Impact Strength

Dynamically vulcanized blends of polyoxymethylene (POM) and ethylene propylene diene terpolymer (EPDM) with and without compatibilizer were prepared by melt mixing in a twin screw extruder. Maleic anhydride (MAH) grafted EPDM (EPDM-g-MAH) has been used as a compatibilizer. Dicumyl peroxide was used for vulcanizing the elastomer phase in the blends. Mechanical, dynamical mechanical, thermal, and morphological properties of the blend systems have been investigated as a function of blend composition and compatibilizer content. The impact strength of both dynamically vulcanized blends and compatibilized/dynamically vulcanized blends increases with increase in elastomer content with decrease in tensile strength. Dynamic mechanical analysis shows decrease in tanδ values as the elastomer and compatibilizer content increased. Thermograms obtained from differential scanning calorimetric studies reveal that compatibilized blends have lower Tm values compared to dynamically vulcanized blends, which confirms strong interaction between the plastic and elastomer phase. Scanning electron microscopic observations on impact fractured surface indicate reduction in particle size of elastomer phase and its high level of dispersion in the POM matrix. In the case of compatibilized blends high degree of interaction between the component polymers has been observed. POLYM. ENG. SCI., 47:934–942, 2007. © 2007 Society of Plastics Engineers

A novel fluorinated thermoplastic (FT) was synthesized from diglycidyl ether of bisphenol A (DGEBA), and 3-(trifluoromethyl)aniline. FT was found to be miscible with DGEBA as shown by the existence of a single glass transition temperature (Tg) within the whole composition range. On the basis of several experimental techniques, it was found that upon heating etherification reaction takes place between FT and DGEBA. A DGEBA-aromatic diamine (4,4′-methylenebis(3-chloro 2,6-diethylaniline) formulation was modified with the FT. The influence of FT on the epoxy-amine kinetics was investigated. Both structural parameters, gelation, and vitrification, were found to be affected by etherification reaction between epoxy and hydroxyls groups belonging to FT. The presence of ether linkages induced system stoichiometry modification. In addition, the curing conditions influence on FT migration towards the surface was studied on samples prepared with 20 wt % of modifier. SEM–EDX analysis confirmed that modified systems exhibits notable fluorine enrichment within the uppermost 200 μm. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2781–2792, 2007

Flour rice husk (FRH) was employed as a filler in block copolymer polypropylene (PPB) in order to prepare polymer-based reinforced composites. Four coupling agents were selected to modify the surface of the rice husk in the composite materials, including two types of functionalized polymers [PP homopolymer grafted with maleic anhydride (MA-PP) and an elastomer styrene–ethylene–butadiene–styrene triblock copolymer grafted with MA (MA-SEBS)] and two bifunctional organometallic coupling agents (silane and titanate with linear low-density polyethylene as a carrier). The influence of each type of coupling agent on the interfacial bonding strength was studied by dynamic mechanical analysis, scanning electronic microscopy, and rheological tests. The results showed that strong interactions were formed between the coupling agents and the filler surface. The addition of a coupling agent with an elastomeric carrier (MA-SEBS) increased the loss tangent and reduced the storage modulus of the composite. A similar but less intense effect was observed for the titanate coupling agent. However, an antagonistic performance was obtained when MA-PP and silane were employed as coupling agents. In addition, when the percentage of MA-SEBS was increased, the impact properties of FRH/PPB blends were improved and the strength was reduced. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1823–1831, 2006

