Main Damage Modes Research Articles

Mechanical Properties and Interlaminar Fracture Toughness of Glass‐Fiber‐Reinforced Epoxy Composites Embedded with Shape Memory Alloy Wires

The effects of the content and position of shape memory alloy (SMA) wires on the mechanical properties and interlaminar fracture toughness of glass‐fiber‐reinforced epoxy (GF/epoxy) composite laminates are investigated. For this purpose, varying numbers of SMA wires are embedded in GF/epoxy composite laminates in different stacking sequences. The specimens are prepared by vacuum‐assisted resin infusion (VARI) processing and are subjected to static tensile and three‐point‐bending tests. The results show that specimens with two SMA wires in the stacking sequence of [GF2/SMA/GF1/SMA/GF2] and four SMA wires in the stacking sequence of [GF4/SMA/GF2/SMA/GF4] exhibit optimal performance. The flexural strength of the optimal four‐SMA‐wire composite is lower than that of the pure GF/epoxy composite by 5.76% on average, and the flexural modulus is improved by 5.19%. Mode‐I and II interlaminar fracture toughness tests using the SMA/GF/epoxy composite laminates in the stacking sequence of [GF4/SMA/GF2/SMA/GF4] are conducted to evaluate the mechanism responsible for decreasing the mechanical properties. Scanning electron microscopy (SEM) observations reveal that the main damage modes are matrix delamination, interfacial debonding, and fiber pullout.

Braided textile composites for sports protection: Energy absorption and delamination in impact modelling

Composites reinforced with braided textiles exhibit high structural stability and excellent damage tolerance, making them ideal materials for use in sports-protection equipment. In sports impact scenarios, braided composites need to maintain their structure integrity and dissipate impact energy to protect a human body. Thus, it is crucial to study the dynamic response of a composite structure and its energy-dissipation mechanisms. Here, a multi-scale computational approach was explored to capture main damage modes of a braided textile composite; simulations were supported by experimental verification. A drop-weight test was performed with a spike-shape impactor to imitate real-life sports impact collision scenarios, followed by X-ray computed micro-tomography to characterize damage morphology of the specimen. The experimental results were compared with analytical models. The extent of delamination was quantified by applying surface- and element-based cohesive zone models. A ply-level model with three-dimensional continuum and shell elements was employed to explore the effect of through-thickness failure modes on energy absorption of the composite. The propagation mechanism of matrix cracks is also discussed. In addition, with the developed model, impact-attenuation performance of a shin-guard structure was simulated. The presented modelling capability can improve design of braided composite structures for sports and other protective and structural applications.

Fatigue Damage Mechanical Model of the Envelope Material for Stratospheric Airships

As a major part of the stratospheric airship structure, the envelope material is used to contain lifting gas and keep the aerodynamic configuration. The main force on the envelope material comes from differential pressure between inside and outside the structure, which is cyclic stress because of the alternative temperature. Three different damage modes of the envelope material, including fracture damage of fabric yarns, cracking damage of resin matrix and functional membrane are investigated in this paper. A theoretical model to predict fatigue life of the envelope material under cycle load is developed base on the damage evolution properties of the material. The results indicates that the theoretical model can well predict the fatigue life. In addition, it can be seen from the results that the fracture of fabric yarns is the main damage modes for the material with off-axial angle of 0°and 90°, while the cracking damage of resin and functional membrane is the main damage modes for the material with other off-axial angles.

Low-velocity impact property of alumina/epoxy/metal laminated composites

With Al foil, Cu foil and steel mesh as the metal interlayers, respectively, three types of alumina/epoxy/metal laminated composites were fabricated with epoxy resin adhesive as a binder via a simple process. The impact tests were performed and the fracture patterns and impact response of all the three laminates were analyzed. The experimental results indicate that the absorbed energy is mainly determined by metal interlayer. The peak load depends on not only alumina substrate but also metal interlayer. The Al2O3/epoxy/Cu laminates sustain the maximum peak load and Al2O3/epoxy/steel mesh laminates have the largest threshold energy for penetration. The fracture analysis shows that the main damage modes are Al2O3 matrix cracking and metal deformation for lower impact energies, and complete breakage and penetration for higher impact energies.

