Advanced Structural Composites Research Articles

In‐plane compressive properties and failure mechanisms of modified three‐dimensional multi‐axial warp knitted fabrics reinforced composites at different temperatures

AbstractThree‐dimensional multi‐axial warp knitted (3D MWK) reinforced composites are important components of advanced structural composites. The interfacial bonding between fiber and matrix is key to achieving high mechanical properties. In this work, graphene oxide (GO) and poly(oxypropylene) diamines (D400) were grafted on glass fiber (GF) multi‐axial warp knitted (MWK) fabrics to construct a “flexible‐rigid” structure. The surface morphologies of GF were characterized by SEM and EDS. Then, 3D MWK‐reinforced composites were prepared based on four kinds of modified fabrics using the VARTM method. The in‐plane compression properties were obtained at different high temperatures and their failure modes were analyzed. The strain–stress curves showed that the composites exhibited brittle fracture modes. D400 and GO‐modified multi‐scale composites exhibited outstanding compression properties. The strength of the related composited was improved by 55.78%, 76.78%, 52.19%, and 56.78% compared to that of desized composite at 30°C, 60°C, 120°C and 150°C, respectively. The damage to D400‐GO modified and D400 modified composites was the most serious, where shear fracture modes were obvious in addition to layer debonding features. This protocol provides a potential strategy to manufacture of D400 and GO‐modified hierarchical reinforced composites.Highlights The modified 3D MWK glass fabrics based on poly(oxypropylene) diamines (D400) and graphene oxide (GO) were prepared. The compressive properties of 3D desized, D400‐, D400‐GO‐, and GO‐MWK fabrics reinforced epoxy composites were obtained and analyzed at different temperatures of 30°C, 60°C, 120°C, and 150°C. The failure mechanisms of 3D desized, D400‐, D400‐GO‐, and GO‐MWK fabrics reinforced epoxy composites at different temperatures were analyzed.

2D graphene oxide and MXene nanosheets at carbon fiber surfaces

Carbon fibers, which are known for their high strength to weight ratio and thermal and chemical stability, are key components in advanced structural composites. Controlling the fiber-matrix interface is key to achieving required physical performance. Functional two-dimensional (2D) materials that can conformally coat the fiber surface facilitate interface and interphase engineering for enhanced mechanical properties and added functionalities. Understanding how 2D flakes bond, integrate, and perform at carbon fiber interfaces is key to developing multifunctional high-strength composites. In this study, we focus on the surface interactions of graphene oxide (GO) and Ti3C2Tx MXene nanoflakes at the surface of low-tension carbon fibers with and without amine functionalization by in-depth multimode scanning probe microscopy. We suggest that beyond strengthening the interfaces, GO and MXene provide efficient charge transfer with MXene also adding conductivity to the fiber surface, extending potential applications of composites to broad areas including structural supercapacitors and battery cooling/packaging materials. GO and MXene modified fibers not only create opportunities for increased interfacial adhesion in composites via increased surface roughness, but also act as anchors for bonding, energy dissipation, charge transport, and local interface stiffening.

STUDY AND CHARACTERIZATION OF THERMALLY STABLE POLYAMIDES SYNTHESIZED FROM HETEROCYCLIC MOIETY IN THE MAIN CHAIN

Colored compounds were formed by polycondensation reaction of s-triazine consuming diamines with secondary amine morpholine. The diazotization coupling reaction with α-Naphthol showed dark coloration property. Initially, secondary amines binded with s-triazine at lower temperature and then smoothly proceeded at room temperature and further compiled with coupling product to result out the required series. The inherent viscosities were obtained in between 0.21-0.42 g/dL which was measured by Ubbelohde viscometer. The colored series was identified by several techniques like NMR, IR, and UV spectroscopy. Furthermore, thermal degradation properties were determined by DSC and TGA techniques. The thermal stability was evaluated in the temperature range of 200°C-800°C. The DSC explained about increase in Tg value with an increase in the aromatic contentin between 220-300°C. The obtained series showed excellent thermal stability with their temperature weight loss (10%) around 450°C and 480°C. Synthesized polyamides can be utilized as multipurpose roles in medicine, electronics, aerospace, and advanced structural composites. This paper will briefly review the role of obtained complex which involves processability, stability and performance of the materials.

