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Highlights Poly(p‐phenylene terephthamide) (PPTA) is an aromatic para‐polyamide with a rigid rod‐like main chain and superior intrinsic mechanical properties but is insoluble in all organic solvents. It has been demonstrated that introducing amino groups to the phenyl rings on the PPTA main chain yields organic‐soluble aminated para‐polyamide known as poly(p‐aminophenylene aminoterephthalamide) ((NH2)2‐PPTA). In this study, an organic‐soluble bismaleimide (BMI)‐grafted (NH2)2‐PPTA (BMI‐g‐(NH2)2‐PPTA) was synthesized by reacting the amino groups of (NH2)2‐PPTA with the double bonds of BMI via Michael addition reaction. BMI‐g‐(NH2)2‐PPTA was then employed as a new macromolecular reinforcing agent that significantly enhances the mechanical properties of BMI/2,2′‐diallyl bisphenol A (BD) resin. With the addition of merely 0.5 wt% of BMI‐g‐(NH2)2‐PPTA, the strength and toughness of both BD resin and BD/carbon fiber (CF) composite laminates are significantly improved without decreasing the heat resistance of the matrix. The uniform dispersion of BMI‐g‐(NH2)2‐PPTA in BD resin and its strong interaction with the matrix result in a more significant enhancement in the mechanical properties compared to directly incorporating (NH2)2‐PPTA into the matrix, providing a new and efficient method for enhancing the mechanical properties of BD resin and its CF composites. A novel BMI‐grafted aminated para‐polyamide, BMI‐g‐(NH2)2‐PPTA, is synthesized. BMI‐g‐(NH2)2‐PPTA is organic‐soluble and can disperse uniformly in BD resin. BMI‐g‐(NH2)2‐PPTA at 0.5 wt% enhances the strength of BD resin by 50.8%. BMI‐g‐(NH2)2‐PPTA is more efficient than (NH2)2‐PPTA in strengthening BD resin. Mechanical properties of BD/CF laminates are also enhanced by BMI‐g‐(NH2)2‐PPTA. [ABSTRACT FROM AUTHOR]

This work presents the experimental results of a quasi-static penetration test of laminates on a polyurea-polyurethane matrix, reinforced with aramid, carbon and flax fibers. A total of 15 series of samples with different reinforcement configurations were prepared. A quasi-static penetration test was performed for coefficient SPR = 5. The SPR = Ds/Dp was calculated as the ratio of the support hole diameter (Ds) to the punch diameter (Dp). A punch with a rounded 9-mm diameter tip was used to penetrate the material. Percentage changes of penetration energy (%E) and maximum load (%P) compared to a non-hybrid laminate were calculated in order to estimate the impact of hybridization on the properties of laminates. The energy absorbed during the quasi-static penetration test was used to calculate the PSS (punch shear strength) of the laminates. Damage analysis was performed after the puncture test. It was observed that both the type of reinforcement and the configuration of the reinforcement layers have a potential impact on the obtained results and the laminate damage mechanism. [ABSTRACT FROM AUTHOR]

Environmental concerns drive the demand for sustainable alternatives to synthetic materials, as high synthetic usage leads to waste and toxic emissions, while natural fibers offer biodegradability, low cost, and lightness. In this study, Mariscus ligularis fiber, developed into bidirectional mats with orientations of ±45°, ±60°, and 0°/90° (A, B, and C), was reinforced with epoxy resin LY556 and hardener HY951. Nine composite laminates with 20, 30, and 40% fiber weight fractions were fabricated using hand lay-up techniques. The mechanical, viscoelastic, thermal, heat distortion temperature (HDT), Vicat softening temperature (VST), and water absorption properties were characterized according to ASTM standards. The mechanical characterization reveals that the 0°/90° laminate with 40% fiber (C40) exhibited the best tensile strength (22.97 MPa) and flexural strength (45.31 MPa). The ±60° laminate with 40% fiber (B40) had the highest impact strength (8 J) and hardness (93.25). The viscoelastic studies indicated that the C40 composite exhibited the most elevated storage modulus (Eʹ) and loss modulus (Eʺ), and the highest glass transition temperature (Tg), signifying strong interfacial bonding and effective stress transfer. The thermal stability of the composites is up to 270 °C. C40 had an HDT of 60.2 °C, a VST of 75.3 °C, and a minimal water absorption of 4.5% after 24 h. The microstructural study confirmed favorable fiber-matrix adhesion and structural properties, making these composites suitable for automotive interior panels and lightweight applications. [ABSTRACT FROM AUTHOR]

A ply-level based modeling strategy for predicting the delamination behavior of laminated composites under pure and mixed mode loading conditions is implemented within the framework of the Finite Element Method. Each ply and each interface of the laminate is explicitly modeled, with the plies represented by various element types such as conventional shell, continuum shell, and continuum elements, and the interfaces are discretized using cohesive zone elements. The comparison between all models is examined in terms of delamination onset and growth including load-displacement curves, delamination area, computation time, and mode-mixity. The results show that all ply-level based modeling strategies exhibit very good agreement with the analytical results. Moreover, ply-level approach based on shell elements in combination with finite thickness cohesive zone elements offers a numerically efficient simulation tool to predict delamination behavior in laminates. [ABSTRACT FROM AUTHOR]