Influence of 4 wt.% Cr addition on the corrosion-wear synergistic effect for Al2O3/Fe(Al) composites

Abstract In this work, the corrosion-wear synergistic effect for nanocrystalline Fe(Al), 20 wt.% Al2O3/Fe(Al) composites with and without 4 wt.% Cr in artificial seawater (3.5% NaCl aqueous solution with 60 kg/m3 quartz sand) was investigated. The results showed that the main damage behavior of Al2O3/Fe(Al) composites was a corrosive effect because of its poor corrosion resistance and high hardness, whereas for Fe(Al) material, the main damage mode was a chiseling action by solid particles, due to its relatively low hardness. With 4 wt.% Cr addition, the erosion weight loss at different erosion rates decreased by more than 30%. The Al2O3/Fe(Al) composites had good pure wear resistance, while poor corrosion resistance resulted in an increase in the interaction of corrosion and wear (about 70% of the total damage amount).

Experimental Investigation of the Three-point Bending Fatigue Properties of Carbon Fiber Composite Laminates

The three point bending fatigue properties of carbon fiber epoxy matrix composite laminates were compared for fatigue loading stress levels of 75, 80 and 85%, and fatigue loading frequencies of 10, 15 and 20Hz, respectively. The experimental results showed that: the bending fatigue life of the composites obviously decreased with the increase of the fatigue loading stress level or the loading frequency. The fatigue damage accumulation process could be divided into three distinct stages according to the accumulation rate: fast, slow and then fast. When the loading stress level was increased from 75 to 85%, the duration of the third stage decreased from 40 to 10% of the overall fatigue life. When the loading frequency was increased from 10 to 20Hz, the duration of the third stage increased from 20 to 40% of the overall fatigue life. Matrix cracking, fiber breaking, interface debonding and delamination were identified as the main three-point bending fatigue damage modes of the carbon fiber composite material, and the stress level and the loading frequency were found to significantly influence the fatigue failure properties of the composites.

Experimental investigation of the three-point bending fatigue properties of carbon fiber composite laminates

The three-point bending fatigue properties of carbon fiber epoxy matrix composite laminates were compared for fatigue loading stress levels of 75, 80 and 85%, and fatigue loading frequencies of 10, 15 and 20 Hz, respectively. The experimental results showed that the bending fatigue life of the composites obviously decreased with the increase of the fatigue loading stress level or the loading frequency. The fatigue damage accumulation process could be divided into three distinct stages according to the accumulation rate: fast, slow and then fast. When the loading stress level was increased from 75 to 85%, the duration of the third stage decreased from 40 to 10% of the overall fatigue life. When the loading frequency was increased from 10 to 20 Hz, the duration of the third stage increased from 20 to 40% of the overall fatigue life. Matrix cracking, fiber breaking, interface debonding and delamination were identified as the main three-point bending fatigue damage modes of the carbon fiber composite material, and the stress level and the loading frequency were found to significantly influence the fatigue failure properties of the composites.

Progressive damage analysis and strength properties of fiber-bar composites reinforced by three-dimensional weaving under uniaxial tension

A new geometric model is reported for fiber-bar composites reinforced by three-dimensional weaving (FBCR3DW) having 0/90, 45/135 and 0/90/45/135 weavings. An anisotropic progressive damage analysis model is proposed based on the Hashin-type failure criterion and the Murakami–Ohno damage theory, with shear nonlinearity considered in the stiffness matrix of the yarn and fiber-bar. Finite element models coupled with a progressive damage analysis model were developed to study the progressive damage behavior and strength properties under uniaxial tension. A cohesive zone model was adopted to evaluate the effect of the strength of the interface between the matrix and the fiber-bar on the tensile properties of the FBCR3DW. Several specimens were prepared and used in tensile testing. The stress–strain curves and strengths obtained by the numerical simulations were in good agreement with the experimental results. The failure mechanisms of the composites were revealed in the simulation studies. The numerical results showed that the main damage modes of FBCR3DW were matrix damage, yarn transverse damage and yarn longitudinal breakage, which were in good agreement with the experimental findings.

