A New Strengthening Process for Carbon-Fiber-Reinforced Thermoplastic Polyphenylene Sulfide (CFRTP-PPS) Interlayered Composite by Electron Beam Irradiation to PPS Prior to Lamination Assembly and Hot Press

Abstract

Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircraft materials. For maximum safety, the goal is to increase Charpy impact strength (auc) of a carbon-fiber-reinforced thermoplastic polyphenylene sulfide polymer (CFRTP-PPS) composite for potential application to commercial aircraft parts. The layup was three cross-weave CF plies alternating between four PPS plies, [PPS-CF-PPS-CF-PPS-CF-PPS], designated [PPS]4[CF]3. To strengthen, a new process for CFRP-PPS was employed applying homogeneous low voltage electron beam irradiation (HLEBI) to both sides of PPS plies prior to lamination assembly with untreated CF, followed by hot press under 4.0 MPa at 573 K for 8 min. Experimental results showed a 5 kGy HLEBI dose was at or near optimum, increasing auc at each accumulative probability, Pf. Optical microscopy of 5 kGy sample showed a reduction in main crack width with significantly reduced CF separation and pull-out; while, scanning electron microscopy (SEM) and electron dispersive X-ray (EDS) mapping showed PPS adhering to CF. Electron spin resonance (ESR) of a 5 kGy sample indicated lengthening of PPS chains as evidenced by a reduction in dangling bond peak. It Is assumed that 5 kGy HLEBI creates strong bonds at the interface while strengthening the PPS bulk. A model is proposed to illustrate the possible strengthening mechanism.

Increasing Bending Strength of Polycarbonate Reinforced by Carbon Fiber Irradiated by Electron Beam

“…Direct HLEBI activation of 0.22 Mgy to CF plies before being put together with PP plies (the same layup as above, but with PP) slightly increased the bending strength of a [PP] 4 [CF] 3 interlayered composite, by approximately 6% [37]. For an interlayered composite composed of nine CF plies alternating between 10 TP polyamide plies designated [TPA] 10 [CF] 9 , when applying HLEBI, increasing acceleration voltage from the usual 170 kV [32,36,37] to 250 kV for the finished samples, the impact strength could be increased by 25 to 27% compared to the untreated sample [38].…”

“…It follows that low-voltage electron beam irradiation (HLEBI) has been used to improve the mechanical properties of numerous materials [2,[28][29][30][31][32][33][34][35][36][37][38]. For the PC macromolecule, HLEBI generates dangling bonds at bonding sites with the lowest dissociation energies, as shown in Figure 1.…”

“…This is carried out with the ultimate aim of fabricating layered CF/PC As far as the authors know, there have been few or no studies on applying HLEBI to strengthen interlayered CFRTP structures. Therefore, our research has focused on strengthening alternating CF-TP interlayered samples by applying HLEBI prior to assembly and heating by hot press to either the TP plies [36] or CF plies [37], or after molding to finished samples [38] to raise the mechanical properties. For an interlayered composite of four plies of TP polyphenylene sulfide and three plies of CF with layup PPS-CF-PPS-CF-PPS-CF-PPS labeled here as [PPS] 4 [CF] 3 , HLEBI of 5 kGy applied to both sides of PPS plies prior to assembly and hot press was found to raise impact values, particularly those of the lowest strength at low P f , showing that an increase in safety and reliability is possible [36].…”

“…Therefore, our research has focused on strengthening alternating CF-TP interlayered samples by applying HLEBI prior to assembly and heating by hot press to either the TP plies [36] or CF plies [37], or after molding to finished samples [38] to raise the mechanical properties. For an interlayered composite of four plies of TP polyphenylene sulfide and three plies of CF with layup PPS-CF-PPS-CF-PPS-CF-PPS labeled here as [PPS] 4 [CF] 3 , HLEBI of 5 kGy applied to both sides of PPS plies prior to assembly and hot press was found to raise impact values, particularly those of the lowest strength at low P f , showing that an increase in safety and reliability is possible [36]. Direct HLEBI activation of 0.22 Mgy to CF plies before being put together with PP plies (the same layup as above, but with PP) slightly increased the bending strength of a [PP] 4 [CF] 3 interlayered composite, by approximately 6% [37].…”