In this work, a laminate based on bioresin and natural fibers was produced. Flax fabric was selected as the natural fiber. The biocomposite was subjected to strength tests. Stress–strain characteristics and strength indicators were determined. The workability of the laminate produced was also tested using milling technology. The tests were carried out using five carbide shank cutters for different purposes. The cutters with the geometry used in the processing of polymer materials and composites, general purpose cutters, and cutters with the geometry for aluminum and with different numbers of blades were analyzed. In order to obtain information on the workability of the prepared material, machining tests with different configurations of technological parameters were carried out. For each cutter, the effect of cutting speed and feed rate on the quality of the machined surface was tested. Due to the small thickness of the laminate, the machining was carried out in one pass, as a result of which the cutting depth in each case was constant. Changes in cutting speed and feed were evenly distributed over five levels. The quality of machining was assessed in two stages. The first stage included a visual assessment of the machined surface, involving a preliminary qualification of the machining parameters. The criterion was the amount of chips, frays, burrs, etc., remaining after machining that adhered to the surface. The next stage was the measurement of the geometric structure of the surface, during which the roughness parameters were analyzed using an optical microscope with a roughness analysis attachment. Quantitative analysis was performed for the best quality composite surfaces from each measurement series. The studies showed a dependence of the quality of machining on the technological parameters used. High tool speed, regardless of the type, especially at low feed, led to the sticking of chips, which had a very delicate form. In turn, low tool speed and high feed, due to the chip thickness, favored the formation of burrs. Machining with different types of tools showed that the process progresses better for tools with sharp blade geometry. Machining with a regular and polished cutter did not show any differences in the scope of the process progress. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work presents the experimental results of a quasi-static penetration test of laminates on a polyurea-polyurethane matrix, reinforced with aramid, carbon and flax fibers. A total of 15 series of samples with different reinforcement configurations were prepared. A quasi-static penetration test was performed for coefficient: SPR=5. The SPR= Ds/Dp was calculated as the ratio of the support hole diameter (Ds) to the punch diameter (Dp). A punch with a rounded 9-mm diameter tip was used to penetrate the material. Percentage changes of penetration energy (%E) and maximum load (%P) compared to a non-hybrid laminate were calculated in order to estimate the impact of hybridization on the properties of laminates. The energy absorbed during the quasi-static penetration test was used to calculate the PSS (punch shear strength) of the laminates. Damage analysis was performed after the puncture test. It was observed that both the type of reinforcement and the configuration of the reinforcement layers have a potential impact on the obtained results and the laminate damage mechanism.

A ply-level based modeling strategy for predicting the delamination behavior of laminated composites under pure and mixed mode loading conditions is implemented within the framework of the Finite Element Method. Each ply and each interface of the laminate is explicitly modeled, with the plies represented by various element types such as conventional shell, continuum shell, and continuum elements, and the interfaces are discretized using cohesive zone elements. The comparison between all models is examined in terms of delamination onset and growth including load-displacement curves, delamination area, computation time, and mode-mixity. The results show that all ply-level based modeling strategies exhibit very good agreement with the analytical results. Moreover, ply-level approach based on shell elements in combination with finite thickness cohesive zone elements offers a numerically efficient simulation tool to predict delamination behavior in laminates.

Laminated metal‐composite structures, known as fiber metal laminates (FMLs), are modern lightweight materials extensively utilized in diverse industries such as aerospace and automotive manufacturing. These materials offer enhanced impact and fatigue resistance, making them invaluable for various applications. However, machining FMLs poses a challenge due to the occurrence of delamination and heterogenous in nature during conventional methods. Therefore, this study aims to investigate the quality characteristics such as kerf width, surface roughness and kerf taper of Magnesium based FMLs processed with an unconventional machining process namely abrasive water jet cutting (AWJC). These FMLs comprise alternately stacked kevlar/carbon fibers adhesively bonded with epoxy resin matrix filled with varying wt% of reduced graphene oxide (r‐GO), combined with AZ31B alloy sheet as the skin material. AWJC experiments were performed by varying the process parameters including waterjet pressure (275–325 MPa), stand‐off distance (2.5–3.5 mm), and cutting speed (600–800 mm/min) based on the box–behnken experimental design. The findings from the statistical analysis underscore the significant influences of stand‐off distance and waterjet pressure on kerf characteristics, while the inclusion of r‐GO is observed to notably affect the surface quality. In pursuit of enhancing cut quality, a multi‐response optimization was conducted employing the Gorilla Troops Optimization (GTO) algorithm. Comparative analysis with established metaheuristics like the gray wolf algorithm, dragonfly algorithm, and harmony search algorithm reveals GTO's superior performance across various metrics, including rapid convergence, diversity, and spacing values. Further, the cutting‐induced damages such as matrix plowing, fiber‐metal debonding and composite delamination were observed through microstructure analysis. Highlights: Magnesium (AZ31B) fiber metal laminate comprising with various wt% of reduced graphene oxide was fabricated.Abrasive waterjet cutting of FMLs were performed based on box–behnken design experimental approach.Statistical analysis and influence of process parameters on the kerf width, surface roughness and kerf taper were investigated.Multi‐response optimization was carried out using metaheuristic‐based gorilla troops algorithm. [ABSTRACT FROM AUTHOR]

Alumina-based multilayer laminates with layers of varied porosities and ceramic fiber reinforcements, which can be achieved by including paper-derived ceramic layers, are interesting candidates for chemically stable and thermal shock resistant materials. In order to investigate the complex sintering behavior of these laminates, the sintering of each alumina layer contained within a laminate, each one with its individual sintering anisotropy and sintering shrinkage, has to be considered separately. For this purpose, sintering curves are determined by dilatometry measurements, serving a consecutive examination by an analytical model. Modeling parameters specific to each layer, are applied in finite-element-type sintering simulations for symmetrical multilayer laminates. Differences in the sintering shrinkages may cause internal stresses at layer interfaces and, in turn, may influence the thermal and mechanical properties of multilayer laminates after sintering. Accordingly, the prediction of developing internal stresses within alumina-based multilayer laminates by the presented sintering simulations is a key aspect of this study. [Display omitted] • Individual laminates sintering dilatometry. • Anisotropic sintering assessment by analytic modeling. • Finite element simulation of multilayer laminates sintering. [ABSTRACT FROM AUTHOR]