Analysis of Carbon Fiber Reinforced PEEK Hinge Mechanism Articulation Components in a Rotating Hinge Knee Design: A Comparison of In Vitro and Retrieval Findings

Carbon fiber reinforced poly-ether-ether-ketone (CFR-PEEK) represents a promising alternative material for bushings in total knee replacements, after early clinical failures of polyethylene in this application. The objective of the present study was to evaluate the damage modes and the extent of damage observed on CFR-PEEK hinge mechanism articulation components after in vivo service in a rotating hinge knee (RHK) system and to compare the results with corresponding components subjected to in vitro wear tests. Key question was if there were any similarities or differences between in vivo and in vitro damage characteristics. Twelve retrieved RHK systems after an average of 34.9 months in vivo underwent wear damage analysis with focus on the four integrated CFR-PEEK components and distinction between different damage modes and classification with a scoring system. The analysis included visual examination, scanning electron microscopy, and energy dispersive X-ray spectroscopy, as well as surface roughness and profile measurements. The main wear damage modes were comparable between retrieved and in vitro specimens (n = 3), whereby the size of affected area on the retrieved components showed a higher variation. Overall, the retrieved specimens seemed to be slightly heavier damaged which was probably attributable to the more complex loading and kinematic conditions in vivo.

Investigation on the Tribological Behavior and Wear Mechanism of Five Different Veneering Porcelains

ObjectivesThe primary aim of this research was to investigate the wear behavior and wear mechanism of five different veneering porcelains.MethodsFive kinds of veneering porcelains were selected in this research. The surface microhardness of all the samples was measured with a microhardness tester. Wear tests were performed on a ball-on-flat PLINT fretting wear machine, with lubrication of artificial saliva at 37°C. The friction coefficients were recorded by the testing system. The microstructure features, wear volume, and damage morphologies were recorded and analyzed with a confocal laser scanning microscope and a scanning electron microscope. The wear mechanism was then elucidated.ResultsThe friction coefficients of the five veneering porcelains differ significantly. No significant correlation between hardness and wear volume was found for these veneering porcelains. Under lubrication of artificial saliva, the porcelain with higher leucite crystal content exhibited greater wear resistance. Additionally, leucite crystal size and distribution in glass matrix influenced wear behavior. The wear mechanisms for these porcelains were similar: abrasive wear dominates the early stage, whereas delamination was the main damage mode at the later stage. Furthermore, delamination was more prominent for porcelains with larger crystal sizes.SignificanceWear compatibility between porcelain and natural teeth is important for dental restorative materials. Investigation on crystal content, size, and distribution in glass matrix can provide insight for the selection of dental porcelains in clinical settings.

Study on the low-velocity impact response and CAI behavior of foam-filled sandwich panels with hybrid facesheet

Foam-filled sandwich panels with six types of facesheets were manufactured by vacuum-assisted resin injection (VARI) process. Low velocity impact test and compression after impact (CAI) test of the prepared panels were performed. Failure modes of different sandwich panels were analyzed by observing the contact surface and the cross section through damage region. Scanning electron microscope (SEM) was carried out to study the microstructure of the impacted specimens. It is found that matrix cracking, fiber breaking, foam cracking and debonding are the damage modes of sandwich panel with pure carbon facesheet, while other specimens merely show some of these modes after impact test. Panels with pure carbon facesheet have poor impact resistance properties, while panels with pure glass facesheet have preferable properties among all the specimens. Hybrid panel with ply mode of [C2/G2/Foam core/G2/C2] could provide higher maximum contact force and absorb more impact energy by carbon fiber breaking on the contact surface. In CAI test, wrinkling of facesheet and buckling of foam and skin are the two main damage modes. [C4/Foam core/C4] shows highest compress strength decline rate, while [G4/Foam core/G4] shows lowest rate. Decline rate of [C2/G2/Foam core/G2/C2] is very low but the compress strength of its undamaged specimen is not high.

Tribology and high temperature friction wear behavior of MCrAlY laser cladding coatings on stainless steel

Temperature can have a significant effect on the extent of wear damage of metallic components. Thermal barrier coatings can improve the high temperature tribological and friction wear behavior. In this work the dry friction and wear behavior at low and high temperature of NiCoCrAlY and CoNiCrAlY laser cladding coatings were evaluated, as well as for the austenitic stainless steel AISI 304 used as substrate. Dense coatings, with good bonding to the substrate was obtained by coaxial laser cladding tracks (40% overlapping), with previously optimized laser parameters. Tribological wear tests were performed by sliding wear at room temperature and 500°C, with an Al2O3 ball on disk configuration tribometer. The wear scar surface was evaluated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) microanalysis. The 3D topography of the wear track was determined by inductive contact profilometer which enabled the wear rate calculation. The microstructure of the coatings consists of γNi/β-NiAl or γCo/β-(Co,Ni)Al phases depending on the chemical composition of the alloy, as confirmed by X-ray diffraction (XRD) analysis. The wear test results show a reduction in wear rate at high temperature for all materials tested. For the NiCoCrAlY coating, the high temperature also reduces the friction coefficient, while it significantly increases the friction coefficient of CoNiCrAlY coating. The main damage mode is abrasion and adhesion, caused by the oxide and partially-oxidized particles in the contact surface. The coatings and substrate results were compared, resulting in an improved wear behavior.

