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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.8, #2)
Experimental Studies on Damage Growth in Composites under Dynamic Loads by S. Ravi; N. G. R. Iyengar; N. N. Kishore; A. Shukla (pp. 79-97).
Experimental investigations have been carried out to study the dynamic damage growth in glass/polyester composites. Detonation of two PETN explosive charges on a modified single edge notch (MSEN) specimen provides the dynamic load in the form of a planar tensile wave. High speed photography is used to record the dynamic damage events. The results show that damage grows perpendicular to the loading direction, similar to the static growth; the damage zone splits analogous to the crack branching in unreinforced polyester. The damage propagation velocity in a composite is higher than the crack propagation velocity in polyester resin. The damage area grows at an average rate of 4.3 m2/sec. Static experiments show that about 4 percent of the total energy is spent on the fiber-matrix interface debonding. The damage zone under dynamic loads is much higher than under static loads.
Keywords: transparent glass/polyester composites; stress wave loading; dynamic and static damage growth
Exothermic Temperature History in the Processing of Resin Infused Composite Structural Components by L. Zhao; M. Cordovez; V. M. Karbhari (pp. 99-131).
Resin Infusion Processes such as SCRIMP, VA-RTM, and variations thereof, are increasingly being considered for the fabrication of large structural components such as bridge decks and ship hulls wherein preform elements consist not only of varying fabric architectures but also include foam cores. Based on the method of infusion – high permeability distribution media or resin channels/microgrooves, flow through the preform can be tailored to be either 1-D, 2-D, 3-D or a combination thereof. This paper emphasizes the effect of exothermic temperature history on flow & cure phenomena, and mechanical properties of a series of structural elements ranging from a flat plate to a typical truss-core type structure. The effect of geometry and flow on exothermic characteristics is experimentally monitored, and results correlated to provide guidance in the further use of the process. Critical areas lacking in detailed understanding are identified and a set of preforming and process induced defects that cause changes in thermal history are described.
Keywords: composites; SCRIMP; resin infusion; exotherm; E-glass; flow; defects
Simulation of Impulse Resistance Welding for Thermoplastic Matrix Composites by Christophe Ageorges; Lin Ye (pp. 133-147).
The impulse resistance welding (IRW) process is modelled using a three-dimensional transient finite element model (FEM) featuring heat transfer and consolidation. The welding of single lap joints is simulated for APC-2 laminates, with additional PEEK film inserted at the welding interface. The effects of the power signal on (a) temperature uniformity in the welding interface and (b) processing times are investigated. Two welding configurations are evaluated; in the first one, the heating element outside the welding stack is left in-air, while in the second case, it is embedded in a conductive medium in order to improve temperature homogeneity within the welding interface. Based on criteria of consolidation and thermal degradation, optimum processing windows were simulated.
Keywords: impulse resistance welding; heat transfer; consolidation; processing window; APC-2; CF-PEEK composites