Superior Damage Resistance Research Articles

Static and Impact Properties of Flax-Reinforced Polymers Prepared with Conventional Epoxy and Sustainable Resins.

The study assessed the tensile, flexural, and impact properties of composite materials reinforced with flax fibers, employing three distinct resin types. The composite laminates were fabricated using three commercial resins: a conventional epoxy resin, an epoxy resin with a 31% weight concentration of bio-renewable content, and a recyclable methyl methacrylate infusion resin. This aims to assess if there exists a commercially available alternative to the traditional epoxy resin that can reduce the overall carbon footprint of composite materials. To investigate the influence of humidity on the mechanical behavior of the flax layers, a drying treatment was applied to the fibers before the infusion process. Micro-computed tomography analysis revealed that heat treatment resulted in a reduction of porosity, although it did not affect the mechanical response of the composite laminates. Moreover, laminates produced with non-recyclable and sustainable resins exhibited no significant change in tensile and flexural modulus. In contrast, those produced with recyclable resin demonstrated a slight reduction in the strengths of the composite laminates. Conversely, out-of-plane impact tests and repeated impact tests indicated that composites prepared with recyclable and bio-epoxy resin formulations present superior damage resistance to repeated impact compared to traditional epoxy resin.

Experimental and numerical investigation on low‐velocity impact response of sandwich structure with functionally graded core

AbstractThe present research investigates optimizing the impact resistance of functionally graded sandwich structures using experimental and numerical approaches. The low‐velocity impact (LVI) responses of functionally graded sandwich composite (FGSC) with different configurations with skin material jute/rubber/jute (JRJ) and core material having epoxy and sea sand by volume fraction of sea sand at 0%, 10%, 20%, and 30%. Sandwich structures were impacted with LVI (5.89, 10.92, and 15.18 m/s), with the impactor dropped from heights of 0.5, 1, and 1.5 m with precompressed spring loads. FGSC samples are considered a deformable body, and the impactor is modeled as a rigid body using commercially accessible dynamic explicit software. The burn‐out test and weight method were used to test the core's gradience; both methods' results substantially matched, and the variance in gradation could be observed. The proposed sandwich structure characteristics are examined by energy absorption, peak force, energy loss percentage, and coefficient of restitution. Results showed that SC30S provides greater energy absorption and superior damage resistance when tested on LVI. To evaluate the accuracy of experimental findings in predicting the indentation behavior of the sandwich structure, the finite element analysis was used to compare with the experimental results. According to the examination of these proposed FGSC overall performance, they could potentially be employed as sacrificial materials for LVI applications like claddings to shield major structural components. The systematic approach used in this work serves as a standard for choosing and using FGSC effectively for LVI applications.Highlights Low‐velocity impact behavior of sandwich structures was investigated. Combining flexible skin and epoxy core enhances energy absorption. Based on impact energy levels, impact damage areas were determined. Examined sandwich structure advantages in structural and aerospace uses. In terms of time and cost, the numerical analysis method would be useful.

Seismic performance of full-scale prefabricated semi-rigid bolted connection between RC column and composite beam

This paper presents a novel proposal for an assembled bolted joint between precast reinforced concrete (RC) column and steel-concrete composite beams, focusing on its seismic performance. To evaluate the joint's behavior, a comprehensive experimental investigation was conducted on a full-scale RC column to composite beam joint specimen subjected to pseudo-static loading. The study aimed to analyze the joint's failure mode, bearing capacity, ductility, and energy dissipation characteristics. The joint stiffness was assessed by analyzing the bending moment-rotation (M-θ) curve of the beam in accordance with the European standard BS EN 1993-1-8:2005. The experimental results demonstrate that the proposed assembled bolted joint exhibits semi-rigid behavior under positive moments and approaches rigidity under negative moments. To further enhance our understanding of the joint's performance, a finite element model was developed using ABAQUS. The stress distribution in each joint component, as well as the failure mode and ultimate bearing capacity, were analyzed in conjunction with the experimental results. Based on the findings from both the experimental and finite element analyses, an improved joint design is proposed. Additionally, parametric analysis was conducted on the enhanced joint configuration. The study findings indicate that the improved joint exhibits superior damage resistance, seismic performance, and enhanced assembly efficiency compared to the original design. This research contributes to the advancement of assembled bolted joints between precast RC columns and steel-concrete composite beams, offering valuable insights for practical applications in seismic regions.

