Advanced Structural Applications Research Articles

Tailoring Strength and Ductility in Dual-Phase High-Entropy Alloys: Insights from Deep Learning Molecular Dynamics Simulation on FCC/BCC Thickness Ratios

This study investigates the influence of FCC/BCC thickness ratios on the mechanical properties of AlCoCrFeNi dual-phase high-entropy alloys (DP-HEAs) using deep learning-enhanced molecular dynamics simulations. The results demonstrate that varying the thickness ratio significantly affects the stress-strain behavior, dislocation density evolution, and local structural transformations during tensile deformation. DP_0.5, with a thinner BCC phase, exhibits higher dislocation densities and enhanced strain hardening, resulting in increased strength but reduced ductility. In contrast, DP_3.0, with a thicker BCC phase, shows lower dislocation densities, leading to improved ductility but lower strength. The phase transformation from BCC to HCP structures is a key mechanism contributing to plastic deformation, with the BCC/FCC interface playing a critical role in dislocation nucleation and propagation. These findings provide valuable insights into optimizing the microstructural design of DP-HEAs to achieve a tailored balance of strength and ductility, offering the potential for advanced structural applications.

Tuning of the mechanical properties of a laser powder bed fused eutectic high entropy alloy Ni30Co30Cr10Fe10Al18W2 through heat treatment

Eutectic high entropy alloys (EHEA) with an exceptional combination of strength and ductility are promising candidates as advanced structural materials. However, achieving an optimal balance between the properties in additively manufactured EHEAs is an outstanding challenge. In this work, Ni30Co30Cr10Fe10Al18W2 EHEA was additively manufactured using the laser powder bed fusion (LPBF) technique. In the as-fabricated state, it exhibits a dual-phase nano-lamellar structure consisting of FCC/L12 and B2 phases. Post-fabrication heat treatments were explored for modulating microstructure and, in turn, enhancing the mechanical properties, so as to achieve an optimum balance between strength and ductility. Upon heat treatment at 750 °C for 1 h, part of the B2 phase transformed into FCC, with the appearance of the tungsten-rich precipitates inside the B2 phase. The average interlayer spacing of the FCC/L12 lamellae increased to 124 nm, while that of B2 lamellae decreased to 86 nm, resulting in an alloy with an ultimate tensile strength (UTS) of 1811 MPa, although the strain to failure (εf) decreased to 2 %. Upon increasing the heat treatment temperature to 1000 °C, the average interlayer spacings of the FCC and B2 phases increased to 210 and 187 nm, respectively, which resulted in a more balanced mechanical behavior with UTS and εf of 1332 MPa and 9.3 %, respectively. This study provides an effective approach for microstructural modulation and enhancement of mechanical properties of LPBF fabricated EHEA via post-fabrication heat treatment, offering insights for developing future high-performance alloys for advanced structural applications.

The influence of cooling time on the alloy distribution in weld metals

This research explores the impact of cooling time on the distribution of alloying elements within weld metals of high-strength steel, a critical factor in optimizing welding processes for advanced structural applications. Using gas metal arc welding (GMAW) and two different filler materials, this study systematically varies cooling times to analyze the resulting chemical compositions. Energy Dispersive X-ray (EDX) analysis was employed to examine the alloy content in the weld metal, base material, and heat-affected zone (HAZ). The results demonstrate that cooling time significantly influences the concentration of alloying elements, such as chromium, nickel, and manganese, within the weld metal, revealing complex diffusion behaviours that are dependent on the thermal cycles introduced during welding. Notably, an in-depth analysis of the HAZ shows a distinct diffusion pattern for silicon, indicating intricate microstructural changes. These findings highlight the importance of controlling cooling time to optimize the microstructural and chemical properties of welded joints in high-strength steels, with implications for improving weld performance and reliability.

Study on enhancing mechanical and thermal properties of carbon fiber reinforced epoxy composite through zinc oxide nanofiller

This study investigates the enhancement of mechanical and thermal properties of carbon fiber reinforced epoxy composites by incorporating zinc oxide (ZnO) nanofillers. The composites were developed by adding 3–15 g of ZnO nanoparticles into the epoxy matrix and were evaluated through experimental testing. The results showed significant improvements in mechanical performance, with the maximum tensile strength of 112.49 MPa and flexural strength of 114.82 MPa at the 15 g ZnO concentration. SEM analysis revealed a reduction in void content and improved fiber-matrix adhesion, enhancing load transfer. Thermal conductivity is 13.47 W/mK, while the coefficient of linear thermal expansion is 9.29 × 10−5/°C, indicating superior thermal stability. TGA analysis demonstrated a shift in decomposition temperature from 310 to 375 °C, confirming enhanced thermal stability. These results highlight the positive influence of ZnO nanofillers on both the mechanical and thermal properties of carbon fiber reinforced epoxy composites, making them more suitable for advanced structural applications.