The usage of jute/cotton natural composites has surged in almost all fields of engineering due to their advantage of possessing high strength to weight ratio and biodegradability. This paper deals with the fabrication and investigation of mechanical properties of jute/cotton fiber reinforced epoxy composite which is relatively a hybrid composite. In this study, the composite is fabricated by a hand layup process followed by compression molding method with varying the number of layers of composite laminates also with different cutting angles. The composites are prepared with four different proportions of jute/cotton fibers. Various mechanical tests are conducted and the result shows that the 14-layer jute/cotton composite has optimum properties achieved and also observed that 90° has better properties than the others cutting angles. Statistical analysis of composites was done by ANOVA-table; based on mean effective plots, the optimum levels of parameters have been identified, and significant contribution of parameters is determined by analysis of variance Also, failure morphology analysis is done using a scanning electron microscope (SEM) through which the internal structures of the tested specimen are analyzed. [ABSTRACT FROM AUTHOR]

Carbon fibre is the most common reinforcing phase in composite materials. However, it is difficult to determine the performance parameters of a monofilament. This paper provides an efficient method for performing the global layup optimization of composite laminates, considering the relationship between material characteristics and process parameters. In particular, a new method is proposed that, by integrating commercial tools, can support designers in the design and construction of carbon fibre components. The approach involves four functional groups that interact with each other: requirements and specifications, material definition, process implementation, and design and simulation. The idea is to create a continuous process to realize continuous product optimization. The approach was applied to the optimization of the front wing of a Formula 4 vehicle. After the validation method phase, through a comparison between real data and numerical simulations, product optimization was conducted. Different optimized solutions were obtained, and the solution minimizing the mass but 'allowing the vehicle to bear stress and strain values within the required limits was chosen. This methodology can be applied to support the designer during both the early design phase and the optimization phase of laminated products. [ABSTRACT FROM AUTHOR]

Polymer composites are becoming more popular as a feasible alternative to conventional engineering materials due to superior physio-mechanical qualities, corrosion resistance, moisture resistance, damage tolerance, and tailored properties. The epoxy matrix molecular structure significantly affects mechanical performance because of its high crosslink structure, density, and stiffness. This paper deals with the evaluation of mechanical and thermal characteristics of carbon (C) and glass fiber (G) stacked composites modified by multiwall carbon nanotube (MWCNT). The conventional hand-layup method (HLM) was employed to fabricate nanocomposite samples in different MWCNT wt% (0, 0.45, 0.90,1.35). Tensile and Flexural testing examined the mechanical behavior of the developed composite. Thermogravimetric analysis and dynamic mechanical analysis compute the thermal and viscoelastic behavior of the nanocomposite specimens. Scanning electron microscopy describes the failure mechanisms on the damaged surfaces of the nanocomposite samples. The MWCNT supplements in the stacked composite make it more efficient than pristine samples and augment the mechanical characteristics of structural components. The MWCNT-modified stacked samples show improved tensile and flexural behavior than the stacked samples for the desired application. This work reveals that adding MWCNTs as the third phase reinforcement into the stacked (C–G–C) nanocomposites could improve the mechanical and thermal characteristics. [ABSTRACT FROM AUTHOR]

In the equivalent single-layer theories of anisotropic laminates, the coupling tensor B describes the relation between the in- and out-of plane behaviour of the plate. This tensor has some peculiar characteristics and in particular it is not defined, so it is normally considered as an unbounded tensor. We show in this paper a way to determine some relations between the polar invariants of B and those of the tensors describing the in- and out-of plane behaviours of the laminate, A and D , respectively. These relations constitute a set of bounds for the invariants of all the tensors of the laminate, A , B and D. It is hence shown that also the components of B must satisfy some conditions. Some peculiar cases, interesting for applications, are also considered. [ABSTRACT FROM AUTHOR]

We address the fundamental difference between solid-solid and liquid-liquid phase transitions within the Ericksen's nonlinear elasticity paradigm. To highlight ideas, we consider the simplest nontrivial 2D problem and work with a prototypical two-phase Hadamard material which allows one to weaken the rigidity and explore the nature of solid-solid phase transitions in a "near-liquid" limit. In the language of calculus of variations we probe limits of quasiconvexity in an "almost liquid" solid by comparing the thresholds for cooperative (laminate based) and non-cooperative (inclusion based) nucleation. Using these two types of nucleation tests we obtain for our model material surprisingly tight two-sided bounds on the elastic binodal without directly computing the quasiconvex envelope. [ABSTRACT FROM AUTHOR]

This paper introduces a unique finite element analysis (FEA) technique designed to predict elastic response in polymer matrix composites (PMCs). Extensive research has been conducted to model the manufacturing process of multiple 'L'-shaped components, fabricated from SPRINTTM materials (GLP 43 and GLP 96) at two thicknesses (15 mm and 25 mm). Three distinct FEA methodologies were utilised to determine the impact of thermal loads and rigid fixtures. An error deviation of 3.23% was recorded when comparing simulation results to experimental data, thereby validating the effectiveness of the FEA methodology. [ABSTRACT FROM AUTHOR]

