Climbing Drum Peel Research Articles

Characterization and Simulation of the Interface between a Continuous and Discontinuous Carbon Fiber Reinforced Thermoplastic by Using the Climbing Drum Peel Test Considering Humidity.

The objective of this paper is to investigate the debonding behavior of the interface between continuously and discontinuously fiber reinforced thermoplastics using the climbing drum peel test. The study emphasizes on the importance of considering different climatic boundary conditions on the properties of thermoplastics. Specimens with varying moisture contents, from 0m.% up to above 6m.% are prepared and tested. It is observed that an increase in moisture content from 0m.% to 2m.% results in an increase of the fracture surface energy from 1.07·103J/m2 to 2.40·103J/m2 required to separate the two materials, but a further increase in moisture to 6.35m.% conversely results in a subsequent decrease of the required energy to 1.91·103J/m2. The study presents an explanatory model of increasing plasticization of the polymer due to increased polymer chain mobility, which results in more deformation energy being required to propagate the crack, which is corroborated in SEM investigations of the fracture surface. A further increase in humidity leads to polymer degradation due to hydrolysis, which explains the subsequent reduction of the fracture energy. The experimental set up is modeled numerically for the first time with cohesive surfaces, which could successfully reproduce the effective force-displacement curve in the experiment by varying the interface parameters in the model over an influence length, allowing the conclusion of a process induced variation in the interface properties over a specific consolidation length.

An investigation on enhancing the bonding properties of PA11-CFRP interface in type IV high pressure hydrogen storage vessel through nanosecond pulsed laser treatment and failure mechanism research

At present, several key technologies remain to be addressed in the development of type IV high-pressure hydrogen storage vessels, especially the prevention of plastic liner collapse, which demands urgent resolution. One major factor contributing to plastic liner collapse is the weak interfacial bonding between the plastic liner and carbon fiber reinforced polymer (CFRP). Therefore, enhancing the bonding properties of the plastic liner-CFRP interface can effectively reduce the risk of liner failure. Nanosecond pulsed laser surface treatment, known for its high efficiency, precise control, and automation capabilities, was employed in this study to modify the surface of the PA11 liner. The bonding properties of the PA11-CFRP interface were comprehensively investigated through climbing drum peel (CDP) tests, flatwise tensile (FWT) tests, and surface performance assessments. Utilizing the Optimization module within the Response Surface Method (RSM) software Design Expert for analysis, it was found that, under the optimal parameters of 400 mm/s, 20 kHz, and 12.7 W for nanosecond pulsed laser treatment, the CDP strength increased to 24.1 N mm/mm, which was 4.74-fold higher than that of untreated samples. The FWT strength reached 2.43 MPa, which was 8.35-fold higher than that of untreated samples. The increase in interfacial bonding strength after laser treatment primarily resulted from the formation of periodic grooves on the PA11 surface, along with an increase in surface roughness. This approach presents a promising direction for the surface treatment of plastic liners in type IV hydrogen storage vessels prior to winding and is poised to enhance the safety of such vessels.

Optimization of interfacial bonding properties between thermoplastic liners and carbon fiber‐reinforced composites by atmospheric‐pressure plasma and failure mechanism study

AbstractWeak interfacial bonding properties between thermoplastic liners and carbon fiber‐reinforced composites (CFRP) can easily lead to debonding failure, which is a major challenge in development of type IV composite hydrogen storage vessels. We optimized Box–Behnken design atmospheric‐pressure plasma process parameters for maximizing interfacial bonding properties between thermoplastic liner (PA11 liner) and CFRP using Design‐Expert software. From various designs, plasma process parameters, including time (t), nozzle‐to‐specimen distance (d) and gas flow rate (r) of treatment were selected for optimization to assess the effects of their interactions on climbing drum peel (CDP), flatwise tensile (FWT) and asymmetric double cantilever beams (ADCB). The CDP strength, FWT strength and strain energy release rate (GADCB) of untreated samples were 4.2 N·mm/mm, 0.26 MPa and 87.2 J/m2, respectively. After the plasma treatment, optimum process parameters of t = 200 s, d = 12.5 mm, and r = 700 L/h were used to achieve 33.8 N·mm/mm, 2.97 MPa and 1008.4 J/m2, respectively, which were 8.0, 11.4 and 11.6 times that of untreated PA11 surface, respectively. This method has the potential for guiding thermoplastic liner surface treatment of type IV hydrogen storage vessels before winding.

