Interlaminar Shear Fracture Research Articles

Bio-inspired copper ion-chelated chitosan coating modified UHMWPE fibers for enhanced interfacial properties of composites

Ultra-high molecular weight polyethylene (UHMWPE) fibers are broadly applied in lightweight and high-strength composite fiber materials. However, the development of UHMWPE fibers is limited by their smooth and chemically inert surfaces. To address the issues, a modified UHMWPE fibers material has been fabricated through the chelation reaction between Cu2+ and chitosan coatings within the surface of fibers after plasma treatment, which is inspired by the hardening mechanism, a crosslinked network between metal ions and proteins/polysaccharides of the tips and edges in arthropod-specific cuticular tools. The coatings improve the surface wettability and interfacial bonding ability, which are beneficial in extending the application range of UHMWPE fibers. More importantly, compared to the unmodified UHMWPE fiber cloths, the tensile property of the modified fiber cloths is increased by 18.89% without damaging the strength, which is infrequent in modified UHMWPE fibers. Furthermore, the interlaminar shear strength and fracture toughness of the modified fibers laminate are increased by 37.72% and 135.90%, respectively. These improvements can be attributed to the synergistic effects between the surface activity and the tiny bumps of the modified UHMWPE fibers. Hence, this work provides a more straightforward and less damaging idea of fiber modification for manufacturing desirable protective and medical materials.

Fracture toughness response of glass/epoxy composite in symmetric and asymmetric design layup

Composites are used in transportation industries for their exceptional strength, reduced weight, and cost. Their performance depends upon many factors, such as stacking sequence, fiber volume fraction (FVF), etc. In the present work, glass/epoxy composites are prepared in symmetric (ɸn/θ2n/ɸn//ɸn/θ2n/ɸn) and asymmetric (θn/ɸ2n/θn//ɸn/θ2n/ɸn) configuration with FVF of 48.13 and 61.34%. The laminate performance was evaluated using interlaminar shear strength, flexural, and mode-II interlaminar fracture toughness tests. The results indicate that symmetric layup has better mechanical strength than asymmetric layup. The interlaminar shear strength, flexural, and fracture toughness of asymmetric layup were lower by 14.72–16.39, 12.54–16.72, and 11.92–17.98%, respectively. Further, low FVF specimens had better mechanical strength, and high FVF specimens showed lower strength by 3.67–5.56, 10.75–15.17, and 23.53–28.79%, respectively,

Mechanical and Viscoelastic Properties of Carbon Fibre Epoxy Composites with Interleaved Graphite Nanoplatelet Layer

The use of interleaving material with viscoelastic properties is one of the most effective solutions to improve the damping capacity of carbon fibre-reinforced polymer (CFRP) laminates. Improving composite damping without threatening mechanical performance is challenging and the use of nanomaterials should lead to the target. In this paper, the effect of a nanostructured interlayer based on graphite nanoplatelets (GNPs) on the damping capacity and fracture toughness of CFRP laminates has been investigated. High-content GNP/epoxy (70 wt/30 wt) coating was sprayed on the surface of CF/epoxy prepregs at two different contents (10 and 40 g/m2) and incorporated at the middle plane of a CFRP laminate. The effect of the GNP areal weights on the viscoelastic and mechanical behaviour of the laminates is investigated. Coupons with low GNP content showed a 25% increase in damping capacity with a trivial reduction in the storage modulus. Moreover, a reduction in interlaminar shear strength (ILSS) and fracture toughness (both mode I and mode II) was observed. The GNP alignment and degree of compaction reached during the process were found to be key parameters on material performances. By increasing the GNP content and compaction, a mitigation on the fracture drop was achieved (−15%).

Self-assembled nano-polymers modified water-based sizing agent for enhancing the dual interfacial properties of carbon fibre/epoxy resin composites

The dual interface-enhanced sizing agents are prepared to simultaneously exhibit high surface roughness and high interfacial wettability through self-assembled nano-polymers. Five self-assembled nano-polymer modified water-based sizing agents (NPSAs) with various cross-linking structures are synthesized in this paper. It is demonstrated strong characteristics of homogeneous particle size in the 90–200 nm range and heat stability below 200 °C. NPSAs significantly improve the CF surface properties of both surface roughness and surface energy, with reached high values of 13.89 nm and 40.22 mN m-1. Notably, the interlaminar shear strength (ILSS), flexural strength, and fracture toughness (KIC) of CF/ER composites sized by NPSAs are enhanced to 70%, 51%, and 120% compared with the unoptimized composite, respectively. The NPSA reinforcing mechanism, enhancing interfacial properties of CF/ER composites in the interfacial interlocking and adhesion ability, was clarified by the coefficient of thermal expansion (CTE1). Additionally, NPSAs have the advantage of being applicable for simple one-pot synthesis methods, and secondly, no toxic solvents were used.

