PROCESS-RELATED DEFECTS AND HIGH-STRAIN RATE IMPACT DAMAGE EVALUATION OF RESIN TRANSFER MOLDED COMPOSITES THROUGH A COMPREHENSIVE NDE APPROACH
U. K. Vaidya, K. Fotedar, H. Mahfuz, and S. Jeelani Center of Excellence for Advanced Materials, Tuskegee University, Tuskegee, AL 36088, USA
Keywords: NDT, Composite, Impact Damage, Defect, Rasin Transfer Molding
ABSTRACT
Composite Armored Vehicles (CAV) utilize light weight, easily deployable, agile and survivable ballistic damage-resistant fabric composite constructions in the upper and lower hull, crew capsule, rear engine bulkhead, ramp and sidewalls. These constructions are typically thick-section monocoques and/or hybrids with ceramic tile inserts in polymeric skins, processed using resin transfer molding (RTM). In recent years, RTM is gaining considerable attention as a low-cost, near net-shape and environmentally clean composites manufacturing alternative. Given the numerous process and material parameters involved in RTM, the composites manufacturing through this technique suffer anamolies in the through-the-thickness and in-plane directions, which in turn affects their ballistic performance. In this article, nondestructive evaluation (NDE) studies are performed in resin transfer molded composites S-2 glass/vinyl ester epoxy composites at two stages;
for insitu monitoring of the resin flow through the fibrous preform in a closed-mold environment (fiber wetting, race tracking, improper resin distribution), and
post-ballistic impact damage assessment.
For the process-evaluation, a combination of dielectric cure monitoring, heat sensor, and ultrasonic NDE has been applied to gather a comprehensive information on the influence of process (injection pressure, resin viscosity, cure temperature, mold release, additives, etc. ) and material (fabric type, weave architecture, number of tows, geometry of undulations etc. ) parameters. High-strain rate test using a tensile Hopkinson's bar setup have been conducted on the RTM composites at different strain levels. The mechanisms of damage initiation, progression and final failure have been investigated in light of ultrasonic, accost-ultrasonic and vibration NDE parameters. The results from this investigation will be presented, emphasizing mainly on the NDE studies.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 4, pages 2443 - 2446 Publisher:Ashgate Publishing Company
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