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Adhesion at the interface between dissimilar materials in the semiconductor industry is an important topic, but reliable quantitative methods for strongly adhesive or highly plastic layers are hardly available. This study aims to investigate the suitability of the cross-sectional nanoindentation (CSN) method for determination of the critical energy release rate of thin film stacks in the presence of a polyimide layer as a representative structure for such a case. For this purpose, the adhesion of a deliberately weakened Si/SiOx interface in a Si/SiOx/Al/SixNy/polyimide stack is examined by systematic variation of the experimental parameters. This allows for a limitation of the plastic energy dissipated in the polyimide layer during delamination, while still investigating its influences on the overall delamination behavior. The results and evaluability of individual experiments were strongly affected by the geometry of the indenter tip and the distance of indentation to the interface, while other internal control parameters of the nanoindenter were more relevant for ease of the experimental procedure. An optimized choice of the mentioned parameters, 8 μm distance from the deposited layers for the cube-corner tip geometry, and 10 μm for the Berkovich geometry, led to 30 % of evaluable results, considered as high for quantitative adhesion testing of thin films. A multi-stage finite element analysis was developed to consider the effect of plasticity in the polyimide layer. Using this, the critical energy release rates (Gc) of the Si/SiOx interface was determined to be 9.61 J/m2 and 10.85 J/m2 for the cube-corner and Berkovich tip geometries, respectively. This work presents a novel promising way to extend the application fields of the CSN method for the determination of the energy release rate of systems containing layers with a high plasticity.

Background: Modern literature has brought into question if wear of tibial inserts made from conventional or highly crosslinked polyethylene (HXL PE) is still a factor limiting longevity of total knee arthroplasty (TKA) in the mid- to long-term. It is the objective of this study to determine: 1) most common causes of mid- to long-term TKA failure, 2) the prevalence of delamination, and 3) the medial/lateral linear wear rates of conventional and HXL PE tibial inserts retrieved in the mid- to long-term. Methods: A tibial insert retrieval cohort of 107 inserts (79 conventional, 28 HXL PE) with a minimum time in situ of 6.5 years (mean 11.7 ± 4) was studied. Failure causes were determined from chart-review, delamination presence was assessed microscopically, and medial/lateral linear wear was determined by minimal thickness changes measured with a dial-indicator. Results: The most common mid-to long-term etiologies for failure were instability (44.9%), PE wear 15%), aseptic loosening (14%), and infection (13.1%). Delamination occurred in 70% of inserts (72.1% conventional, 64.3% HXLPE). Gross material loss due to delamination appeared to be the underlying reason for at least 33.3% of cases exhibiting instability. Of the cases removed for infection, 75% exhibited no histopathological hallmarks of acute infection. The medial/lateral wear rates were 0.054/0.051 (conventional) and 0.014/0.011 (HXL) mm/y, respectively. Conclusions: Polyethylene wear still appears to be a major primary and secondary cause for TKA revision in the mid- to long-term. Wear may manifest as destabilizing delamination or as continuous release of fine wear particles potentially resulting in inflammatory responses and subsequent failure.

This study investigates the failure mechanisms of curved woven Glass/Polyphenylene sulfide (G/PPS) composites and characterizes the critical strains associated with the occurrence of damages during unfolding. Tensile-bending tests were carried out to study the damage development. The damages were observed by using acoustic emission sensors, a scanning electron microscope, and a camera. The results for the (0,90) ply orientation showed that the mechanism of failure changes from intraply-dominated to interply-dominated as the laminate thickness increases. Furthermore, the change in layup for the thinnest samples, with [(0,90)]2s, [(90,0)]2s, and [(±45)]2s layups, caused a change in the mode of the damage initiation, although all of them showed initiation at the fiber/matrix interfaces. Intra-yarn cracks were found at the compression side of all 4-ply samples. These cracks caused surface yarn buckling in the [(0,90)]2s and [(±45)]2s samples, but not in the [(90,0)]2s.

The impact-echo (IE) method is effective for evaluating invisible defects. However, it might return misleading results when its signals are invalid. This challenge aggravates when the tests are conducted using robotic devices that automatically collect massive data. This study proposes an automatic method to eliminate invalid signals based on the ResNet model. First, the signals are visualized into two-dimensional images as the input for ResNet. The input data can then be classified into valid and invalid data via the ResNet model, which is trained with 11,290 signals and tested with 5664 signals. Finally, defects can be detected using the dominant frequencies of the valid-class data. A case study with IE data from two concrete bridges was employed to validate the feasibility of the proposed approach. The results indicate that the method can achieve an average accuracy of 90.6% for eliminating invalid signals and significantly improve the IE test accuracy.

Current research uses a novel recycled milled carbon (rmCF), recycled milled Kevlar (rmKF), and innovative Hybrid fillers (rmHF) of both to increase glass/epoxy composite laminate delamination resistance. This study examines how crack propagation and fibre orientation affect laminated composite delamination fracture toughness. Recycled milled Fillers in the interlayer increase stiffness, delamination resistance, and fracture toughness by increasing the energy needed to crack the interlaminar domain. Here, Mode I, Mode II, and Mixed Mode (I/II) with GIGII = 25 %, 50 % and 75 % were studied for four different Interface fibre orientations. It appears [06/902/06] increased delamination toughness. Adding the novel recycled milled fillers improved delamination resistance. Among the three fillers, rmCF increased fracture toughness by 271 % and rmHF and rmKF composites had 220 % and 182 % higher fracture toughness. The synergy compensated for Kevlar's lower fracture toughness in the hybrid (rmHF). SEM analysis of fractured surfaces revealed crack deflection, individual debonding, and filler/matrix interlocking, all of which increase fracture toughness on different levels.

The increasing use of composite materials across various industries necessitates a detailed understanding of the machining processes involved in their production. This study presents a comprehensive bibliometric analysis focused on the drilling of composite materials, aiming to identify key trends, advancements, and research gaps in this critical area. The novelty of this research lies in its systematic approach to mapping the intellectual landscape surrounding drilling processes, particularly emphasizing underexplored topics such as hybrid composites and alternative drilling techniques like laser and ultrasonic methods. An analysis of 927 relevant publications using the Scopus database and VOSviewer software revealed significant insights into the concentration of research on Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP), while highlighting a lack of focus on sustainable drilling practices and real-time defect detection methods. The results suggest that while optimization of traditional drilling parameters is well-covered, there is a pressing need for future research on tool wear mechanisms and environmentally friendly drilling approaches. These findings provide valuable guidance for improving the efficiency, precision, and sustainability of drilling processes, thereby enhancing the industrial application of composite materials.