One environment that hinders the performance of reinforced concrete is fire. In most cases, this results in the affected part or the entire structure being rendered useless or completely collapsing. When fire mishaps happen in structures, this is the case. This study reviews green structural retrofitting materials for reinforced concrete buildings in an effort to repair damaged structures in an environmentally friendly manner. The information gathered from earlier laboratory test results is assembled to comprehend the impact of room temperature strength properties and varied concrete mix material composition on the residual mechanical properties of concrete. The performance of various fibers, synthetic and natural, as laminate materials for concrete were evaluated, and the study showed that to a significant extent, distressed structural elements could be repaired with retrofits. However, provision of appropriate guidelines for using natural fibre laminates for retrofitting has not been overly explored. This review has highlighted areas that require further study in order to fully understand the residual strength characteristics of concrete exposed to high temperatures, particularly damaged concrete that have been retrofitted with fibers. Overall, the review's findings will be helpful to academics, professionals in the field of civil engineering, and those engaged in construction. [ABSTRACT FROM AUTHOR]

The J-integral is applied to the single cantilever beam (SCB) and double cantilever beam (DCB) test specimens subjected to both mixed-mode I and II loading and large displacements. The methods proposed and resulting closed-form theoretical equations allow for the instantaneous evaluation of J during laboratory tests, requiring only the applied load and angular rotation of the specimen loading link, loading points, and remaining ligament. These measurands can be acquired using a common load cell and markers, a digital video camera, and image analysis software. In general, the equations do require knowledge of the specimen elastic moduli and shear moduli, as well as the specimen linear dimensions. Since the test data can be analyzed and J determined throughout the test instantaneously, and since, due to geometric nonlinearities, the ratio of mode I and mode II loading will likely vary significantly throughout the test, each specimen can be used to generate multiple data points. If crack length is determined throughout the test, presumably by directly measuring the crack length optically, or if the load drops abruptly due to crack growth, then when the crack advances, critical values of J for mixed-mode loading can be determined using the methods and results presented. It is noted that moderate to large translational and rotational displacements may improve the accuracy of the results using these methods. The results are applicable to standard pure mode I or pure mode II SCB and DCB tests as well and reduce to known equations in those special cases. [ABSTRACT FROM AUTHOR]

The analysis of the mathematical and mechanical properties of thermoelastic coupling tensors in anisotropic laminates is the topic of this paper. Some theoretical results concerning the compliance tensors are shown and their mechanical consequences analyzed. Moreover, the case of thermally stable laminates, important for practical applications, is also considered. The study is carried out in the framework of the polar method, a mathematical formalism particularly well-suited for the analysis of planar anisotropic problems, introduced by Prof. G. Verchery in 1979. [ABSTRACT FROM AUTHOR]

The incorporation of sustainability into the design of transport vehicles has become increasingly important in recent years. A low carbon footprint makes wood-based structures attractive to replace other lightweight materials such as aluminum or fiber-reinforced plastics. This paper investigates and compares the static and dynamic impact behavior of thin Beech wood veneer laminates in standardized mechanical tests. The results obtained from Quasi-Static Indentation (QSI) and dynamic Low-Velocity Impact (LVI) tests reveal similarities and differences with regard to load vs. displacement behavior, damage mechanisms, permanent deformation, and energy absorption. While yield strength and damage modes are comparable in both test cases, it is found that the bending stiffness is strain-rate sensitive. Plastic deformation in compression is identified as the governing mechanism for energy absorption. These results can guide the design of sustainable wood-based structures for future transport applications where a thorough understanding of impact and crashworthiness is important. [ABSTRACT FROM AUTHOR]

Thermoplastic matrix composites are a viable option to reduce the carbon footprint during the life of an aircraft due to their ability to be molten and resolidified again. Tape‐based layup processes, such as automated tape placement, are well‐examined but have not seen extensive use in large‐scale joining applications, since they have to be processed layer‐by‐layer. In contrast, the advanced laser in situ joining method (CONTIjoin) utilizes fully consolidated and cut‐to‐size multilayered laminates, enabling the continuous layup of tailored laminates aligned with the mechanical application requirements. Herein, sample joints are manufactured using CONTIjoin technology, describing the general process principle, and are compared with samples produced using a standard heat press process. The base material, carbon fiber‐reinforced LMPAEK (low‐melt polyaryletherketone) is characterized using infrared spectroscopy. Using a 3.5 kW carbon dioxide (CO2) laser (10.6 μm wavelength) coupled with highly dynamic beam deflection, multidirectional reinforced laminates with up to six plies are processed to produce 24‐ply plates. The influence of joining temperatures up to 400 °C on the joint quality is investigated. Cross‐cuts are examined and interlaminar shear strength tests are conducted. With CONTIjoin, maximum strengths of 48.5 MPa are observed, reaching over 90% of the heat press reference. [ABSTRACT FROM AUTHOR]

