Composite Material Laboratory

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PART 1: VACUUM BAG PROCESSING OF PREPREGS. 1.1. Introduction and objectives. The purpose of this experiment is the fabrication of two specimens of composite materials using the vacuum bag processing. This technique is suited to prepeg components with thin sections and large sandwich structures. The vacuum bag technique involves the placing and seating of a flexible bag over a composite lay-up and evacuating all the air from under the bag. The removal of air forces the bag down onto the lay-up with a consolidation pressure of 1 atmosphere (1bar). The completed assembly, with vacuum still applied, is placed inside an oven with good circulation, and the composite is produced after a relatively short cure cycle. Unidirectional carbon fibers prepregs will be used. The material will be cut from a roll and placed to prepare a symmetric laminate with the stacking sequence [0/90/90/0] and an asymmetric one [0/0/90/90]. 1.2. Materials. The components of the usual lay-up for high-quality applications are displayed below: * Mould/tool. * Release film or agent. * Peel ply. * Bleeder film. * Bleeder fabric. * Barrier. * Breather fabric. * Edge dam. * Vacuum bag. * Vacuum valve. The group of students wiil work with the following materials: * Roll of unidirectional carbon fibre prepreg. * Tooling for fabrication (scissors, gloves, etc). * Metallic slab (mould). * Rest of consumables. 1.3. Procedure. 1) Draw and cut square specimens with dimensions 15x15 cm from the prepeg roll. 2) On the left side of the mould, place the first prepreg layer with the fibers parallel to the short dimension of the mould. This will be the zero-degree orientation. 3) Place three additional layers following the stacking sequence 90/90/0. This completes a 4 layer symmetrical laminate

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