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Needle-punching is used as an alternative to expensive and sophisticated three-dimensional (3D) weaving processes to prepare a 3D composite. In this study, a 3D needled carbon–carbon (C/C) composite structure was examined using X-ray tomography and scanning electron microscopy (SEM). The effects of manufacturing porosities, needling diameter and needling density on the thermal conductivity of the composite were determined through multiscale finite-element modelling. The degradation of thermal conductivity caused by the manufacturing porosity was higher in the longitudinal direction than in the through-thickness direction. Moreover, it was found that the through-thickness thermal conductivity of the composites increased with increasing needling diameter and density.

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Natural fibres have been used in a wide range of polymer composite reinforcements to produce new composites with good properties that can be used in many applications. In this study, the fracture toughness, acoustic, and thermal properties of date palm fibre (DPF)/polyester composite and DPF/sheep wool hybrid reinforced polyester were investigated. Physical properties, such as water absorption and thickness swelling, have also been reported. Finally, scanning electron microscopy (SEM) images of the composites and hybrids were obtained. The composites and hybrids were produced by compression moulding and cut into standard shapes before being tested. DPF and DPF/sheep wool contents (wt%) were 0%, 10%, 20% and 30%. The test results indicate that the fracture toughness improved from 3.45 MPa·m1/2 (with 0% additive content) to 11.55 MPa·m1/2 (with 20% DPF content) and 13.95 MPa·m1/2 (with 20% hybrid content). The energy release rate increased from 3.99 kJ/M2 (with 0% additive content) to 39.82 kJ/M2 (with 20% DPF content) and 53 kJ/M2 (with 20% hybrid content) due to the good adhesion between the matrix and fibres. DPF improved the acoustic insulation properties of the polyester/DPF composite with mass fractions of 10%, 20%, and 30%. At a frequency of 2000 Hz, the acoustic attenuation in decibels (dB) increased from 16.2 dB with pure polyester to 17.2, 18.2, and 19.5 dB with 10%, 20%, and 30% DPF content, respectively. The increase in sheep wool and DPF hybrids in the polyester matrix increased the acoustic attenuation to 18.4, 20.6, and 24 dB, respectively, because DPF and sheep wool have good acoustic insulation properties. Thermal conductivity was 0.161 W/m·C with 0% additive content, decreasing to 0.133, 0.107, and 0.082 W/m·C with 10%, 20%, and 30% DPF content, respectively, and 0.112, 0.073, and 0.051 W/m·C for 10%, 20%, and 30% DPF/sheep wool hybrid content, respectively, owing to good thermal insulation properties of DPF and sheep wool. Water absorption gradually increased with DPF and DPF/sheep wool hybrid because DPF and sheep wool have good absorption properties. Thickness swelling increased with increasing DPF and DPF/sheep wool hybrid contents but not to the same extent. SEM images indicated good distribution and bonding of DPF with the polyester matrix up to 20% and good results for DPF/sheep wool with the polyester hybrid at 10% and 20% hybrid content.

The human body normally uses alternative materials such as implants to replace injured or damaged bone. Fatigue fracture is a common and serious type of damage in implant materials. Therefore, a deep understanding and estimation or prediction of such loading modes, which are influenced by many factors, is of great importance and attractiveness. In this study, the fracture toughness of Ti-27Nb, a well-known implant titanium alloy biomaterial, was simulated using an advanced finite element subroutine. Furthermore, a robust direct cyclic finite element fatigue model based on a fatigue failure criterion derived from Paris’ law is used in conjunction with an advanced finite element model to estimate the initiation of fatigue crack growth in such materials under ambient conditions. The R-curve was fully predicted, yielding a minimum percent error of less than 2% for fracture toughness and less than 5% for fracture separation energy. This provides a valuable technique and data for fracture and fatigue performance of such bio-implant materials. Fatigue crack growth was predicted with a minimum percent difference of less than nine for compact tensile test standard specimens. The shape and mode of material behaviour have a significant effect on the Paris law constant. The fracture modes showed that the crack path is in two directions. The finite element direct cycle fatigue method was recommended to determine the fatigue crack growth of biomaterials.