To enhance the ductility of carbon fiber-reinforced polymer (CFRP) composites, a variety of nacre-inspired structures with discontinuities were constructed based on the ratio of overlapping length to CFRP laminate thickness. The damage mechanisms and tensile characteristics of discontinuous laminates were elucidated using finite element analysis and experimental investigation. To anticipate the mechanical behavior of the CFRP laminate, an improved Chang-Chang failure criteria was devised. Moreover, a model adopts the Benzeggagh-Kenane criterion on cohesive surfaces for delamination initiation and propagation. The predicted stress-strain values are validated using experimental data under tensile stress. Furthermore, a mathematical model accurately predicted the relationship between the tensile performance of nacre-inspired laminate and overlapping length. According to the findings, the longer the overlapping length (more than 19.5 mm) is, the lower the pseudo-ductility. Meanwhile, the shorter the overlapping length (less than 17.5 mm) is, the lower the tensile strength. Furthermore, the laminate exhibits some pseudo-ductility as well as little decrease in tensile strength when the overlapping length is approximately 18.5 mm. Highlights • A mathematical model for predicting the tensile properties of various nacreinspired laminates was established. • The relationship between the discontinuous structure and the pseudoductility of the nacre-inspired laminate was revealed. Compared with other similar structural laminates, the laminate with an overlapping length of 17.5 mm has better overall performance. • Proposed an improved Chang-Chang progressive failure criterion that was utilized to simulate and analyze the mechanical response and damage of the nacre-inspired laminates under tension. [ABSTRACT FROM AUTHOR]

The paper deals with bifurcation and/or non-bifurcation post-buckling curves of composite plates under biaxial compression. For different lay-up sequences, a coupling, i.e. extension-bending (EB) is considered. The current investigations present distinct equilibrium paths describing when they have bifurcation-type and/or non-bifurcation-type responses. The novel parameter (i.e. EB coupling imperfection) is calculated to show the amount of non-bifurcation in the equilibrium path as a quantitative parameter. For the case of non-square plates, a novel mixed-mode analysis is conducted. The effects of different characters in laminated composites such as layer arrangement, loading ratio, aspect ratio, and boundary conditions are investigated. A novel result concluded in the numerical examples where there are some possibilities to have different mode shapes in linear and non-linear buckling analysis. FEM results of ANSYS software verify the results of analytical equations. [ABSTRACT FROM AUTHOR]

Veneer is one of the most esthetic, conservative, and durable form of restoration. Case selection, tooth preparation, and cementation of veneer on maxillary anterior teeth have been thoroughly discussed in this case report. Here, we present a case of a 26-year-old male patient with a complaint of fracture of 21 for the past 1 year. On examination, the tooth was vital, and the treatment option given to the patient was veneer. Veneer is one of the breakthrough treatments when it comes to restoring the esthetic with minimal invasiveness. A proper case selection with a precise treatment results in the excellent outcome. Hence, ceramic veneers is the better option compared to the conventional approach.

In this work, a laminate based on bioresin and natural fibers was produced. Flax fabric was selected as the natural fiber. The biocomposite was subjected to strength tests. Stress–strain characteristics and strength indicators were determined. The workability of the laminate produced was also tested using milling technology. The tests were carried out using five carbide shank cutters for different purposes. The cutters with the geometry used in the processing of polymer materials and composites, general purpose cutters, and cutters with the geometry for aluminum and with different numbers of blades were analyzed. In order to obtain information on the workability of the prepared material, machining tests with different configurations of technological parameters were carried out. For each cutter, the effect of cutting speed and feed rate on the quality of the machined surface was tested. Due to the small thickness of the laminate, the machining was carried out in one pass, as a result of which the cutting depth in each case was constant. Changes in cutting speed and feed were evenly distributed over five levels. The quality of machining was assessed in two stages. The first stage included a visual assessment of the machined surface, involving a preliminary qualification of the machining parameters. The criterion was the amount of chips, frays, burrs, etc., remaining after machining that adhered to the surface. The next stage was the measurement of the geometric structure of the surface, during which the roughness parameters were analyzed using an optical microscope with a roughness analysis attachment. Quantitative analysis was performed for the best quality composite surfaces from each measurement series. The studies showed a dependence of the quality of machining on the technological parameters used. High tool speed, regardless of the type, especially at low feed, led to the sticking of chips, which had a very delicate form. In turn, low tool speed and high feed, due to the chip thickness, favored the formation of burrs. Machining with different types of tools showed that the process progresses better for tools with sharp blade geometry. Machining with a regular and polished cutter did not show any differences in the scope of the process progress.

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

AbstractShape memory alloys (SMAs) are widely used across various industries, including medicine, due to their inherent properties such as the shape memory effect, pseudo-elasticity, antigenicity, decomposition, biodegradability, biocompatibility, resistance to corrosion, and wear. This review article aims to cover different aspects of SMAs, including their fundamental concepts such as origin, exceptional properties, fabrication techniques, and structural analysis. Exploring the SMAs at the nanoscale using molecular dynamics analysis and recent studies that integrate machine learning techniques. Finally, the article concludes with a discussion of various applications of SMAs, considering the properties and potential fields of use. [ABSTRACT FROM AUTHOR]

Imperfect geometry beams with functionally graded carbon nano tubes (CNT) have recently been used in many structural applications, and many numerical analyses have been performed to assess the stiffness property in beams and structures. Where the stiffness enhancement of a beam greatly contributes to its stability by augmenting the geometrically defective beam's deformation withstanding capabilities under loading. However, the stiffness enhancement in terms of imperfect geometrical design characteristics has not been considered in previous research. Hence in this paper, a novel Persuaded Resilient Design is introduced in which the geometric imperfection is induced in the design in the form of a hollow trapezoidal laminate in such a way that the designed imperfect layered laminate enhances the flexural rigidity of the beam. Additionally, by employing a Parametric Stability Analysis, the act of the curved beam is structured by meshing the design with FEA applying UDL, and three-point bending. The peak and trough sustainability of the unique designed geometrically flawed beam incorporating functionally graded CNTs is determined via a finite element model. Thus, the FG-CNT reinforced curved beam behavior of the novel design is efficiently analyzed. [ABSTRACT FROM AUTHOR]