Evaluation of a climbing drum laminate peel test to determine the interlaminar mode I fracture toughness of thin CFRP laminates—Comparison with the standard mode I DCB test and a mandrel laminate peel test proposed by ESIS TC4

A recently proposed mandrel laminate peel (MLP) test for quantification of delamination propagation in Fiber-Reinforced Polymer (FRP) composites is compared with a climbing drum laminate peel (CDLP) test, and the standard quasi-static Mode I fracture test with Double Cantilever Beam (DCB) specimens. MLP and CDLP both are applicable to thin laminates, for which the Mode I DCB test is not suitable. MLP and CDLP, however, do not yield delamination initiation values. Delamination propagation resistances from the three tests performed with different types of FRP, one partly and one fully cured epoxy laminate, and one thermoplastic laminate, all with unidirectional fiber lay-up agree within about 20%. Reduction of the diameter of the climbing drum (100 mm for the standard climbing drum peel test for adhesives) indicates a minimum diameter on the order of 50 mm for the CDLP test. Additional tests with selected laminates investigated potential effects of specimen width. It is concluded that FRP laminate specimens 20 mm wide and 180 mm long are sufficient for consistent results from CDLP and MLP tests. The CDLP test yielded less scatter (around 10%), i.e., better repeatability than the MLP (round 13%) and the Mode I DCB test (around 17%). Hence, the CDLP test is considered advantageous for industrial application, also due to the simplicity of the test set-up and of the data analysis.

Unravelling the interphase - bond strength relationship in novel co-bonded thermoplastic - thermoset hybrid composites for leading edge protection of wind turbine blades

The relation between the bond strength of the co-bonded thermoplastics (ABS, PC) and fiber-reinforced thermoset polymers (polyester/glass) and the interphase morphology of a novel integrated leading edge protection (LEP) solution for wind turbine blades is investigated. Interphase morphology is characterized via optical microscopy and the mechanical properties of the interphase are obtained by means of nanoindentation. Bond strength of the co-bonded hybrid composites is tested via climbing drum peel test, after which, fractography is carried out to link the fracture behavior to interphase morphology. It was seen that ABS establishes a stronger bond with polyester/glass, constituting a better candidate as an LEP material. The superior bond strength of ABS was linked to its higher affinity to polyester, promoting a no-phase separated, tough interphase undergoing extensive plastic deformation. The interphase between PC and polyester/glass, however, exhibited phase separation, which triggered brittle failure at the interface between the interphase and the polyester/glass.

RETRACTED: Mechanical Properties Study on Sandwich Composites of Glass Fiber Reinforced Plastics (GFRP) Using Liquid Thermoplastic Resin, Elium®: Preliminary Experiments

Composite sandwich structures have been used in high performance applications such as wind turbine blades, due to their unique lightweight structure and superior mechanical properties. In the current study, a new liquid thermoplastic and thermoset resin were used to fabricate four different composite sandwich panels with two various foam types and densities. Composites made with epoxy resin are presented to comprehensively compare the mechanical properties of sandwich structures to elium resin. In the case of the mechanical properties and due to a new liquid thermoplastic resin, extensive comparisons of three-point bending, climbing drum peel, and flatwise tensile strength were investigated and compared with each other. The flexural and flatwise strength of sandwich composite increased by 53% and 75%, respectively, when using Elium resin. Then, the highest value was shown in the GF/PVC/ELIUM structure. The results revealed that Elium resin could be excellent in the case of mechanical properties to replace traditional resins to fabricate various composite structures and manage the challenge of recyclable composites. Elium resin can replace thermoset-based resins for the manufacturing of laminates and composites that are fully recyclable at room temperature with comparable mechanical properties.

