Delamination Propensity Research Articles

Suppression of compression induced delamination in tapered laminated composites using a ply scarfing method

Thickness tapering of composite laminates is a common strategy for efficient and lightweight composite structures. The termination of specific plies necessary to achieve such tapering is well known to introduce sites for delamination initiation in laminates. This propensity for delamination is highly dependent on the thickness of the terminated ply, which presents a significant challenge in using thicker materials to improve the production rate of large-scale composite structures.In this work, the effectiveness of ply scarfing in improving the compressive failure stress of tapered laminates made using thick, unidirectional non-crimp fabrics (NCF) was experimentally investigated for the first time. Unidirectional tapered laminates were manufactured using two different NCFs with fibre areal weights of 620 and 1070 g/m2 via resin infusion. Specimens made of the 1070 g/m2 material which incorporated a ply terminated using the ply scarfing method were compared with those including plies terminated using the conventional ply-drop method. which incorporated a ply terminated using the ply scarfing method. The compression failure behaviour of the specimens was analysed using a high-speed camera. The results showed that ply scarfing suppressed delamination of the belt plies under compression and increased the failure stress by ∼60%. Furthermore, the tapered geometry of the terminated ply’s end was effective in preventing the void entrapment at the ply drop and significantly reducing the manufacturing variability.

Stiffness influence on particle separation in polydimethylsiloxane-based deterministic lateral displacement devices

Polydimethylsiloxane (PDMS) is a popular material to rapidly manufacture microfluidic deterministic lateral displacement (DLD) devices for particle separation. However, manufacturing and operation challenges are encountered with decreasing device dimensions required to separate submicron particles. The smaller dimensions, notably, cause high hydraulic resistance, resulting in significant pressure even at relatively low throughputs. This high pressure can lead to PDMS deformation, which, in turn, influences the device performance. These effects may often be overlooked in the design and operation of devices but provide a systematic source of error and inaccuracies. This study focuses in detail on these effects and investigates pillar deformation in detail. Subsequently, we discuss a potential solution to this deformation using thermal annealing to stiffen the PDMS. We evaluate the influence of stiffness on the separation performance at elevated sample flow rates with submicron particles (0.45 and 0.97 µm diameter). An excellent separation performance at high throughput is successfully maintained in stiffer PDMS-based DLD devices, while the conventional devices showed decreased separation performance. However, the increased propensity for delamination constrains the maximal applicable throughput in stiffer devices. PDMS deformation measurements and numerical simulations are combined to derive an iterative model for calculating pressure distribution and PDMS deformation. Finally, the observed separation characteristics and encountered throughput constraints are explained with the iterative model. The results in this study underline the importance of considering pressure-induced effects for PDMS-based DLD devices, provide a potential mitigation of this effect, and introduce an approach for estimating pressure-induced deformation.

A thermodynamic framework for additive manufacturing, using amorphous polymers, capable of predicting residual stress, warpage and shrinkage

A thermodynamic framework has been developed for a class of amorphous polymers used in fused deposition modeling (FDM), in order to predict the residual stresses and the accompanying distortion of the geometry of the printed part (warping). When a polymeric melt is cooled, the inhomogeneous distribution of temperature causes spatially varying volumetric shrinkage resulting in the generation of residual stresses. Shrinkage is incorporated into the framework by introducing an isotropic volumetric expansion/contraction in the kinematics of the body. We show that the parameter for shrinkage also appears in the systematically derived rate-type constitutive relation for the stress. The solidification of the melt around the glass transition temperature is emulated by drastically increasing the viscosity of the melt. In order to illustrate the usefulness and efficacy of the constitutive relation that has been developed, we consider four ribbons of polymeric melt stacked on top of each other such as those extruded using a flat nozzle: each layer laid instantaneously and allowed to cool for one second before another layer is laid on it. Each layer cools, shrinks and warps until a new layer is laid, at which time the heat from the newly laid layer flows into the previous laid layer and heats up the bottom layers. The residual stresses of the existing and newly laid layers readjust to satisfy equilibrium. Such mechanical and thermal interactions amongst layers result in a complex distribution of residual stresses. The plane strain approximation predicts nearly equibiaxial tensile stress conditions in the core region of the solidified part, implying that a preexisting crack in that region is likely to propagate and cause failure of the part during service. The free-end of the interface between the first and the second layer is subjected to the largest magnitude of combined shear and tension in the plane with a propensity for delamination.