Fabrication and Experimental Estimation of Mechanical Properties of Kevlar-Glass/Epoxy Interwoven Composite Laminate

Hybrid composites made of natural and synthetic fibers are stronger, lighter, cheaper, biodegradable, and greener than conventional metals, and they are replacing conventional metals. The primary objective of the study was to examine the mechanical properties of interwoven hybrid composite laminates. Kevlar and glass fiber are used as reinforcement for this work. The fibers are woven together using various weaving techniques. 1 × 1, 3 × 3, and 5 × 5 weaving patterns are considered to explore the properties of the laminates. The composites are woven using a conventional handloom method. As a matrix, LY556 resin and HY951 hardener are combined at a ratio of 10 : 1. The composites are cured using compression molding. The cured composites are assessed for their tensile strength, flexural strength, compressive strength, interlaminar shear strength, impact strength, and fracture toughness. The highest tensile, compressive, and flexural strength were found in the 1 × 1 pattern, shear strength and fracture toughness were found in the 5 × 5 pattern, which finds applications in aerospace and defense sectors, and 3 × 3 dominated in impact strength; as a result, it can be used in bulletproof applications. At last, a scanning electron microscope (SEM) was used to visualize the matrix-reinforcement bonding. The microscopic images show the ripped-out fibers because of the tensile test. The shards in SEM are evident that impact force breaks the matrix elements in a brittle manner.

Piezoresistive damage sensing and mechanical characteristics of carbon/glass hybrid thermoplastic composites

A comprehensive experimental investigation is performed to understand the damage sensing capabilities of thermoplastic intra-ply carbon/glass laminated composites embedded with Carbon Nanotubes (CNTs) under quasi-static interlaminar shear and mode-I fracture loading conditions. CNTs are dispersed in thermoplastic Elium® resin using a combination of ultrasonication and shear mixing processes. This resin mix is used in a vacuum infusion process to fabricate four different intra-ply laminated composites orientations; G-0-C-90 [Carbon fibers are in the longitudinal direction], G-90-C-0 [Glass fibers are in the longitudinal direction], G-45-C-45(R) [carbon and glass fibers are at +45°, and −45° from the longitudinal direction and form a repeating layup], and G-45-C-45(A) [carbon and glass fibers are at +45°, and −45°, but with alternating directions for each lamina in the layup]. Four-circumferential probes are utilized to obtain the piezo-resistance measurements associated with damage inside the composites under shear and mode-I loadings. In the shear experimentation, the G-45-C-45(A) orientation demonstrated the largest interlaminar shear strength, at 50% greater than the G-45-C-45(R) orientation. Both G-45-C-45(A) and G-45-C-45(R) had significantly larger shear strains compared to the G-90-C-0 and G-0-C-90 orientations. However, the best resolution in shear damage sensing was seen with the G-0-C-90 composites. In the mode-I fracture experiments, the greatest fracture initiation toughness is shown with the G-0-C-90 orientation, which is 80% greater than the G-90-C-0 orientation. Compared to all orientations, the G-0-C-90 orientation also provided the most sensitive electrical response.

A Critical Review on Nanoparticle Filled Adhesives for Structural Applications

The objective of this review paper is to highlight some of the noteworthy research that has been done on the use of nanoparticles (NPs) to improve the performance of adhesively bonded joints (ABJs) against delamination initiation and propagation. Various nanoparticle applications, such as carbon-based, ceramic-based, and mineral-based nanoparticles, are covered. Interlaminar shear strength, fracture toughness, and fracture energy are the major parameters that have been considered for enhancing FRP delamination and fatigue resistance.The reported results indicatethat the inclusion of NPs in polymeric matrices leads to improvement of various material properties,even though some discrepancies in the results have been noted. Notwithstanding, additional researchis required to address some of the issues that have not yet been tackled.

