Effects of cellulose fibers in polypropylene composites

lengths. Also the Mode 11 critical energy release rates for both CNF and ENF are found to be in good agreement. Bismaleimide resins--chemistry and performance characteristics Barrett, K. A., Chaudhari, M. A. and Lee, B. H. SA M P E Journal Vo125 No 2 (March~April 1989) pp 17-20 The development and properties of a bismaleimide resin, based on an aromatic diamine, designated RD85-101 are reported. It is suggested as a candidate material for a matrix resin for advanced composite structures for use at high temperatures. The characterization of elastic moduli and damping capacities of graphite/epoxy composite laminated beams in hygrothermal environments Lee, C. Y., Pfeifer, M., Thompson, B. B. and Gandhi, M. V. Journal o f Composite Materials Vo123 N o 8 (1989) pp819--845 This paper presents a combination of theoretical and experimental investigations into the dynamic elastic moduli and damping capacities of composite laminated beams exposed to different hygrothcrmal conditions. This aim is to link the two disciplines of dynamic response characteristics of polymeric composites under isohygrothermal conditions and their static mechanical response characteristics in hygrothermal environments. Hygrothermalelastodynamic response-data is thus presented with a good correlation with theoretical predictions being found. Closure of the cubic tensor polynominial failure surface Jiang, Zhiquing and Tennyson, R. C. Journal o f Composite Materials Vo123 (March 1989) pp 208-231 This paper describes a new approach establishing the necessary criteria to ensure 'local' closure of the cubic form of the tensor polynomial strength criterion. The closure conditions are presented and closed failure surfaces for two different graphite/epoxy materials are described using the methodology. The agreement with test data was good. Dielectric cure monitoring---a critical review Ciriscioli, P. R. and Springer, G. S. S A M P E Journal Vo125 No 3 (1989) pp 35-42 The usefulness of dielectric techniques in the cure of thermoset matrix compoisites is tested. The permittivitics and loss factors are recorded during the cure of Fiberite T300/976 and Hercules AS/3501-6 graphite-epoxy composites. The ionic conductivities are thus deduced by both the Day and Kranbuel methods and compared with viscosities, rates of cure and degrees of cure as calculated by chemical methods. It is indicated that ionic conductivities, as calculated by either method, cannot provide the viscosity, degree of cure, or rate of cure as a function of time for the composites tested. Dynamic behaviour of delamination and transverse cracks in fiber reinforced laminated composites Awal, M. A., Kundu, T. and Joshi, S. P. Engineering Fracture Mechanics I,Iol 33 No 5 (1989) pp 753-764 A versatile numerical method is established to study the dynamic behaviour of delamination and transverse cracks in composite laminates under dynamic loadings. The method is capable of handling delamination

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and transverse cracks with any orientation in multilayered composite laminates. The variational principle is adopted in the frequency domain to obtain the finite element equations. The numerical difficulty associated with the singular behaviour of the stress field near the crack tip is avoided by using quarter point elements. The method is an extension of the finite element formulation of elastodynamic problems involving isotropic layers and delamination cracks, derived by Kundu and Hassan. Effect of fiber reinforcement geometry on single-shear and fracture behavior of threedimensionally braided glass/epoxy composite