Laboratory intercomparison for the evaluation of the delamination propensity of glass containers for pharmaceutical use

AbstractThis paper is the result of two round robin activities run by the Technical Committee TC12, Pharma Packaging, of the International Commission on Glass (ICG). It deals with the phenomenon of delamination, that is, the formation of lamellae or flakes in drug products due to specific and localized corrosion of glass vials, and it follows a first paper PDA J Pharm Sci Technol. 2018, 72, 553–565where a testing protocol for the evaluation of the delamination propensity was proposed. The results showed that the protocol gives information on the quality of vials with respect to the propensity to corrosion, but no direct correlation with delamination could be demonstrated, as no lamellae formation was observed.In response, further testing was carried out on five sets of vials with expected low delamination propensity, compared to a set of vials with high expected delamination propensity using both the proposed protocol and a more aggressive protocol. The objective was to observe lamellae at least in the high propensity vials to show a correlation to initial test protocols.The results show that there is a very good consistency between the results of the two testing protocols and therefore, with a good level of reliability, the degree of glass surface corrosion can be estimated by the testing protocol proposed by the Technical Committee. In some cases, the glass surface corrosion results may indicate an increased risk of delamination (depending on the individual interaction between the pharmaceutical solution and the inner vial surface).

Evaluation of Glass Delamination Risk in Pharmaceutical 10 mL/10R Vials

Glass delamination is characterized by the dissociation of glass flakes from the glass surface. Since glass delamination is time dependent, 5 vial types were investigated to assess delamination under accelerated stress conditions published as quick tests in literature and compared to stress testing recommended per United States Pharmacopoeia <1660>. A broad panel of analytical techniques was employed to test the solution for visible/subvisible particles and leachables and characterize topography and composition of the surface. The vial types showed significant differences in surface durability when applying the same stress conditions. An increase in glass leachables and change in topography were shown for uncoated vials. An indication for an elevated delamination risk was confirmed for Expansion 33 vials only by the compiled analytical data set including particle assessment and change in elemental composition of the near glass surface investigated by dynamic secondary ion mass spectrometry. The delamination test protocols differ in test solution, handling, and time. Before choosing the most appropriate protocol to predict delamination propensity and mimic real-time conditions, long-term storage data are needed. A combination of analytical techniques to study the risk for long-term corrosion of glass is highly recommended covering the 3 aspects: visible/subvisible particle assessment, solution analysis, and surface characterization.

Complexing agents and pH influence on chemical durability of type I moulded glass containers.

Among the factors that affect the glass surface chemical durability, pH and complexing agents presence in aqueous solution have the main role (1). Glass surface attack can be also related to the delamination issue with glass particles appearance in the pharmaceutical preparation. A few methods to check for glass containers delamination propensity and some control guidelines have been proposed (2,3). The present study emphasizes the possible synergy between a few complexing agents with pH on the borosilicate glass chemical durability. Hydrolytic attack was performed in small volume 23 ml type I glass containers autoclaved according to EP or USP for 1 hour at 121°C, in order to enhance the chemical attack due to time, temperature and the unfavourable surface/volume ratio. 0,048 M or 0.024 M (moles/liter) solutions of the acids citric, glutaric, acetic, EDTA (ethylenediaminetetraacetic acid) and sodium phosphate with water for comparison, were used for the trials. The pH was adjusted ± 0,05 units at fixed values 5,5-6,6-7-7,4-8-9 by LiOH diluted solution. Since silicon is the main glass network former, silicon release into the attack solutions was chosen as the main index of the glass surface attack and analysed by ICPAES. The work was completed by the analysis of the silicon release in the worst attack conditions, of moulded glass, soda lime type II and tubing borosilicate glass vials to compare different glass compositions and forming technologies. Surface analysis by SEM was finally performed to check for the surface status after the worst chemical attack condition by citric acid.

Nanomechanical and nanotribological behaviors of hafnium boride thin films

Nanocrystalline HfB2, HfBN and multilayer HfB2/HfBN films were deposited using chemical vapor deposition. Half of the amorphous as-deposited films were subjected to annealing at 700°C to obtain their annealed equivalent samples. Nanoindentation and nanoscratch experiments were performed to measure their mechanical properties, friction and scratch/wear behavior. The annealed films showed higher hardness values compared to the as-deposited films, with the HfB2 film exhibiting the highest hardness. All three films exhibited similar shear strength around 3GPa for as-deposited and 5.5GPa for annealed films, implying reduced delamination propensity for the annealed samples. The annealed HfBN and multilayer HfB2/HfBN films exhibited lower friction and wear, compared to the rest of the films. Specifically, the annealed multilayer HfB2/HfBN films, exhibited an order of magnitude lower wear, compared to the HfB2 films, making them excellent candidates for low friction and low wear hard coating applications.

A quick test to monitor the delamination propensity of glass containers.

