Defect and Diffusion Forum Vol. 447

Abstract: Carbon fiber reinforced polymer (CFRP) composites are highly valued in aerospace for their superior strength and fatigue resistance. However, the structural complexity of CFRP components leads to inevitable internal defects during manufacturing, with complex geometry being a key factor hindering detection. This paper investigates the ultrasonic propagation characteristics in CFRP multidirectional plates with complex geometries via finite element simulations, focusing on the multifactor coupling effects in CFRP members. Acoustic tracing is conducted for the anisotropic and multilayered CFRP multidirectional plates. Through bottom reflection method and full-focus imaging inspection experiments, the propagation behaviors of ultrasonic waves in CFRP are systematically analyzed. Results reveal that the material’s multilayer structure, elastic anisotropy, and complex geometry significantly affect the imaging quality, defect localization accuracy, and defect distribution range in full-focus ultrasonic array inspection. The optimized algorithm achieves accurate detection of hole defects in complex-shaped CFRP multidirectional plates, reducing the imaging array performance indicator (API) value to 0.7 and the defect localization error to less than 0.3 mm. Keyword: CFRP components; complex geometries; non-destructive testing; acoustic tracing; full-focus imaging;

Abstract: This research aims to study the properties of polishing pads made from polyurethane mixed with rice husk fiber for use in chemical mechanical polishing (CMP) of sapphire. After cleaning and sizing, the rice husk fiber was modified using hydrochloric acid (HCl). Then, both unmodified and modified rice husk fibers were mixed with polyurethane at ratios of 7.5, 10, and 12.5 phr to form polishing pads. The hardness and polishing performance of these pads in sapphire CMP were then tested. The experimental results showed that polishing pads from rice husk fiber could be successfully formed and remained stable. The natural fibers were evenly distributed across the contact surface of the pads. The hardness of polishing pads from rice husk fiber was smaller than conventional polishing pad (SUBA800) in range of 40.5–47.5%. Polishing results revealed that pads made from polyurethane mixed with unmodified and modified rice husk fiber achieved the highest material removal rates (MRR) of 94.2% and 64.7%, respectively, compared to the conventional pad. These results indicate that both types of fibers able to be used as a material for manufacturing polishing pads for adding value and reducing the waste from the agricultural.

Abstract: The influence of filler type and content on the wettability and interfacial bonding between thermoplastic elastomer (TPE) and polypropylene (PP) by using the injection overmolding process was investigated in this study. Calcium carbonate (CaCO₃) and talcum (Talc) masterbatchs, ranging from 0 to 40 percent by weight (wt%), were mixed into the PP matrix as fillers. The bond strength of TPE overmolded onto PP composites was characterized by the tensile and tear tests. Good compatibility was observed between TPE and PP filled with various amounts of CaCO₃ and Talc. In the case of the tensile test, the crack initiation stress, ultimate tensile strength, strain at break, and bond energy were found to decrease with increasing filler content. The results obtained from the tear test indicated that the propagation strength, ultimate tear strength, strain at break, and bond energy of injection overmolded TPE-PP filled with various CaCO₃ contents did not significantly change compared to those obtained from Talc. This can be attributed to the high reinforcing efficiency of Talc in comparison with CaCO₃, which can enhance the stiffness and thermal resistance of the PP matrix. As a result, the contact area becomes more resistant to molecular diffusion of TPE chains, particularly at high Talc loadings (30 and 40 wt%), leading to the reduction of interfacial bonding.

Abstract: This study presents the synthesis of polyurethane (PU) films using recycled polyethylene terephthalate (rPET) as a sustainable substrate. The rPET was depolymerized through the glycolysis reaction to produce a polyol, which was then reacted with polymeric methylene diphenyl diisocyanate (PMDI) via solution polymerization to form Polyurethane Film. The effect of varying NCO/OH molar ratios (1.00, 1.25, and 1.50) on the properties of the resulting films was investigated, with a focus on enhancing mechanical performance. The PU films were characterized by their physical appearance, FT-IR spectroscopy, and mechanical properties. At the NCO/OH ratio of 1.00, the PU remained in the form of sticky substance like glue and was unable to form into a solid film. However, increasing the ratio to 1.25 and 1.50 resulted in continuous, flexible films with significantly improved mechanical strength. FT-IR analysis confirmed the formation of urethane linkages, as evidenced by a clear reduction in –OH and –NCO functional groups after the film forming. The best performance was observed at an NCO/OH ratio of 1.50, yielding a PU film with a Young’s modulus of 0.528 N/mm², tensile strength of 1.289 N/mm², and elongation at break of 496.587%. These results highlight the importance of the NCO/OH ratio in tailoring films with suitable properties and support the potential of rPET-based PU as a sustainable material for advanced applications.