Geometrical Parameters Optimization of Malaysia Rubber Wood through Honeycomb Structure as Composite Sandwich Core

Rubber wood has multiple functions especially in the furniture industry and other wood products such as plywood whereas the sawdust is further processed to become medium density fiberboard or wood plastic composites. These composites are useful yet are unable to become the structural components where mechanical performance is critical. An investigation was carried out to find out the mechanical properties of rubber wood honeycomb core in the fiber reinforced composites with glass fiber as its facesheet and epoxy as its matrix. Cell diameter fabricated at 7 mm with increasing cell wall thicknesses ranging from 1 mm to 3 mm respectively. In the flatwise tensile test, the results showed that the interfacial bonding strength increased by 21.6% with increasing wall thickness. As higher density increased and minimum strength improvement, the specific strength will be reduced. Meanwhile, wall thickness of 3 mm is only 1% away from the sandwich composite with solid rubber wood which has the most similar bonding strength as in climbing drum peel test with lower density.

Bond Strength of Co-Bonded Thermoplastic Leading Edge Protection (LEP): The Effect of Processing-Driven Interphase Morphology

Integrated leading edge protection (InLEP) is a novel LEP method that involves co-bonding a tough thermoplastic to the blade shell of the wind turbine made of fiber-reinforced thermoset polymer. In the co-bonding process, as a result of the interdiffusion of the bonded thermoplastic and thermoset polymers, an interphase is formed between them. An important factor affecting the level of interdiffusion is the cure temperature. In this work, we investigate the influence of cure temperature on the interphase morphology and bond strength of ABS-polyester/glass and PC-polyester/glass hybrid composites. The hybrid composites are manufactured via vacuum-assisted resin transfer molding. Interphase morphology is observed and the interphase thickness is measured via optical microscopy. Bond strength is tested via climbing drum peel testing and subsequently, fractography analysis is carried out on the fractured samples. It was found that both the interphase thickness and bond strength decrease with an increase of cure temperature. The decrease in bond strength at high temperatures was accompanied by an increase in the extent of interfacial failure, while interphase failure at low temperatures promoted higher bond strength.

Adherend effect on the peel strength of a brittle adhesive

Peel tests are widely used to characterize the peel strength of bonded joints and control adhesion quality. There are various configurations of peel test, such as the T-peel test, peel testing at 180°, the floating roller peel test, and the climbing drum peel test. These methods have been widely used mainly in the aeronautical industry, as a way of assessing the peel strength of metallic joints. However, with the growing use of composite materials in industry, it is necessary to characterize bonded joints with these materials when subjected to peeling loads. In this research, the adherend effect on the peel strength of a brittle adhesive is experimentally studied using the floating roller peel test with the aim of evaluating how adherend changes affect adhesion properties of brittle adhesives and also to assess the viability of using the floating roller peel test in composite-to-composite and composite-to-aluminum joints, as well as make a comparison with aluminum-aluminum joint performance. It is also intended to prove the applicability of this test for quality control of adhesion and determination of peel strength in joints with composite materials. The results show the Araldite® AV138 performance falls within the characteristic values of peel strength of other structural adhesives, particularly when composite adherends are concerned, and with reasonable repeatability considering it is a brittle adhesive.

