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Characterization of Kevlar-Polypropylene based composite material system under high strain rate loading has been investigated using Split Hopkinson Pressure Bar (SHPB) test for varying specimen aspect ratios. Flat laminates of 16, 24 and 30 layered Kevlar composite were compression molded and laser machining to get cylindrical specimensof desired aspect ratios. Based on SHPB experiments, stress-strain plots were obtained and analysed to reveal compressive material behaviour as function of growing strain rate. The peak stress, strain and toughness exhibited considerable increase with growing strain rate of loading. With increasing strain rates peak specimen stress increased by 90%, for lowest thickness composite. The aspect ratio studies suggests application of thin laminates for better performance of composite laminates. [ABSTRACT FROM AUTHOR]

This paper investigates the characterization of in-plane shear properties of thermoplastic composites reinforced with Kevlar/basalt fabrics. Different fabrics had architectures of two dimensional plain woven (2D-P) and three dimensional angle-interlock (3D-A). Intralayer hybridization was performed during the weaving of the fabrics with the combination of Kevlar and basalt yarns. Five 2D-P and three 3D-A composite laminates were manufactured with polypropylene (PP) as a matrix, using compression molding. Iosipescu shear tests were carried out to evaluate the in-plane shear properties. The experimental results revealed that the shear properties including shear modulus, shear strength and shear failure strain of homogeneous composites were improved by 6.5–14.9%, 4.3–19.7%, and 3.2–46.7%, respectively. Similarly, change in the fabric architecture from 2D-P to 3D-A also enhanced the shear strength and shear failure strain by 32.0–41.6% and 7.2–22.5%, respectively. Intralayer hybrid composites had better in-plane shear properties than the interlayer hybrid composites. The fracture morphologies of the specimens were examined by scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

Kevlar ® fabric reinforced plastics (KFRPs) are specialized composites with multiple layers of fabrics (∼ranging from 20 to 50 layers) designed for high impact applications. In this work, Kevlar-129 fiber was reinforced with polyetherimide (PEI) and polypropylene (PP) to obtain two groups of laminates in three configurations i.e. 16, 24 and 30 layers. Holes of diameter 11.6 mm were profile cut using fiber laser machining system operating at 1070 nm wavelength. Effects of polymeric matrix on the failure of the Kevlar – polyetherimide (K-PEI) and Kevlar – polypropylene (K-PP) laminates were characterized by studying the following: (i) threshold laser power required to make the holes (ii) surface morphology using scanning electron microscopy (iii) damage zone along the laser cut path using scanning acoustic microscopy and optical microscopy. K-PEI laminates underwent material separation at much lesser line energy (ratio of laser power to velocity) than K-PP laminates during laser machining. Scanning electron microscopy (SEM) was used to further analyze the laser cut surfaces. A prominent observation on the laser-irradiated surface was: less recast/resolidified polymer covered the Kevlar fabric in K-PEI as compared to a thicker polymeric layer in K-PP. Heat affected zone and damage factors were evaluated using scanning acoustic microscopy (SAM). Surface roughness and kerf width were also analyzed to understand the effect of laser machining of Kevlar laminates. [ABSTRACT FROM AUTHOR]

In this study, low velocity impact (LVI) behaviors of composite laminates reinforced with fabrics of different architecture are investigated. Three kinds of fabric architecture, namely, two-dimensional plain woven (2D-P), three-dimensional orthogonal (3D-O) and three-dimensional angle interlock (3D-A), are prepared with Kevlar 29 (Kevlar) yarns. Composite laminates are manufactured with Kevlar fabrics and polypropylene (PP) resin. These composites are impact tested at 4 m/s and 6 m/s impact velocities. The post-impact response of the composites of different fabric architecture is studied. The results revealed that the impact resistance is mainly dependent on the in-plane stiffness of the laminates. The energy absorption ability is predominantly influenced by the existence of yarns in the thickness direction. The 3D composites absorbed 14–26% higher energy than the 2D laminates. Especially, 3D-A laminates exhibited a higher peak load (14.21–30.25%), more energy absorption (12.7–26.2%) and lower cone formation at the back of the target (25–39%) as compared to 3D-O and 2D-P composites. [ABSTRACT FROM AUTHOR]