In recent decades, material performance improved by the discovery of new bulk materials have slowed down. By contrast, novel or unprecedented material properties have been demonstrated under the concept of “architected materials”, where the material properties are dominated by material microstructure instead of constituents. Knowing that mother nature is “a master of material architecture” through millions of years evolution – nearly all natural materials have elegantly fine and organized structures showing excellent impact resistance and damage tolerance. In this study, we design material architectures mimicking biomaterials and 3D print architected beams with dynamic performance far beyond their bulk constituents. By performing dynamic three-point bending tests and digital image correlation analysis, we characterize five types of bioinspired microstructures and propose the criteria of architecture selection adopting the concept of material indices. Why certain microstructures are preferred by certain organisms and how to optimally select material architectures for specific engineering applications are illustrated. Then, microstructure integration approaches that work on multiple length scales (hierarchical designs) and on one specific length scale (hybrid designs) are investigated. Applying these approaches, we design architected beams that are flexible and strong, strong and tough, dissipative and stiff, and flexible and responsive, which are typically exclusive in bulk materials. Additionally, material architectures give extra control of fracture patterns, improving the critical impact energy by over 6 times. This work provides insights to the structure –property relationships and will facilitate the development of architected material with tailored performances of flexibility, strength, toughness, energy dissipation, and fast response.

Reciprocating micro-scale sliding tests and micro-scale repetitive impact tests were performed with diamond probes on un-doped, Si-doped and W-doped diamond-like carbon (DLC) coatings on hardened steel with a nanomechanical test instrument. Analytical modelling showed that differences in coating behaviour during sliding contact could be interpreted by differences in the stress distribution that develops. The softer W-doped DLC exhibited the lowest wear resistance in reciprocating sliding. The deformation in the wear track under the test conditions (R = 25 µm, P ≤ 500 mN, total sliding distance = 1 m) was largely controlled by plastic deformation and hence hardness, since micro-scale fatigue wear was only a small contributor. The relationship between friction and wear was more complex, due to the changing influence of surface topography, asperity ploughing and wear with increasing reciprocating sliding cycles. The Si-doped DLC showed the lowest resistance to repetitive impact. The hardest and highest H3/E2 coating, un-doped DLC, was also susceptible to fracture throughout the load range. Although the W-doped DLC was the softest coating studied and had low wear resistance in reciprocating sliding, it was significantly more damage tolerant to repetitive impacting than the other coatings despite its low hardness and low wear resistance in reciprocating tests.

This paper deals with an innovative integrated hollow (space) E-glass/epoxy core sandwich composite construction that possesses several multi-functional benefits in addition to the providing lightweight and bending stiffness advantages. In comparison with traditional foam and honeycomb cores, the integrated space core provides a means to route wires/rods, embed electronic assemblies, and store fuel and fire-retardant foam, among other conceivable benefits. In the current work, the low-velocity impact (LVI) response of innovative integrated sandwich core composites was investigated. Three thicknesses of integrated and functionality-embedded E-glass/epoxy sandwich cores were considered in this study—including 6, 9 and 17 mm. The low-velocity impact results indicated that the hollow and functionality-embedded integrated core suffered a localized damage state limited to a system of core members in the vicinity of the impact. The peak forces attained under static compression and LVI were in accordance with Euler's column buckling equation. Stacking of the core was an effective way of improving functionality and limiting the LVI damage in the sandwich plate. The functionality-embedded cores provided enhanced LVI resistance due to energy additional energy absorption mechanisms.

Marine recreational fisheries and fish communities have been mostly studied separately, severely hampering the detection of possible interactions. Here we monitored recreational fishery landings (angling and spearfishing) and assessed the reef fish community through underwater visual censuses in Trindade, an isolated oceanic island in the southwestern Atlantic Ocean. The study was conducted in zones of high and low fishing effort, along three different years spread over a seven-year period. We found high catch per unit effort (CPUE; kg*fisher À 1 *hour À 1) associated with high fishing intensity. However, the biomass of the targeted species in the natural environment decreased by 58% over time, while fishing effort increased about 270%, and CPUE decreased by 40%. Inverse relationships between effort and CPUE, and effort and biomass in the environment, were stronger in zones of high fishing effort. We conclude that the recreational fishery activity quickly responded to overfishing, creating a harvesting process that negatively impacted reef fish communities in this isolated oceanic island. Thus, conservation strategies should incorporate long-term recreational catch and fish community monitoring programs. Here we discuss options for the sustainability of the recreational fisheries and reinforce the importance of dialogue among scientists, managers and users for the achievement of conservation goals.

