Search

Abstract Nanocomposites with platelet reinforcements are emergent materials whose deformation mechanisms still need to be carefully investigated. In this study, we first present the studied class of nanocomposites (Polypropylene reinforced by Montmorillonite clay nanoplatelets). From uniaxial tensile tests, it is shown that some mechanical characteristics of the nanocomposite (Young's modulus, yield stress) significantly increase compared to the matrix even for very low volume fraction of reinforcements (maximum of 7% mass fraction for our tested specimen). The Ponte Castañeda and Willis [6] bound is adopted to account for the evolution of the elastic behavior of the material [71. Adapting the Hill-type incremental method [13] allows the simulation of the non linear behaviour of the material. However, it is shown that this scheme requires careful choice of the aspect ratio, in the plastic domain, to provide good predictions of plasticity. [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]

Modification of Polylactic acid (PLA), a biopolymer, is a strategy still to be fully explored for the next generation of bioresorbable vascular stent (BVS) biomaterials. With this focus, inclusions upto 5% of Polycaprolactone (PCL) and Magnesium in PLA were tested in the rat subcutaneous model and their cellular and tissue interactions characterized, specifically with respect to inflammatory response, angiogenesis and capsularization. The cytokines IL6, TNF Alpha and IL-1Beta were estimated in the peri-implant tissue, all of which showed a non-significant difference between the non-implanted animals and those containing PLA by 8 weeks, speaking to the benign nature of PLA as an implant biomaterial. Both modified materials, had increased macrophage counts and cytokine levels, except IL6 at 8 weeks. Vascularization only at 8 weeks in PLA PCL containing tissue was significantly higher than pure PLA, which may be more carefully controlled along with the material hydrophobicity for possible efforts towards therapeutic angiogenesis. Capsule thickness, measured by staining with both Hematoxylin & Eosin and Masson's Trichome did not show any differences between materials, including PLA. [ABSTRACT FROM AUTHOR]

Abstract: In this research article, novel porous microcellular ABS foams were fabricated and subsequently investigated for their morphological attributes. Initial research focuses on developing ultra-low density closed cell foams through cyclic microcellular foaming process. First stage foaming process develops microcells which affect the second stage of the batch foaming process. Hence, the effect of repeated foaming process on foam density and its morphology are discussed. Subsequently, ultrasound excitations were utilized to rupture the closed cell walls, thereby developing porous structure. The combined cyclic solid-state foaming and ultrasound excitation provides a way to fabricate ultra-low density porous polymers. [Copyright &y& Elsevier]

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]