Armand F. Lewis

Surface flocking as a possible anti-biofoulant

Abstract Fouling organisms create difficulties for aquaculturists by weighing down materials and constricting net openings. Research on anti-fouling began with toxic chemicals and has more recently moved to non-toxic methods focusing on settlement cues of invertebrates. Surface texture is one physical cue to which both invertebrate larvae and algal spores respond. Flocking is a process that makes smooth surfaces fibrous by adding electrostatically charged fibers to an adhesive coated surface. To test the effects of flocking on recruitment, polyvinyl chloride (PVC) plastic panels that were untreated, primed with adhesive, and flocked were deployed subtidally in the Westport River estuary, Westport, MA, USA for 1 month exposure periods in 1998. Species composition was determined and compared among treatments. To test for effects only on barnacle recruitment, wood panels were deployed subtidally in Clarks Cove, New Bedford, MA and PVC panels were deployed in the subtidal of Eel Pond, Woods Hole, MA; Cape Cod Canal at Massachusetts Maritime Academy, Bourne, MA; and in Point Judith Pond, RI. Flocking surfaces resulted in lower recruitment of green and brown algae, but had no effect on red algae. For invertebrates, flocking was effective at inhibiting the recruitment of encrusting animals, had no effect on stoloniferous animals, and increased the abundance of tube-building polychaetes and solitary ascidians.

Manufacture of Thick Cross-Section Composites Using a Pre-Catalyzed Fabric Technique

The development of a technique is reported for the manufacture of thick unsaturated polyester matrix resin composites using pre-catalyzed glass fabric. Composites over 2 cm thick using glass fabric that was pre-catalyzed (sized) with benzoyl peroxide were compared to composites made using conventional premixed catalyst and resin compounds. The pre-catalyzed fabric is shown to result in reduced internal temperatures during curing. This allows for the construction of thick fiber reinforced composite materials that do not suffer thermal degradation during the curing process. Mechanical testing of prepared thick composites demonstrated that the pre-catalyzed glass fabric composites were significantly stronger than conventionally prepared composites. The center regions of pre-catalyzed composites were about 80% stronger under tension, 25% stronger in compression and 35% stronger under shear than those of conventionally prepared composites of the same thickness. The pre-catalyzed composites were also more uniformly consolidated. Previous work aimed at the manufacture of thick composites has utilized controlled curing by use of expert systems, local resistance heating within the composite or the addition of chemical inhibitors. A method for staged curing has also shown considerable promise. None of these methods, however, has enabled high volume production of high quality thick composites. This paper presents the results of a new method for manufacture of thick composites based on a pre-catalyzed fabric technique.

Fabrication and Mechanical Characterization of Jute Fiber/Epoxy Laminar Composites

Alkali and Silane surface treatments based off of work published previously (J Appl Polym Sci 71(4):623–629, 1999; Polym Eng Sci 49(7):1253–1272, 2009; Mater Sci Eng A 508(1–2):247–252, 2009) were applied to plain weave and unidirectional jute fabric to improve epoxy compatibility and reduce moisture affinity. Efficacy of treatments was proven with the use of wicking tests. Studies performed on the hand-layup method showed unacceptable void content. Laminated jute/epoxy composites were fabricated using Vacuum Infusion to create void-free samples. This process was improved through optimization for use with jute and the addition of a pre-compaction step to increase fiber volume fraction from 25 % to a maximum of 40 %. Mechanical testing on composites fabricated with raw and treated jute fabrics showed a 300 % increase in elastic modulus for treated jute fabric over neat epoxy resin. Moisture absorption testing (ASTM D570) showed a significant improvement in moisture resistance for silane-treated fabrics.

Impact force loss behavior of flocked surfaces

The impact force loss behavior of flocked energy absorbing materials (FEAM) was experimentally studied in the context of double-side flocked FEAM element layered structures. A ball drop test determined the force loss per cent (FL%) properties of various assembled panels. This study showed that: (a) FEAM layers are most effective when used in multiple layer configurations. (b) When fabricating multi-layer two-side flocked FEAM layer configurations, a film or fabric divider sheet should be placed between adjacent flocked layers to prevent the flocked fibers from intermeshing with each other during compressional deformation. (c) FEAM elements perforated with 6.4 mm (¼”) diameter holes, 12.7 mm (½”) off staggered centers, exhibit a higher FL% per areal density compared to non-perforated FEAM panels. (d) Promising improvements in FL% properties are found by sandwiching either foam or spacer fabric between two FEAM layers. These three-layer structures are found to have higher FL% values than individual foam or spacer fabric components. A possible synergistic effect might be operating. (e) Low strain rate (5 and 50 mm/min) compressional load deflection rate data on combination FEAM/ vinyl nitrile foam/FEAM layers have shown that the initial ‘hump’ in the foam’s stress–strain curve is eliminated. FEAM layers and their foam and spacer fabric combinations should lead to creating effective impact energy absorbing pads for sport, military and civil servant applications.