This research work is concerned with the evaluation of the mechanical properties—modulus, Poisson's ratio and strength—of woven jute fabric-reinforced composites. The specimens are prepared using hand lay-up techniques as per the ASTM standard. This is the first report by any single group of researchers in which tensile strength, compressive strength, flexural strength, impact strength, inplane shear strength, interlaminar shear strength and hardness are given. This work being an experimental study on untreated (`as received' jute fabric) woven jute fabric-reinforced polyester composites, demonstrates the potential of this renewable source of natural fibre for use in a number of consumable goods.

Some mechanical properties of untreated jute fabric-reinforced polyester composites

The indentation resistance of foams, both of conventional structure and of a novel re-entrant structure giving rise to negative Poisson's ratio, was studied using holo graphic interferometry. In holographic indentation tests, re-entrant foams had higher yield strengths σy and lower stiffness E than conventional foams of the same original relative density. Damage in both kinds of foam occurred primarily directly under the indenter. Calculated energy absorption for dynamic impact is considerably higher for re-entrant foam than conventional foam

/pdf/indentability-of-conventional-and-negative-poisson-s-ratio-133psgbpmq.pdf

Indentability of Conventional and Negative Poisson's Ratio Foams

Low velocity impact of combination Kevlar/carbon fiber sandwich composites

Impact behaviour and post impact compressive characteristics of glass–carbon/epoxy hybrid composites with alternate stacking sequences have been investigated. Plain weave E-glass and twill weave T-300 carbon have been used as reinforcing materials. For comparison, laminates containing only-carbon and only-glass reinforcements have also been studied. Experimental studies have been carried out on instrumented drop weight impact test apparatus. Post impact compressive strength has been obtained using NASA 1142 test fixture. It is observed that hybrid composites are less notch sensitive compared to only-carbon or only-glass composites. Further, carbon-outside/glass-inside clustered hybrid configuration gives lower notch sensitivity compared to the other hybrid configurations.

Impact response and damage tolerance characteristics of glass-carbon/epoxy hybrid composite plates

The interface between the matrix and reinforcing phases can have a significant effect on the mechanical properties of the resulting composite material. The interface can be studied by a number of surface analysis techniques and the interaction modelled. Such studies, and such modelling, can help understanding of the mechanisms which composites undergo during their lifetime. The current review discusses the role of the interface and the methods by which it can be studied; two case studies are presented which illustrate these methods and the value that such knowledge of the interface has brought to larger investigations.

The Interface and Interphase in Polymer Matrix Composites: Effect on Mechanical Properties and Methods for Identification

The impact response of various composite sandwich panels has been investigated These composite sandwich panels, consisting of various fabric facesheet materials and different densities of poly(vin

Instrumented Impact Testing of Composite Sandwich Panels

The mechanical behavior of several filler-modified epoxy resins was inves tigated. Modifications of matrix resin with thermoplastic particulates or ceramic whiskers were proposed as an alternative to rubber-toughening for improving the impact resistance of epoxy resins. Addition of 10 % by weight of untreated thermoplastic powders in an epoxy resin only slightly increased the impact energy of the epoxy resin. A reduction in flexural strength of this thermoplastic particulate-filled resin was observed. This is most likely due to poor particulate-matrix bonding. Dispersion of 10 % of ceramic whiskers in an epoxy resin improved appreciably the impact energy, flexural strength and modulus of the epoxy. The impact energy absorbed by a resin was enhanced by the approach of partic ulate/ whisker hybridization. A uniform dispersion of either particulates or whiskers in the epoxy matrix is essential to the achievement of balanced mechanical properties. Deforma tion and failure mechanisms in these composites were a...

Structure-property relationships in thermoplastic particulate- and ceramic whisker-modified epoxy resins

Fracture behavior of advanced interlaminar hybrid composites has been investigated. Single-matrix/double-fiber, double-matrix/single-fiber, and double-matrix/ double-fiber hybrids as well as their single-fiber/single-matrix control versions were stud ied. The addition of glass fiber-PPS (polyphenylene sulfide) laminas in graphite fiber-PPS composites was found to be effective in improving the impact resistance of the material. As the percentage of glass fibers increased, so did the maximum load tolerated and impact energies absorbed by the material. The intermixing of glass- and graphite-fiber plies also helped decrease the sudden catastrophic failure mode, which is usually associated with graphite-fiber composites. This was due to the extra strain energy dissipated by massive delamination and the subsequent crack blunting mechanism. Adding thermoplastic PPS fiber laminas in epoxy/graphite fiber plies was also found to enhance the impact energy ab sorption capability of the otherwise brittle thermoset com...

Impact Behavior of Hybrid-Fiber and Hybrid-Matrix Composites:

The mechanical properties of continuous graphite fiber reinforced com posites containing filler modified epoxy matrix have been investigated. Modification of epoxy resin with either thermoplastic p...

Particulate and Whisker Modifications of Matrix Resin for Improved Toughness of Fibrous Composites

An investigation was conducted to systematically evaluate the structure- property relationships in both 3-D and the corresponding 2-D composites. Macroscopic failure modes and microfailure mechanisms in these composites were studied as a function of various material parameters. In particular, the influence of the stitched Z-direction fibers on the mechanical behavior of an otherwise 2-D composite was investigated. The 3-D composites have been found to possess a greater damage resistance than the conven tional 2-D composite materials. The Z-direction (or third-direction) fibers effectively reduce the extent of delamination by increasing the interlaminar surface energy. The total energy absorbed by a composite during impact loading, three-point, and four-point bend ing test is therefore raised without creating an excessive amount of delamination. The third directional fibers are found to have a profound effect on the failure mechanisms.

B.Z. Jang

Papers

Instrumented Impact Testing of Composite Sandwich Panels

Structure-property relationships in thermoplastic particulate- and ceramic whisker-modified epoxy resins

Impact Behavior of Hybrid-Fiber and Hybrid-Matrix Composites:

Particulate and Whisker Modifications of Matrix Resin for Improved Toughness of Fibrous Composites

Mechanical Properties of Multidirectional Fiber Composites