The current work investigates the effects of drilling parameters on hole quality, including delamination and circularity, produced in hybrid composite materials consisting of neat glass fibre (NG) and hybrid glass fibre/Al-wire mesh in two distinct sequences, the first one being with Al-mesh in the outermost layers (AG) and the other with Al-mesh in the central layer (GA). The operation's process parameters are feed rate (F = 20, 40, and 60 mm/min), spindle speed (N = 1000, 2000, and 3000 rpm), and drill point angle (Ɵ = 90°, 120°, and 135°). Taguchi's L9 orthogonal array is used for the study. The optimal levels and effects of the process parameters were determined. Gray relational analysis (GRA) was employed to examine the complicated interactions influencing the results and ANOVA was used to evaluate the influence of process parameters. The results indicated that for all specimens, push-out delamination was more severe than peel-up. Circularity is minimized by using N = 3000 rpm, F = 20 mm/min, and Ɵ = 90°. At speed (N) of 3000 rpm circularity reduces by 83.5% and 76.5% compared to 1000 or 2000 rpm, respectively. Compared to other specimens, AG-specimen produced minimal delamination and circularity by an average of 6% and17.38%. The results of the confirmation test and regression model provide good agreement between the experimental and predicted results.

During the evolution process, a bamboo stem achieves a significant height (up to 20 m) to fulfil its phototropic requirements. While on land, the stem is mostly subjected to bending load which makes it liable to fail by uprooting. However, this failure is prohibited by smart structure of bamboo stem which includes graded arrangement of fibre bundles in the cross-section and a tapered cantilever form of the stem. This paper attempts to understand the optimal design of bamboo stem through the relationship between the stellar arrangement of stiff fibre bundles in the cross-section and the tapered form. In this work, a comparison between two types of stellar arrangement, namely uniform and graded, is presented in view of non-linear bending analysis through elastica theory and fracture-induced delamination, both numerically. It is observed from the results that a bamboo stem prefers to evolve with graded stellar arrangement which provides gradation of stiffness and toughness over the cross-section; the trend in toughness being opposite to that of stiffness. Moreover, interplay of stellar arrangement and gradation of stiffness-toughness thereof is found to be the governing mechanism for ensuring its mechanical integrity and stability in view of an optimal design perspective. The smart structure of bamboo is recommended for bio-mimicking.

This work investigates the fatigue crack growth behavior of adhesive joints under pure modes I and II within epoxy matrix composites reinforced with unidirectional carbon fibers. Experimental tests are made using Double Cantilever Beam (DCB) and End-Notched Flexure (ENF) setups for modes I and II respectively, considering exposure periods of one week and twelve weeks in a salt spray chamber. Control specimens are also studied for comparison.Static tests were conducted to securely establish the levels of Energy Release Rate (ERR) that were subsequently used to obtain the fatigue initiation curves (G-N) and fatigue crack growth curves (G-da/dN). A probabilistic model based on a Weibull distribution is applied to analyze fatigue initiation data.The fatigue limit in mode I, for all aging periods, is around 25 % of the static strength, while in mode II, it is around 20 %. These results are very close at all aging levels (0, 1, and 12 weeks). From this, it is inferred that aging in a saline environment of the studied joints does not have a significant impact on the fatigue limit.In the crack growth zone, for mode I, the velocity is higher in the specimens aged in both periods than in the unaged specimens. The same cannot be said for mode II, where a clear trend cannot be appreciated.

A new approach was used in drilling woven glass fiber reinforced polymer (GFRP) composites to clamping the specimen by a controllable force at drill entry and exit sides. The influence of cutting and support conditions on thrust force, push-out and peel-up delaminations, and burr factor was investigated. A series of ASTM tests were implemented to determine tensile, in-plane shear, Mode I and Mode II fracture toughness properties, which were used to predict the critical thrust force (CTF) at delamination initiation. The delamination and burr areas were accurately measured via inexpensive, easy, and accurate image processing technique. Result from drilling processes revealed that the supported specimens are approximately free from burr accompanied with insignificant peeling within the drill (10 mm)/support hole (12 mm) tolerance. By using support plates, the thrust force was increased up to 8.3% compared to the unsupported conditions. On the other hand, the delaminations were decreased by about 65.5%. The delaminations were dominated by Mode I fracture toughness, which is lower than that of Mode II by 41%. The predicted CTF using concentrated load models are slightly lower than the measured values, which interpret the occurrence of delamination damage on the cutting zone.

Metastructures hold significant potential for applications such as adaptive structures and soft robotics. Architectures of fiber-reinforced polymer metastructures may relate to modular arrangement of straight and curved laminates, with their connections to resemble perfect cracks, thus susceptible to delamination. This study investigated geometrical effects on the load-carrying capabilities of these connections upon a global tensile deformation, as well as lean modeling tools to facilitate the development of architected composite metastructures. Numerical fracture mechanics approach on different connection geometries and thicknesses showed that connection delamination is a critical failure mode, but crack-driving-force has low dependence on connection shape for given ligament thickness (and stiffness). Adopted analytical models could capture either moment or force-driven delamination failure, while the intermediate regime necessitates numerical tools. First-ply failure may precede depending on shape and ligament stiffness. These trends were also verified on an exemplary rotating chiral composite geometry. Furthermore, interface load-carrying capability improvements were studied via design considerations including connection filler material and element variable thickness. Indicatively, the latter showed a 157 % increase in bending deflection (and global deformations), while reducing crack driving force by 38 % for a given load case. The conducted analysis offers valuable insights into the design of lightweight, load-carrying composite metastructures.

Nano-structured materials gain a vast market acceptance mainly due to their overarching endurance. Nanofibrillar cellulose (NFC) is one example of an augmenting agent unviable for production by small and medium enterprises (SMEs) due to the underlying process complexity. This study aims to characterise the NFC-alternative cells denoted as TRX-cellsⓇ, which is a mix of cellulose and non-cellulose components, ruling out its status as ‘cellulose nanofibers, CNF’. The aim to test-fit the TRX-cells® production process into the circularity model was executed by deliberating on the usability of the byproduct. In doing so, fibrous oil palm empty fruit bunch (EFB) was treated with dioxydanyl radicals (DIOR) and homogenised. The rapid EFB-DIOR reaction at 70°C targeting dearomatisation reaction in a 10%-solid open system was performed before refining the DIOR-treated EFB to micro-scale fibres. Subjecting the micro-fibres to 17 kWh/mt PFI-milling yielded 85–95% of nano-scale fibrous mass. Relative to the stiff micro-fibres, the nano-scale cells web exhibit 34–41% softness enhancement judged from the web tear resistance profile associated with inter-fibre space reduction. Advanced chromatographic evidence for 27% xylan amongst TRX-cells®’ total aldo-sugars was one form of the non-cellulose nano-component. High-resolution Transmission Electron Microscopy hyphenated to Energy Dispersive Analysis of X-ray (HRTEM-EDX) elemental mapping showed a 0.4 atomic percentage of nano-biominerals, confirming the presence of the redistributed dearomatised cells adjacent to cellulose held in the web of the hemicellulose. Shearing at the dearomatised inter-cell wall layers by PFI mill peeled 5 nm–100 nm thickness laminae. The smorgasbord of cellulose and non-celluloses resulted in crystallinity comparable to softwood NFC of approximately 60%, with unique preservation and precision-printing enabling properties. Given the non-recyclability of the DIOR-treated EFB microfibres, nestling the rapid waste transformation process into the circularity model shed light on circular bio-nanotechnology to the spectrum of opportunity for zero-waste, reduced emission and net zero carbon practices on top of an added value from waste transformation to a product.