Due to the high interest in the use of glass/epoxy laminates in aerospace applications, aviation, and as cryogenic tanks, it is crucial to understand the behavior of composites under challenging environmental conditions. Polymer composites are exposed to low temperatures, including cryogenic temperatures, which can lead to the initiation of microdamage. This paper investigates damage initiation/accumulation and its influence on the properties of cross-ply woven glass fiber epoxy composites at low temperatures compared to room temperature conditions. To evaluate the influence of a low-temperature environment on the mechanical performance of glass fiber reinforced epoxy composite (GFRP) laminates, three types of test campaigns were carried out: quasi-static tensile tests and stepwise increasing loading/unloading cyclic tensile tests at room temperature and in a low-temperature environment (−50 °C). We demonstrated that the initial stiffness of the laminates increased at low temperatures. On the other hand, there were no observed changes in the type or mechanism of developed damage in the two test conditions. However, the reduction in stiffness due to the accumulated damage was more significant for the laminates tested at low temperatures (~17% vs. ~11%). Exceptions were noted in a few formulations where the extent of damage at low temperatures was insignificant (<1%) compared to that at room temperature. Since some of the studied laminates exhibited a relatively minor decrease in stiffness (~2–3%), we can also conclude that the formulation of matrix material plays an important role in delaying the initiation and formation of damage. [ABSTRACT FROM AUTHOR]

Low-temperature plasma treatment with atmospheric discharge with runaway electrons (DRE) was shown to be an efficient way to activate carbon fiber's (CF) surface and subsequently increase its interlayer shear strength (ILSS) values. It was demonstrated that an acceptable ILSS level was achieved after a DRE plasma treatment duration of 15 min. The treatment of CFs resulted in their surface roughness being increased and their functional groups grafting. The XPS data showed a change in the chemical composition and the formation of reactive oxygen-containing groups. SEM examinations of the PPS/CF laminates clearly demonstrated a difference in adhesive interaction at the PPS/CF interface. After the DRE plasma treatment, CFs were better wetted with the polymer, and the samples cohesively fractured predominantly through the matrix, but not along the PPS/CF interface, as was observed for the sample reinforced with the untreated CFs. The computer simulation results showed that raising the adhesive strength enhanced the ILSS values, but reduced resistance to transverse cracking under the loading pin. In general, higher flexural strength of the PPS/CF laminates was achieved with a greater interlayer adhesion level, which was consistent with the obtained experimental data. [ABSTRACT FROM AUTHOR]

Veneer is one of the most esthetic, conservative, and durable form of restoration. Case selection, tooth preparation, and cementation of veneer on maxillary anterior teeth have been thoroughly discussed in this case report. Here, we present a case of a 26-year-old male patient with a complaint of fracture of 21 for the past 1 year. On examination, the tooth was vital, and the treatment option given to the patient was veneer. Veneer is one of the breakthrough treatments when it comes to restoring the esthetic with minimal invasiveness. A proper case selection with a precise treatment results in the excellent outcome. Hence, ceramic veneers is the better option compared to the conventional approach. [ABSTRACT FROM AUTHOR]

Pressure‐sensitive adhesive tapes are used in several industrial applications such as construction, railway vehicles and the automotive sector, where the burning behavior is of crucial importance. Flame retarded adhesive tapes are developed and provided, however, often without considering the interaction of adhesive tapes and the bonded materials during burning nor the contribution of the tapes to fire protection goal of the bonded components in distinct fire tests. This publication delivers an empirical comprehensive knowledge how adhesive tapes and their flame retardancy effect the burning behavior of bonded materials. With a special focus on the interaction between the single components, one flame retarded tape and one tape without flame retardant are examined in scenarios of emerging and developing fires, along with their bonds with the common materials wood, zinc‐plated steel, mineral wool, polycarbonate, and polymethylmethacrylate. The flame retardant significantly improved the flame retardancy of the tape as a free‐standing object and yielded a V‐2 rating in UL 94 vertical test and raised the Oxygen Index by 5 vol.%. In bonds, or rather laminates, the investigations prove that the choice of carrier and substrates are the factors with the greatest impact on the fire properties and can change the peak of heat release rate and the maximum average rate of heat emission up to 25%. This research yielded a good empirical overall understanding of the fire behavior of adhesive tapes and bonded materials. Thus, it serves as a guide for tape manufacturers and applicants to develop tapes and bonds more substrate specific. [ABSTRACT FROM AUTHOR]

The corresponding author had the pleasure of attending an excellent symposium titled "Experimental and Theoretical Micro- and Nano-Mechanics: Honoring the Contributions of Prof. Kyung-Suk Kim" organized by Professors Ashraf Bastawros, Wendy Crone, Yanfei Gao, and Ruike (Renee) Zhao as part of the 2022 Society of Engineering Sciences Annual Technical Meeting held in College Station, TX on October 16-19, 2022. The symposium was held in honor of Prof. Kim's 70th Birthday and celebrated over 40 years of Prof. Kim's independent research achievements across several areas of Applied Mechanics. The present paper is dedicated to Prof. Kim, a great colleague at Brown University. We present a new formulation for the multilayer isogeometric Kirchhoff-Love (KL) shells, where the individual layers are assumed to interact through no-penetration and frictional contact. This work is largely motivated by the experiments and analysis presented in Poincloux et al. (2021, "Bending Response of a Book With Internal Friction," Phys. Rev. Lett., 126(21), p. 218004). We utilize a regularized version of Coulomb's friction law to model the tangential traction between the contacting shell surfaces. To ensure objectivity (i.e., reference-frame invariance) in the frictional model, we propose two different strategies to extrapolate the velocity vectors of the contact pair at the contact interface: (i) using the underlying KL kinematics of the individual shell layers and (ii) using the Taylor series-based extension from Kamensky et al. (2019, "Peridynamic Modeling of Frictional Contact," J. Peridyn. Nonlocal Model., 1(2), pp. 107-121). We compare the performance of both approaches through a numerical benchmark example. We then validate our multilayer shell formulation using the "bending response of a book with internal friction" experiments of Poincloux et al. (2021, "Bending Response of a Book With Internal Friction," Phys. Rev. Lett., 126(21), p. 218004). [ABSTRACT FROM AUTHOR]