Delamination Testing of AlSi10Mg Sandwich Structures with Pyramidal Lattice Truss Core made by Laser Powder Bed Fusion

Sandwich structures possess a high bending stiffness compared to monolithic structures with a similar weight. This makes them very suitable for lightweight applications, where high stiffness to weight ratios are needed. Most common manufacturing methods of sandwich structures involve adhesive bonding of the core material with the sheets. However, adhesive bonding is prone to delamination, a failure mode that is often difficult to detect. This paper presents the results of delamination testing of fully additive manufactured (AM) AlSi10Mg sandwich structures with pyramidal lattice truss core using Laser Powder Bed Fusion (LPBF). The faces and struts are 0.5 mm thick, while the core is 2 mm thick. The inclination of the struts is 45°. To characterise the bonding strength, climbing drum peel tests and out-of-plane tensile tests are performed. Analytical formulas are derived to predict the expected failure loads and modes. The analytics and tests are supported by finite element (FE) calculations. From the analytic approach, design guidelines to avoid delamination in AM sandwich structures are derived. The study presents a critical face sheet thickness to strut diameter ratio for which the structure can delaminate. This ratio is mainly influenced by the inclination of the struts. The peel tests resulted in face yielding, which can also be inferred from the analytics and numerics. The out-of-plane tensile tests didn’t damage the structure.

Combatting rain erosion of offshore wind turbine blades by co-bonded thermoplastic-thermoset hybrid composites

An integrated thermoplastic-thermoset hybrid leading edge protection system is developed based on the co-bonding process. Co-bonding is a joining method in which a prefabricated part joints with a thermoset composite during the curing process. In such a multi-material hybrid design, the reliability of the bonding between the prefabricated protection layer and the main body of the blade is of crucial importance to prevent any delamination failures. Nevertheless, the adhesion of prefabricated thermoplastics to the thermoset remains a challenge as the interphase between two dissimilar materials is prone to form defects and irregularities. Such interface defects may lead to early failure and reduced structural integrity of the components. Therefore, the focus of this study is on achieving a strong, and reliable bonding between the prefabricated thermoplastic leading edge protection system and thermoset main body of the blade. In this study, the effect of processing temperature on the interphase quality and thickness during the co-bonding process is investigated. Next, mechanical characteristics and microstructure of the interphases are examined by Vickers’ microhardness tests. The effect of processing condition on the fracture toughness of structure is examined by climbing drum peel tests (CDP). Finally, fractography investigations are used to provide an understanding of failure mechanisms and its correlations with interphase morphology and microstructure.

Overview of Gc Tests Used to Evaluate Composite–Composite Adhesive Joints

The quality of composite–composite bonded joints is a very important issue for industries, especially for the aerospace sector. A deficient joint may stop the manufacturing process and its repairing may include very high costs. Nowadays, the quality of the joint is obtained by means of interlaminar fracture toughness tests, estimating the [Formula: see text] value (Energy Release Rate used to produce crack propagation) over coupons with (theoretically) the same conditions as those included in an actual part. Usually, [Formula: see text] is obtained by means of a Double Cantilever Beam (DCB) test. Although DCB is the reference test, it may present some drawbacks when a non-symmetrical coupon is used and when the adherents stiffness is low. An alternative to DCB is the Climbing Drum Peel (CDP) test which is able to address some of the DCB drawbacks. Nevertheless, both tests need the use of a universal testing machine, then they cannot be done in situ. In the present investigation, DCB and CDP main characteristics are analyzed and a new device, called Horizontal Drum Peel (HDP), which includes the advantages of previous tests and the possibility to perform the test over an actual part is presented.

Improvement of the adhesion of continuously manufactured multi-material joints by application of thermoplastic adhesive film