Physical and mechanical properties of kenaf/flax hybrid composites

AbstractThis research investigates the physical and mechanical properties of hybrid composites made of epoxy reinforced by kenaf and flax natural fibers to investigate the hybridization influences of the composites. Pure and hybrid composites were fabricated using bi‐directional kenaf and flax fabrics at different stacking sequences utilizing the vacuum‐assisted resin infusion method. The pure and hybrid composites' physical properties, such as density, fiber volume fraction (FVF), water absorption capacity, and dimensional stability, were measured. The tests of tensile, flexural, interlaminar shear and fracture toughness (Mode II) were examined to determine the mechanical properties. The results revealed that density remained unchanged for the hybrid compared to pure kenaf/epoxy composites. The tensile, flexural, and interlaminar shear performance of flax/epoxy composite is improved by an increment of kenaf FVF in hybrid composites. The stacking sequence significantly affected the mechanical properties of hybrid composites. The highest tensile strength (59.8 MPa) was obtained for FK2 (alternative sequence of flax and kenaf fibers). However, FK3 (flax fiber located on the outer surfaces) had the highest interlaminar shear strength (12.5 MPa) and fracture toughness (3302.3 J/m2) among all tested hybrid composites. The highest water resistance was achieved for FK5 with the lowest thickness swelling.

Influence of hygrothermal ageing on the novel infusible thermoplastic resin reinforced with quadriaxial non-crimp glass fabrics

Elium® is a novel liquid Methylmethacrylate thermoplastic (TP) matrix that can be cured at room temperature. Elium® resin provides the properties of TP polymer composites and is a competitive alternative to epoxy-based composites. In this work, a quadriaxial non-crimp (NC) glass fabric/Elium® based polymer composites were manufactured using vacuum assisted resin transfer moulding (VaRTM). The static mechanical properties of these composites were evaluated under the tensile and flexural loads. Further, interfacial properties like interlaminar shear strength (ILSS) and fracture toughness (Mode-I and Mode-II) were characterised. To study the influence of ageing on the mechanical properties of glass fabric/Elium® (GF/E) based composites, the test samples were aged in distilled water at a temperature of 60°C for 60 days. The obtained mechanical properties were compared between dry samples (control) and post-water immersed (aged) samples. It was found that water ageing degraded the properties of tensile, flexural strength, ILSS and Mode-II toughness by 30%, 59%, 46%, 37%, respectively. On the contrary, Mode-I fracture toughness of aged samples was 90% higher, indicating significant fibre bridging due to ageing. The microscopy and scanning electron microscopy (SEM) revealed significant failure as the degradation of fibre/matrix interface due to hygrothermal ageing. The overall performance of GF/E composites with infusible TP resin is sensitive to hygrothermal ageing.

Mechanical behavior and failure mechanisms of CFRP and Titanium tubular adhesive lap joints at extreme temperatures

In this study, the mechanical behavior and failure mechanisms of thin-walled carbon fiber reinforced polymer (CFRP) and titanium adhesive tubular lap-joints (TLJs) at cold-temperature, room-temperature, and elevated-temperature are investigated. The prediction of TLJ’s performance at extreme temperatures is challenging due to their non-linear behavior and competing damage modes. To better understand their behavior, finite element analysis, static tensile tests, and design of experiments are employed to investigate the competing damage mechanisms within the TLJs, leading to a more detailed damage classification at extreme temperatures. Results show a mixed-mode failure region at elevated-temperature, where TLJs fail by either interlaminar shear or titanium net-section fracture. X-ray micro-computed tomography reveals that the initiation, propagation, and coalescence of delamination at the inserted end of the CFRP are created by shear stresses during deformation of the titanium. By utilizing numerical, experimental, and statistical techniques, this work aims to provide insights into the parameters and damage mechanisms affecting the performance of adhesively bonded thin-walled TLJs at extreme cold and hot temperature conditions.

Prominence of quantitative fiber loading on free vibration, damping behavior, inter‐laminar shear strength, fracture toughness, thermal conductivity, and flammability properties of jute–banana hybrid fiber phenol‐formaldehyde composites

AbstractThe primary purpose of this study is to realize quantitative fiber loading effects on free vibration, damping behavior, fracture toughness, thermal conductivity, inter‐laminar shear strength, and flammability of jute–banana fiber phenol‐formaldehyde (PF) hybrid composites. These composites were manufactured with fiber weight percentages ranging from 30% to 60% using hot press technique. Hybrid composite with equal amount of fiber and resin (PJB‐2) had a higher natural frequency in the range of 4.8%–59%, a higher inter‐laminar shear strength varying from 30% to 54%, a higher fracture toughness with minimum of 19 to maximum of 44%, and a low damping factor in the range of 25%–59% to that of other composite having unequal amount of fiber and resin loading. In contrast to other composites, the composite containing 30 wt% fiber (PJB‐4) has a high heat conductivity of about 10%–20%. However, the thermal conductivity of jute–banana fiber PF composites declined as the fiber content increased beyond 30 wt%, while the flame resistance was improved as the resin concentration increased. Additionally, Scanning electron microscopy (SEM) studies clearly indicates the failure patterns of fiber matrix interface under Inter laminar shear strength and fracture toughness tests were supports to justify the experimental results.