Mix proportion design and life cycle assessment of ultra-high-performance lightweight concrete with hollow microspheres

Achieving high strength and low weight in cement-based composites remains a critical objective in material and structure engineering. This study presents the development of an ultra-high-performance lightweight concrete (UHPLC) composite with a density not exceeding 1950 kg/m³ and a compressive strength of at least 100 MPa. The UHPLC mix design was optimized using the central composite design (CCD) response surface methodology, and a life cycle assessment (LCA) was conducted for the first time on UHPLC from cradle to gate. The interactions between cement content, hollow microspheres, and their effects on workability, mechanical properties, and durability were analyzed. The results show that using the CCD response surface method for designing UHPLC mix proportions is feasible, allowing effective optimization for various objectives, such as balancing both strength and density, highlighting low density, or emphasizing ultra-high strength. the designed UHPLC exhibits mechanical and durability properties comparable to or better than UHPC. LCA results show higher energy consumption and environmental impact for UHPLC in the cradle-to-gate stage, mainly due to the microsphere production phase. Monte Carlo uncertainty analysis reveals that ADP, HTP, POCP, and EP are most sensitive to microsphere content, while GWP and AP are more affected by cement content. The optimized UHPLCs in this study can be selected depending on specific technical or environmental scenarios. Introducing HMs into the UHPC system for UHPLC production shows excellent performance, making it a promising material for advanced structural applications.

Achieving precise multiparameter measurements with distributed optical fiber sensor using wavelength diversity and deep neural networks

The development of advanced distributed optical fiber sensing systems that are capable of performing accurate and spatially resolved multiparameter measurements is of great interest to a wide range of scientific and industrial applications. Here, we propose and experimentally demonstrate a wavelength diversity based advanced distributed optical fiber sensor system to accomplish multiparameter sensing while greatly enhancing measurement accuracy. A suite of deep neural network (DNN) algorithms are developed and verified for data denoising, rapid Brillouin frequency shift estimation, and vibration data event classification. As a proof-of-concept, we demonstrate the effectiveness of the proposed advanced wavelength diversity distributed fiber sensor system assisted by DNN for simultaneous, independent measurements of static strain, temperature, and acoustic vibrations over a 25 km long sensing fiber at 3 m spatial resolution. These results suggest the potential for an intelligent multiparameter monitoring system with enhanced performance in advanced structural health monitoring applications.

Microstructure and mechanical properties of a severely cold-rolled and annealed dual-phase compositionally complex alloy (CCA) with an exceptionally deformable Laves phase

A novel CCA was designed by substituting Nb in (FCC + C14 Laves) CoCrFeNi2.1(Nb)0.2 CCA by (Hf + Nb + Ta). The (HfNbTa)0.2 CCA was homogenized, heavily cold-rolled, and isothermally annealed at 800 °C and 1000 °C for different time intervals. The (HfNbTa)0.2 alloy revealed the presence of a Hf and Ni enriched cubic C15 Laves phase. The considerations of site occupancy behavior, formation energy, and highly off-stoichiometric composition stabilized the (Hf, Ni) rich cubic C15 Laves phase. In contrast to the brittle hexagonal C14 Laves phase in (Nb)0.2 CCA, the C15 Laves phase in (HfNbTa)0.2 CCA showed exceptional deformability owing to the high propensity for nano-twin formation. Meanwhile, the FCC matrix developed a deformation-induced nano-lamellar structure with a spacing of ∼45 nm. Annealing resulted in ultrafine recrystallized FCC matrix and precipitation of DO19 structured ε nano-precipitates. The isothermal grain growth kinetics revealed a high grain growth exponent (n) ∼7, which confirmed a Zener-drag mediated process due to the ε nano-precipitates. The Hall-Petch analysis of the hardness data showed relatively high friction stress originating from the dissolution of Hf, Nb, and Ta in the FCC matrix. A high Hall-Petch coefficient indicated increased shear stress for plastic flow across the boundaries, resulting from the elongated Laves phase at the boundaries. The highly deformable Laves phase, ultrafine grain size, and ε nano-precipitates resulted in high yield strength (∼975 MPa) and superior ductility (∼16 %) in the (HfNbTa)0.2 CCA, even surpassing the (Nb)0.2 CCA. It was envisaged that strong yet deformable Laves phases could pave the pathway for developing Laves phase-based CCAs for advanced structural applications.