Electrospun short nanofibers to improve damage resistance of carbon fiber composites

AbstractCarbon composites are sensitive to matrix cracking, delamination, and fiber‐matrix debonding induced by external transverse loading. Such invisible damages demand frequent non‐destructive testing (NDT) owing to their tendency to propagate in brittle composites. Application of carbon composites in safety critical structures have urged researchers to design for superior damage resistance. Bulk modification of matrices through nanoparticles is one such technique that exploits high surface area and mechanical properties of nano‐reinforcements to engineer desired interfaces and improve mechanical properties. This study adopts the same technique to investigate effect of electrospun nylon 6 short nanofiber addition on damage resistance of carbon fiber/epoxy composites. Different concentrations (0.05, 0.1, 0.2, and 0.4 wt% of epoxy) of short nanofibers were prepared to modify epoxy and fabricate carbon laminates. Quasi‐static indentation tests confirmed improvement of 8.7, 8.8, and 53% in peak force, displacement and elastic toughness of carbon composites at optimum nanofiber concentration (0.05 wt%). External damage area marginally improved though directional damage growth was suppressed. Delaminated area reduced by 12.6% at optimum nanofiber concentration. Suppression of compressive fiber failure and enhanced interlaminar bonding were credited to offer superior performance. In general, development of nanofiber‐rich zones declined the load bearing response above optimum concentration.

Grain size-dependent phase-specific deformation mechanisms of the Fe50Mn30Co10Cr10 high entropy alloy

The present work reports the effect of initial microstructures (i.e., the material annealed at 600 °C (A600) with the fine grain single FCC phase vs. the material annealed at 900 °C (A900) with the coarse grain FCC/HCP dual phase) on deformation mechanisms, damage resistance, and mechanical properties of the Fe50Mn30Co10Cr10 HEA. The strength of A600 is higher than A900, and the ductility of both materials is similar with the total elongation exceeding 50%. A900 shows a higher strain hardening rate than A600 below 0.2 true strain, which could be attributed to simultaneous deformation accommodation from the FCC/HCP dual phase. The FCC grains mainly exhibit deformation-induced HCP phase transformation while the HCP grains show multiple deformation mechanisms, i.e., various slip modes (Shockley partial dislocations, perfect dislocations, extended dislocations, and dislocations present on prismatic planes), the HCP to FCC reverse transformation, the formation of kink bands. The strain hardening rate of both materials is similar above 0.2 true strain, which could be related to higher TRIP kinetics of A600 than A900. The A600 shows the refinement of the crack size due to its fine size of grains and HCP phase. The superior damage resistance could lead to the large ductility of A600 even in the presence of the non-recrystallized areas in its initial microstructure. The present work could provide microstructure design solutions for metastable HEAs with superior strength-ductility combination and damage resistance.

Understanding the effects of altering impact velocities and temperatures on basalt textile: An experiment approach

Basalt textiles are finding new applications in several industries due to less complicated composition, high elastic modulus and remarkable tenacity. Present study examines the low-velocity impact (LVI) performance of basalt textile at four distinct incidence velocities: 1, 2, 3, and 4 m/s. The effect of changing external temperatures, particularly −50, 0, 25, and 100 °C, are also investigated. To evaluate the low-velocity impact response, two types of surface coated basalt textiles were tested (i) single-layer basalt textile or SLBT and (ii) double-layered basalt textile or DLBT. Different parameters such as first-crack load, deflection at first-crack, peak impact load, ultimate deflection, energy absorbed at peak load, total energy absorption are considered and compared. The temperature influence factor (TIF) was measured and compared with the reference sample at room temperature to assess the influence of external temperature variations on SLBT. The cumulative failure probability of textile under LVI at varied loads and temperatures revealed a substantial variation in mechanical performance. The failure patterns and microscopic morphologies of fractured textiles demonstrated that two layers of textiles give superior damage resistance under LVI condition.

