Thermoplastic Composite Cylinders for Underwater Applications

Abstract

A study of thermoplastic matrix composites has been performed to investigate their use in underwater applications such as oceanography, submarine, and sub-sea offshore structures. This article first presents six candidate materials. Results from simple mechanical and seawater aging screening tests on flat specimens are then described. Glass/epoxy and carbon/epoxy composites are used as reference materials. Two materials emerged from this process, glass/PEI and carbon/PEEK. Cylinders of both were manufactured and subjected to hydrostatic pressure tests, and results are compared to those for glass/epoxy and carbon/epoxy cylinders of similar geometry. The carbon/PEEK material appeared most promising. It resisted pressures in excess of 90 MPa and was retained for damage tolerance assessment studies. Drop weight impact damage zones were smaller in carbon/PEEK than carbon/epoxy for the same impact energies but the loss in residual collapse strength was more rapid in the thermoplastic composite. This was attributed to a change in failure mode, impact damage initiated a local buckling failure.

About the impact behavior of woven-ply carbon fiber-reinforced thermoplastic- and thermosetting-composites: A comparative study

“…Impact-induced damage is particularly critical because it drastically reduces the residual mechanical properties of the structure [2][3][4]. Very few authors have compared the impact behavior of TS-and TP-based composite structures, and their effects on residual strength [5][6][7][8][9][10], as well as the damage tolerance of UD-ply and woven-ply laminates [10][11][12]. It appears from literature that TP-based composites display a better resistance to the impact damage than epoxy-based composites.…”

Carbon/polyamide 6 thermoplastic composite cylinders for deep sea applications

“…Based on experience [21], high levels of through thickness attenuation (over 20dB) usually correspond to the presence of significant voids. On the other hand, low levels of attenuation (below 10dB) indicate a good cylinder quality.…”

“…A study in the USA on Carbon/PEEK (C/PEEK) was described by Gruber et al [20]. At Ifremer, studies were performed from 2000 onwards, to examine different thermoplastic matrix polymers for underwater cylinders [21]. These tubes were supplied by American companies, first small diameter (55mm, 6mm wall thickness) then larger (175 mm diameter, 20 mm thick).…”

Composite Failures: A Comparison of Experimental Test Results and Computational Analysis Using XFEM

“…For example, composite cylinders designed for underwater applications are first subjected to rigorous impact and implosion testing to determine their structural efficacy. 1,2 The design of composite structures that are exposed to extreme loading events requires that attention be paid to material failure and damage absorption characteristics. 3 Material properties can be derived from testing of circular tubes, and the analytical solutions can be derived.…”