In this study, a novel chemical modification was proposed to introduce carboxylate copper onto the woven carbon fiber (CF) surface, and then the modified CF/Al-2219 composites were successfully fabricated by powder metallurgy. The results showed that the chemical modification of CF improved the infiltration of Al-2219 matrix into woven CFs, thus significantly reduced the defects. The average ultimate tensile strength (UTS) of the modified CF/Al-2219 composites was improved by approximately 13.2 %, and the woven CFs were able to strengthen the composites in multiple directions. This work provides a convenient method of CF pre-treatment for the fabrication of CF/Al composites.

The investigation of damage development is essential for the design and optimization of hybrid structures. This paper provides a reference for the structural design of brittle–ductile hybrid LVI-resistant laminates through analyzing the damage development mechanism of carbon/Kevlar fabric-reinforced composite laminates. The effects of Kevlar fabric hybrid ply and intercalation on the damage development of carbon/Kevlar composite laminates under low-velocity impact (LVI) were investigated using quasi-static indentation (QSI). It was found that an increase in the Kevlar hybrid ratio significantly reduced the peak load and stiffness of these laminates (the maximum decreases in strength and stiffness were 46.03% and 41.43%, respectively), while laminates with identical hybrid ratios but different plying configurations maintained a comparable stiffness under QSI, with differences of less than 5%. Interestingly, Kevlar fibers exhibited irregular fractures as the yarn was splitting, while carbon fibers presented neat breaks, which indicated material-specific failure modes. Notably, the introduction of Kevlar hybridization beyond pure Kevlar configurations (KKKK) resulted in a decrease in the percentage of fiber damage (CCCC, CCCK, CCKK, and KCCK accounted for 80%, 79.8%, 70%, and 60% of fiber damage, respectively), attributed to an increase in resin cracks and lower levels of Kevlar yarn breakage. The internal damage diameter of specimens was accurately predicted from the diameter of visible damage on the QSI surface. Compared with CCCC and CCKK setups, which are affected by resin cracks formed via the carbon surface on the loading side propagating along the yarn direction (including the yarn settling direction), KCCK demonstrated less delamination between the first and second ply.

In this study, the thin-walled plate with the central open hole made of carbon-epoxy composite was investigated. The plate was tested in tension to investigate the mechanism of crack formation in the composite structure. The studies were carried out using two individual methods: experimental and numerical. In the experiment test, load was measured as the function of plate elongation. The Plate elongation was analysed using the Aramis optical non-contact measurement system. In the numerical study, the FEM model reproducing the experimental conditions was developed in the Abaqus software. The cracking process was modelled using the XFEM method (extended finite element method). This procedure allowed the of the composite to be examined over the full range of the tensile load. The behaviour of the plate with a circular open hole was investigated before damage symptoms and the damage initiation load was determined. The study continued to analyse the initial cracking and delamination of the laminate layers, together with crack propagation leading to cracking of all the laminate layers (complete failure of the composite structure). The novelty of this study is that it uses the popular XFEM method to describe the cracking and failure of the composite structure. In addition, the study proposes the novel method for determining the crack initiation and failure loads of the composite plate under tension, and the results obtained thereby are verified numerically.

Several existing reinforced concrete structures (RC) requires improvement in performance for reasons of deterioration. This is due to many factors such as change in code requirements. The current study was assisted by experimental models to investigate the behavior of RC slabs strengthened with carbon fiber reinforced polymer (CFRP) laminates and sheets. Seven RC slabs strengthened with CFRP (laminates and sheets) were tested. The slabs were divided into four groups. The first phase includes one slab without strengthening (reference slab), the second phase includes one slab strengthened with CFRP laminates, and the third phase includes one slab strengthened with CFRP sheets. The fourth phase includes four slabs strengthened with different areas of sheets. The major test parameters included the different types of strengthening materials and the corresponding types of epoxy used for each type of CFRP. A comparison between the two types of CFRP was conducted. The load deflection, load strain and mode of failure were investigated. Test results demonstrated that the flexural strength increased and the ductility reduced with the increase in the area of CFRP sheets. for almost equivalent applied area, CFRP Sheets has more significant influence on the behavior of the strengthened slabs than laminates. Strengthening of RC slabs with CFRP improves the flexural strength capacity for both types. For the same CFRP strength, the sheets showed a cost reduction of 70%. The difference is attributed to the difference in the mechanical properties and the bonding quality of the CFRP material.