The delamination phenomena of laminated glass structures are issues that are not perfectly understood and remain problematic to predict due to the nonlinearity of the geometric response. A research study is undertaken to investigate the behavior of laminated glass curved beams with initial delamination exposed to different boundary conditions. A mathematical model which contains nonlinear field equations and boundary conditions is developed. An iterative procedure for the solution of field equations is implemented. In addition, experiments are conducted and finite element model is developed to determine the effectiveness of model. The results are in good agreement. These results contribute to a better understanding of the complex response phenomena exhibited by curved laminated glass beams subjected to initial delaminations. Research findings allow a better insight in the behavior of the delamination in laminated glass, including the deflections and stresses. Based on the developed model it is possible to determine the effects of position and size of delaminations on the behavior of laminated glass curved beams under different boundary conditions.

The adoption of deep learning models for ground penetrating radar (GPR) data analysis has great potential for advancing the field of infrastructure condition monitoring, especially in the early detection of bridge deck distresses. This work presents a deep learning approach to detect delamination in concrete bridge decks using GPR data, employing one-dimensional convolutional neural networks (1D-CNN). The experiment uses GPR data from the SDNET2021 dataset containing five in-service bridge decks. The main objective is to classify each GPR A-scan as either 'sound' or 'delaminated', thus allowing efficient and timely detection of subsurface structural problems. The proposed method incorporates a contextual information approach to enhance the accuracy and reliability of delamination detection. Two techniques were evaluated and compared to identify the optimal approach. The results demonstrate that the A-scan data, when combined with the average filter, significantly improves the detection performance with a 0.9940 weighted average F1 score compared to the raw A-scan only with a 0.7735 weighted average F1-score. Moreover, a real case study is introduced with a transfer learning approach. The detection results achieved 92.6 % accuracy when a pre-trained model was fine-tuned with 5 % of the labels from the new data. The findings of the research contribute to the advancement of non-destructive testing methodologies by providing the first approach to benchmark and work with the GPR data of the SDNET2021 dataset.

A high-strength-ductility 304L stainless steel with heterogeneous lamella structure (HLS) was fabricated by cold rolling and subsequent partial recrystallization. The HLS was composed of lamellar recrystallized grains (mean grain size of ∼4.1 μm) embedded in a hard matrix of ultra-fine grains (mean grain size of ∼0.65 μm) and dislocation-cell structure. It exhibited a superior cryogenic impact property compared with coarse-grained, fine-grained and cold-rolled 304L stainless steels. This was mainly attributed to the suppression of crack propagation by lamellar recrystallized grains, dislocation-cell structure and TRIP effect. In addition, the extra fracture energy was also caused by the delamination in ultra-fine grains. This work will give an important theoretical guidance for the cryogenic applications of the HLS 304L stainless steel.

Two-photon lithography (TPL) is a representative fabrication process for micro 3D structures with a sub-micron fabrication resolution. As the TPL process is developed and commercialized, the TPL process requires higher process yield to be a considered reliable manufacturing technique for mass production. However, delamination is one of the main factors that reduce the yield of the TPL process. In this study, a double-step laser scanning method is proposed as a reliable high-yield TPS process to reduce the delamination effect. The method entails a simple process that polymerizes the initial interfacial layer between the structures and substrate twice. The additional laser scanning step induces a strong crosslinking in the polymer, and thereby preventing swelling and delamination. Furthermore, the effectiveness of the method is evaluated with large-scale microlens arrays. Although the process time is slightly increased, the process yield is significantly improved through the use of the double-step laser scanning method. Hence, the double-step laser scanning process can be employed as a reliable additive manufacturing process for various 3D microscale devices, and more importantly, it can be used to increase the manufacturing yield through the reduction of defects caused by surface delamination.

Damage modelling of composite material delamination is an intense field of research to understand the complex composite failure behaviour and predict the residual strength of damaged structures. One of the widely employed methods to simulate delamination is the cohesive zone modelling (CZM) technique. To successfully utilize this approach, accurate characterisation of the interlaminar fracture toughness is crucial, while the composite delamination is dominated by Mode I and Mode II fracture in most cases. Numerous studies have been conducted on composite materials delamination under Mode I loadings using double cantilever beam (DCB) tests. Accordingly, the ASTM standard testing procedure and data reduction scheme to obtain Mode I fracture toughness (GIc) have been well established and widely accepted. However, it is still challenging to characterize the composite Mode II delamination resistance due to the susceptibility problems inherent to the existing testing methods and the lack of robust data reduction schemes to accurately identify the initial crack tip and monitor the crack growth. This study attempts to find a reliable solution to obtain the Mode II fracture toughness (GIIC) and an effective modelling strategy to simulate Mode II delamination in laminated composites. First, we reviewed the existing testing set-ups and surveyed the data reduction schemes conventionally used to obtain GIIC. The advantages and drawbacks of the three most used test methods, and particularly the standard end-notched flexure (ENF) test (ASTM D7905/D7905M) and the end-loaded split (ELS) test (ISO 15114:2014) were examined. Second, the advantages of the effective-crack-length-based data reduction schemes against the classical data reduction schemes were empirically studied with the ENF tests conducted on G40-800/5276-1 carbon-fibre reinforced composite laminate coupons. Although many studies have studied the accuracy of the effective-crack-length-based approaches from different aspects, there is a lack of direct comparison between the numerical results and experimental data. Our modelling study demonstrates that among the five data reduction schemes that are examined, the compliance calibration method (CCM) required by ASTM D7905 yields the most conservative GIIC values, which is suitable for establishing material property for a design purpose. The compliance-based beam method (CBBM) may generate the least conservative GIIC values, which are deemed to be the most accurate ones for modelling and simulation validation purposes. Finite element (FE) modelling of the ENF tests using the CZM technique was carried out and comprehensive parametric studies were conducted to achieve an efficient and robust strategy for delamination modelling of composite laminates under Mode II shear loadings.