Abstract: This research aimed to recycle polyethylene terephthalate (rPET) from drinking water bottles using a commercial multi-functional chain extender (Joncryl®ADR4468) with low content, to improve the properties of low molecular weight recycled PET, giving it a long chain with branching structure. The effects of the chain extender on the structural change, viscosity, thermal properties and thermal stability of modified recycled PET (modified-rPET) were studied by using Fourier transform infrared (FTIR) spectrometer, a rotational rheometer, a differential scanning calorimeter (DSC) and thermogravimetric analysis technique (TGA). The results indicate that the chain extender can increase the molecular weight and modify the structure of rPET to a long chain with branching structure and improve the viscosity. Furthermore, the thermal properties and thermal stability analysis from this research could be great evidence to support the assumption that the use of low dose of Joncryl®ARD4468 could turn the molecular structure of rPET into long chain with branching structure, without gel, perfectly.

Abstract: The flexibility and durability of biopolymers are enhanced by the supplementation of plasticizers. Various types of plasticizers are commonly utilized. This research aims to investigate the effects of different plasticizer types on the characteristics of biopolymer films prepared from tamarind kernel powder (TKP) and gelatin crosslinked with glutaraldehyde. Three types of plasticizers were examined: glycerol, sorbitol, and polyethylene glycol. The concentration of plasticizers was controlled at 1% w/w. The chemical and mechanical properties of the films were analyzed. The results indicated that the plasticizers differentially improved the mechanical properties of the biopolymer films. Additionally, the opacity, color, and water solubility of the films were influenced by the type of plasticizer used. The TKP-gelatin film supplemented with sorbitol exhibited improved mechanical properties, as indicated by both higher tensile strength and elongation at break, compared with that supplemented with glycerol and polyethylene glycol.

Abstract: In this study, a multifunctional air filtration material was developed by coating polypropylene (PP) nonwoven fabric with a chitosan/TiO₂ (P25) composite. The aim was to enhance air filtration efficiency. The chitosan–P25 composite was applied onto the PP nonwoven via a solution spray method followed by drying. Scanning electron microscopy (SEM) analysis revealed a uniform coating layer with good adherence to the PP fiber surface. X-ray diffraction (XRD) analysis confirmed the presence of crystalline TiO₂ in the P25 phases, as well as the semi-crystalline nature of the PP substrate. Air permeability tests showed a moderate reduction in air flow rate due to surface coating, while maintaining acceptable breathability for filter applications.

Abstract: The potential for biomass as an alternative source of energy is being studied widely. In this study, process flow design is done to analyse the pyrolysis of biomass and its products and how energy can be generated from its products. The energy used per process is calculated and the heat required in the processes were also calculated. The optimization of process parameters for the production of energy from wood biomass via pyrolysis was conducted using the Response Surface Methodology (RS) in the Design Expert 2022 environment using the following range of process parameters: temperature (400-1000°C), vapour residence time (5-30 min) and particle size (0.5-2.0 mm). The feasible combination of process parameters from the design of experiment was validated via physical experimentation having three responses namely: yield of char, yield of biofuel and yield of syngas. The designed experiments and corresponding outcomes produced three predictive models for estimating the yields of char, biofuel and syngas as a function of temperature, vapour residence time and particle size. The results obtained indicated that low temperature favours the formation of biochar while moderate temperature favours the formation of biofuel and the production of syngas is favoured by elevated temperature. The optimal values of process parameters and responses obtained include: temperature (642.271 °C), vapour residence time (6.248 min), particle size (0.603 mm), yield of char (71.9%), yield of biofuel (71.9%) and yield of syngas (76.5%). This study adds to the literature on the pyrolysis process for the conversion of wood biomass to energy. It also contributes to the fields of renewable and sustainable energy generation.Keywords: Biomass, biofuel, char, renewable and sustainable energy, RSM, syngas

Abstract: The increasing demand for sustainable energy solutions has intensified research into biodiesel production, which relies on chemical catalysts that have an environmental impact. This study investigates the alternative methods of biodiesel production by utilizing agricultural waste, specifically rice husk, coconut husk, and chicken manure as a catalyst for biodiesel production. Laboratory experiments were conducted to extract metal oxide from agricultural waste to be used as a catalyst in the transesterification process. The obtained ash was characterized, and it was revealed that rice husk ash contained 98% SiO₂, coconut husk ash had 72.62% of K₂O, and chicken manure ash had 46.56% CaO, with higher metal oxide compositions in each material. The transesterification reaction was conducted by varying alcohol to oil ratio from 3:1, 6:1, 9:1, and 12:1, temperature (40-80°C), catalyst concentration (1.5-4.5%wt), and reaction time (20-120min) to assess catalyst efficiency. Pure CaO was used as a control catalyst for comparison. Characterization of the produced biodiesel from all catalysts was conducted and compared to ASTM D6751 standards. The results for acid value, moisture content, density, viscosity, free fatty acid, flash point, pour point, and cloud point were analyzed and found to comply with ASTM D6751 standards. On quantity determination of produced biodiesel, the most effective catalyst was chicken manure ash with a yield of 80% and the least effective catalyst was rice husk ash with 68% yield. Using agricultural waste reduces up to 40% production cost.