Multi-functional amorphous/crystalline interfaces rendering strong-and-ductile nano-metallic-glass/aluminum composite

Metal matrix composites (MMCs) are the materials-of-choice for a large range of important applications under harsh service conditions. However, owing to the high phase contrast between the matrix and the reinforcements, the strength-ductility conflict of MMCs is still outstanding. Here we fabricated a novel aluminum (Al) matrix composite reinforced by deformable, cobalt-zirconium-boron (CoZrB) metallic glass nanoparticles. The amorphous CoZrB/Al composite with only 2.0 vol.% particle reinforcements possessed a uniaxial tensile strength of 387.0 ± 1.2 MPa, showing over 80 % improvement over the unreinforced pure Al matrix at a similar uniform elongation. The strength-ductility synergy of the composite was also significantly superior to that of the composite reinforced by fully crystallized nanoparticles. These findings were rationalized by the unique multi-functionality of the amorphous particle/matrix interfaces, which effectively transferred the load from the matrix to the particles, coordinated the co-deformation of the nanoparticles and the matrix, and imparted a transgranular fracture mode in the composite with extensive matrix plastic deformation. The methodology developed in this study was shown to be generally effective for other matrix and metallic glass nanoparticle compositions, and our work may shed new light on the development of high-performance metal matrix composites for advanced structural applications.

Mechanical properties of Al–Si alloy/Si3N4 interpenetrating phase composite based on a preform fabricated at 1200 °C

Interpenetrating phase composites with three-dimensional co-continuous architecture are promising materials for advanced structural applications due to their excellent combination of properties. In this work, a novel and low-cost Al–Si alloy/Si3N4 IPC was fabricated via squeeze infiltration of Al11Si alloy melt into a porous Si3N4 preform manufactured at a low temperature of 1200 °C using H3PO4 as pore-former and binder. Microstructures of IPC show a good infiltration quality and strong interfacial bonding between metal and ceramic phases without any intermediate reaction products. The fabricated IPC exhibited significantly higher specific hardness and stiffness than the Al11Si alloy. Moreover, an excellent damage tolerance, a substantial increase in compressive strength of 420 %, flexural strength of 168 %, and a significant reduction in wear rate of 95 % in the IPC was achieved with respect to Al11Si. The flexural strength and fracture toughness values of the fabricated IPC compare well to values of Al alloy/Si3N4 IPCs reported in the literature, despite being processed using a porous Si3N4 preform fabricated at a much lower temperature.

Developing strong-yet-ductile light-weight medium-entropy alloy via the unusual oxide doping effect

High or medium entropy alloys (M/HEAs) possess outstanding mechanical and thermal properties, but their high mass density severely restricts their practical applications. In this study, we designed a novel light-weight MEA based on the TiAlCrNb-x(ZrO2) system. These ZrO2 particles doped can completely dissolve in the β-phase structure of the TiAlCrNb MEA, which contrasts with conventional ceramic strengthening introduced through powder metallurgy. Consequently, it promotes the formation of Ti3Al nanoparticles and simultaneously substantially reduces grain size, thereby achieving a remarkable strength-ductility combination with a high specific yield strength of 225/250 MPa/(g·cm−3) while maintaining an excellent tensile ductility of 19.5/10.1% in the newly designed TiAlCrNb-(1.2/1.5)(ZrO2) MEAs. This performance outperforms most other light-weight M/HEAs. Strengthened mechanisms analysis indicates that the strength increment is attributed to grain-refinement-induced Hall-Petch strengthening and solid-solution strengthening from the dissolved oxygen. The results offer insight into the innovative design of ultrastrong and ductile light-weight MEAs for advanced structural applications.

