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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.9, #6)
Influence of Matrix Ductility and Fibre Architecture on the Repeated Impact Response of Glass-Fibre-Reinforced Laminated Composites by Bernard Schrauwen; Ton Peijs (pp. 331-352).
This paper describes the results of falling weight impact tests on glass-fibre-reinforced laminates. The test program consisted of (i) falling weight impact tests for the determination of the penetration energy and the influence of laminate construction on damage development and (ii) repeated falling weight impact tests for the determination of the impact fatigue lifetime and damage development under repeated impact conditions at sub-penetration energy levels. The objective of this work is to compare the impact behaviour of cross-ply laminates based on a brittle unsaturated polyester resin and a more ductile vinyl ester resin system and two types of glass reinforcement, i.e. woven- and multiaxial non-crimp fabric. The penetration energy of the various composite laminates appeared to be mainly influenced by the type of reinforcement, whereas damage development during (repeated) impact is strongly influenced by both fibre architecture and resin. No significant effect of the different material parameters investigated on the number of impacts to penetration (impact fatigue lifetime) is observed. Especially when the repeated impact energy is normalised with respect to the penetration energy, all laminates showed similar behaviour.
Keywords: glass-fibre-reinforced plastics; woven fabric; non-crimp fabric; impact strength; repeated impact; impact fatigue; damage; delamination
Tensile and Compressive Properties of FRP Composites with Localised Fire Damage by C. P. Gardiner; Z. Mathys; A. P. Mouritz (pp. 353-367).
The effect of localised fire damage on the tensile and compressive properties of fibre-reinforced polymer (FRP) composites is investigated. A simple model based on rule-of-mixtures is presented for determining reductions to the tensile stiffness, tensile strength, compressive stiffness and compressive strength of composite panels with localised fire damage of any shape and size. The validity of the model is rigorously tested against experimental tension and compression property data for a glass/polyester composite with localised fire damage in the shape of a circle, oval, square, diamond or in a irregular shape. The model is found to accurately predict the tension and compression properties of composites with localised fire damage of any shape, and is expected to be a useful model for estimating the residual structural integrity of fire-damaged composite panels.
Keywords: mechanical properties; fire damage; combustion; delamination; modelling
Mechanical Properties of Date Palm Fiber Reinforced Composites by Faleh A. Al-Sulaiman (pp. 369-377).
Mechanical properties of several laminates of date palm leave (DPL) reinforced composites are investigated. Three different processes to construct these composite laminates are assessed. These are wet lay-up with simple vacuum bagging, autoclaving with vacuum bagging and Vulcan press moulding. Several fiber orientation and dimensions are tested. Two types of resins are selected. The first is a high temperature curing Phenolic (phenol formaldehyde) resin. The second is a two-component Bisphenol resin with amine-based slow curing agent. The average tensile strength ranged between 127.4 and 152.3 MPa for long unidirectional fibers and 8.4 to 62.6 MPa for short and medium length fibers respectively (depending on process and resin type). The Bisphenol laminates have better mechanical properties. These laminates have consistently 25 to 50% higher tensile strength than Phenolic laminates. The bending strength ranged between 120.6 and 342.3 MPa (at 500 mm/min loading speed) depending on fiber length. Short fiber Bisphenol laminates have excellent fatigue life characteristics (over 466,000 and 653,000 cycles at 70% and 60% of maximum stress loads respectively). The process parameters and resin types have significant effects on the laminate properties. The water absorption of the laminates ranged between 2.3 to 5.8% for the Phenolic laminates (depending on the test method and manufacturing process used). The water absorption of Bisphenol laminates ranged between 10 and 40%. The produced laminates were very stable to handle all required machining processes as construction panels. They were successfully subjected to several machining processes such as milling, end milling, hack sawing and drilling.
Longitudinal Creep Behaviour of a SiC/Ti-6242 Composite in a Vacuum Atmosphere by A. Faucon; E. Martin; B. Coutand; N. Carrere; J. F. Fromentin; L. Molliex; B. Dambrine (pp. 379-393).
This study deals with the longitudinal creep behaviour of a unidirectionally reinforced SM1140+/Ti-6242 composite at 500○C in a vacuum atmosphere. The monitoring of acoustic emission and microstructural observations show that filament fracture develops during the creep test. This damage results from the stress relaxation in the matrix, which increases the axial stress in the filament. Time till the creep rupture can be predicted with a model describing the filament damage accumulation.
Keywords: titanium alloy matrix; silicon carbide filaments; creep testing; damage mechanisms; Weibull distribution; Monte-Carlo method