Optimal synergy between micro and nano scale: Hierarchical all carbon composite fibers for enhanced stiffness, interfacial shear strength and Raman strain sensing

Multifunctional hierarchical reinforcements are fabricated by growing multi walled carbon nanotubes (CNTs) onto carbon fibers (CFs) via chemical vapor deposition. In contrast to typical hybrid multi scale reinforced composites, the biomimetic approach of hierarchical interconnection between CFs and CNTs is followed in order to provide the dimensional confinement required for the effective synergy between the nanophase i.e. the CNTs and the micron phase i.e. the CFs. Compared to the reference CF: (i) ASTM single fiber tensile tests reveal up to 50% increase in tensile modulus together with the expected decrease in tensile strength, (ii) Single Fiber Fragmentation Tests (SFFT) reveal up to 134% enhancement for Interfacial Shear Strength (IFSS), (iii) the frequency of the Raman 2D graphitic vibrational mode with strain shows a strain sensitivity enhancement up to 87.4% and (iv) fractographic investigation shows bridging of the CNTs only for specific growth conditions, which correspond to the optimal IFSS. Furthermore, a direct correlation between the Raman strain sensitivity with the young moduli of the CF and the hierarchical CF-CNT is found, proving the efficient stress transfer from the nano to micron scale in a “composite” fiber. Overall, an optimal synergy between the reinforcing graphitic phases is achieved, attaining for the first time an equivalent stiffness for the CNT reinforcement close to theoretically obtained values. Thus, biomimetic hierarchical reinforcements provide the roadmap for the full exploitation of the unique properties of the nanophase in advanced structural composites.

Strength and Performance Enhancement of Bonded Joints by Spatial Tailoring of Adhesive Compliance via 3D Printing.

Adhesive bonding continues to emerge as a preferred route for joining materials with broad applications including advanced structures, microelectronics, biomedical systems, and consumer goods. Here, we study the mechanics of deformation and failure of tensile-loaded single-lap joints with a compliance-tailored adhesive. Tailoring of the adhesive compliance redistributes stresses and strains to reduce both shear and peel concentrations at the ends of the adhesive that determine failure of the joint. Utilizing 3D printing, the modulus of the adhesive is spatially varied along the bondlength. Experimental strength testing, including optical strain mapping, reveals that the strain redistribution results in a greater than 100% increase in strength and toughness concomitant with a 50% increase in strain-to-break while maintaining joint stiffness. The tailoring demonstrated here is immediately realizable in a broad array of 3D printing applications, and the level of performance enhancement suggests that compliance tailoring of the adhesive is a generalizable route for achieving superior performance of joints in other applications, such as advanced structural composites.

Designing advanced structural composites based on mechanical performances analysis of the variable topology spacecrafts

Increasingly complex space operations require novel advanced structural composites for reconfigurable spacecrafts to have excellent flexural strength in reconfiguration processing and orbital maneuvering. Functionalized multiwalled carbon nanotubes (MWCNTs) are performed to fabricate the MWCNTs/carbon fiber/N, N′‐4, 4′‐bimaleimide diphenyl methane/diallylbisphenol A (MWCNTs/CF/BMI/DBA) composites. ANSYS analysis reveals that the requiring lowest flexural strength of the composites is 1,150 MPa to meet actual requirements. The flexural strength of the MWCNTs/CF/BMI/DBA composites with 1 wt% functionalized MWCNTs can fully meet the actual use for reconfigurable spacecrafts. And the thermal stabilities of the MWCNTs/CF/BMI/DBA composites are increased with the increasing addition of MWCNTs. POLYM. COMPOS., 35:2018–2022, 2014. © 2014 Society of Plastics Engineers

Fibre-Fibre Hybrid Composites for Aerospace Applications

The extruded poly ether ether ketone (PEEK) and glass fibre were used to obtain the co-woven hybrid fibre fabrics and converted into composites using compression moulding technique. The effect of shear stress and shear rate on the shear viscosity of PEEK was investigated to optimise the process conditions for converting hybrid fabrics into composites. The mechanical properties such as flexural strength and inter laminar shear strength (ILSS) as a function of number of layers of fabric have been evaluated. Low velocity (2.1 m/s) repeated drop weight impact tests were carried out on the fabricated composites at 5 and 10 J incident energy. Dielectric properties as a function of temperature and frequency have been carried out. Flammability behaviour of composites has been carried out using cone calorimeter. The data generated shows that glass-PEEK based composites are excellent potential materials for advanced structural composites.