Effects of carbon nanotubes on the interlaminar shear strength and fracture toughness of carbon fiber composite laminates: a review

Effects of carbon nanotubes on the interlaminar shear strength and fracture toughness of carbon fiber composite laminates: a review

Material Parameters Identification for Modelling of Carbon Rod Structures Delamination

The aim of the present work is to compare the interlaminar shear strength and fracture toughness of glued carbon fiber rods obtained using different experimental approaches and provide the effective way to characterise the interlaminar properties for reliable simulation of the delamination. Five different test methods (tension, single shear test, and double shear test, mode I and mode II delamination tests) were performed. Using the explicit LS-DYNA code the finite element model capable of simulating the damage process of bonded connection was developed. The interlaminar connection and delamination criteria were calibrated using the parameter identification methodology implemented in LS-OPT optimization tool.

Structural analysis of sol-gel derived TiO2 nanoparticles: a critical impact of TiO2 nanoparticles on thermo-mechanical mechanism of glass fiber polymer composites

The incorporation of inorganic nanoparticles with thermosetting epoxy polymer is an emerging field of research over the past few years. It is well analyzed that epoxy matrix is brittle in nature that shows rapid crack initiation and rapid propagation without increasing applied stress value. Therefore, researchers are showing their interest in nanoparticles embedded epoxy composites to improve their fracture resistance (brittleness and toughness). In this investigation, the dispersion of TiO2 nanoparticles at different weight fractions (0-2 %) with glass fiber reinforced epoxy composites is performed to enhance structural and thermo-mechanical properties. The TiO2 nanoparticles are prepared by sol-gel method and structural analysis of TiO2 nanoparticles shows greater interfacial bond with epoxy matrix and glass fibers due to fine dispersion of nanoparticles. From obtained results, a significant enhancement in their tensile strength (38.56 %), flexural strength (30.52 %), inter-laminar shear stress (25.22 %), impact strength (327.10 %), micro-hardness (48.53 %) and fracture energy (40.19 %) with a minimal detrimental effect on toughness was revealed for GFRP-T1.0 compare to GFRP-T0.0 composite laminates. The stiffness and rigidity also improved up to 52.72 % and 34.13 % respectively for GFRP-T1.5 compare to GFRP-T0.0 composite laminates. The effects of nanoparticles contents and clustering size on thermal stability and glass transition temperature of developed composites are observed by thermo-gravimetric analysis. The surface morphology of TiO2 nanoparticles is characterized by transmission electron microscope (TEM) while the dispersion of nanoparticles and failure of developed composites were analyzed by scanning electron microscopy (SEM).

Role of dry ozonization of basalt fibers on interfacial properties and fracture toughness of epoxy matrix composites

Abstract The mechanical properties of basalt fiber-reinforced epoxy composites (BFRPs) are significantly dependent on the interfacial adhesion between basalt fibers (BFs) and the epoxy matrix. In this study, we proposed a simple and efficient method for deep and stable penetration of BFs into the epoxy matrix through dry-ozone treatments. To confirm the efficiency of the proposed method, BFRPs were fabricated using two types of composites: untreated BFs and dry-ozonized BFs in varying amounts, and the optimum amount of BFs for all the composites fabricated in this work was 60 wt%. With the addition of this amount of dry-ozonized BFs, the interlaminar shear strength and fracture toughness of the composites were enhanced by 21.2 and 23.2%, respectively, as compared with untreated BFs. The related reinforcing mechanisms were also analyzed, and the enhanced interfacial adhesion was mainly attributed to the mechanical interlocking effect. This approach shows that the dry-ozone treatment of BFs is a simple and efficient method for the preparation of BFRPs with excellent interfacial adhesion, which can be a potential application in the auto parts industry.

Mechanical, Thermal and Thermomechanical Properties of Sponge Iron Slag filled Needle-Punched Nonwoven Jute Epoxy Hybrid Composites

In the present research work, the needle-punched nonwoven jute epoxy composites are fabricated by varying the weight percentages of sponge iron slag in vacuum assisted resin transfer molding technique. This study examines the physical, mechanical and thermomechanical properties (i.e., density, water absorption, tensile, flexural, inter-laminar shear strength, compression, impact, fracture toughness and dynamic mechanical analysis) of unfilled and 8 wt.%, 16 wt.% and 24 wt.% of sponge iron slag filled composites under controlled operating conditions. Moreover, it is shown that all the mechanical properties improved with the increased in sponge iron slag content except for tensile strength which increased only upto 16 wt.%. This study also attempted for the analysis of thermal conductivity of the unfilled and particulate filled composites in experimentally by hot disc method. This work also presents both existing empirical models and numerical simulation analysis to evaluate the thermal conductivity of the developed composites. The numerical simulation values of the thermal conductivity demonstrated good agreement with the experimental values. At the end, Cole-Cole plot is drawn between loss modulus and storage modulus to understand the nature of the proposed composites.