The term ‘impact’ is everywhere. Organizations and individuals want to fund projects for impact, measure impact, and showcase the impact of effort, expertise and financial investment, but clear definitions and understandings of what having an impact really means for people and institutions appear lacking or ad-hoc. This paper explores ‘impact’ in the areas of education and research into government practice. For governments, the impact agenda involves operating in increasingly tight fiscal environments with mounting pressure to articulate and demonstrate return on investment. For education providers, there are increasing calls to justify and prove why investment in education is an efficient and effective endeavor. For universities, this includes a shift from a traditional publication-focused research impact culture to a wider societal impact one that demonstrates direct and indirect benefits to society. This paper conceptualizes impact as a “puzzle” with many pieces, with education and research making up key pieces that can and need to fit together better. In doing so, the paper identifies four problem areas to help guide thinking toward clarity about what ‘impact’ entails. To aid collective progress in this space, we detail key issues facing the education and research sectors. Based on our analysis we arrive at a set of questions intended to help guide thinking and actions toward collectively increasing the ability to generate and demonstrate the impact of both into government practice and society at large.

The mechanical properties and water absorption of low-density polyethylene/sawdust composites were investigated. The relationship between the filler content and the composite properties was also studied. Different degrees of esterification of the sawdust with maleic anhydride were obtained with different reaction times. The experimental results demonstrated that the treatment of sawdust by maleic anhydride enhanced the tensile and flexural strengths. The water absorption for maleic anhydride treated sawdust indicated that it was more hydrophobic than untreated sawdust. The effects of the addition of benzoyl peroxide during the preparation of composite samples on the water absorption and mechanical properties were also evaluated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The main issue of this research to improve and develop the mechanical properties of the socket composite material for below-knee (BK) prosthesis; several composite materials were proposed, consisting of perlon, Kevlar and carbon fibers, and natural fibers were added as a new idea for the research. Making the theory calculations were for several layers of materials, by using mathematical model, to obtain the best lamination with and without kenaf by calculating the best modulus of elasticity and the best E /ρ ratio. So the experimental tests were carried out on the lamination with a total of 12 layers for thickness (4 mm) each of them, (Group G/withot kenaf) and (Group D/ with kenaf). The experimental part included examining the samples by tensile test, bending test, impact test. The results of the tensile test results were for the first lamination and the second lamination for the ultimate tensile strength (134.47 MPa) and (187.39MPa) respectively. As for the elasticity modulus, it was as follows (16.78 GPa) without kenaf and (17.49 GPa) for kenaf lamination. Through the theoretical and experimental results, it was found that the use of natural kenaf fibers led to the improvement of the maximum tensile strength 39.35% and modulus of elasticity 4.23%. The impact resistance was improved by using kenaf by 8.8% due to its durability higher than perlon fiber.

A sustainable multifunctional biobased composite with 61% renewable resource content exhibiting superior toughness was successfully engineered using polylactide (PLA) and organosolv lignin (OL). Reactive extrusion of PLA with OL in presence of poly (vinyl acetate), PVAc and glycidyl methacrylate (GMA) improved interfacial adhesion in resulting a novel biobased elastomer. A constrained mixture design was adopted to evaluate the effect of OL, PVAc and GMA on performance of the composites. Optimized composites displayed superior toughness (elongation at break of ~340% and notched impact strength of ~900 J/m) with lowered tensile strength and modulus. FTIR analysis suggested that interfacial adhesion between GMA and PLA occurred during melt processing. One of the most significant findings of this study is the generation of single glass transition temperature of the complex structured composites. This new material offers a sustainable novel strategy for producing high performance PLA materials with value-added uses of lignin to replace petroleum-based thermoplastic elastomers.