Mechanical properties and manufacturing processes of Glass Fiber/Polypropylene (GF/PP) composites for application of flexible internal long bone fracture fixation plates have been investigated. PP/Short Chopped Glass Fiber (PPSCGF), PP/Long Glass Fiber (PPLGF) and PP/Long Glass Fiber Yarn (PPLGFY) were used in fabrication of the fixation plates. The PPSCGF and PPLGF plates were made by the heat-compressing process and Three-dimensional (3D) printing method was used to make the PPLGFY ones. The values of Young’s modulus, tensile strength, flexural modulus and strength, and impact strength of the PPSCGF in the fiber longitudinal direction were found to be [Formula: see text]GPa, [Formula: see text]MPa, [Formula: see text]GPa, [Formula: see text]MPa and [Formula: see text]kJ/m2, respectively. Where, these values for the PPLGF were to [Formula: see text]GPa, [Formula: see text]MPa, [Formula: see text]GPa, [Formula: see text]MPa, and [Formula: see text]kJ/m2 and for the PPLGFY were to [Formula: see text]GPa, [Formula: see text]MPa, [Formula: see text]GPa, [Formula: see text]MPa and [Formula: see text]kJ/m2. These have been found to be in close agreement with the human bone properties. Furthermore, the strength and modulus values of the plates were reasonable to be used as a bone implant applicable for bone fracture reconstructions. Hence, the study concluded that the GF/PP composites are useful for load-bearing during daily activities and would be recommended as a choice in orthopedic fixation plate applications. It will help the researchers for development of new fixation designs and the clinicians for better patient’s therapy in future.

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In this paper, the variations of the failure strength and pattern of human proximal femur with loading orientation were analysed using a novel quantitative computed tomography (QCT)-based linear finite element (FE) method. The QCT images of 4 fresh-frozen femurs were directly converted into voxel-based finite element models for the analyses of the failure loads and patterns. A new geometrical reference system was used for the alignment of the mechanical loads on the femoral head. A new method was used for recognition and assortment of the high-risk elements using a strain energy-based measure. The FE results were validated with the experimental results of the same specimens and the results of similar case studies reported in the literature. The validated models were used for the computational investigation of the failure loads and patterns under 15 different loading conditions. A consistent variation of the failure loads and patterns was found for the 60 different analysed cases. Finally, it was shown that the proposed procedure can be used as a reliable tool for the failure analysis of proximal femurs, e.g. identification of the relevant loading directions for specific failure patterns, or determination of the loading conditions under which the proximal femurs are failure-prone.

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This paper investigates the fracture mechanism of wood-plastic composites (WPCs) in tension utilizing a direct observation method. Several WPC specimens with various weight fractions (with and without coupling agent) were prepared via injection molding to create complex structures of irregular-shaped wood particles randomly dispersed in a thermoplastic high-density polyethylene matrix. The crack initiation and growth in WPC samples under tension were observed using a portable tensile test setup. It was observed that debonding between the wood particles and matrix was the primary fracture mechanism in WPCs with no compatibilizer. Moreover, the orientation of the wood particle significantly affected the fracture mechanism. On the other hand, the occurrence of wood cracking in the samples made with coupling agents was indicative of the bond strengthening property of these agents. The results indicated that the added compatibilizer affected the fracture mechanism and significantly reduced the ductility. Moreover, the increased amount of wood flour reduced both the ductility and the strength of WPCs. However, it was also observed that the strength reduction can be compensated by adding coupling agent.

Metallic bone fixations, due to their high rigidity, can cause long-term complications. To alleviate metallic biomaterials’ drawbacks, in this research new Glass Fiber/Polypropylene (GF/PP) composite internal fixations were developed, and an investigation of their mechanical behavior was performed through in vitro biomechanical experiments. Short randomly oriented, long unidirectional prepreg, and long unidirectional fiber yarn were considered as reinforcements, and the effects on their mechanical properties of different manufacturing processes, that is, 3D printing and heat-compressing, were investigated. The constructed fixation plates were tested in the transversely fractured diaphysis of bovine tibia under axial compression loading. The overall stiffness and the Von Mises strain field of the fixation plates were obtained within stable and unstable fracture conditions. The samples were loaded until failure to determine their failure loads, strains, and mechanisms. Based on the results, the GF/PP composite fixation plates can provide adequate interfragmentary movement to amplify bone ossification, so they can provide proper support for bone healing. Moreover, their potential for stress shielding reduction and their load-bearing capacity suggest their merits in replacing traditional metallic plates.

An experimental study was carried out to investigate the effect of temperature on the mechanical properties and the fracture mechanism of wood-plastic composites (WPCs) under tension. The specimens were prepared via injection molding of various weight fractions of pine wood particles and high-density polyethylene (with and without coupling agent, maleic anhydride-grafted polyethylene (MAPE)). The deformation and fracture behaviors of the samples at different temperatures were studied using a portable microscope setup during the test. The results indicated the significant effect of the test temperature on the fracture mechanism of WPC specimens. At room temperature, the dominant fracture mechanism for the samples without MAPE was debonding, whereas wood cracking was the dominant fracture mechanism in the presence of MAPE. At high temperatures, debonding was prominent over wood cracking in all samples (with and without MAPE), whereas at low temperatures (below 0 C) wood cracking was the dominant fracture mechanism.