Stack fabric felting to get PCM GIIc improvement and LVI tolerance

In this work, there was developed a three-axis CNC felting machine with one barbed needle. Felting is a kind of needle-punch technology for joining fabric stack by broken and pulled fibres. The density of needle hits is a valuable factor to make the required shear strength of polymeric composite materials in the specified places. Using the glass-fibre reinforced plastic (GFRP) with plain weave felted fabric, a noticeable decrease in strength with an increase in the needle hits density from 0 to 90 cm−2 is shown. For a laminated GFRP made from a stack of fabrics, it has been shown that the shear strength of the single-lap joint and the interlaminar shear fracture toughness GIIC significantly increase with an increase in the needle hits density. This is important for modern aircraft shells exposed to random low-velocity impacts during ground or flight operations.

Experimental and analytical investigation on the interlaminar shear strength of carbon fiber composites reinforced with carbon nanofiber z-threads

This paper combines an experimental study of the interlaminar shear strength (ILSS) and fracture behavior of CFRPs reinforced with carbon nanofiber (CNF) z-threads (i.e., ZT-CFRPs) together with an analytical model to explain and predict the shear behaviors improved by the CNF z-threads. The ZT-CFRP prepreg was manufactured from resin film containing electrical-field-aligned CNFs by using a modified hot-melt flow-transfer process. The short-beam shear (SBS) test was conducted on the ILSS of ZT-CFRP laminates together with a microscopic morphology study to understand the roles of the CNF z-threads during the shear fracture process. The study revealed the significance of the alignment of the CNFs to increase the ILSS of CFRP laminates. It was shown that CNF z-threads statistically significantly increased the ILSS and the required shear fracture work of CFRPs when compared to the unmodified CFRP and the CFRPs reinforced with randomly dispersed CNFs due to energy transfer and mechanical interlocking from the CNF z-threads. Furthermore, calculations showed that CNF z-threads reduce unwanted stress concentrations, kIC during the double-notch shear (DNS) test. The analytical model helps to understand the interlaminar shear behavior of ZT-CFRPs further and is useful to predict additional experimental data and guide material design in the future.

Effect of ozone-treated single-walled carbon nanotubes on interfacial properties and fracture toughness of carbon fiber-reinforced epoxy composites

In this study, superior mechanical properties were obtained for composite materials using single-walled carbon nanotubes (SWCNTs) subjected to a simple surface treatment. The effects of ozone-treatment on the surface properties of the SWCNTs/CFs/epoxy multi-scale composites were investigated in terms of interfacial properties and fracture toughness. The resultant surface free energy after ozone-treated SWCNTs (O-SWCNTs) markedly increased the polar component of the contact angle. In addition, the surface morphology image showed that the surface roughness of O-SWCNTs increased, suggesting that the surface roughness and the number of oxygen functional groups were effectively increased by ozone-treatment. Due to the surface modification, the interlaminar shear strength and fracture toughness of multilayered composites increased by 79.98% and 54.59%, respectively. This shows a direct linear relationship between the morphological changes of O-SWCNTs and the specific polar component of the surface free energy of the material as well as its mechanical properties.

Fabrication and mechanical properties of carbon fiber/epoxy nanocomposites containing high loadings of noncovalently functionalized graphene nanoplatelets

Carbon fiber-reinforced polymer (CFRP) composites containing graphene nanoplatelets (GNPs) were prepared and characterized. Bonding via π−π interactions with poly(4-aminostyrene) (PAS) improved the degree of dispersion of the GNPs in an epoxy matrix. Differences in dispersion and reinforcement between pristine GNPs and PAS-GNPs were established by ultraviolet–visible spectroscopy and scanning electron microscopy. The PAS-GNP/epoxy nanocomposites were characterized by their fracture toughness. The results were discussed in terms of the dispersion quality of the GNPs. Furthermore, the PAS-GNP/epoxy nanocomposites were applied to carbon fiber fabric and the interlaminar shear strength (ILSS) and fracture toughness were measured. The greatest improvements in ILSS (252%) and fracture toughness (142%) were obtained with 4 wt% PAS-GNPs. The superior mechanical properties of the CF/PAS-GNP/epoxy nanocomposites are attributed to better filler dispersion and crack bridging.