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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.8, #5)
Tensile Behaviour and Strength Distribution of Polyvinyl-Alcohol Fibre at High Strain Rates by Yang Wang; Yuanming Xia; Yuxi Jiang (pp. 297-306).
Mechanical properties of Polyvinyl-alcohol (PVA) fibre bundles were studied at three high strain rates (270/s, 600/s and 1500/s). It was found that, except for the elastic modulus, which remains unchanged, both the maximum stress and the failure strain show an apparent increase with strain rate. Two failure modes of PVA fibre under tensile impact were observed. A four-parameter Weibull function was adopted to describe the strength distribution of PVA fibre and the Weibull parameters were obtained by a fibre bundle testing method. Consistency between simulated and experimental results indicates that such a function and the method are valid and reliable.
Keywords: fibre bundles; tensile impact; strength distribution
Stress and Failure Analysis of Composite Laminates with an Inclusion under Multiaxial Compression-Tension Loading by P. Berbinau; C. Filiou; C. Soutis (pp. 307-326).
The present paper investigates the failure of orthotropic laminates with a filled hole subjected to biaxial compression-tension loading. This is an idealised case that simulates a situation where the impact damaged laminate has been repaired by drilling a hole and then plugging the hole with a perfect-fit core made of a dissimilar material. The exact stress distribution in the laminate has been determined using the complex variable mapping method. These stresses are then employed in a fracture mechanics failure model to predict the failure load of a laminate with a filled hole under in-plane compression-dominated multi-axial loading. Failure strength predictions are compared to open hole results and experimental data.
Keywords: composite laminates; multi-axial loading; open-hole; filled-hole; inclusion; stress distributions; complex variable mapping; compression; fibre microbuckling; strength prediction
Matrix Modification for Improved Reinforcement Effectiveness in Polypropylene/Glass Fibre Composites by Gustav Jannerfeldt; Ronnie Törnqvist; Nicolas Rambert; Louis Boogh; Jan-Anders E. Månson (pp. 327-341).
The influence of matrix modification on the interfacial shear strength (IFSS) and the mechanical performance of polypropylene/glass fibre composites is investigated. Two different modifiers were used: a highly reactive hyperbranched polymer grafted polypropylene (HBPgPP) and a maleic anhydride grafted polypropylene (MAHgPP). The interfacial shear strength increased with the addition of the modifiers, with HBPgPP giving the highest values. To evaluate the effects of the matrix modification on the composite strength, a method to normalise the composite strength with respect to fibre orientation and fibre concentration is presented. The normalised strength values followed the same trend as the measured IFSS values, namely that the HBPgPP modified composite displayed the highest strength and the unmodified material the lowest.
Keywords: short fibres; mechanical properties; interface; PP composites
Fiber-Reinforced Syntactic Foams as a New Lightweight Structural Three-Phase Composite by Michel Palumbo; Ezio Tempesti (pp. 343-359).
The mechanical behavior of hybrid beams made of an isotropic core (syntactic foam) and a fiber reinforced plastic skin is investigated theoretically and experimentally. The beams are subjected to three point bending tests. The analytical approach developed is compared to the experimental evidence reported in this study and a very good agreement is found.
Keywords: composite materials; fiber-reinforced polymer (FRP); syntactic foams; hybrid composite beam; shear deformation; buckling; Brazier effect