Composite materials are increasingly used to help in reducing the carbon footprint of transportation and upscaling renewable energy infrastructure that provides clean energy for future cities. However, the inherent susceptibility of carbon fibre reinforced polymers to impact damage results in knock-down in design and is linked to the micro-mechanistic response of the material to damage. In situ experimental and high-resolution imaging techniques using X-ray computed tomography (X-ray CT) have been used to gain a mechanistic understanding of the key factors controlling crack path — and hence macro-scale toughness within a composite. Multiscale Synchrotron Radiation Computed Tomography (SRCT) and lab-based micro-focus X-ray CT are used to investigate different material systems toughness response from standard Double Cantilever Beam tests. The crack transition to the weaker ply region of the composite is identified as a controlling factor across a scale of mm’s, and ‘trigger’ regions are reported on and investigated. The ‘trigger’ regions were identified as gaps in the ply adjacent to the interlayer. This work feeds directly into delamination growth predictions, a better understanding of material response, and enabling informed manufacture and design, allowing for reduced material usage, longer life and more sustainable vehicles and infrastructure.

The abrasive water jet (AWJ) cutting technique is one of the promising techniques used in machining of composite materials due to lack of thermal damage, lower tool wear and higher productivity. In this study, the AWJ cutting of a cross-ply CFRP laminate was investigated experimentally and numerically. The purpose is to understand the underlying physics of the AWJ cutting of a composite plate, which can be later used to control the process as well as optimizing its parameters. In the performed tests of the plate with a stacking sequence of [0°/90°/0°/90°] and having a total thickness value of 0.84 mm, where the pressure of particles and impact angle were varied, different failure characteristics such as fiber pull-out, fiber breakage, fiber debonding, matrix cracking and delamination were noticed. A three-dimensional FE model of the process was developed using ABAQUS finite element software to understand the underlying physics. In the model, the pure water jet particles following the linear Hugoniot form of the Mie-Grüneisen equation of state and highly rigid abrasive particles were modelled using smooth particle hydrodynamics. While the three dimensional Hashin damage model was used to simulate the intra ply damage, cohesive zone elements were used to predict the delamination. The damage characteristics in the composite plate was investigated for different process parameters. When the speed of the AWJ particles increased from 300 m/s to 600 m/s, the amount of delamination decreased from 6.44% to 5.69% at the top interface with no more delamination observed at the middle and bottom interfaces. The delamination performance of 0°/90°/0°/90° orientation was found to be better than those of 0°/90°/90°/0° and 0°/0°/90°/90° orientations. The impact angle of the particles affected the material removal rate in the process significantly. The failure behaviour of the laminate subjected to AWJ and pure water jet cuttings (PWJ) were also compared.

Due to the high applicability of poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) in organic electronics, current research is focused on providing new ways to further improve its functionality. In this paper, we have described a one-step process of electrochemical grafting of commercially available diazonium salts to the surface of a Pt electrode as a method to increase mechanical stability of PEDOT:PSS, simultaneously decreasing its charge transfer resistance and increasing capacitance. Pretreatment of Pt electrodes with electrografted layers of 4-nitrobenzene-, 4-methoxybenzene-, and 3,5-dichlorophenyl diazonium tetrafluoroborates is shown to improve charge storage capacity (235 mC/cm2 at the scan rate of 10 mV/s), decrease charge transfer resistance (15.0 ± 0.5 Ω) and enhance capacitance (13.3 ± 0.8 mF). The described method is also efficient in providing coatings with better affinity to the electrode and higher adhesion force.

Co-precipitation was used to prepare a copper, zinc, and aluminium hydrotalcite-like precursor to make a methanol synthesis catalyst. Treatment of the wet precursor with an aqueous miscible organic solvent led to the delamination of the sheet-like structure of the precursor phase, dramatically increasing the surface area to 340 m2 g−1 in comparison to 22 m2 g−1 for the untreated material. We show that the copper is initially sequestered within the hydrotalcite phase, and during calcination a CuO phase evolves out from the lamellar structures. Reduction proceeds to Cu0, and neither the calcination nor reduction of the material cause the loss of the lamellar morphology. This leads to high Cu0 surface areas in the final catalyst (66 m2 g−1) and high activity in the methanol synthesis reaction.

The formability of steel–polymer sandwich composites was investigated using a new forming limit diagram (FLD) while considering delamination and fracture. The acoustic emission (AE) technique was used to observe delamination during the forming process. Several tests, including tensile and lap shear tests, were performed to identify the AE features of delamination. In addition, finite element simulations were carried out using the cohesive zone model to predict the delamination of steel–polymer sandwich composites. An FLD of the sandwich composite was also constructed using the finite element model. Finally, the effect of interfacial adhesion on the formability of sandwich composites was investigated, from which the optimal condition for interfacial adhesion (in terms of ensuring the formability of the sandwich composite) was obtained.

An extensive dataset with mixed-mode fracture resistance experimental data (R-curves) and fracture process parameters is presented. The fracture resistance values are extracted from double cantilever beam specimens subject to un-even bending moments. The tested specimens are made of a unidirectional composite which undergoes large-scale fibre bridging during fracture. The data set contains both raw data (forces from two load-cells, time, acoustic emission signals, and opening displacement measurements) and processed data (J-integral, end-opening displacements, fracture process parameters) of each test. In the repository, MATLAB scripts are also provided to facilitate recreating the processed data from the raw data.

Fiber reinforced polymer (FRP) composite materials have huge demand in various fields due to their low weight and better mechanical qualities. Machining of FRP composite materials without damage is quite difficult using traditional machining systems owing to their intrinsic anisotropy, heterogeneity, and temperature sensitivity. Abrasive water jet machining (AWJM) is a known versatile technique to address the machining of FRP composite with minimal damage. However, kerf taper and delamination are the significant damages usually recorded in AWJM. The present work aims to minimize the above-said damages by applying a hybrid grey relational analysis (GRA)-principal component analysis (PCA) mathematical model. The glass and carbon fibers are used as reinforcements in the epoxy matrix. Nine experiments are conducted by considering hydraulic pressure, the mass flow of abrasive, standoff distance and transverse speed as machining parameters at three different levels each. The experimental and empirical results reveal that the mass flow of abrasive and hydraulic pressure are significant parameters to minimize the kerf damage, whereas the mass flow of abrasive and standoff distance are the parameters to reduce the delamination damage. The confirmation experiment based on the recommended optimized parameter records the reduction in delamination damage and kerf width damage to 33.9% and 11.72%, respectively. The adequacy and accuracy of the proposed mathematical model is being performed with the value of indicators R2 and adjR2, which are all closer to one.

