Abstract: The analysis of damage resulted from concentrated out-of-plane impact forces is a concern in case of fiber reinforced polymeric composite aerostructures. Thereby, it can be quantified in terms of resulting size/damage type by drop weight impact testing. The aim of the present research was to evaluate the impact response of CFRP laminates by FEA and experimental tests. For FEA, two failure criterions were used, energetic criterion and Tsai Wu criterion. In both modeling scenarios the laminate was fractured. In case of the energetic criterion it was observed a meandering crack along with internal delamination of the material plies, while in case of the Tsai Wu criterion the impactor passes through the specimen, destroying the impacted area. Experimental tests performed at 0.7 meters height and 33 J of impact energy showed that all material plies were visible damaged, but the impactor didn’t pass through all specimen thickness. Different damage modes were observed on the tested specimens, the impacted face of the specimen presented a combined damage consisting in large cracks with fiber breakage indentation/puncture and a dent while on the non-impacted side of the specimen splits, cracks and a small swelling were observed. Considering the results from FEA and experimental tests, it can be said that regarding the damage shape, the experimental results are in a good agreement with a combination of the results obtained from the two failure models of FEA.
Abstract: In this work, a new software for computer-aided design of composite materials with predefined thermomechanical properties is presented in case of incomplete input data. The mathematical basis of underlying computational method of the properties identification is a modified method of multiscale homogenization named reversible multiscale homogenization method. The system has a modular architecture and includes software implementation of the reversible multiscale homogenization method based on a new technique of construction of software implementations of complex computational methods. The latter was named «Graph-based software engineering» (GBSE) and is based on category and graph theories. The corresponding numerical and experimental results were obtained and compared. The expediency of GBSE approach is discussed for the case of the development of complex computational methods required when solving the applied problems of the design of new heterogeneous materials.
Abstract: This research focuses on the mechanical and morphological properties of acacia wood (AW) reinforced polyhydroxyalkanoates (PHA) bio-composites. Acacia woods waste in the form of sawdust was processed into short wood fiber, which was later mixed with pure PHA with different fiber loading (5wt%, 10wt%, 15wt% and 20wt%). The acacia wood fibers were chemically modified by using the naturalization technique (which used both acidic and alkaline base) using acetic acid and sodium bicarbonate. The hot press machine was used to fabricate the samples. Tensile and flexural samples were fabricated and tested according to the ASTM standards. The SEM images show that the chemically modified acacia wood reinforced PHA (M-AW-PHA) bio-composites create desirable adhesion which contributed to better mechanical strength at 15wt%, when compared with untreated acacia wood reinforced PHA (U-AW-PHA) bio-composites.
Abstract: In present research work, metal injection molded cylindrical samples containing the mixture of carbonyl iron powder and high-density polyethylene (HDPE) were compressed at various strain rates. Three mixtures of carbonyl iron powder and HDPE were prepared to contain 80 %( Material A), 86 %( Material B) and 92 %( Material C) metal powder by weight. Compression tests were performed on the cylindrical samples at different crosshead velocities of Universal Testing Machine varying from 0.6-25 mm/min. True stress-true strain behavior of these samples under uniaxial compression test was studied. Based on these curves, polynomial equations were formulated to describe the plastic deformation behavior of the various mixtures at various cross head velocities. The Material C samples showed higher strength as compared to samples from the other two materials. However, Material A showed superior deformation behavior.
Abstract: Rheological study has been performed experimentally by using melt flow index (MFI) tester on a mixture of CI (Carbonyl Iron) powder and HDPE (High-Density Polyethylene) polymer. The rheological properties such as volume flow rate (cm3/s), shear strain rate (s-1) and viscosity (Pa.s) are investigated for varying conditions of temperature and weight (pressure). This also includes experimental determination of viscosity dependence over parameters like temperature, shear strain rate and CI powder loading by weight added in HDPE. For this experimental conditions selected are temperatures 4480K-5230K in steps of 250K, weights in MFI tester (ultimately converted to shear strain rate) 0.325, 1.20, 2.16, 3.80, 5.00Kg and carbonyl iron powder loading in binder HDPE (by weight) 80%-92% in steps of 6%. A constitutive equation for viscosity is formulated which considers all factors affecting viscosity with the maximum percentage error of about 4% between experimental value and value predicted by the formulated equation is obtained.
Abstract: Three different hydrophobic agents were considered for internal hydrophobation of cementitious composites. The dosage varied between one and two percent of cement weight and these admixtures were introduced to the composite during the mix procedure. capillary suction test, pore protection factor (PF) test and compressive strength test where conducted for material characterization. The results show reduction in water permeability of modified samples and rapeseed oil was the most effective admixture between these agents. While water resistance in the PF test of the modifies samples were increased between 21% to 33%, the compressive strength was reduced between 10% to 18%. In cases where reducing water permeability is a major challenge in cementitious composites, using rapeseed oil for internal hydrophobation can be an environmentally friendly solution.
Abstract: The aim of this study is fabricated bone void filler (BVF) made from hydroxyapatite (HA)-rice starch (RS) composite. We provided HA derived from cockle shells and RS derived from Thai rice starch. BVF was prepared by adding the pore former method to mimic the pore structure of bones. The samples were heated at 1250°C for 3 hours. Then, the composites were prepared by dipping and coating surface of the samples with RS gel. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) confirmed that bovine bone and BVF are made of HA phase. Film of RS gel coated on surface of samples indicated that BVF without toxicity and would increased the proliferation of bone cells. Moreover, it was found that BVF after coated RS gel had water absorption value higher than before coated as 25% that exhibited a good capacity of regeneration bone.
Abstract: In this study, we have demonstrated that bone void filler made from hydroxyapatite (HAP) which derived from cockle shell. This sample mixed with rice starch and can be used to augment new bone growth in the empty space defects of damaged hard tissue, such as bone, spine and skull. The chemical compositions of HAP get along with standard specification for composition of ceramic HAP for surgical implants (ASTM International: F1185-88). The starch content was in the safety range of classical cell culture formulation. 60 patients were treated with this bone void filler show successfully healing and recovery, after 6 months period of follow up, confirmed safety and efficacy of the medical device properties. It should be an alternative choice for bone substitute in the future.
Abstract: In the current work, the degradation of poly (3-hydroxybutyrate) (PHB) and poly (3-hydroxybutyrate-co-3-hydroxy-4-methylvalerate) (PHB4MV) films was studied in vitro by pancreatic lipase. The changes in film properties were traced by several analytical methods: the change of weight, molecular weight, and Young’s modulus (by nanoindentation) were measured. During the six months of polymer films degradation the weight of samples decreased slightly, while a great increase in Young's modulus due to the relatively fast degradation of the amorphous areas was observed, as well as molecular weight of polymers decreased significantly. Weight loss of PHB4MV is faster than degradation rate of PHB, but the molecular weight of PHB 1700 decrease rapidly than PHB4MV; the Young’s modulus of polymers remained relatively unchanged.