Dual heterogeneous structure enabled ultrahigh strength and ductility across a broad temperature range in CrCoNi-based medium-entropy alloy

Developing alloys with exceptional strength-ductility combinations across a broad temperature range is crucial for advanced structural applications. The emerging face-centered cubic medium-entropy alloys (MEAs) demonstrate outstanding mechanical properties at both ambient and cryogenic temperatures. They are anticipated to extend their applicability to elevated temperatures, owing to their inherent advantages in leveraging multiple strengthening and deformation mechanisms. Here, a dual heterostructure, comprising of heterogeneous grain structure with heterogeneous distribution of the micro-scale Nb-rich Laves phases, is introduced in a CrCoNi-based MEA through thermo-mechanical processing. Additionally, a high-density nano-coherent γ' phase is introduced within the grains through isothermal aging treatments. The superior thermal stability of the heterogeneously distributed precipitates enables the dual heterostructure to persist at temperatures up to 1073 K, allowing the MEA to maintain excellent mechanical properties across a wide temperature range. The yield strength of the dual-heterogeneous-structured MEA reaches up to 1.2 GPa, 1.1 GPa, 0.8 GPa, and 0.6 GPa, coupled with total elongation values of 28.6 %, 28.4 %, 12.6 %, and 6.1 % at 93 K, 298 K, 873 K, and 1073 K, respectively. The high yield strength primarily stems from precipitation strengthening and hetero-deformation-induced strengthening. The high flow stress and low stacking fault energy of the dual-heterogeneous-structured MEA promote the formation of high-density stacking faults and nanotwins during deformation from 93 K to 1073 K, and their density increase with decreasing deformation temperature. This greatly contributes to the enhanced strain-hardening capability and ductility across a wide temperature range. This study offers a practical solution for designing dual-heterogeneous-structured MEAs with both high yield strength and large ductility across a wide temperature range.

Syensqo expands its bio-based portfolio with a new MTM® epoxy prepreg

On February 27, 2024, Syensqo, previously part of Solvay Group, announced it had developed a new version of its flagship MTM® 49-3 resin that contains 30% bio-sourced monomers. The new product variant complements the portfolio of the company's MTM® advanced prepregs and targets structural automotive applications, including body panels, chassis components and spoilers.

Microstructure Characterization, Mechanical and Wear Behavior of Silicon Carbide and Neem Leaf Powder Reinforced AL7075 Alloy hybrid MMC’s.

The demanding material quality criteria in the automotive and aerospace industries have recently had an impact on the development of lightweight aluminium alloys. The choice and application of metal-matrix composites as structural materials in this context are known to offer a variety of benefits. These benefits include the ability to combine high elastic modulus, toughness, and impact resistance; minimum sensitivity to change in temperature or thermal shock; durability of the surface is good; moisture absorption leads to the potential issue while minimum exposure which leads to environmental degradation; and improved fabricability with conventional metalworking equipment. Aluminium metal matrix composites (AMMCs) are a potential material for advanced structural, aviation, aerospace, marine, and defence applications, as well as for the automotive sector and other related fields, due to their outstanding combination of qualities. The stir casting procedure is used to create an aluminium metal matrix composite (AMMC), which is the most efficient way to do so. In this study, the aluminium alloy 7075 is strengthened using neem leaf powder and SiC. The Vickers hardness examination method is used to govern the hardness of hybrid composites. Eventually, the mechanical and tribological properties of the composites were assessed, and their relationship to the composites' matching microstructure and wear was addressed.

Evolution of dielectric properties of Kevlar/epoxy laminated composites after hybridization by naturally woven Coco Nucifera sheaths

The present work was undertaken to examine the evolution of interfacial properties of Kevlar/epoxy laminated composites hybridized by naturally woven Coco Nucifera sheath (CNS). Hand lay-up method followed by hot pressing was performed to fabricate our laminated composites. Broadband Dielectric Spectroscopy (BDS) was adopted to investigate the effect of varying CNS fractions (0%, 25%, 50%, 75% and 100%) on the molecular dynamics and the interfacial adhesion between Kevlar/epoxy and CNS/epoxy. The surface and cross-section morphology of the samples were studied in order to analyze the weaving structures of Kevlar and CNS and the interfaces between epoxy matrix and reinforcements. Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR) were carried out to control the characteristic temperatures and the interactions between the two kinds of fibers (Kevlar and CNS) and the epoxy resin. The BDS results revealed different relaxations: the conduction phenomenon, the primary [Formula: see text] -process and the interfacial polarization, called also MWS polarization, whose dielectric strength [Formula: see text] was calculated using the WinFit software. Hence, Kevlar fibers can be successfully replaced by 25% of CNS natural fibers for advanced structural applications where interfacial adhesion is prime requirement.