In this study, experimental investigations on Kevlar fiber reinforced polypropylene (PP) woven composites under high strain rate compression loading are discussed. Kevlar/PP composite laminates with 8 and 24 layers are fabricated using vacuum assisted compression molding technique. Maleic anhydride grafted-PP (MAg-PP) is added to PP to improve the interfacial property between Kevlar fiber and PP resin. The through-thickness properties at high strain rates from 1370 to 6066 s −1 are obtained using split Hopkinson pressure bar (SHPB) setup. The behavior of PP resin is found to be different than the commonly used thermoset resins, such as epoxy. Dynamic stress–strain relations are drawn to reveal the mechanical properties at high strain rates and these relations appear to be rate sensitive. As a result, the peak stress increased by three times, toughness increased by almost ten times and strain at peak stress increased by as much as two times with an increase in the strain rate. The final failure of the specimens is examined by scanning electron microscopy (SEM) to explore the possible failure mechanisms such as, delamination, fiber failure and shear fracture. [ABSTRACT FROM AUTHOR]

• Vacuum compression moulded Basalt-Polyeteherimide (PEI) composites manufacturing. • Optimization of Basalt-PEI composite manufacturing moulding parameters. • Basalt-PEI composite under quasi-static and dynamic high strain rate loading. • Elastic recovery of Basalt-PEI composite can help in reflecting the blast wave. High temperature blast and ballistic resistant light weight fibre reinforced plastic composites are very much in demand. Accordingly, the present investigation is focused on the quasi-static and high strain rate behaviour of Basalt/Polyetherimide (PEI) composite. Nine different types of composite samples were fabricated by compression moulding. The moulding pressures and temperatures were varied in the range of 15–25 bars and 325 °C−375 °C, respectively. Quasi-static testing was done at the rate of 3 mm/min to establish the optimum moulding parameters. High strain rate compression tests in the strain rate range of 900/s−3200/s were performed on the optimum moulded composite specimens. High strain rate testing revealed that 40 layered Basalt/PEI composite moulded at 25 bar pressure and 350 °C attained highest stress of 932 MPa whereas, the same was found to attain 446 MPa under quasi-static loading conditons. Thus, establishing the rate depedency of Basalt/PEI composite. Damage studies revealed that Basalt/PEI undergoes brittle damage, typically resulting in shear plane angle of 42°−45°. SEM micrographs revealed brittle fibre failure and matrix free fibre bundles, indicating the importance of process parameter optimiation. [ABSTRACT FROM AUTHOR]

The present study deals with the quasi-static and high strain rate characterization of Kevlar-129 based thermoplastic composites. Two different thermoplastic matrices, namely, Polypropylene (PP) and Polyetherimide (PEI) were used to manufacture composite laminates. Quasi-static compression tests were performed at strain rates of 0.041 s−1 and 0.045 s−1. High strain rate tests were performed using a split Hopkinson pressure bar apparatus within the strain rates ranging from 2548 s−1 to 4379 s−1. Stress-strain relations reveals the rate-sensitive behaviour of composites. Kevlar/PP (K-PP) showed higher peak stress under quasi-static loading as compared to the high strain rate test. Comparable peak stresses were revealed under quasi-static and high strain rate loading for Kevlar/PEI (K-PEI) composite. Also, high strain rate compression properties such as peak stress, peak strain and toughness of K-PP were 25%, 27% and 6% higher than that of the K-PEI composite. The failure mechanisms of both the composites were characterized through macroscopic and scanning electron microscopy. K-PP failed majorly due to matrix crush and fibre failure while K-PEI failed due to shear cracking. Damage study reveals that a single fibre based composite system can be tailored to act as an energy-absorbing or dissipating material system by varying the thermoplastic matrix materials. • Static and dynamic compressive properties of Kevlar reinforced high-performance polymers. • Kevlar/Polypropylene outperforms over Kevlar/Polyetherimide under both the quasi-static and high strain rate loads. • The quasi-static strength of Kevlar/Polypropylene is 25% higher than its high strain rate strength. • Polypropylene matrix results in ductile failure, while the Polyetherimide matrix results in brittle failure. [ABSTRACT FROM AUTHOR]

Quasi-static tensile test of UHMWPE fiber-reinforced composite laminate is challenging to perform due to low interlaminar shear strength and low coefficient of friction. Tensile tests proposed in the literature were conducted and limitations associated with each method led to the evolution of a new method. Tensile test of single-ply was realized as the best representative of tensile strength of a composite than tensile test of UHMWPE laminate. A fixture was developed for single-ply tests which increased friction and provided the mechanical constraint to slipping. The fixture is easy to fabricate and has provided repeatable results for eight grades of UHMWPE fiber-based (0/90) fabrics. Reported tensile strengths are in quite high range of 900–1500 MPa. • Ballistic composites are quite different from structural composites. • Tensile strength difficult to determine with standard methods. • All available methods tested for efficacy. • A new method is suggested for efficient testing. • Properties of wight commercial grades determined by suggested method. [ABSTRACT FROM AUTHOR]