Wear Behavior of Graded Glass/Zirconia Crowns and Their Antagonists

Monolithic zirconia crowns have become very popular; their surface finish is considered a key factor for restoration longevity. While polishing has shown excellent results in vivo, the surface glass infiltration of zirconia may offer superior damage resistance and aesthetic advantages by using tooth-colored glasses. Thus, the purpose of this study is to evaluate the efficacy of polishing and glass infiltration on the wear behavior of monolithic zirconia crowns. The wear behavior of intact natural molar teeth was investigated as a reference. Zirconia crowns were divided into 3 groups: PolZ—sintered then polished; PolGZ—polished in the presintered state and then glass infiltrated and sintered; NoPolGZ—as machined, glass infiltrated and sintered. Crowns were adhesively bonded to a dentin-like abutment. Zirconia crowns and molar teeth (n = 15) were subjected to contact-slide-liftoff cyclic loading (200 N, 1.25 million cycles) with a steatite sphere (r = 3 mm) as an antagonist in water. Surface and subsurface damages were investigated with optical and scanning electron microscopies. Wear depth and volume loss were determined with micro–computed tomography. PolGZ and NoPolGZ crowns exhibited shallow wear scars, where material loss remained within the glass/zirconia layer with no visible cracks. Meanwhile, PolZ crowns presented no visible wear damage. Volume loss (mm3) in the steatite antagonist was as follows (mean ± SD): PolZ = 0.022 ± 0.007, PolGZ = 0.011 ± 0.004, and NoPolGZ = 0.014 ± 0.006. Molar teeth yielded no measurable wear on the antagonist, while the wear scar on the teeth was greater than that on zirconia crowns, ranging from 0.07 to 0.35 mm3. The combination of polishing and glass infiltration on the occlusal surface of monolithic zirconia crowns yielded reduced wear on both crown and antagonist.

Explosive blast damage resistance of three-dimensional textile composites

The damage resistance of 3D textile composites when subjected to shock wave loading caused by an explosive blast is experimentally investigated. Non-crimp 3D orthogonal textile carbon-epoxy composites with different volume contents of through-thickness z-binder yarns are subjected to explosive blasts of increasing intensity, and the resultant damage is compared to a 2D woven carbon-epoxy laminate. At high blast impulse, the 3D textile composites are highly effective at resisting large delamination crack growth, and display superior damage resistance compared to the 2D laminate. The delamination resistance of the 3D textile composites at high blast impulse increases with their z-binder yarn content, and this correlates with higher modes I and II interlaminar fracture toughness properties. Furthermore, the 2D laminate completely shatters under high blast impulse whereas the 3D textile composites remain intact, which is also evidence of higher explosive damage resistance.

Surface damage behavior of polyurethane O-rings in automated material handling system for glass panels

Automated material handling systems (AMHSs) are widely utilized in general manufacturing processes. The precision motion control and wear resistance of rolling parts of an AMHS are important factors to ensure sufficient reliability of the final product. Polyurethanes are widely used in the manufacturing process due to their superior damage resistance and adequate rolling friction properties. In this work, friction and wear behaviors of polyurethane O-ring rollers sliding against a glass plate specimen were investigated with respect to sliding speed, temperature and relative humidity. A pin-on-reciprocating sample tribotester in an environmental chamber was used to assess the friction and wear properties of the polyurethane O-rings. It was found that the wear resistance increased for higher sliding speed, higher temperature, and lower relative humidity conditions. The results of this work are expected to provide optimized O-ring transfer equipment operating conditions to improve the productivity of the TFT-LCD manufacturing process.

Field Validation of a Thermal Cracking Resistance Specification Framework for Modified Asphalt

Current Superpave® performance grade (PG) binder specifications, such as those used in Wisconsin and many other states, were developed primarily for unmodified binders and are valid only within the linear viscoelastic range of properties. Further, performance benefits from modification are not limited to continuum rheological properties because modified binders often demonstrate superior damage resistance not captured in the current PG system. This paper discusses the results of a recently completed research project sponsored by the Wisconsin Department of Transportation in Madison; the objective was to identify promising procedures through a comparison of test results with field performance and the development of appropriate modified binder specification criteria for thermal cracking resistance. A number of procedures have been introduced in recent years to address the need for damage characterization test procedures for proper assessment and selection of modified binders. In this study, the single-edge notched bending (SENB) procedure was found to correlate well with the observed field thermal cracking when tests were conducted at the project location low-temperature PG specification temperature. The device used was a modified bending beam rheometer (BBR), which could perform displacement-controlled loading with higher load cell capacity, and accommodated notched BBR beams. On the basis of the results of this study, a procedure was introduced for thermal cracking resistance potential of modified binders with the BBR-SENB test at an average annual minimum pavement temperature of +10°C. A preliminary failure limit and acceptance criterion were defined to qualify binder results in terms of the failure properties measured.