Impact responses and residual flexural properties of narrow CFRP laminates

This study aims to identify the impact responses and residual flexural properties of narrow carbon fiber reinforced plastic (CFRP) laminates using the energy profile diagram (EPD). A serial of impact tests was performed with different thicknesses of narrow CFRP laminates to examine the damage process and extent from initiation to complete breakage. The quasi-static three-point bending tests were carried out to characterize the degradation of residual flexural properties induced by the impact. The overall impact energies are clearly separated into three regions by the penetration threshold and crack threshold respectively determined by the EPD. The main damage modes are matrix cracking for lower impact energies, delamination and fiber breakage for middle impact energies and complete breakage for higher impact energies. It is also found that the degradation of normalized residual flexural properties can be divided into three regions using these abovementioned two thresholds, of which the greatest loss occurs in the middle energy region, whilst the maximum reductions of normalized flexural strength and flexural modulus are smaller than 20% in the first region. By comparison, the 6-ply specimens are of lower impact resistance and lower residual flexural properties than the 9-ply specimens under same impact energy; and the residual flexural strength is more sensitive to impact loading than flexural modulus.

Impact velocity effect on the delamination of woven carbon–epoxy plates subjected to low-velocity equienergetic impact loads

The low velocity impact behaviour of a woven carbon fibre/epoxy composite has been analysed in this work. The study has been divided in two experimental phases performed in a drop-weight machine. Firstly, an impact has been carried out to determine the main damage mechanisms appearing over the structure for impact energies between 1 and 20 J. Force time curve patterns and three different damage inspection techniques have been employed to define an incident impact energy range (between 1.75 and 8.8 J) where delamination is the main damage mode over the structure. Secondly, two impact energy levels within this range have been chosen to analyse the impact velocity effect on the generated delamination. Equienergetic impact loads, achieved with different mass and velocity combinations, have been carried out for this analysis. Results show how delaminated area can increase in a 45% while increasing impact velocity, and how this delamination growth, can lead to a 20% reduction of the residual stiffness of the structure within the analysed energy and velocity ranges.

Mechanical behavior and failure micromechanisms of hybrid 3D woven composites in tension

The deformation and failure micromechanisms of a hybrid 3D woven composite were studied in tension. Plain and open-hole composite coupons were tested in tension until failure in the fill and warp directions, as well as fiber tows extracted from the dry fabric and impregnated with the matrix. The macroscopic evolution of damage in the composite coupons was assessed by means of periodic unloading–reloading (to obtain the elastic modulus and the residual strain), whereas the microscopic mechanism were established by means of X-ray computed microtomography. To this end, specimens were periodically removed from the mechanical testing machine and infiltrated with ZnI-containing liquid to assess the main damage modes as a function of the applied strain. The experimental observations and the predictions of an isostrain model were used to understand the key factors controlling the elastic modulus, strength and notch sensitivity of hybrid 3D woven composites in tension. It was found that the full contribution of the glass fibers to the composite strength was not employed, due to the premature fracture of the carbon fibers, but their presence increased the fracture strain and the energy dissipated during fracture. Thus, hybridization of the 3D woven composite led to a notch-insensitive behavior as demonstrated by open-hole tests.

Requirement Analysis and Countermeasures of Health Monitoring and Safety Management for Mobile Cranes

With good performance of mobility, mobile cranes are widely used in various industries of the national economy. However, the work locations of mobile cranes are not fixed, the management personnel and operation personnels qualities are not high, and the management systems are not perfect currently. A considerable part of mobile cranes can not get timely inspection and supervision, some even operating with injuries. So the personal injury and equipment damage accidents often happened, with great loss of people's lives and properties. Therefore, it is necessary to study the measures for strengthening health monitoring and safety management of mobile cranes, aiming to reduce the possibility of accidents. The common types of accidents and their causes are summarized in this paper. The main damage modes of mechanical structure are analyzed. Based on the analysis, countermeasures to the health monitoring and safety management of mobile cranes are put forward.