In Situ Lignin Modification Enabling Enhanced Interfibrillar Interactions in Lignocellulosic Nanomaterials toward Structural Applications

Lignocellulose nanopaper (LNP) assembled from lignocellulose nanofibrils (LCNFs) is an emerging eco-friendly structural material applicable to a variety of fields. Lignin serves as a crucial functional component in the LNP matrix; however, it negatively affects the interfacial hydrogen-bonding behaviors among LCNFs and consequently the inferior mechanical performance of LNP. In this study, a mild ozone-oxidation strategy was used to modify lignin macromolecules in situ without significant degradation of carbohydrate polymers (i.e., cellulose and hemicellulose) in LCNFs whereupon the interfacial hydrogen-bond energy was dramatically improved in the assembly and deformation process of LNP as validated by molecular dynamics simulation. Consequently, the lignin-modified LNP exhibited significantly enhanced tensile strength (from 83 to 140 MPa) and toughness (from 1.9 to 7.1 J/m3), which even surpassed those of conventional cellulose nanopaper. Benefiting from the well-preserved lignocellulosic structure, lignin-modified LNP maintained its inherent favorable water and thermal stability and intriguing optical performance, which supported our developed LNP to be a multifunctional structural material for diversified fields, for example, flexible electronic applications. Additionally, the estimated production cost for our developed LNP was approximately half of that for conventional cellulose nanopaper due to its significantly lower resource inputs such as the material, water, and energy. Overall, our study provides a site-specific macromolecular modulation strategy for the economically and environmentally feasible fabrication of high-performance lignocellulosic nanomaterials toward advanced structural applications.

Tribological Properties of CNTs-Reinforced Nano Composite Materials

High modulus of about 1 TPa, high thermal conductivity of over 3000 W/mK, very low coefficient of thermal expansion (CTE), high electrical conductivity, self-lubricating characteristics and low density have made CNTs one of the best reinforcing materials of nano composites for advanced structural, industrial, high strength and wear-prone applications. This is so because it has the capacity of improving the mechanical, tribological, electrical, thermal and physical properties of nanocomposites. So, this study is aimed at providing the latest discoveries on the tribological behavior of CNTs-reinforced composites. The composites reviewed included metal matrix composites (MMCs), polymer matrix composites (PMCs) and ceramic matrix composites (CMCs) reinforced with CNTs. Their tribological characteristics, uses, production challenges, conclusion and recommendations are presented. The work presented the best technique to disperse CNTs on matrices to avoid its agglomeration, since agglomeration is one of the major challenges in reinforcing with CNTs. It was discovered that ball milling destroys the outer walls of CNTs but recommended that ultrasonication and functionalization before ball milling eliminate this adverse effect of ball milling. In addition, it was discovered that addition of CNTs to composite matrices improved the wear resistance, reduced the wear volume, decreased the coefficient of friction (COF) and provided self-lubricating effect on MMCs, PMCs and CMCs.

Mechanical performance of solid and sheet network-based stochastic interpenetrating phase composite materials

Nature-inspired architected materials premise effective property combinations that are well beyond the limits of classical engineering materials. The current study expands the concept of architected, interpenetrating phase composites (IPC) with regular periodic inner phase reinforcements to the realm of stochastic designs. Schoen's Wrapped Package minimal surface (IWP) is used as base reinforcement phase structure, while implicit functions are employed for the creation of stochastic solid and sheet topologies. The study is performed for various reinforcement volume fractions as low as 20 and up to 40%, using a resin-based 3D printer for the specimen fabrication. The strong directional dependence of the uniaxial properties of regular IWP-based designs is highlighted, while their linear and nonlinear material attributes are compared with the ones of stochastic architectures. It is shown that stochastic, sheet-based single phase and IPC material architectures can yield comparable effective mechanical properties or outperform the energy absorption capacity of regular designs at low volume fraction reinforcements. The stochasticity of the strain fields is experimentally verified through digital image correlation (DIC), associating the arising failure modes with the regular or stochastic nature of the inner reinforcement phase. Moreover, functionally graded stochastic architectures are engineered and characterized, establishing a fundamental control of the deformation and resulting stress-strain response along a desired material direction. The high-performing effective material attributes, combined with the directional independence premised by the stochasticity of the IPC metamaterial architectures constitute objectives beyond the performance limits of regular cellular materials, opening new frontiers in the design of advanced structural applications.