Damage characterization in thin-ply composite laminates under out-of-plane transverse loadings

Composite laminates with thin-ply layers are expected to exhibit superior damage resistance to the standard composite laminates. This study investigated the damage characteristics of carbon fiber/toughened epoxy thin-ply laminates subjected to transverse loadings. Quasi-isotropic laminates were prepared using both standard prepregs and thin-ply prepregs in order to examine the effect of ply thickness on the damage accumulation processes. Clear difference on damage accumulation process between standard laminates and thin-ply laminates was identified; fiber fractures were susceptible to formation in thin-ply laminates. Finally, the reason of the difference on damage process was investigated using finite element analyses, and it was clarified that the accumulated delamination position has a significant effect on the fiber fractures during the indentation.

Damage resistance and roughness retention of work rolls in cold rolling mills

For every mill the ideal roll can be considered as one that can be used in a mill stand indefinitely. Unfortunately for the roll user, such ideal rolls do not exist. One major reason for work roll changes (planned or unplanned) is “wear”. In the context of cold rolling and temper rolling, “wear” primarily refers to loss of roughness and/or surface texture. Another limitation to roll performance is the fact that mill incidents – minor as well as major incidents – inflict damage on the work rolls, requiring redressing in the roll shop. If a major defect is present in a forged roll, e.g. due to a mill incident, catastrophic roll failure may occur in a violent, explosive manner. Improvement of the value-in-use of a work roll implies a superior wear resistance, a superior damage resistance, and elimination of the safety risks associated with explosive roll failures. In order to deal with this in a concerted R&D approach, a consortium of two roll users in the steel industry, a leading roll manufacturer, a high-tech supplier of roll damage detection equipment, and specialised research institutes have joined forces. Cold rolling trials have been performed, using pilot mills as well as industrial mills, with both novel forged HSS work rolls and conventional forged 3–5%Cr steel work rolls. Separate trials have been designed to focus on either the aspect of roughness evolution or damage resistance. Complementary data from various laboratory tests and industrial mill and roll shop data have been collected. Models have been developed for damage evolution in a roll, and for roughness evolution of the roll surface. In addition, novel non-destructive detection systems and sensors have been designed and tested. This paper provides a concise overview of the results achieved.

Impact behaviour of composites with different fibre architecture

This article presents a detailed investigation of the impact behaviour of different fibre reinforced composites. A testing programme of low-velocity and high-velocity impact was carried out to evaluate the damage resistance and tolerance of laminates, non-crimp fabric (NCF) reinforced and three-dimensional (3D) woven fabric reinforced composites. The results showed that 3D woven composites have the best damage resistance and tolerance in low-velocity impact, while NCF composites show superior damage resistance in high-velocity impact. Laminate composites have the best in-plane mechanical properties.

The role of shape memory alloy on impact response of glass/epoxy laminates under low temperature

The paper aims to evaluate the impact response of glass/epoxy laminates with embedded shape memory alloy (SMA) subject to low velocity impact at various temperatures. For the goal, the impact tests were performed by using an instrumented impact-testing machine at three temperatures: 293K, 263K and 233K for the baseline (laminates without SMA wires) and SMA laminates (laminates with embedded SMA wires). And the resultant damages were inspected through the scanning acoustic microscope (SAM). Also, based on the impact force history and the damage configuration, the impact resistance parameters were employed to evaluate damage resistance of laminates with embedded SMA wires. As a result, it was observed that the damage resistance of glass/epoxy laminates is influenced by embedded SMA wires and embedding SMA wires into laminates does not compromise the structure any differently to laminates without wires. In fact, it has been shown that under lower temperature, the SMA laminates have a little superior damage resistance compared with the baseline laminates.

Optimization Strategy for Minimizing Damage in Postbuckling Stiffened Panels

Composite materials are finding increasing use on primary aerostructures to meet demanding performance targets while reducing environmental impact. This paper presents a finite-element-based preliminary optimization methodology for postbuckling stiffened panels, which takes into account damage mechanisms that lead to delamination and subsequent failure by stiffener debonding. A global-local modeling approach is adopted in which the boundary conditions on the local model are extracted directly from the global model. The optimization procedure is based on a genetic algorithm that maximizes damage resistance within the postbuckling regime. This routine is linked to a finite element package and the iterative procedure automated. For a given loading condition, the procedure optimized the stacking sequence of several areas of the panel, leading to an evolved panel that displayed superior damage resistance in comparison with nonoptimized designs.