pins Malkan, S. R. and Ko, F. K. Journal o f Composite Materials Vol 23 No 8 (1989) pp 798-818 The optimization of single-shear properties through controlled microstructure of glass/ epoxy composite pins is addressed. The p r o d u c t i o n of n e a r - n e t shape threedimensional braided cylindrical preforms and subsequent impregnation with epoxy resin is established. The relationship between fibre reinforcement geometry (FRG) and transverse single-shear and fracture behaviour of composite pins is determined. Scanning electron microscopy is used to study the fracture surfaces with the FRG being shown to influence the failure mechanism of the samples to a greater extent than it did the stress strain properties. Effects of cellulose fibers in polypropylene composites Bataille, P., Richard, L. and Sapiana, S. Polymer Composites Vol 10 No 2 (1989) pp 103-105 The effect of pretreatment of cellulose fibres and processing time on the mechanical properties of the polypropylene cellulose system is investigated. Silane coupling agents are applied to the fibres, XPS being used to monitor the quantity present. Elastic moduli, yield stress and ultimate stress are correlated with the fibre content. The effect on the interfacial adhesion and mechanical properties of silane coupling agents is reported. Scanning electron microscopy is used to reveal the mode of failure occurring in the fibres as opposed to the interface, the addition of maleic anhydride modified polypropylene to improve the properties of the composites was successful. Effects of fibre bridging on Gtc of a unidirectional glass/epoxy composite Huang, X. N. and Hull, D. Composites Science and Technology Vo135 No 3 (1989) pp 283-299 The Mode I fracture properties of a unidirectional glass/epoxy composite are studied using a double cantilever beam specimen geometry. Firstly, a crack is propagated by repeated loading-unloading cycles. Specimens deviate from linear elastic beam and linear elastic fracture mechanics predictions with respect to their compliance and critical load. Here G~c shows a continuous increase with crack growth. It is found that fibrebridging becomes significant for a crack growth of 5mm from the tip of an unbridged crack. Secondly, the crack is propagated in a similar manner but the bridging fibres are removed periodically by treatment with 2N HCI. This effectively restores the elastic beam behaviour and reduces G1c to a constant, unabridged value.

Effects of sorbed caprolactam on the crystallinity, morphology, and deformation behaviour of polyether ether ketone and poly(phenylene sulfide) Wilfong, D. L. Polymer Composites Vol 10 No 2 (1989) pp 92-97 The high temperature sorption of caprolactam by polymer composites is considered. Glass fibre reinforced poly(phenylene sulphide), polyetherctherketone (PEEK), glass fibre reinforced PEEK and carbon fibre reinforced PEEK are the systems considered. The sorption is correlated with the melting behaviour, mechanical properties and fracture surface features of the systems. Scanning electron microscopy is used to examine the tensile fracture surfaces and assess the degree of adhesion between the fibre and matrix. The effects of time, temperature and stress on the long-term behaviour of CFRP Ponsot, B., Valentin, D. and Bunsell, A. R. Composites Science and Technology Vol 35 No 1 (1989) pp 75-94 A study to estimate the role of the rheological properties of the matrix on the rate of damage accumulation during the steady loading of unidirectional carbon fibre-reinforced resins is presented. An epoxy resin, modified with different amounts of flexibilizer, was used as the matrix and creep tests were carried out on fiat unidirectional samples, loaded in the fibre direction. Damage accumulation was monitored using an acoustic emision technique. It is shown that the deduced kinetics can be d e s c r i b e d a n a l y t i c a l l y a n d a timetemperature-stress equivalence was demonstrated. Different types of behaviour were observed at low and high stress levels and it is suggested that two different processes for activating fibre breakage exist.

Electron-beam irradiation effects on mechanical properties of PEEK/CF composite Sasuga, T., Seguchi, T., Sakai, H., Nakakura, T. and Masutani, M. J. Mater. Sci Vol 24 (1989) pp 1570-1574 A number of previous studies have indicated that some aromatic polymer matrix composites show good resistance to radiation. This paper investigates the mechanical properties (as a function of temperature) of a carbon fibre reinforced polyarylether-ether-ketone (PEEK) composite, previously irradiated at various doses with an electron beam. Results indicate that at room temperature the flexural strength, flexural modulus and interlaminar shear strength are unaffected by radiation doses of up to 180 MGy. However, the high temperature properties of irradicated specimens decrease at a slower rate with increasing temperatures than unirradiated specimens. This behaviour was shown to be due to an upward shift in glass transition temperatures of the PEEK, caused by radiation induced crosslinking. Failure mechanisms in continuous carbonfibre reinforced PEEK composites Hine, P. J., Brew, B., Duckett, R. A. and Ward, I. M. Composites Science and Technology Vo135 No I (1989) pp 31-51 A study of the fracture behaviour of unidirectional carbon fibre-reinforced PEEK over the temperature range -60-100°C is presented. Double cantilever beam tests were used to study crack propagation parallel to the fibre direction for two different planes of