The in-situ damage progression in three carbon fibre reinforced cross-ply composite systems under tensile loading is examined, namely, carbon IM7/epoxy, carbon IM7/PEEK and carbon AS4/polyamide. Epoxy is a thermoset polymer while polyether ether ketone (PEEK) and polyamide are thermoplastic. The thermoset composite is manufactured in an autoclave using matrix pre-impregnated with unidirectional carbon fibres, while the thermoplastic composites are manufactured using laser-assisted automated tape placement (LATP). A tensile microtester is mounted in a scanning electron microscope to observe the damage mechanisms in-situ under tensile loading. X-ray computed tomography scans are also carried out to examine porosity in the material systems. IM7/epoxy and IM7/PEEK displayed similar damage mechanisms: transverse cracking in 90° plies followed by fibre breakage in the 0° plies at the fillets and interlaminar fracture. AS4/polyamide displayed a different mechanism with fibre fracture appearing first in the 0° plies, followed by transverse cracking and interlaminar fracture. The effect of autoclave treatment on the materials manufactured by LATP has also been examined.
Fibre composites are being used in various applications from aerospace, military, marine boats and submarine to renewable energy generation. Higher energy demands across the developed and growing world for the usage and replacement of conventional materials with polymer composite materials for engineering applications which is always questioned by the end user, unless the research oriented reliable supporting certification is made available. The reinforcement materials are highly hygroscopic, the matrix material provides protection to the reinforcement. When the parts made of composite materials are exposed to environment, water molecules travel along the reinforcement and cause damage to the interfacial bonding, further the performance of the composite laminate get effected. In this scenario, the investigation related to this aspect requires quantitative assessment which is carried out with accelerated simulation of the real time situation to provide a scope to chacterization of Glass fibre reinforced polymer composite (GFRP) laminates subjected to variable environmental conditions. This investigation was to study the effect on weight gain and mechanical property of GFRP laminate subjected to different environmental conditions. The test results reviled that remarkable reduction in tensile property and moisture absorption for samples in water absorbed more moisture than NaOH and salt water.
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