The development of tailored lightweight solutions is especially required for the support of the structural change from combustion to electric driven vehicles, due to the still challenging weight of the currently used lithium-ion batteries. The manufacturing of tailored multi-material structures consisting of steel and carbon fibre reinforced thermoplastics (CFR-TP) within a continuous roll forming process is a promising approach to combine innovative lightweight design and large-scale production capability.Nevertheless, fusion bonding as joining technology for steel and carbon fibre reinforced thermoplastics within a continuous process is still challenging because of not achieving sufficient joint strength. The application of adhesive films, which can be easily integrated in a roll forming line by coil-coating processes, seems to be promising to increase the adhesion between metal and CFR-TP. Therefore, a thermoplastic adhesive multilayer-film, consisting of functionalized polymers in different thermoplastic layers, is used within this study. The most important challenge consists in the even heating and consolidation of the multi-material structure within the limited joining time in a continuous fusion bonding process.To enable a variation in joining time, the existing test set-up is extended to a reversible, continuous process. The manufactured hybrid specimens as well as high pressure blasted references without adhesive film application are tested mechanically by climbing drum peel test to determine the production-related influence. In addition, micrographs of specimens are evaluated analytically by scanning electron microscopy.The examinations show the significant improvement of adhesion between steel and CFR-TP by application of thermoplastic adhesive multilayer-film. Lower steel temperatures in combination with reversing operation result in peel resistances almost comparable to sequential process.

A new in situ peeling test for the characterisation of composite bonded joints

At the moment, bonded joints quality on composites used in aeronautical industry is verified based on the determination of the interlaminar fracture toughness (Gc) obtained by means of the Double Cantilever Beam (DCB) or the Climbing Drum Peel (CDP) tests. Although they are well-established tests, they have known limitations. This investigation presents the design and validation of a new device that carries out a peeling test, its main advantage being the capability to perform the test in situ, i.e. directly on the actual aircraft production line without the necessity to extract coupons for a laboratory test. An experimental campaign has been carried out, the obtained results being comparable to those obtained with the traditional DCB and CDP procedures. Numerical studies have allowed to understand the delamination mechanisms presented at the different tests, confirming that experimental Gc evaluation obtained is adequate.

Mode I Delamination Testing of REBCO Coated Conductors via Climbing Drum Peel Test

The mode I interface fracture energy for a selection of commercial coated conductors was determined using a climbing drum peel test. Coated conductors with different Ag and copper stabilizer thicknesses were examined. The hypothesis that larger stabilizer thicknesses would result in increased interface fracture energy was broadly confirmed. The location of the fracture in the substrate-buffer-HTS stack was variable. For low stabilizer thicknesses the interface fracture energy was consistent with expected values of the intrinsic G 0 for ceramic layers.

High-tensile joints of continuously fusion bonded hybrid structures

Tailored hybrid structures manufactured within a continuous production process, for instance in a continuous roll forming line, offer a high potential for the automotive industry, due to its weight reduction compared to pure metal parts. Therefore, the hybrid roll formed parts consist of steel sheets reinforced by carbon fibre reinforced thermoplastic tapes (CFR-TP).Both materials are joined by fusion bonding whereby the surface of the thermoplastic matrix is melted on the steel surface. The pre-treatment of the steel with a primer, customized for joining of steel and CFR-TP, is a promising approach, due to its easy implementation into continuous coil-coating processes. Major challenges consist in achieving sufficient joint strength as well as developing of a testing method for the evaluation of the adhesion between both materials.Relating to joint strength, various process parameters (i.e. temperature of steel and CFR-TP) are examined. The fracture pattern are analysed optically by microscopy to detect possible primer damage. Furthermore, the evaluation is carried out by mechanical testing of peel specimens within climbing drum peel test to determine the production-related influence in a continuous process. The examinations show the usability of climbing drum peel test and the increase of joint strength with higher energy input.