Extrinsic non-autonomic self-healing of composite material is elucidated in two cases of crack, one of them has bridging phenomena which has been created during sample formation and the other has normal crack without bridging. Experiments for mode I composite fracture failure was carried out on a double cantilever beam (DCB) specimen. An open wooden mould technique was used to manufacture the test specimen which was made of unidirectional E-glass fiber and polyester resin. In both cases, healing required some form of manual intervention, with the healing agent being manually catalysed and then injected into the delamination. Before and after healing, an experimental study of the function of fibre bridging was conducted. Before and after the healing process, samples with and without bridging were compared. The average healing efficiency of non-bridging specimens is 101%, with a maximum healing efficiency of 113.5%, while the average healing efficiency of bridging specimens is 112.4%, with a maximum healing efficiency of 132.6%. The results show the great role of crossing fiber in bridging cases, which increases the efficiency of crack healing, so the transcendence of bridging healing is obvious.

Delamination is a major failure mode affecting laminated composite structures. This failure mechanism, if not properly monitored, can lead to uncontrolled cracks growth and premature structural collapse. Thus, predicting delamination propagation is mandatory to determine the structural integrity. At present, delamination has been extensively investigated in laminated composite structures but only a few studies have been performed on how the intralaminar damages influence the interfacial release energy and, consequently, the delamination evolution. In this paper, the well-established SMart-Time XB delamination simulation tool, has been coupled with a Hashin Criteria based User-Material Subroutine (UserMat) to study the role of the intralaminar damages in delamination propagation. A benchmark case based on the mixed-mode I/II Single Leg Bending (SLB) specimen for delamination evolution assessment under quasi-static loading has been investigated. Subsequently, a composite material plate, characterized by an artificial circular delamination, under compression has been considered. This study proved to be valuable by underlining the influence of fibre and matrix breakage on the interlaminar damages evolution. Interestingly, taking into account the effect of intralaminar flaws changes the local energy release rates values on the delamination front and, consequently, the crack shape and evolution.

Various studies have correlated the mechanical properties of the aortic wall with its biochemical parameters and inner structure. Very few studies have addressed correlations with the cohesive properties, which are crucial for understanding fracture phenomena such as aortic dissection, i.e. a life-threatening process. Aimed at filling this gap, we conducted a comprehensive biochemical and histological analysis of human aortas (the ascending and descending thoracic and infrarenal abdominal aorta) from 34 cadavers obtained post-mortem during regular autopsies. The pentosidine, hydroxyproline and calcium contents, calcium/phosphorus molar ratio, degree of atherosclerosis, area fraction of elastin, collagen type I and III, alpha smooth muscle actin, vasa vasorum, vasa vasorum density, aortic wall thickness, thicknesses of the adventitia, media and intima were determined and correlated with the delamination forces in the longitudinal and circumferential directions of the vessel as determined from identical cadavers. The majority of the parameters determined did not indicate significant correlation with age, except for the calcium content and collagen maturation (enzymatic crosslinking). The main results concern differences between enzymatic and non-enzymatic crosslinking and those caused by the presence of atherosclerosis. The enzymatic crosslinking of collagen increased with age and was accompanied by a decrease in the delamination strength, while non-enzymatic crosslinking tended to decrease with age and was accompanied by an increase in the delamination strength. As the rate of calcification increased, the presence of atherosclerosis led to the formation of calcium phosphate plaques with higher solubility than the tissue without or with only mild signs of atherosclerosis. STATEMENT OF SIGNIFICANCE: This study presents a detailed biochemical and histological analysis of human aortic samples (ascending thoracic aorta, descending thoracic aorta and infrarenal abdominal aorta) taken from 34 cadavers. The contribution of this scientific study lies in the detailed biochemical comparison of the enzymatic and non-enzymatic glycosylation-derived crosslinks of vascular tissues and their influence on the delamination strength of the human aorta since, to the best of our knowledge, no such comprehensive studies exist in the literature. A further benefit concerns the notification of the limitations of the various analytical methods applied; an important factor that must be taken into account in such studies., Competing Interests: Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Background: For extensively burned patients in whom donor sites for skin coverage are scarce, cultured epidermal autografting (CEA) is a reliable method for developing tissue coverage. A biodegradable temporizing matrix (BTM) can be applied for wound bed temporization while CEA is being manufactured. This temporizing matrix allows for the integration of vascular tissue supporting a neodermis onto which a skin graft can be applied. Delamination of the sealing membrane overlying this neodermis is required before skin grafting. CEA manufacturer guidelines suggest wound bed preparation occur one to two days prior to CEA grafting, and traditional practice amongst burn surgeons, including at our institution, is to delaminate BTM the day before CEA placement. However, optimal timing of delamination prior to CEA has not been investigated and variability in this practice exists. Methods: In this case report, we compare BTM delamination 24 h prior versus immediately before CEA placement in a patient with 75% total body surface area burns whose wounds were covered with BTM and subsequently treated with CEA. The “take” of autograft at two sites that were delaminated in a delayed versus immediate fashion were compared. Results: The BTM from the patient’s anterior trunk was delaminated a day prior to CEA placement, while his anterior left leg BTM was delaminated with immediate CEA placement. On day 13 after CEA placement, we observed 100% and 90% take at the anterior torso and anterior left leg, respectively. At 1 and 5 months after CEA placement, the anterior left leg was also found to have complete graft take. Conclusion: Although the reconstruction site where BTM delamination with delayed CEA placement seemed to initially demonstrate minor improvement in skin graft take in the early post-operative period in this patient, the ultimate outcome was complete graft take at both sites without morbidity regardless of the delayed versus immediate approach. If similar outcomes between these approaches are confirmed in prospective studies, broader use of immediate CEA placement after BTM delamination may reduce the number of operative cases, overall operative time, hospital length of stay, and overall costs while providing expeditious care of the extensively burned patient.

As per most other earth science engineering problems, the underground coal geotechnical environment and the way in which roof and rib support interacts with the rock mass are complex issues. It is therefore generally recognised that without prudent simplification, the complexity of the problem will overwhelm all current geotechnical methods of modelling, not least for the reason that a rock mass can never be characterised to a level that allows a “non-simplified” analysis. The fact that numerical models, which are commonly purported to be a “simulation” tool and the so-called epitome of advanced geotechnical engineering, always need to be “calibrated” to a known reality is taken to be conclusive proof of this statement. While the problem should not be oversimplified (i.e. the dominant failure mechanisms or critical data input parameters should not be ignored), without question judicious simplification is at the heart of all engineering design, to the point that it has a well-established name – “reductionism”. The hypothesis addressed in this paper, is that horizontal and vertical stress-driven slender beam and column behaviour (which includes unstable Euler Buckling) are respectively the dominant (but not only) roadway roof and ribline behavioural mechanism that (if not controlled) can lead to excessive deformation, failure and eventual collapse. As a part of the Scientific Method, a hypothesis can only be tested via real-world observations, measurements and analyses in establishing it is a credible Theory. Utilising the Scientific Method, this paper demonstrates that slender beam/column behaviour is the dominant instability mechanism within a coal mine roof/rib subject to elevated horizontal/vertical stress conditions and therefore, must be representatively accounted for in any credible empirical, analytical, or numerical approach to coal mine roof/rib stability assessment and associated ground support design.