Experimental characterization of strength and damage resistance properties of thin-ply carbon fiber/toughened epoxy laminates

Composite laminates manufactured from thin-ply prepregs are expected to have superior damage resistance properties compared to those from standard prepregs. Although the use of thin-ply prepregs leads to increase in manufacturing cost, the damage resistance properties against matrix cracking and delamination increase. This study investigates several strength properties as well as the damage resistance properties of carbon fiber/toughened epoxy composite laminates for the applicability of thin-ply prepregs to aircraft structures. Specifically, compressive strengths of open hole laminates (OHC strength) and laminates after impact loadings (CAI strength) are investigated by the comparison of results between laminates manufactured from the thin-ply prepregs and the standard prepregs. It is shown that laminates using thin-ply prepregs have superior strength compared to those using standard prepregs. It is expected that the design limit of composite aircraft structures increase by using thin-ply prepregs.

Materials design in the performance of all-ceramic crowns

Results from a systematic study of damage in material structures representing the basic elements of dental crowns are reported. Tests are made on model flat-layer specimens fabricated from various dental ceramic combinations bonded to dentin-like polymer substrates, in bilayer (ceramic/polymer) and trilayer (ceramic/ceramic/polymer) configurations. The specimens are loaded at their top surfaces with spherical indenters, in simulation of occlusal function. The onset of fracture is observed in situ using a video camera system mounted beneath the transparent polymer substrate. Critical loads to induce fracture and deformation at the ceramic top and bottom surfaces are measured as functions of layer thickness and contact duration. Radial cracking at the ceramic undersurface occurs at relatively low loads, especially in thinner layers. Fracture mechanics relations are used to confirm the experimental data trends, and to provide explicit dependencies of critical loads in terms of key variables: material—elastic modulus, hardness, strength and toughness; geometric—layer thicknesses and contact radius. Tougher, harder and (especially) stronger materials show superior damage resistance. Critical loads depend strongly (quadratically) on crown net thickness. The analytic relations provide a sound basis for the materials design of next-generation dental crowns.

パーライトレール鋼とベイナイトレール鋼における摩耗および転動疲労挙動

Resistance to wear and surface damaging (shelling) in pearlitic and bainitic steel rails with various tensile strengths ranging from 850 to 1400 MPa were examined by wear and rotating contact fatigue tests. The pearlitic steels showed better wear resistance than the bainitic steels for all the test conditions tested, although the amount of wear varied according to the strength range and contact pressure used in the wear tests. The wear behavior of the pearlitic steels was roughly described by a Holm's-type equation (W=kP/H; where W: amount of wear, P: contact pressure, H: hardness and k: constant), while that of the bainitic steels showed complex dependencies on the strength and contact pressure. The bainitic steels, however, showed superior damage resistance to the pearlitic steels for all the test conditions tested: at a fixed tensile strength of 850 MPa, significant shelling was observed in the pearlitic steel after 200 h testing, while no damage was detected in the bainitic steel even after 500 h. The resistance to shelling of the pearlitic steels was improved by strengthening, but the opposite trend was obtained in the bainitic steels. These results were analyzed taking work hardening on the sample surface into consideration. Additionally, the formation behavior of the "white phase", which was the martensite phase formed on the rail-head surface by friction between rails and wheels, was compared in pearlitic and bainitic steels and discussed metallurgically.

Damage-resistant SrO-doped Ce- tzP/Al 2O 3 composites

Simultaneous additions of SrO and Al 2O 3 to ZrO 2 (12 mol.% CeO 2) lead to the in-situ formation of SrO·6Al 2O 3 platelets in the Al 2O 3/Ce- tzp matrix. These composites have superior damage resistance compared to Al 2O 3/Y- tzp ceramics despite their lower strength. The increased damage resistance appears to be primarily related to the higher residual stress as a result of grinding with smaller contributions due to micromechanical toughening. High damage resistance was also obtained by introduction of temperature-induced surface compressive stresses in layered composites. Damage resistance is only obtained at low temperatures (<500°C). The applicability of conventional powder processing (slip casting or spray drying) to these tailored microstructures is demonstrated.

Lexan polycarbonate for automotive forward lighting

Through a mutual development effort between the Ford Motor Company USA and General Electric Plastics, the introduction in 1983 of the all plastic aerodynamic composite headlamp made from Lexan∗∗Lexan is a registered trademark of the General Electric Company polycarbonate is revolutionising the automotive forward lighting industry. European headlamp manufacturers have been working over the last several years with the automotive companies and GE Plastics Europe to develop a European design using plastic materials. Several European car models including Ford & Volvo are to be exported in 1985 to the US with plastic headlamps and reflectors made from Lexan polycarbonate. This paper discusses the many advantages and benefits which plastic headlamps offer both the manufacturer and the consumer. These advantages include excellent optical precision, superior damage resistance, unprecedented styling, improved aerodynamics and light weight.