If pharmaceutical products do not match properly with the glass containers used, the creation of delaminated glass flakes can occur. This process is slow and time-dependent and mostly visible after month or years. With the Schott Delamination Quicktest a rapid method is developed that provides a fast measure for a rough indication of a higher risk for a delamination behavior. The application of the test gives quick evidence and can be used as a release criterion.

Determining the Delamination Propensity of Pharmaceutical Glass Vials Using a Direct Stress Method

An accelerated lamellae formation (ALF) methodology has been developed to determine the delamination propensity and susceptibility of pharmaceutical glass vials. The ALF process consists of a vial wash and depyrogenation mimic procedure followed by stressing glass vials with 20 mM glycine pH 10.0 solution at 50 °C for 24 h and analyzing the resulting solutions by visual inspection for glass lamellae. ALF results demonstrate that while vial delamination propensity generally correlates with glass hydrolytic resistance, ALF is a more direct test of glass delamination propensity and is not affected by post-production vial washing that can affect results obtained using hydrolytic resistance tests. ALF can potentially be used by pharmaceutical companies to evaluate and screen incoming vial lots to minimize the risk of delamination during the shelf life of parenteral therapeutics, and by glass vial manufacturers to monitor and improve their vial manufacturing processes. Glass flakes can sometimes appear in liquid pharmaceutical drugs contained in glass vials. These glass flakes are a result of several factors related to the glass vial production process, glass vial sterilization procedures, and the formulation of the liquid pharmaceutical drug. Vial testing is routinely done in order to select glass vials that are less likely to form glass flakes. The factors leading to the formation of glass flakes were studied and applied to a method designed to directly screen vials for their propensity to form glass flakes. The washing of vials followed immediately by sterilization at high temperatures was determined to be a critical factor in the formation of glass flakes. As a result, a laboratory mimic of this procedure was incorporated into the newly developed method for screening vials. This mimic procedure as well as robust accelerated incubation conditions and a sensitive visual inspection procedure are key aspects of this vial screening method.

Delamination Propensity of Pharmaceutical Glass Containers by Accelerated Testing with Different Extraction Media

The delamination of pharmaceutical glass is a serious issue, as it can cause glass particles to appear in vials, a problem that has forced a number of drug product recalls in recent years. In Type I pharmaceutical glass vials, delamination occurs generally at the bottom and shoulder, where extensive flaming during the conversion process can favor a strong evaporation of alkali and borate species and the formation of heavily enriched silica layers. The contact with parenteral preparations dissolved in an alkaline medium increases the rate of glass corrosion, while the differential hydration of these layers can cause the detachment of flakes. The purpose of this study was to investigate the effect of the pH and the composition of the extraction solutions on the propensity of different glass types to delaminate. Repeated autoclave extractions at 121 °C were carried out on different glass types with different extraction media, including organic extractants like citric and glutaric acid. When vials were in contact with alkaline solutions and similarly aggressive media, an increase in silica extraction values indicated glass corrosion and an increasing risk for further delamination. Under such conditions expansion 33 glass is extensively corroded, showing high silica concentration and heavy flaking as compared to other glass types. Sulfur-treated glass also showed early flaking, even if SiO(2) concentration was very low. A similar ranking was observed with extractions carried out with glutaric and citric acids, but at far much higher SiO(2) concentration levels. Extractions with 0.9% KCl solution can be used as an accelerated test to highlight the propensity of a glass to delaminate, but in no case it can be taken as a guarantee that the glass will not delaminate when exposed to the pharmaceutical drug, whose extraction ability requires case-by-case study. How can injectable drug manufacturers prevent glass delamination? The issue of delamination is a serious one, as it can cause glass particles to appear in vials, a problem that has forced a number of drug product recalls in recent years. To combat this, pharmaceutical and biopharmaceutical manufacturers need to understand the reasons for glass delamination. The most recent cases of product recall due to the presence of particles in the filling liquid have involved borosilicate glass containers carrying drugs made of active components with known ability to corrode glass and to dissolve the silica matrix. Sometimes these ingredients are dissolved in an alkaline medium that dramatically increases the glass corrosion and potentially causes the issue. As this action is strongly affected by time and temperature, flaking may become visible only after a long incubation during storage and requires systematic monitoring to be detected at its early stage. If the nature of the filling liquid is the driving force of the phenomenon, other factors are of primary importance. The surface morphology created during vial forming is a key issue, being a function of the forming temperature that is higher in the cutting step and the forming of the bottom. Delamination occurs generally on the vial's bottom and shoulder, where extensive flaming can favor a strong evaporation of alkali and borate species and the formation of heavily enriched silica layers. When these layers are in contact with a solution, they are subject to a differential re-hydration that may result in cracking and detachment of scales. The purpose of this investigation is to identify testing conditions and parameters that can be used as indicators of an incipient delamination process. Extractions with 0.9% KCl solution for 1 h at 121 °C can be used to simulate a long-term contact with aggressive pharmaceutical preparations, while SiO(2) concentration in the extract solution can be taken as an index of glass dissolution. The conclusions developed by this study can provide pharmaceutical manufacturers with information needed to help prevent glass delamination in their processes.