The improvement of the impact resistance of carbon fiber reinforced epoxy (CF/EP) composite is of great significance for its application in safety protection. Herein, an approach to improve the compressive mechanical properties of CF/EP composites by self-interlocking Ti3C2Tx/polyvinyl alcohol (PVA) aerogel (TPA) has been developed. Mechanical responses and strain rate effects of CF/EP and TPA/CF/EP composites in longitudinal, transverse and through-thickness directions under quasi-static/dynamic loading have been studied. The results show that the stitching effect of TPA leads to the fact that the fracture has been dominated by cohesive failure and fiber breakage. Compared with CF/EP composites, TPA/CF/EP composites exhibit higher compressive strength and Young's modulus in the strain rate range from 0.003 s−1 to 2369 s−1. TPA/CF/EP composites have different damage evolution under quasi-static and dynamic loading and exhibits obvious strain rate sensitivity. Moreover, high-speed camera photographs and micro-morphological characteristics show that TPA/CF/EP laminates have different failure modes and fracture mechanisms for different loading directions. The well understanding of fracture mechanism can strengthen people's capability of and offer insights into designing advanced energy-absorbing materials and structures.

This research work focused on simulating different fracture modes in the high-stress concentrated region of an advanced SiC/SiC CMC component at the macroscopic scale in consideration of increasing cost and time during experimental tests of CMCs. A hybrid of extended-finite-element-method (XFEM) and cohesive-zone-modeling (CZM) was utilized to predict mode-I and mode-II fracture behavior, respectively. The cohesive element (CE) layers were used as fiber-tow interfaces in the stress-concentrated region where mode-II failure was supposed to occur. The 1st crack initiation and its further propagation were found to be dependent on XFEM damage criteria, whereas delamination was observed at the damage-front CE layers. The simulated force-displacement relationships were compared with the experimental ones, where stiffness and serrations in the force-displacement curve corresponding to the delamination matched quite well. With concern to predicting the fracture behavior in a complex-shape component of SiC/SiC CMCs, XFEM with CZM methodology can be a reliable method in the near future.

Composite materials are finding their way to various applications where their safe usage is of concern. In this regard, accurate inspection techniques must be developed and verified. Composite samples with predefined defects are needed to objectively and accurately assess various damage detection techniques. This study presents a methodology for manufacturing composite plates with engineered defects. The three most common damages in composite parts - delamination, fiber breakage, and matrix crack - are investigated here. This approach can be used by researchers working on damage detection techniques to fabricate composite samples and control the type, size, and location of the embedded defects. Manufacturing and verifying such samples with engineered defects are indispensable to all damage detection studies on composite materials. The samples in this study were 25.4 mm thick, 305×305 mm square plates manufactured via the vacuum infusion method. Stitched triaxial fiberglass fabric and epoxy vinyl ester resin were used as the reinforcement and matrix. The sizes, shapes, and locations of the defects were predetermined and kept constant in all the manufactured samples with high consistency. X-ray tomography was used to verify the characteristics of the defects in the composite plates. The X-ray images showed that defects occurred in their predefined locations, shapes, and sizes with high accuracy.

Delaminations are a concern for the structural integrity of fibre composite structures. The decisive material parameter for delaminations is fracture toughness. Structures usually have a multidirectional ply stacking. However, interface orientation dependant fracture toughness values and R-curve effects are neglected in numerical delamination analysis. This work investigates interface orientation specific fracture toughness values and considers R-curve effects in mode I to improve simulation accuracy. Therefore, mode I, mode II and mixed mode fracture toughness values of different interface ply orientations are determined experimentally and verified using numerical analysis of the characterisation specimens with cohesive zone modelling. In this way, an engineering methodology is provided for the experimental characterisation and comprehensive numerical modelling of delaminations in mesoscale progressive damage analysis of multidirectional composite structures. In addition, a full parameter set for the simulation of four different interfaces of M21-T700GC prepreg material is given. It can be shown that the use of standard 0°//0°-values leads to very conservative results. The use of interface specific values increases the accuracy. Ultrasonic scans of the DCB specimens are used to compare the crack front shapes for validation. Not only the load displacement curves of the characterisation specimens are well captured, but also the crack front shapes. This demonstrates that by smearing the microscale effects, the material behaviour can be captured phenomenologically correct by mesoscale modelling suitable for industrial use.

ABSTRACT: The focus of this paper is to investigate the deformation and failure response of a new class of bioresorbable composites subject to flexural loading. The composite consists of a biocompatible polylactic acid (PLA) matrix reinforced by long, continuous, bioresorbable silk fibers, which shows great promise for making load-bearing bone fixation devices. Three-point bend tests were carried out to characterize the material's flexural behavior. Experimental results show that the composite fails due to delamination, which is evident from images processed using the Digital Image Correlation (DIC) technique. To predict crack propagation in the composite, an enhanced fracture energy-based Smeared Crack Approach (SCA) was developed and implemented in a Finite Element Analysis (FEA) framework. The new SCA model incorporates orthogonal cracks that allow for complete energy dissipation under mode-I and mode-II failure types, with the approach being validated through benchmark studies of Double-Cantilever Beam (DCB) and End-Notched Flexure (ENF) simulations. The new fracture model, coupled with a micromechanics-based elastic model, successfully predicts the deformation and progressive damage response of the bioresorbable composite subjected to three-point bending. Effects of the strength and toughness of the binding polymer on the resulting composite response were investigated, providing crucial information for the design of new bioresorbable composites with target properties.

The damage tolerance (DT) allowables for the design of a composite structure are typically determined through experiments on the coupon level. The present study examines the transferability of the DT behavior from the coupon level to a structural level. For that purpose, a DT critical panel with two stiffeners was designed and tested. In one quasi-static and two cyclic compression after impact tests, the damage evolution behavior was studied and compared with results achieved on the coupon level. Similar phenomena were found on both scales: a long interval of load cycles, without any detectable damage evolution is succeeded by the sudden propagation of the delamination and the fiber fracture. Afterward, the ultimate failure occurs within few load cycles. Even though the stiffened panel offers a significant possibility to transfer load from the damaged skin, a significant damage stabilization could not be achieved. The no-growth interval was found to be shorter on the structural scale, however, an analytical DT analysis suggests the different damage size as the most likely cause. However, it was found that the stiffeners slow down the damage propagation. Eventually, the study confirms the no-growth design approach as the preferred method to account for the DT of stiffened, compression-loaded composite structures.

