Characterization of Environmentally Conditioned Quartz–Cyanate Ester Composites for Radome Applications

Abstract

Because quartz–cyanate ester (QCE) composites are employed to fabricate missile and aircraft radomes, retaining their structural and electromagnetic (EM) integrity after prolonged exposure to environmental stresses is essential for long-term deployment as radar protectors. Therefore, in this study, QCE composite samples were subjected to environmental conditioning tests, namely, transient temperature (transition from −67 to 145 °C), high-temperature storage (cycling between 35 and 85 °C), thermal shock (cycling between −55 and 100 °C), fluid contamination (immersion in mineral and turbine oils), and humidity cycles (conditioning at 30 °C and 85% RH), to observe the effect of conditioning on the physical, morphological, thermal, mechanical, and dielectric properties of composites. Interfacial damage was observed in all the conditioned samples. Samples after fluid immersion test were found to have the highest deviation in properties compared to unconditioned ones. Fluid diffusion led to higher surface crack width, lower impact damaged area, and higher EM energy dissipation (higher dielectric loss tangent). High-temperature storage tested samples had the highest surface crack intensity, while humidity cycles caused matrix plasticization, resulting in lower density and thermal conductivity values. A high degree of postcuring in thermally shocked samples resulted in brittleness of cyanate ester, leading to an increase in density and impact damaged area. Although a slight degree of damage is reported, the change in QCE composite properties postconditioning is not significant enough to prevent its application as uncoated radome materials, except for rain erosion at 150 m/s.

Adhesion and tribological characteristics of modified polyurethane coating on composite substrate

“…It is also evident that the coating surface was not completely damaged in certain regions (i.e. at regions-1 the polyurethane coat is clearly visible, in regions-2 epoxy coating is visible after the erosion of the polyurethane top coat), which shows that the coating is intact with the composite surface and exhibit an extent of viscoelastic recovery indicating material erosion durability [15,16].…”

“…It is also evident that the coating surface was not completely damaged in certain regions (i.e. at regions-1 the polyurethane coat is clearly visible, in regions-2 epoxy coating is visible after the erosion of the polyurethane top coat), which shows that the coating is intact with the composite surface and exhibit an extent of viscoelastic recovery indicating material erosion durability [15, 16].

Figure 14 (a) The surface of the coated composite after 1 h of rain erosion test (b) After 2 h of rain erosion test and region 1 indicates no damage to the coating; region 2 indicates erosion of PU top coat (epoxy primer is intact); region 3 indicates erosion of PU top coat and epoxy primer (only glass fibres are visible).

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“…For surface wettability and improving adhesion and bond strength, various surface treatment techniques have been addressed in recent years [6][7][8][9][10][11]. Adhesion properties (cross-cut, pull-off adhesion and peel strength), corrosion resistance, water immersion studies, tribological performance (taber abrasion and pin-on-disc), tensile properties, DSC, FTIR and TGA studies, WCA were investigated and reported by a few authors [12][13][14][15][16][17][18][19][20][21][22].…”

Preparation and Appraisal of High‐Modulus Resin‐Based Composites Reinforced by Silica‐Coated Multi‐Walled Carbon Nanotubes

“…As a high performance thermosetting resin, cyanate ester resin (CE) features outstanding mechanical properties, high temperature resistance, dimensional stability and dielectric properties [12–16] . It also possesses processing properties similar to epoxy resin, presenting good infiltration and lay‐up with fiber reinforced materials, and can be molded by advanced processes such as winding, hot press cans and resin transfer molding [17–23] .…”

“…As a high performance thermosetting resin, cyanate ester resin (CE) features outstanding mechanical properties, high temperature resistance, dimensional stability and dielectric properties. [12][13][14][15][16] It also possesses processing properties similar to epoxy resin, presenting good infiltration and lay-up with fiber reinforced materials, and can be molded by advanced processes such as winding, hot press cans and resin transfer molding. [17][18][19][20][21][22][23] Whereas cyanate resin curing reaction is time consuming and requires high temperature, [24] which sets several hurdles to the processing, and the demanding performance requirements of aerospace satellite structural materials due to the increased crosslink density of the system after curing, resulting in insufficient material toughness.…”