Composite materials and structures are widely used and applied in many industries owing to their advantages, such as satisfactory stiffness-to-mass ratio and corrosion resistance. However, during their operating life, responsible parts subject to complex loads may change and their properties might deteriorate. To ensure structural integrity it is necessary to monitor and regularly check the performance of composite structures. This paper investigates the change of frequency characteristics of two rectangular composite (carbon-epoxy) plates after inflicting structural damage. Following the necessary preparation of the structure's upper surfaces by white-and-black stochastic pattern, the responses (free vibratory movement) of structures to momentary excitation were recorded by an optical, contactless 3D digital image correlation (DIC) system that contains a set of ultrafast cameras. In order to determine the natural frequencies of the plates, the recorded time-domain responses were post-processed, i.e. converted to the frequency domain by fast Fourier transform (FFT). The reduction in values of natural frequencies is observed on the damaged structures. The performed experiments demonstrate the applicability of the DIC method in the structural health monitoring of composite parts.

Abstract This research deals with the flexural performance of reinforced concrete beams which contain Recycled Concrete Aggregates (RCA) and were strengthened by Carbon Fiber Reinforced Polymers (CFRP). For this purpose, seven Reinforced Concrete (RC) beams were manufactured using RCA as a replacement of Normal Coarse aggregates (NCA) with percentages of (0%, 25%, 50%, and 100%). The cross-section of all beams was 150 × 300 mm and 2100 mm overall length and with loaded span of 1800 mm. Firstly four beams (group A) with different RCA ratios were loaded in a four-point loading configuration until failure. Secondly three beams (group B) were loaded to 30% of its ultimate load after that group B beams were strengthened using CFRP laminates on the lower face of the beams to be strengthened to resist flexural stress. Crack pattern, initial cracking load, ultimate load, mid-span deflection, and strain in main reinforcement were monitored. The results show that increasing RCA ratios generally leads to decreasing in the ultimate loads, for RCA ratios of 25%, 50% and 100% the decrease in beams ultimate load was with ratios 4.8%, 25.5% and 26.8%, respectively compared to control beam (0% RCA). The preloaded beams that were repaired with CFRP laminates have higher ultimate loads than beams without CFRP laminates and lower mid span deflection at maximum load (for instance repaired beam with 50% RCA ratio with CFRP laminate has shown higher ultimate load with 56.6% and less deflection with 36.9% compared to its corresponding unstrengthen beam).

The paper deals with bifurcation and/or non-bifurcation post-buckling curves of composite plates under biaxial compression. For different lay-up sequences, a coupling, i.e. extension-bending (EB) is considered. The current investigations present distinct equilibrium paths describing when they have bifurcation-type and/or non-bifurcation-type responses. The novel parameter (i.e. EB coupling imperfection) is calculated to show the amount of non-bifurcation in the equilibrium path as a quantitative parameter. For the case of non-square plates, a novel mixed-mode analysis is conducted. The effects of different characters in laminated composites such as layer arrangement, loading ratio, aspect ratio, and boundary conditions are investigated. A novel result concluded in the numerical examples where there are some possibilities to have different mode shapes in linear and non-linear buckling analysis. FEM results of ANSYS software verify the results of analytical equations.

[Display omitted] • Exploitation of the impact delamination phenomenon. • Novel mechanical method to separate HDPE from laminates for recycling. • Fine tuning of shredding operation to separate HPDE while cutting. • Reduced amounts of solvent wastes and improved environmental friendliness. • Very rapid HDPE separation, reduced unit operations and plant footprint. High-density polythene (HDPE) is difficult to separate from food packaging waste for recycling because the packaging occasionally has multilayer plastic labels attached. Solvents are employed in the current separation techniques to remove undesirable layers from HDPE substrates. The possibility of separating HDPE via the impact-delamination phenomenon was explored both theoretically and experimentally. Using the cohesive zone model (CZM), the decohesion of layers in a model two-layer laminate made of HDPE and LDPE layers was studied theoretically. According to this study, stress waves emerge and severely damage the adhesion between the layers as a cutting blade strikes the laminate at speeds greater than 40 m/s. The damage can be enhanced by increasing the strike velocity and the apex radius of the blade. These findings show that a novel plastic delaminator that can cut and delaminate the laminates simultaneously can be designed. The proposed machine will feature two sets of blades with varying edge apex radii. One set of blades can be designed to cause the most adhesion damage while the other blades cut the laminate. This unique combination of cutting and delamination operations has several benefits, including less solvent waste and downstream processes, greater environmental friendliness, and faster HDPE separation. Laminates from HDPE milk bottles were cut using a high-speed cutter-blender with six blades to test the predicted results. The cut HDPE flakes were separated pneumatically. According to FTIR analysis and SEM, only a trace of adhesive was present on the cut and separated HDPE flakes. [ABSTRACT FROM AUTHOR]

The problem of determining the general and relevant mechanical and mathematical properties of the stiffness, B , and compliance, B , tensors describing the bending-extension coupling of anisotropic laminates is addressed in this paper. A set of theoretical results is proposed, showing some peculiarities of these tensors, from the mathematical and mechanical point of view. The theoretical analysis and the mechanical results are obtained through an extensive use of the so-called polar formalism, introduced as early as 1979 by Prof. G. Verchery. [ABSTRACT FROM AUTHOR]

We present a class of models of elastic phase transitions with incompatible energy wells in an arbitrary space dimension, where in a hard device an abundance of Lipschitz global minimizers coexists with a complete lack of strong local minimizers. The analysis is based on the proof that every strong local minimizer in a hard device is also a global minimizer which is applicable much beyond the chosen class of models. Along the way we show that a new demonstration of sufficiency for a subclass of affine boundary conditions can be built around a novel nonlinear generalization of the classical Clapeyron theorem. [ABSTRACT FROM AUTHOR]