Flexural Modulus Values Research Articles

Mechanical behaviour of carbon and glass hybrid fibre reinforced polyester composites

Mechanical behaviour of carbon fibre/glass mat/polyester resin hybrid composites of sandwich construction is studied through tension, flexure, impact and post-impact tension tests. Tensile and flexural strength, modulus and failure strain values are compared to the calculated values. Total impact fracture energy and residual (after impact) tensile strength values of hybrid composites are analysed with regard to corresponding values of carbon/polyester composites. Failure of tested coupons was analysed by visual inspection and observation by scanning electron microscopy.

Wood Flour/Polypropylene Composites: Influence of Maleated Polypropylene and Process and Composition Variables on Mechanical Properties

Abstract The mechanical properties of wood flour/polypropylene composites may be improved by using coupling agents to enhance the bonding between filler and matrix. We used a two-level, full-factorial experiment to examine the effectiveness of a commercially available additive, Epolene E-43, on strength (tensile, flexural, and cantilever-beam), modulus, impact energy, density, and melt viscosity of composites. The effect of Epolene E-43 was studied alone and in combination with three other variables: the weight ratio of wood flour to total polymer in the composites (45/55 or 55/45), size of wood flour particles (nominal 20 or 40 mesh), and extruder residence time (one or three extrusions). Of all the variables, Epolene E-43 had the greatest effect on strength. This effect was somewhat enhanced by using the 40-mesh wood flour and three extrusions; for this combination of variables, Epolene E-43 caused a 30 percent increase in strength. The combination of Epolene E-43 with a 55/45 wood flour/polymer ratio and 40-mesh wood flour resulted in the largest values of flexural and cantilever-beam modulus. Addition of Epolene E-43 slightly decreased notched impact energy but possibly increased unnotched impact energy. None of the variables had a significant effect on melt viscosity. Average wood flour particle size was decreased by processing, particularly in the presence of Epolene E-43. Overall, these findings indicate that Epolene E-43 exerts some degree of coupling action, which results in improvements in mechanical properties that have practical value. The higher cost of Epolene E-43 can be compensated by increasing the ratio of wood flour to polypropylene.

4909056 Method and an apparatus for cold-roll forming of annular workpieces : Christia Ragettli, Zurich, Switzerland assigned to Christian Ragettli AG

‘Melding’ is a novel in situ method for joining thermosetting composite structures, without the need of adhesives. Laminate joining is achieved using uncrosslinked resin matrix of the pre-preg. This study used Hexply914C pre-preg material to characterize melded CFRP structures produced using the melding method. A designated area of a laminate was maintained at temperatures below 40 °C retaining uncured (B-staged) material, while the remainder of the laminate was cured at 175 °C. After a 2.5 h cure cycle, the cured region showed a high degree of cure (0.88) and glass transition temperature (176 °C). The uncured area of the same laminate was cured in a second stage, simulating an in situ melded joint. By controlling the temperature and duration of the intermediate dwell and affecting minimum viscosity values prior to final cure, low values of porosity (<0.5%) were achieved. The mechanical properties of the resulting joint were consistent throughout the melded laminate. Flexural strength (1600 MPa), flexural modulus (100–105 MPa) and short beam strength (105–115 MPa) values observed where equivalent or greater than those found in the recommended autoclave cured control specimens. After the entire laminate was post cured, glass transition temperatures of 230 °C (peak tan δ) were observed in all areas of the laminate.

Flexural fatigue strength of lime-laterite soil mixtures : Bhattacharya, P G; Pandey, B B Trans Res RecN1089, 1986, P86–92

Laterite soils, which are the producs of tropical or subtropical weathering, have been stabilized with lime to evaluate the dynamic modulus and the flexural fatigue strengths of the lime-soil mixtures. Tests have been carried out on four types of laterite soils compaced at three dry density ranges-light, medium, and heavy. Least-squares regression analysis was used to establish relationships betwen stress ratio and the logarithm of the number of stress cycles to failure. Heavily compacted lime-soil specimens were found to have considerably higher dynamic modulus and fatigue life than those having standard Proctor compaction. Increased values of dynamic flexural modulus and strength at the higher dry density favor the use of lime-laterite soil as a road base.

Block polymers from isocyanate‐terminated intermediates. IV. Properties of cured butadiene–ε‐caprolactam block polymers

AbstractButadiene–ε‐caprolactam block polymers containing a high proporation of 1,2 units in the butadiene‐segments were synthesized and physical properties were measured on the cured copolymers. Flexural strength and impact resistance both increase regularly with increasing ε‐caprolactam content in peroxide cured copolymers. This behavior is explained by the higher values of flexural modulus and impact resistance for poly(ε‐caprolactam) compared with peroxide‐cured polybutadiene resins. Copolymers reinforced with silica showed higher heat distortion temperatures but lower impact resistance than corresponding unfilled samples. Arrhenius plots of flexural properties at various test temperatures were linear. Both flexural modulus and strength decreased regularly with increasing test temperature. Flexural properties of filled copolymers were relatively unaffected by heat aging up to 204°C for several weeks, however, dramatic decreases in these properties were noted in a matter of days when heat aging was done at 260–316°C. These results are explained by the rapid degradation of poly(ε‐caprolactam) above its melting point. Block polymers whose butadiene segments contained a high proportion of 1,4 units were also synthesized. These copolymers were elastomeric when cured with either sulfur or peroxide.