Damage analysis and fracture toughness evaluation in a thin woven composite laminate under static tension using infrared thermography

This work deals with the issue of damage growth in thin woven composite laminates subjected to tensile loading. The conducted tensile tests were monitored on-line with an infrared camera, and tested specimens were analysed using Scanning Electron Microscopy (SEM). Combined with SEM micrographs, observation of heat source fields enabled us to assess the damage sequence. Transverse weft cracking was confirmed to be the main damage mode and fiber breakage was the final damage leading to failure. For cracks which induce little variation of specimen stiffness, the classic “Compliance method” could not be used to compute energy release rate. Hence, we present here a new procedure based on the estimation of heat source fields to calculate the energy release rate associated with transverse weft cracking. The results are then compared to those computed with a simple 3D inverse model of the heat diffusion problem and those presented in the literature.

Fatigue life prediction of an asphalt pavement subjected to multiple axle loadings with viscoelastic FEM

A model for determining bituminous pavement degradation due to multiple-axle moving traffic loads is presented. The developmental work has been based on a viscoelastic finite element method (FEM) dedicated to bituminous pavements subjected to multiple-axle traffic loads, through reliance on the following variables: pavement structure, load speed, load configuration, and bituminous material temperature. The Load Equivalent Factor (LEF) relative to various axle configurations is approximately proportional to the number of axles within a given axle group. For flexible pavements, the fatigue life predictions using the Homsi model exceed the other two models (i.e. the French standard fatigue law, developed by LCPC–SETRA [7], and the interface fatigue law developed by Diakhaté et al. [31]). Results obtained indicate that the design concept based on bending fatigue in bituminous layers is insufficient to realistically predict the degradation of a bituminous pavement structure. The phenomenon of shear at bituminous interfaces must also be taken into account, as revealed by simulation results for the degradation of two pavement structures from the French design code [8] (i.e. flexible pavement and thick asphalt pavement). For the thick asphalt pavement structure, the main damage mode is of the “bottom-up cracking” type, whereas “interface cracking” damage is typically displayed for flexible pavements. Even before determining life expectancy by means of fatigue models, the LEF clearly indicates in every pavement structure the spot where degradation was most severe (at either the interface or bottom of asphalt layers).

Impact of the 11 March 2011, Great East Japan earthquake and tsunami on the chemical industry

The Great East Japan earthquake and tsunami damaged or destroyed many industrial facilities housing or processing hazardous substances, such as refineries, petrochemical facilities and other types of chemical industry. This showed that also generally well prepared countries are at risk of suffering natural hazard triggered technological (Natech) accidents. An analysis of data collected from open sources and through interviews with authorities was performed to understand the main reasons for the industrial damage and downtime as well as the extent of hazardous-materials releases and the associated impact on society. The analysis of the data set confirmed the findings from other studies with respect to main damage and failure modes, as well as hazardous-materials release paths. In addition, gaps in Natech risk management were identified. Based on the data analysis and interviews lessons learned in support of a more far-reaching Natech risk management are presented.

Friction and wear behaviour of UHMWPE against titanium alloy ball and alumina femoral head due to torsional fretting

The torsional wear behaviours of ultra high molecular weight polyethylene (UHMWPE) were investigated in ball-on-plate torsional wear device. Alumina femoral head and Ti6Al4V alloy ball, were selected as the counterballs in this study. It was found that the torsional fretting running regimes transferred from partial slip regime (PSR) to slip regime (SR) were analysed, however the mixed fretting regime (MFR) was never appeared in this tests. In PSR (lower angular displacement amplitudes), slight damage occurred at small angular displacement and several wear appeared at large value. Adhesion appeared at the centre zone of all fretting scars in SR. Detachment of particles, ripples and ploughs were observed under higher angular displacement amplitudes. The UHWMPE/Ti6Al4V pair showed higher contact stiffness, friction torque, wear damage and material transfer than that of the presentation of UHWMPE/Al2O3pairs. The wear mechanisms of UHWMPE/Ti6Al4V were combined with abrasive wear and delamination. The generation of radial ripples and micro-cracking were the main damage modes for UHMWPE/Al2O3.