Effect of MWCNTs added by electrostatic flocking method on adhesion of carbon fiber prepreg/Nomex honeycomb sandwich composites

To improve the adhesion of face sheet and core in sandwich composites, multi-walled carbon nanotubes (MWCNTs) were added by the electrostatic flocking method to reinforce the adhesive fillet. MWCNTs on surface and sub-surface of face sheet were taken into account to analyze the effect of adding locations of MWCNTs. The sandwich composites with different weight contents of MWCNTs were prepared by autoclave process. The size of adhesive fillet confirmed that the electrostatic flocking method could ensure the forming quality of sandwich composites with self-adhesive prepreg skin. Climbing drum peel test and flexural test were adopted for mechanical assessment. The results showed that the process of MWCNTs on sub-surface demonstrated a remarkable enhancement of both the peel properties and flexural properties for samples with 1.5wt% MWCNTs in comparison to the samples of pure prepreg. The reinforcing mechanism was analyzed by the microstructures of adhesive fillet and it is found that the different enhancement effect was attributed to the distribution features of MWCNTs in the adhesive fillet.

Improvement in skin–core adhesion of multiwalled carbon nanotubes modified carbon fiber prepreg/Nomex honeycomb sandwich composites

An experimental investigation on the sandwich composites composed of the carbon fiber face sheets and Nomex honeycomb core has been carried out in this study. Multiwalled carbon nanotubes were added into the matrix of prepreg for converting the traditional pure resin adhesive fillet to composites. Resin viscosity was measured to evaluate the effect of the additive amount of multiwalled carbon nanotubes on the rheological properties. The size of adhesive fillet was obtained from the optical microscopy to assess the forming quality. Climbing drum peel test and edgewise compression test were employed for the mechanical assessment. The results showed that the addition of multiwalled carbon nanotubes reinforcement to epoxy resin in the prepreg was very effective in improving the skin–core adhesion. The peel load and peel energy release rate as well as the edgewise compressive strength and edgewise compressive modulus of the sandwich composites varied with different magnitudes due to the additive amount of multiwalled carbon nanotubes. Reinforcing mechanism of the adhesive fillet with multiwalled carbon nanotubes reinforcement was discussed on the basis of the fractographic observations by scanning electron microscopy.

The Climbing Drum Peel Test: An alternative to the Double Cantilever Beam for the determination of fracture toughness of monolithic laminates

The experimental determination of the fracture toughness of inter-ply interfaces in monolithic composite specimens is far from trivial: even in standard test methods such as the Double Cantilever Beam (DCB), some precautions must be taken in the choice of the test configurations and in the post-treatment of the experimental results. Furthermore, non standard measurements such as the crack tip position during propagation are generally required. In this paper, we investigate an alternative test configuration, the Climbing Drum Peel (CDP) test, classically used in the ‘adhesives’ community. The adaptation of the CDP specimen configurations to the testing of monolithic composites is discussed and a systematic comparison is carried out between the CDP and the DCB tests in terms of global and local indicators of the crack propagation behavior.

Design and Verification of Sandwich Structures for High Speed Trains

Sandwich construction is a composite material structure combining low weight, high strength and good dynamic properties. Typically a sandwich composite consists of three main parts: two thin, stiff and strong facing layers separated by a thick, light and weaker inner core. The faces are adhesively bonded to the core to obtain a load transfer between the components. By this way the properties of each separate component is utilized to the structural advantage of the whole assembly leading to a very high stiffness-to-weight and high bending strength-to-weight ratio. As a result sandwich components achieve the same structural performance as conventional materials with less weight. The material characterization described in the paper is aimed at the structural design of the end cub for a high speed train made of composite sandwich materials. A sandwich structure was considered, made of glass fibber polyester face sheets with a polymeric foam core. Initially, the material properties and the rate sensitivity of the skin and core materials were investigated through a series of static and quasi-static tests. Static and dynamic impact tests were then run on the sandwich structure. For all materials tested, no significant strain-rate effects were observed over the range of test conditions investigated in the study. Results show that the structural response of the sandwich depends primarily on the strength properties of the foam core material. Sandwich peel test is intended for determining the comparative peel resistance of adhesive bonds between facing and cores of sandwich constructions tested under specified test conditions. One method, the climbing drum peel method, is most applicable when the peeled facings are relatively thin, but it can not be applicable in tested composite structures. Peel resistance was tested by modified experimental setup.