Porous Ultrahigh Molecular Weight Polyethylene/Functionalized Activated Nanocarbon Composites with Improved Biocompatibility

Ultrahigh molecular weight polyethylene (UHMWPE) materials have been prevalent joint replacement materials for more than 45 years because of their excellent biocompatibility and wear resistance. In this study, functionalized activated nanocarbon (FANC) was prepared by grafting maleic anhydride polyethylene onto acid-treated activated nanocarbon. A novel porous UHMWPE composite was prepared by incorporating the appropriate amount of FANC and pore-forming agents during the hot-pressing process for medical UHMWPE powder. The experimental results showed that the best prepared porous UHMWPE/FANC exhibited appropriate tensile strength, porosity, and excellent hydrophilicity, with a contact angle of 65.9°. In vitro experiments showed that the porous UHMWPE/FANC had excellent biocompatibility, which is due to its porous structure and hydrophilicity caused by FANC. This study demonstrates the potential viability for our porous UHMWPE/FANC to be used as cartilage replacement material for biomedical applications.

Experimental and Numerical Investigation of the Effect of Projectile Nose Shape on the Deformation and Energy Dissipation Mechanisms of the Ultra-High Molecular Weight Polyethylene (UHMWPE) Composite

The effect of projectile nose shape on the ballistic performance of the ultra-high molecular weight polyethylene (UHMWPE) composite was studied through experiments and simulations. Eight projectiles such as conical, flat, hemispherical, and ogival nose projectiles were used in this study. The deformation process, failure mechanisms, and the specific energy absorption (SEA) ability were systematically investigated for analyzing the ballistic responses on the projectile and the UHMWPE composite. The results showed that the projectile nose shape could invoke different penetration mechanisms on the composite. The sharper nose projectile tended to shear through the laminate, causing localized damage zone on the composite. For the blunt nose projectile penetration, the primary deformation features were the combination of shear plugging, tensile deformation, and large area delamination. The maximum value of specific energy absorption (SEA) was 290 J/(kg/m2) for the flat nose projectile penetration, about 3.8 times higher than that for the 30° conical nose projectile. Furthermore, a ballistic resistance analytical model was built based on the cavity expansion theory to predict the energy absorption ability of the UHMWPE composite. The model exhibited a good match between the ballistic resistance curves in simulations with the SEA ability of the UHMWPE composite in experiments.

Strain-rate-dependent progressive damage modelling of UHMWPE composite laminate subjected to impact loading

A comprehensive strain-rate-dependent (SRD) finite element modeling procedure, based on continuum damage mechanics has been developed to predict the behavior of ultra-high molecular weight polyethylene (UHMWPE) fiber composite laminates under impact loading. A user-defined material subroutine implemented into ABAQUS/Explicit is used to define SRD constitutive damage model of UHMWPE composite. The effect of strain rate on the material properties is adapted to the experimental data by introducing a new hyperbolic function and the strain-rate effect factor (SEF) for use in the modeling. The range of [Formula: see text] to [Formula: see text] is considered for strain rate, which includes both high velocity and low velocity impact regimes. A homogenized sub-laminate approach is employed to more accurately capture the out-of-plane failure mechanisms. Cohesive Zone Model (CZM) with the constitutive model based on bilinear traction-separation is implemented to simulate the inter-laminar delamination between the sub-laminates. High velocity ballistic impact as well as low velocity drop-weight impact are simulated, and the results are validated with experimental observations from the literature. Results show that the presented SRD model, offers more accurate prediction of the projectile residual velocity compared to the SRD model using logarithmic function or without considering the strain rate effect. Moreover, detailed views of failure modes such as tension/shear fiber and matrix shear in layers, and the delamination patterns are obtained and investigated.

Design and Characterization of the Surface Porous UHMWPE Composite Reinforced by Graphene Oxide

The surface porous ultrahigh molecular weight polyethylene (UHMWPE) composites were successfully fabricated with NaCl and graphene oxide (GO) in the hot-pressing procedure. The GO sheets were evenly dispersed in UHMWPE with the sedimentation method of GO in saturated NaCl. The morphologies, chemical compositions, mechanical, and tribological properties of GO and surface porous GO/NaCl/UHMWPE were investigated. The results show that GO sheet and NaCl could be evenly dispersed in UHMWPE. The regular pores are present on the surface of UHMWPE after NaCl dissolution in distilled water. The wear resistance properties are improved significantly, and the friction properties increased slightly with the addition of GO and NaCl.

Advanced hybrid materials from epoxy, oxidized UHMWPE fibers and silane surface modified silicon nitride nanoparticles

Aiming the development of highly performant polymer-based hybrid materials, the typical bisphenol-A based epoxy resin was reinforced with oxidized UHMWPE fibers and various amounts of silane surface modified silicon nitride (Si3N4) nanoparticles. The reinforcing phases underwent optimized surface modifications to create a fully connected network for an improved stress transfer between the constituents. The efficiency of the grafting methodology was confirmed by vibrational and morphological analyses. Meanwhile, the effects of the adopted modifications techniques on the mechanical properties were thoroughly discussed. Furthermore, static and dynamic mechanical investigations along with impact tests were conducted to study the effects of various amounts of Si3N4 nanoparticles on the overall performances of the epoxy/UHMWPE composite. The obtained results confirmed the great benefits from creating a fully connected hybrid network. The as such developed hybrids can be seen as promising materials for the intended use.