Microstructure, mechanical and tribological properties of oxide dispersion strengthened CoCrFeMnNi high-entropy alloys fabricated by powder metallurgy

Developing materials with superior strength and wear resistance has always drawn challenging research for advanced engineering applications. Herein, considerable efforts have been devoted to enhancing the strength and wear resistance of face-centered cubic (FCC)-structured CoCrFeMnNi high entropy alloy (HEA) by incorporating HfO2 nanoparticles (NPs) through a powder metallurgy approach. The phase composition, microstructure, mechanical, and tribological properties of HEA composites were investigated. The XRD results reveal that the composite powders consisted of the FCC solid solution along with minor HfO2 phases. In addition, sintered HEAs showed the major FCC phase along with minor Cr-rich and HfO2 phases. Microscopic results confirmed the uniform distribution of HfO2 NPs throughout the matrix during the milling process. With increasing HfO2 contents, the hardness of the HEAs increased from 270 ± 10 to 520 ± 10 HV, while the compressive yield strength increased from 370 to 1500 MPa, due to dispersion and grain boundary strengthening effects. Furthermore, composite HEAs showed a decrease in coefficient of friction and wear rates with increasing HfO2 content due to increased surface hardness and transition in wear mechanism from severe wear to mild abrasive wear. The present study demonstrates the feasibility of producing high-performance oxide dispersion-strengthened HEAs for advanced structural applications.

Ceramic-reinforced HEA matrix composites exhibiting an excellent combination of mechanical properties

CoCrFeNi is a well-studied face centered cubic (fcc) high entropy alloy (HEA) that exhibits excellent ductility but only limited strength. The present study focusses on improving the strength-ductility balance of this HEA by addition of varying amounts of SiC using an arc melting route. Chromium present in the base HEA is found to result in decomposition of SiC during melting. Consequently, interaction of free carbon with chromium results in the in-situ formation of chromium carbide, while free silicon remains in solution in the base HEA and/or interacts with the constituent elements of the base HEA to form silicides. The changes in microstructural phases with increasing amount of SiC are found to follow the sequence: fcc → fcc + eutectic → fcc + chromium carbide platelets → fcc + chromium carbide platelets + silicides → fcc + chromium carbide platelets + silicides + graphite globules/flakes. In comparison to both conventional and high entropy alloys, the resulting composites were found to exhibit a very wide range of mechanical properties (yield strength from 277 MPa with more than 60% elongation to 2522 MPa with 6% elongation). Some of the developed high entropy composites showed an outstanding combination of mechanical properties (yield strength 1200 MPa with 37% elongation) and occupied previously unattainable regions in a yield strength versus elongation map. In addition to their significant elongation, the hardness and yield strength of the HEA composites are found to lie in the same range as those of bulk metallic glasses. It is therefore believed that development of high entropy composites can help in obtaining outstanding combinations of mechanical properties for advanced structural applications.

Buckling and post-buckling of variable stiffness plates with cutouts by a single-domain Ritz method

Structural components with variable stiffness can provide better performances with respect to classical ones and offer an enlarged design space for their optimization. They are attractive candidates for advanced lightweight structural applications whose functionalities often impose the presence of cutouts that requires accurate and effective analysis for their design. In the present work, a single-domain Ritz formulation is proposed, implemented and validated for the analysis of buckling and post-buckling behaviour of variable stiffness plates with cutouts. The plate model is based on the first-order shear deformation theory with nonlinear von Karman strain–displacement relationships. The plate generalized displacements are approximated with trial functions built as products of one-dimensional Legendre orthogonal polynomials. The non linear governing equations system is then deduced from the stationarity of the energy functional; the involved matrices are numerically computed by a special integration algorithm based on the implicit description of the cutout via suitable level-set functions. The formulation has been implemented in a computer code which has been used to validate the method through comparison with literature solutions for variable angle tow laminates with circular cutouts. Several investigations on buckling and post-buckling behaviour of variable angle tow composite plates with cutouts having different shapes and dimensions are then presented to illustrate the approach capabilities, provide benchmark results and point out features and design opportunities of the variable stiffness concept for the buckling and post-buckling design of advanced lightweight structures.