Chisel Edge and Pilot Hole Effects in Drilling Composite Laminates

Previous studies have shown the severe limitations that have to be placed on machining forces when drilling composite laminates due to their propensity for delamination. Delamination, which consists of separation between the plys in a laminate, is due to the relatively poor strength of these materials in the thickness direction. In drilling, delamination is initiated when the drilling force exceeds a threshold value, particularly at the critical entry and exit locations of the drill bit. While abrasive machining results in damage-free holes in most composites, such processes are slow and expensive when compared to drilling with conventional twist drills. Here it is shown that the chisel edge in such drills is a major contributor to the thrust force that is the primary cause of delamination when drilling composite laminates. In this study, a series of drilling experiments were conducted on carbon fiber-reinforced composite laminates to determine quantitatively the effect of the chisel edge on the thrust force. In addition, tests were conducted to determine the effect of pre-drilling the laminate with a pilot hole. The results show a large reduction in the thrust force when a pilot hole is present which, in effect, removes the chisel edge contribution. An analytical model that incorporates the presence of a pilot hole is also described. The results from the thrust force-feed relationships show good agreement with experimentally determined values for the thrust force for a wide range of feeds for drilling tests conducted on laminates with and without pilot holes.

Rapid Tooling for Sheet Metal Forming Using Profiled Edge Laminations—Design Principles and Demonstration

Sheet metal forming dies constructed of laminations offer advantages over more conventional tooling fabrication methods (e.g. CNC-machining) in terms of tooling accessibility, reduced limitations on die geometry and faster fabrication with harder die materials. Furthermore, the recently introduced Profiled Edge Lamination (PEL) tooling method improves upon other lamination-based tooling methods. Adoption of this promising rapid tooling method by industry is being hindered by the lack of formal analysis, design principles, and manufacturing requirements needed to construct dies in such a manner. Therefore, the propensity for delamination of the die is discussed and preventive measures are suggested. The basic machining instructions, i.e., an array of points and directional vectors for each lamination, are outlined for both compound and planar profiled-edge bevels. Laser, AWJ and flute-edge endmilling are experimentally identified as the most promising methods for machining bevels. Development of a stand-alone PEL fabrication machine is suggested over retrofitting commercially-available 5-axis machines. Finally, the general procedure for creating PEL dies is implemented in the construction of a matched set of sheet metal forming tools. These tools are used to successfully stamp a sheet metal part out of draw-quality steel.

Value of a negative cervical smear

Certain types of glass vials used as primary containers for liquid formulations of biopharmaceutical drug products have been observed with glass flake like delamination or 9lamellae9 under certain conditions during storage. The cause of this delamination is in part related to the glass surface defects, which renders the vials susceptible to flaking, and are formed during the high temperature melting and annealing used for vial fabrication and shaping. Current European Pharmacopoeia (Ph. Eur.) method to assess glass vial quality utilizes acid titration of vial extract pools to determine hydrolytic resistance or alkalinity. Four alternative techniques with improved throughput, convenience, and/or comprehension were examined by subjecting seven lots of vials to analysis by all techniques. The first three new techniques of conductivity, flame photometry, and inductively coupled plasma mass spectrometry (ICP-MS) measured the same sample pools as acid titration. All three showed good correlation with alkalinity; conductivity (R2=0.9951), flame photometry sodium (R2=0.9895), and several elements by ICP-MS [(sodium (R2=0.9869), boron (R2=0.9796), silicon (R2=0.9426), total (R2=0.9639)]. The fourth technique processed the vials under conditions that promote delamination, termed the Accelerated Lamellae Formation (ALF), and then inspected those vials visually for lamellae. The visual inspection results without the lot with different processing condition correlated well with alkalinity (R2=0.9474). Due to vial processing differences affecting alkalinity measurements and delamination propensity differently, ratio of silicon and sodium measurements from ICP-MS was the most informative technique to assess overall vial quality and vial propensity for lamellae formation. The other techniques of conductivity, flame photometry, and ALF condition may still be suitable for routine screening of vial lots produced under consistent processes.