Polymer-matrix composites: New fibers offer new possibilities

If one class of material could represent the transition to the new millennium, it would be the polymer-matrix composite (PMC). From missile components to golf clubs, an ever increasing number of products or specifi c devices are made of PMCs. Some are new developments, such as the carbon fi ber composites in modern commercial aircraft. Others are benefi cial to both our health and the environment. Typical examples are the aramid fi ber composites replacing asbestos in automotive brakes and clutch linings, as well as recyclable coconut fi ber composites substituting synthetic fi bers in automobile seat cushions. Polymer-matrix composites are normally composed of a matrix reinforced with a synthetic or natural fi ber. The matrix acts as the intermediate by which an externally applied load is distributed to the stronger and stiffer fi bers that structurally support the composite. It protects the fi bers from outside chemical (or even atmospheric) attack and abrasion. The plasticity of the matrix serves as a barrier to crack nucleation/propagation, and as such prevents catastrophic rupture. The real advantages in terms of fl exibility and expanding potential for the PMC are the different fi bers available. Glass fi ber is the most popular owing to its low price, easy processing, high specifi c strength, and chemical inertness. Carbon fi ber is the current preference for advanced structural composites. It is the stiffest and strongest of all fi bers. Carbon fi ber manufacturing and its composite processing are curPolymer-Matrix Composites: New Fibers Offer New Possibilities

Multiscale Carbon Nanotube−Carbon Fiber Reinforcement for Advanced Epoxy Composites

We report an approach to the development of advanced structural composites based on engineered multiscale carbon nanotube-carbon fiber reinforcement. Electrophoresis was utilized for the selective deposition of multi- and single-walled carbon nanotubes (CNTs) on woven carbon fabric. The CNT-coated carbon fabric panels were subsequently infiltrated with epoxy resin using vacuum-assisted resin transfer molding (VARTM) to fabricate multiscale hybrid composites in which the nanotubes were completely integrated into the fiber bundles and reinforced the matrix-rich regions. The carbon nanotube/carbon fabric/epoxy composites showed approximately 30% enhancement of the interlaminar shear strength as compared to that of carbon fiber/epoxy composites without carbon nanotubes and demonstrate significantly improved out-of-plane electrical conductivity.

Three‐dimensional woven glass fabrics

Textile composites are a class of materials in which reinforcement is provided by textile performs. Owing to their unique combination of light weight, flexibility, strength, and toughness these materials have been used in reinforcement in both structural and other applications. New applications i advanced structural composites using 3‐D braiding (see Figure) are reviewed. magnified image

Novel Hybrid Composites Based on Carbon Foams

ABSTRACTThe extraordinary mechanical properties of commercial carbon fiber are due to the unique graphitic morphology of the spun filaments. Contemporary advanced structural composites exploit these properties by creating a disconnected network of graphitic filaments held together by an appropriate matrix. Carbon foam derived from a blown mesophase pitch precursor can be considered to be an interconnected network of graphitic ligaments. As such interconnected networks, they represent a potential alternative reinforcing phase for structural composite materials. Based on this notion, consideration is given to novel forms of graphitic carbon and the processing routes to create hybrid composites, such as net shape fabrication and fiber placement processes.

Styrene‐terminated polysulfone reactive oligomers: Cure and properties

AbstractOligomers end‐capped by groups capable of thermally induced polymerization have found wide applications in advanced structural composites and adhesives. The styrene‐terminated polysulfone reactive oligomers described in this paper represent an example of such thermosetting systems. The advantage of these compounds, over high molecular weight polysulfone resin, lies in their easier processing and improved solvent resistance. This paper addresses the properties of the neat oligomer as a function of initial molecular weight and those of the resulting cured resin as well as a complete characterization of the curing reaction. Furthermore, a comparison will be made between these oligomers and the better known acetylene‐terminated sulfone oligomers.

The design and application of the traversing infra-red inspection system - TIRIS

A traversing infra-red inspection system (TIRIS) was designed primarily for high-volume production inspection of C-5 aircraft fail-safe strap panels. These panels are boundd laminates of 0.5 mm thick titanium and 3.2 mm thick aluminium. The system is flexible enough to be used for the development of special techniques such as the detection of entrapped water in aluminium honeycomb and the inspection of advanced structural composites. The system injects heat into the panels by means of hot-air guns. Imperfections as small as 7.62 mm in diameter are displayed on a 200 × 250 mm cathode ray tube in real time. The inspection scanning rate is 0.07 m 2s −1. A Polaroid camera is used to produce thermograms which define the size and shape of voids, disbonds, and delaminations which are located directly on the panels with a unique marking device. Principles of operation are explained in detail with the aid of representative thermograms made with the system. A black-body calibration device and special facilities were also designed for the system. It was found that no emissivity coating is required for the inspection of the fail-safe panels because of the surface characteristics of titanium.

High performance reinforcements for advanced structural composites : Dauksys, R. J. SAMPE Quarterly, Vol 3, No 2, pp 1–6 (January 1972)

High performance reinforcements for advanced structural composites : Dauksys, R. J. SAMPE Quarterly, Vol 3, No 2, pp 1–6 (January 1972)