The application of composite materials in structural applications is nowadays commonplace in diverse industrial sectors. Composites are usually joined with adhesive bonding due to the excellent performance and flexibility of this technique, which does not require modifications to the adherend and is able to easily join different materials. However, delamination of adhesively bonded joints with composite adherends is still a major concern as it leads to extremely low joint performance. Diverse studies have proposed techniques to reduce delamination in carbon fibre reinforced polymer (CFRP) single lap joints (SLJs), e.g., using adhesive fillets, using mixed adhesive technique, stitching or Z-pinning. Another subset of techniques attempts to avoid delamination via reinforcement of the adherend, usually by replacing layers of CFRP with polymer or metal (fibre metal laminates) in the surface of the adherend. This paper studies the effect of additional polymer and metal layer thickness inserted in the adherends on failure load and failure mode of bonded joints with composite adherends. Multiple configurations are analysed numerically for quasi-static and intermediate rate conditions using elastic and cohesive zone modelling. A noticeable increase in failure load under an intermediate loading rate was observed by replacing CFRP layers with polymer or metal layers on the outer surface of the adherends. The failure mode for the CFRP SLJs with adherends reinforced with aluminium was changed from delamination to cohesive failure (for both static and intermediate rate loading) and a higher degree of cohesive failure was observed in configurations reinforced with polymer.

Lamination of thin bladed composite marine propellers necessitates dropping layers following thickness variation to produce lighter propeller with good elastic damping. Composite blade is subjected to multiaxial loads resulted from nonuniformly distributed hydrodynamic pressure that cause the blade to undergo combined structural response of bent and twist therefore, strength evaluation of such tapered laminate is a highly nontrivial process that include significant fluid–structure interaction (FSI). This research aims to investigate the strength of composite propeller using unconstrained stacking-sequence optimization based on fully coupled CFD-FEA analysis. Different hub idealization techniques were studied to determine the most accurate treatment in predicting stress and deformation of the blade. Composite model configured for propeller VP1304 after modification on blade thickness and, initial analysis on balanced-stacking of [0, 90, 45,−45] were set as a benchmark for optimization process targeting to minimize failure index; calculated according to Puck failure theory considering fiber and matrix failure as well as delamination. Delamination is evidenced to be utmost critical mode of failure whereas, the optimization resulted in an optimum laminate with unbalanced nonsystematic stacking that succeeded to; reduce interlaminar stresses, avoid failure and, reduce maximum value of IRF (Inverse Reserve Factor) by 50% compared to the predefined balanced-stacking benchmark.

The present work aims at assessing the delamination damage occurring in a hybrid composite material during the drilling process. The hybrid composite selected for work comprises of basalt and carbon fibers as reinforcements and epoxy as the matrix. Process parameters quantified by speed, feed, and drill size are the selected input independent variables. The response variable, delamination factor (Fd), for each experimental combination, is determined using the simple Chen's one-dimensional equation. Taguchi's L27 orthogonal array (OA)-based experimental design with the ‘smaller-the-better’ approach forms the base for experimental runs and optimization in the present work. ANOVA is applied in the present work to investigate the significance of the linear, squared, and interaction effect of speed, feed, and drill diameter on the delamination damage. Besides, the regression prediction model is developed and validated through a set of confirmation experiments. The optimum process parameters in the drilling of hybrid composite concerning delamination are drill diameter (D) of 6 mm, speed (N) of 1250 rpm and feed rate (f) of 50 mm/min. The regression model developed shows a high degree of fitness with both R-sq and R-sq (adj) values above 80%. The results of confirmation experiments show that the predicted model is highly adequate and there exists only an average prediction error of approximately 2%.

Electrochemically producing hydrogen from water via solid oxide electrolysis cells (SOECs) is regarded as one of the promising options for renewable energy storage. However, the delamination of the air electrodes was often observed during long-term tests, which significantly reduces the lifespan of SOECs and hinders the commercialization of this technology. This mini-review will involve the proposed mechanisms accounting for the delamination and possible methods to prevent or alleviate it. We expect that this mini-review will provide rational guidelines for the design of air electrode–electrolyte interface of SOECs which can effectively extend the lifespan.

An artificial solid electrolyte interface (SEI) layer is able to provide mechanical force to constrain or suppress the undesirable growth of dendrite in lithium-ion batteries. This paper performs an axis-symmetrical mechanical analysis to investigate the delamination behavior of artificial SEI layer on the surface of the anode electrode due to dendrite growth. The adhesion force between the SEI layer and the electrode is modeled by using the exponential and the bi-linear traction-separation laws (TSLs), in which the maximum stress and its peak position can be varied. With all of the given TSL profiles, the suppression force of the artificial SEI layer exerted on the dendrite is shown to present a simple relation with the final delamination radius. Further exploration on the change in the dendrite size and the SEI layer thickness demonstrates two findings regarding the relationships among the suppression force, the final delamination radius, the dendrite height, the dendrite radius, and the thickness of the artificial SEI layer.

The insurgence of delamination phenomena of glued slender devices represents a diffuse drawback in numerous technological applications and it is diffusely observed in several biomechanical systems. Starting from the classical Euler elastica, we study the delamination of an inextensible elastic rod, with an end–end confinement, adhered to a rigid flat substrate. This system represents also a prototypical scheme mimicking decohesion induced by differential growth. Using energetic considerations, we draw a phase diagram between two classes of solutions: partially adhered and fully detached equilibrium states. We highlight a discontinuous transition between these two configurations, triggered by the confinement ɛ and regulated by the ratio between the elastocapillary length ℓecand the length of the rod L. Eventually, we provide the approximate formula ɛcr≈L2/(27π2ℓec2), in very good agreement with the numerical results.

Wide bandgap semiconductors such as group III-nitrides and SiC are considered as key materials for the fabrication of smaller, more reliable and efficient power electronics. Fabrication of robust and durable power devices requires an optimized design based on the understanding of the interfacial adhesion properties of the constituent thin-film heterostructures. In this study, the adhesion properties of GaN/AlN layers grown on Si substrates were investigated. Particularly, the influence of the AlN buffer layers, necessary for GaN growth on Si, on the delamination response was determined. The interfacial adhesion strength was obtained using cross-sectional nanoindentation (CSN) and four-point bending (4PB) tests. Analytical models based on beam- and elastic plate theory which were applied respectively to calculate the interfacial fracture energy (Gic) for both methods are found to be in good agreement provided the loading conditions are similar. Detailed transmission and scanning electron microscopy investigations prior and subsequent to delamination reveal the microstructural details of the relevant interfaces and provide insights into the encountered mechanisms of interfacial failure. Finally, the probability of delamination along the weakest interface is discussed based on a fracture mechanics model.

