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·m ^1/2 (with 0% additive content) to 11.55 MPa·m ^1/2 (with 20% DPF content) and 13.95 MPa·m ^1/2 (with 20% hybrid content). The energy release rate increased from 3.99 kJ/M ² (with 0% additive content) to 39.82 kJ/M ² (with 20% DPF content) and 53 kJ/M ² (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.

Reinforced composite materials have many applications in the aerospace, marine, and petroleum industries. Glass fiber-reinforced pipes are of considerable importance as pressurized vessels, infrastructure materials, and petroleum wastewater pipelines. The stress intensity factor due to through-thickness discontinuities is a major parameter in fracture mechanics to understand the failure mechanisms in glass fiber-composite pipes. The stress intensity factor is calculated for a composite cylinder subjected to internal pressure using the linear extended finite element method based on the law of energy release evaluation of surface damage. The analytical model needs two material properties; they are the tensile strength and the fracture toughness; therefore, a standard tensile test was carried out on a standard specimen taken from the pipe’s wall thickness. Moreover, the compact tension test specimen was manufactured from the pipe’s wall thickness to obtain the fracture toughness. The average tensile strength was measured as 21.5 MPa with a standard deviation of 5.59 MPa, moreover, the average Young’s modulus was measured as 32.75 GPa with a standard deviation of 6.64 GPa. The fracture toughness was measured as 2322 ($MPa \sqrt{m}$) with a standard deviation of 142.5 ($MPa \sqrt{m}$), whereas the average surface release energy ($G_{IC}$) was 153.6 kJ/m² with a standard deviation of 22.53 kJ/m². A valuable design equation was extracted from the finite element model to measure the effect of cracks on the hoop stress of the cylinder wall thickness based on a nonlinear model. Moreover, an acceptable equation was used to calculate the correction and shape factor of a cylinder with movable and unmovable through-thickness cracks. This study provides useful tools and guidance for the design and analysis of composite cylinders.

Polymer matrix composites (PMC) have a competitive and dominant role in a lot of industries, like aerospace and automobiles. Short basalt fiber (SBF) is used to strengthen acrylonitrile–butadiene–styrene (ABS) polymers as a composite. The composite material is fabricated using injection molding with a new technique to obtain a uniform distribution for the ABS matrix at an elevated temperature range from 140 °C to 240 °C. Four types of specimen were produced according to the mechanically mixed amounts of SBF, which were (5, 10, 15, 20) wt %. The produced material was tested for tension, hardness and impact to measure the enhancement of the mechanical properties of the ABS only and the ABS reinforced by SBF composite. Wear tests were carried out using a pin on disc at a velocity of 57.5 m/s at three normal loads of 5, 10 and 15 kN. Tensile strength increased with up to 5 wt % of SBF, then decreased with an increasing amount of SBF reinforcement, while surface hardness increased with increasing SBF. The impact strength was found to degrade with the whole increment of SBF. Wear resistance increased with the increasing SBF reinforcement amount at all applied normal loads.

A 6061 aluminum alloy has almost 0.8–1.2 wt.% Mg and 0.4–0.8 wt.% Si content. These two components, along with other alloying elements, therefore, were characterized by high mechanical and abrasive strength. The aims of the present work were to understand the effect of different types of cooling rates through different molds materials and to investigate the effect of casting with ceramic additives on segregation of the aluminum alloy itself as a composite material forum. Therefore, a series of mechanical tests were conducted, such as compression test, Vickers hardness, and pin-on-disc wear test. The samples were cast at 650 °C and in electric furnaces for 2 h to ensure that the metal achieved adequate homogeneity and temperature. Then, abrasive macroparticles of Al₂O₃ and Sic with a size close to 40–60 µm were used. The particles were poured under constant stirring for 1 min. Then, they were cast in two types of molds: steel and graphite. The cast specimens were obtained as a reference without particles and with 0.5 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 8 wt.%. The thermal effect and the heat due to conduction and radiation were calculated. The maximum compressive strength was found to increase by ≈21% with SiCp casted in graphite molds, and HV was found to increase by ≈29% with SiC casted in graphite molds. The same was found for wear resistance, which became good with SiC casted in graphite molds, and it was generally found that the cooling rate through the mold weakened the alloy due to the segregation effect. The presence of tough particulate through the aluminum matrix barrier created a number of loads. Additionally, the high specific heat of graphite, which plays a dominant role in the slaw cooling rate of casting, led to grain enlargement, whereas the higher cooling rate of steel led to grain refinement. These concepts are the main rules of heat treatments through the casting process itself, and they save time and effort.