufacturing company. The postponement of the 2020 Summer Olympics provides a unique opportunity for reflection by the world of sport and time to commission an independent review to evaluate the impact of technology on the integrity of sporting competition. A potential solution to solve this issue can involve the reduction of the stack height of a shoe to 20 mm. This simple and practical solution would prevent shoe technology from having too large an impact on the energy cost of running and, therefore, determining the performance outcome.Electronic supplementary materialThe online version of this article (10.1007/s40279-020-01420-7) contains supplementary material, which is available to authorized users.

Increasing the midsole bending stiffness of shoes alters gastrocnemius medialis muscle function during running

In recent years, increasing the midsole bending stiffness (MBS) of running shoes by embedding carbon fibre plates in the midsole resulted in many world records set during long-distance running competitions. Although several theories were introduced to unravel the mechanisms behind these performance benefits, no definitive explanation was provided so far. This study aimed to investigate how the function of the gastrocnemius medialis (GM) muscle and Achilles tendon is altered when running in shoes with increased MBS. Here, we provide the first direct evidence that the amount and velocity of GM muscle fascicle shortening is reduced when running with increased MBS. Compared to control, running in the stiffest condition at 90% of speed at lactate threshold resulted in less muscle fascicle shortening (p = 0.006, d = 0.87), slower average shortening velocity (p = 0.002, d = 0.93) and greater estimated Achilles tendon energy return (p ≤ 0.001, d = 0.96), without a significant change in GM fascicle work (p = 0.335, d = 0.40) or GM energy cost (p = 0.569, d = 0.30). The findings of this study suggest that running in stiff shoes allows the ankle plantarflexor muscle–tendon unit to continue to operate on a more favourable position of the muscle’s force–length–velocity relationship by lowering muscle shortening velocity and increasing tendon energy return.

An ultralight-weight polymer electrolyte fuel cell based on woven carbon fiber-resin reinforced bipolar plate

Exploration towards the lightweight bipolar plate, composed of cheap and abundant materials, is of great importance to accelerate the commercialization of polymer electrolyte fuel cells (PEFCs). Herein, new bipolar plate is fabricated by carbon fiber plate reinforced with polymeric resin, to alternate the conventional graphite composite (GBP) and metallic ones (MBP). Unlike the previous studies, the woven-type carbon fiber bipolar plates (CFBPs), with an initial thickness of 300 μm, have physically been grinded to 270, 220 and 170 μm, then followed by the deposition of conductive carbon layer, in order to reduce both bulk and interfacial contact resistances. Remarkably, the resultant CFBP even with metallic mesh flow fields exhibited less than 14.6% and 23.6% weight of the GBP and MBP, respectively, which doubles the gravimetric cell power density. Three key properties, i.e., electrical conductivity, mechanical strength and gas permeability, fully satisfied the US DOE's 2020 targets. Furthermore, the PEFC employing the proposed CFBP with metallic mesh flow field showed notable improvements in the ohmic and mass-transport performance, confirmed by both cell polarization and electrochemical impedance spectroscopy. Given the excellent gravimetric power density, this work may draw the first step toward a newly-structured PEFC for an automotive, marinomotive and, particularly, aeromotive powertrain applications.

Adding carbon fiber to shoe soles may not improve running economy: a muscle-level explanation

In an attempt to improve their distance-running performance, many athletes race with carbon fiber plates embedded in their shoe soles. Accordingly, we sought to establish whether, and if so how, adding carbon fiber plates to shoes soles reduces athlete aerobic energy expenditure during running (improves running economy). We tested 15 athletes as they ran at 3.5 m/s in four footwear conditions that varied in shoe sole bending stiffness, modified by carbon fiber plates. For each condition, we quantified athlete aerobic energy expenditure and performed biomechanical analyses, which included the use of ultrasonography to examine soleus muscle dynamics in vivo. Overall, increased footwear bending stiffness lengthened ground contact time (p = 0.048), but did not affect ankle (p ≥ 0.060), knee (p ≥ 0.128), or hip (p ≥ 0.076) joint angles or moments. Additionally, increased footwear bending stiffness did not affect muscle activity (all seven measured leg muscles (p ≥ 0.146)), soleus active muscle volume (p = 0.538; d = 0.241), or aerobic power (p = 0.458; d = 0.04) during running. Hence, footwear bending stiffness does not appear to alter the volume of aerobic energy consuming muscle in the soleus, or any other leg muscle, during running. Therefore, adding carbon fiber plates to shoe soles slightly alters whole-body and calf muscle biomechanics but may not improve running economy.

Mechanical property evolution and life prediction of carbon fiber and pultruded carbon fiber reinforced polymer plate exposed to elevated temperatures