This paper aims to improve the interlaminar fracture toughness of carbon fiber reinforced polymer (CFRP) composites by implanting fine z-pins with the minimum damage on in-plane fibers. Z-pins with diameters as small as 0.1 mm and 0.2 mm were prepared by using carbon fiber tows with different mechanical properties. The effect of the mechanical property of carbon fiber pin on the interlaminar fracture toughness of composite laminate was investigated to reveal the enhancement mechanism. The results show that fine z-pins significantly improve the interlaminar fracture toughness and simultaneously are favorable for maintaining high retentions of in-plane mechanical properties of composite laminate. Compared with control sample, the propagation GIC values of CFRPs implanted with 0.2 mm and 0.1 mm CCF800 z-pins increase by 276 % and 541 % respectively at a low pin volume fraction of 0.16 vol%. Both z-pin pull-out and z-pin fracture failure behaviors can be observed for these fine z-pin reinforced composites. The higher tensile properties of z-pins and better transverse shear resistance tend to result in the failure of z-pin pull-out. With the decrease of z-pin diameter, the probability of z-pin fracture failure becomes greater, and correspondingly stronger pinning effect and larger failure load are achieved.

Additive manufacturing (AM) or 3D printing is process of fabricating polymer, ceramics, metallic and composite parts with complex geometries by means of optimized printing parameters. Fused deposition modeling (FDM) is an extrusion based 3D printing technology most commonly used for printing thermoplastic and fiber reinforced thermoplastic composite materials. This technique is extensively used due to its simplicity in usage, materials alteration and low cost and has the ability to fabricate parts with both short and continuous fibers. Continuous carbon fiber (CCF) are extremely lightweight, stiff and durable and when utilized as reinforcement material, they have a wide range of engineering applications. In this study, we are aiming to combine short carbon thermoplastic material with CCF to form continuous carbon fiber reinforced thermoplastic composite (CCFRTC) material using FDM 3D printing technique. After the fabrication process, the additively manufactured composite specimen undertakes flexural bending test. During the flexural test, delamination occurred. This such caused was studied, discussed and explored by examining the fracture interface study using microscope's micrographs. At last, further study, recommendations and enhancement in the development were also presented.

This study investigates the influence of load ratio and impact damage on the fatigue behaviour of high-performance carbon fibre reinforced polymers (CFRP) with areal fibre weights between 30 gsm and 360 gsm. For undamaged samples, the ultimate tensile and compressive strength, as well as the fatigue properties, are evaluated with regard to their layer thicknesses. The fatigue tests were performed under tension-tension (R=0.1), tension-compression (R=-0.5) and compression-compression (R=10) regime. The results are illustrated as a constant-life diagram, and a piecewise linear interpolation examines a first prediction. The results show that static and fatigue performance improves with decreasing layer thickness. Particularly under tension-compression loading, significant improvements are observed, due to the suppression of matrix cracks and delaminations with thinner layers. In addition, the effect of low-energy impact on the fatigue behaviour of Thin- and Thick-Ply laminates is investigated. The tests demonstrate that although the delamination area is larger, Thin-Ply laminates can sustain higher stresses and still reach the same number of load cycles in contrast to Thick-Ply laminates. Computed tomography measurements visualize 3-dimensional the damage progression after various cycles and prove that the Thin-Ply composites show no increase in the damaged area during fatigue. The interlaminar stress at the delamination is not sufficient for expansion. In contrast, in the case of thicker layers, the damage growths progressively throughout the whole sample with increasing number of cycles.

In the last decades, composite materials have been getting predominance, due to their peculiar characteristics, making their application attractive in the most diverse areas. One of the most used machining processes is drilling. This process allows for the use of mechanical connections to join parts in non-permanent connections, unlike the adhesive joints which are permanent connections.Thus, there is a need for a broad assessment of the damage caused by the drilling to the material. This work presents a study on how the machining parameters affect the delamination extension by drilling a set of carbon fiber reinforced polymer plates. Enhanced radiography and image analysis techniques are utilized and, in the end, a correlation between these results and the mechanical characteristics of the machined plates is obtained. Different drilling parameters are used, namely two feed rates while keeping the spindle speed constant, and three different drill geometries (Step, Brad and Helical). The thrust force is monitored during drilling and after drilling, parts are non-destructively and destructively (bearing, pin-bearing) tested. The results show that, although the thrust force varies and the delamination extension is affected by machining parameters, the mechanical resistance obtained in the tests did not evidence significant variations. The results show that, although the thrust force, varying around 50% in average, and the delamination extension, with a variation of 8%, are affected by machining parameters, the mechanical resistance obtained in the tests did not evidence significant variations, with an average difference of 2%. The main outcome of this work is to demonstrate that existing bearing tests may not the most suitable ones to assess mechanical consequences of drilling damage extension.

Herein, a new 2-dimensional coordination polymer based on copper (II), {Cu2(L)(DMF)2}n, where L stands for 1,2,4,5-benzenetetracarboxylate (complex 1) is synthesized. Interestingly, we demonstrate that both solvent and sonication are relevant in the top-down fabrication of nanostructures. Water molecules are intercalated in suspended crystals of complex 1 modifying not only the coordination sphere of Cu(II) ions but also the final chemical formula and crystalline structure obtaining {[Cu(L)(H2O)3]·H2O}n (complex 2). On the other hand, ultrasound is required to induce the nanostructuration. Remarkably, different morphologies are obtained using different solvents and interconversion from one morphology to another seems to occur upon solvent exchange. Both complexes 1 and 2, as well as the corresponding nanostructures, have been fully characterized by different means such as infrared spectroscopy, x-ray diffraction and microscopy.

Transitions between damage modes have been observed in ultra-thin-ply laminates. Numerical methods can be effectively applied to the design and optimization of the microstructure of ultra-thin ply laminates. It is difficult to precisely predict transitions between complex damage modes of composites, such as fiber breakage, matrix cracking, shear failure and delamination. In this paper, a numerical model was developed to comprehensively consider in-plane damage and delamination. The initiation and in-plane propagation of damage was simulated using a material degradation model (MDM), which was implemented by a user subroutine USDFLD in ABAQUS. A cohesive interaction between the surfaces of adjacent layers was used to simulate delamination. The numerical predictions for the transitions between damage modes in cross-ply and Bouligand thin-ply laminates were verified by comparison with experimental results. The novelty of this study is discovering the dependence of damage modes on the ply-thickness under bending load and revealing the influence of damage competition mechanism on the bending properties of thin-ply composite. The research results could help develop a useful tool for improving microstructure design or elucidating the underlying mechanism for the mechanical behavior of thin-ply microstructures.