AbstractThe fire resistance of carbon fiber reinforced polymer (CFRP) composite is a huge challenge for strengthening and repairing structures in civil engineering. In the present study, the effects of temperature exposure on the mechanical, thermal and microstructure properties of carbon fibers (~700°C) and CFRP plates (~300°C) with the bisphenol‐A epoxy matrix (E51) and hydantoin epoxy matrix (HY) were investigated. The thermal decomposition, void content, surface morphology, and internal microstructures were obtained to reveal the degradation mechanism of CFRP plates. Exposure at elevated temperatures brought about the obvious degradation of the tensile strength of carbon fiber and CFRP plate, and the final tensile strength retention rates of CFRP plates were 72.6% with the low glass transition temperature of CFRP (E51) and 72.3% with the high glass transition temperature of CFRP (HY), respectively. The allowable maximum exposure temperature was estimated to be 200°C to guarantee the desirable tensile stiffness for the CFPR plates. Oxidation of carbon fiber has an inhibition effect on the decomposition of E51 resin in CFRP (E51). By comparison, the decomposition of HY resin and oxidation of carbon fibers were independent in CFRP (HY). The increased void content of CFRP plates at elevated temperatures aggravated the debonding of fiber/resin interface and weakened the synchronous load‐bearing capacity between the fibers, which led to the decrease of mechanical properties. Finally, the rule‐of‐mixture and the elastic mechanics theory were applied to obtain the life prediction model of tensile strength of CFRP plate at elevated temperatures. According to the model, the limit exposure temperatures of tensile strength were 483°C for CFRP (E51) and 466°C for CFRP (HY), respectively.

Mechanical and Electrical Response of Structural Capacitor for Various Dielectric Materials

Due to the run out of the fossil energy sources and environmental issues, new energy storage systems are developed in conjunction with renewable energy technologies. The machines that supplied energy from the batteries consume extra energy because they carry both the weight of the batteries and the structural weight. Recently, the idea of storing energy in structural elements has been studied. In this study, the multifunctionality of structural capacitors made by placed of varied dielectric layers between the carbon fiber plates has been investigated. The effects on the mechanical and electrical properties of different dielectric material combinations has been investigated by the simulation, experimentally and by the calculations based on Hook's law. Thus, the results of structural dielectric capacitors in these combinations have been compared and discussed.

Improving running economy through altered shoe bending stiffness across speeds

Increasing the longitudinal bending stiffness of running shoes decreases energy cost until a low point is reached, suggesting an optimal shoe stiffness. Previous research found optimal stiffness varies among individuals, however, none has determined the causes of variation both between individuals and running speeds. The primary purpose of this study was to understand how optimal shoe stiffness is affected by running speed. A secondary purpose examined the anatomical and biomechanical characteristics associated with optimal stiffness variation. Six shoe stiffness conditions were manufactured with a carbon fibre plate between the midsole and outsole of a standard running shoe. Twenty-one male runners (mass = 67.1 ± 5.0 kg, height = 178.9 cm ± 4.0 cm, age = 26.4 ± 8.4 years) completed testing at 2.98 m/s and 4.47 m/s in all shoe conditions, measuring metabolic cost, and several biomechanical and anatomical variables. Data were separated by foot strike. At the fast speed, average optimal stiffness was 19.29 ± 5.62 N/mm with a metabolic benefit of 3.02 ± 2.62%. Slow speed average optimal stiffness was 17.04 ± 6.09 N/mm with a metabolic benefit of 1.93 ± 1.82%. Only rearfoot strikers demonstrated a significant increase in optimal stiffness (p = .04) across speeds. There were no correlations between any of the measured anatomical or biomechanical variables and optimal stiffness. Optimal stiffness varied between subjects but was not correlated to any of our measured characteristics. Rearfoot striking runners may benefit from a higher stiffness shoe at faster speeds to enable optimal performance.

Study on Fatigue Characteristics of Carbonation Erosion Prestressed Hollow Slabs in Whole Life Cycle

In this paper, the whole life cycle (failure‐reinforcement‐failure) durability and related fatigue properties of prestressed hollow beam under carbonation erosion environment were studied. According to a 20 m hollow slab beam, the model of prestressed hollow beam was designed and made, and the durability and fatigue tests for the whole life cycle of prestressed hollow beam were carried out. The results showed that the compressive strength and elastic modulus of the specimens increased by about 20% under the action of carbonization erosion. With the increase of fatigue loading cycles, the crack occurrence and development speed of carbonized erosion components were greater than those of healthy components, and the fatigue life decreased sharply from 3 million cycles to 50,000 cycles. Pasting carbon fiber and steel plate had better reinforcement effect on the damaged prestressed plate beam and could help improving the fatigue life of the reinforced component. Comparing the reinforcement of different strengthening methods, it is found that the steel‐plate‐reinforced components have better mechanical properties and antifatigue attenuation characteristics than the carbon‐fiber‐reinforced ones. The research results have important theoretical value for improving the durability of structure and prolonging its service life.

Progressive Damage Analysis (PDA) of Carbon Fiber Plates with Out-of-Plane Fold under Pressure

The out-of-plane fold is a common defect of composite materials during the manufacturing process and will greatly affect the compressive strength as well as the service life. Making it of great importance to investigate the influence of out-of-plane defects to the compressive strength of laminate plates of composite materials, and to understand the patterns of defect evolution. Therefore, the strip method is applied in this article to create out-of-plane defects with different aspect ratios in laminated plates of composite materials, and a compressive performance test is conducted to quantify the influence of out-of-plane defects. The result shows that the compressive strength becomes weaker with a greater aspect ratio. When the highest aspect ratio is set to 0.12 in the experiment, the compressive strength reduces by 36.1%. Then we establish a 3-D progressive damage model based on continuum mechanics, and write it into the UMAT subroutine together with the 3-D Hashin criteria and the non-linear degradation criteria of materials. 3-D solid modeling is performed for the samples with an out-of-plane fold based on ABAQUS, and progressive damage analysis is conducted to acquire the inplane evolution process of initial failure strength with different laminates. The experimental results agree well with the simulation results.