Homogeneous Low Voltage Electron Beam Irradiation Research Articles

A New Double-Step Process of Shortening Fibers without Change in Molding Equipment Followed by Electron Beam to Strengthen Short Glass Fiber Reinforced Polyester BMC.

It is vital to maximize the safety of outdoor constructions, airplanes, and space vehicles by protecting against the impact of airborne debris from increasing winds due to climate change, or from bird strikes or micrometeoroids. In a widely-used compression-molded short glass fiber polyester bulk-molded compound (SGFRP-BMC) with 55% wt. CaCO3 filler, the center of the mother panel has lower impact strength than the outer sections with solidification texture angles and short glass fiber (SGF) orientations being random from 0 to 90 degrees. Therefore, a new double-step process of: (1) reducing commercial fiber length without change in molding equipment; followed by a (2) 0.86 MGy dose of homogeneous low-voltage electron beam irradiation (HLEBI) to both sides of the finished samples requiring no chemicals or additives, which is shown to increase the Charpy impact value (auc) about 50% from 6.26 to 9.59 kJm-2 at median-accumulative probability of fracture, Pf = 0.500. Shortening the SGFs results in higher fiber spacing density, Sf, as the thermal compressive stress site proliferation by action of the CTE difference between the matrix and SGF while the composite cools and shrinks. To boost impact strength further, HLEBI provides additional nano-compressive stresses by generating dangling bonds (DBs) creating repulsive forces while increasing SGF/matrix adhesion. Increased internal cracking apparently occurs, raising the auc.

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

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.

Advances in Titanium/Polymer Hybrid Joints by Carbon Fiber Plug Insert: Current Status and Review.

A literature review of up-to-date methods to strengthen Ti/carbon-fiber-reinforced polymer (CFRP) hybrid joints is given. However, there are little or no studies on Ti/CFRP joints by carbon fiber plug insert, which takes advantage of the extremely high surface adhesion area of ~6 μm CFs. Therefore, we cover the current status and review our previously published results developing hybrid joints by a CF plug insert with spot-welded Ti half-lengths to enhance the safety levels of aircraft fan blades. A thermoset Ti/CF/epoxy joint exhibited an ultimate tensile strength (UTS) of 283 MPa when calculated according to the rule of mixtures (RM) for the CF cross-section portion. With concern for the environment, thermoplastic polymers (TPs) allowed recyclability. However, a drawback is easy CF pull-out from difficult-to-adhere TPs due to insufficient contact sites. Therefore, research on a novel method of homogeneous low voltage electron beam irradiation (HLEBI) to activate a bare CF half-length prior to dipping in a TP resin was reviewed and showed that the UTS by the RM of Ti/EBCF/acrylonitrile butadiene styrene (ABS) and Ti/EBCF/polycarbonate (PC) joints increased 154% (from 55 to 140 MPa) and 829% (from 30 to 195 MPa), respectively, over the untreated sample. The optimum 0.30 MGy HLEBI prevented CF pull-out by apparently growing crystallites into the TP around the CF circumference, raising the UTS amount closer to that of epoxy.

An Aluminum/Polycarbonate (Al/PC) Joint by Homogeneous Low Voltage Electron Beam Irradiation (HLEBI) to PC Prior to Lamination Assembly and Hot-Press

An Aluminum/Polycarbonate (Al/PC) Joint by Homogeneous Low Voltage Electron Beam Irradiation (HLEBI) to PC Prior to Lamination Assembly and Hot-Press

Effects of Electron Beam Irradiation on Shear Strength of Laminated Sheet of Bio-Adaptable Polydimethylsiloxane (PDMS) and Polytetrafluoroethylene (PTFE) with Fracture Toughness

Effects of homogeneous low voltage electron beam irradiation (HLEBI) without glue on the adhesive force of tensile shear strength (¸B) at each shear probability (Ps) of laminated PDMS/PTFE sheets of polydimethylsiloxane (PDMS) and Polytetrafluoroethylene (PTFE) were investigated. AlthoughB of shear at low and mid Ps of 0.06 and 0.50 were 0.015 and 0.04MPa before treatment, 0.22MGy-HLEBI enhanced theB up to the largest values of 0.098 and 0.11MPa of the laminated sheets, respectively. They were more than 6 and 3 times larger than those before treatment. On the other hand, additional HLEBI apparently reduced theB of laminated sheets irradiated at more than 0.43MGy as usual radiation damages. The effects of HLEBI on adhesion force ofB can be explained by the enhancement of cross-linking at PDMS/PTFE interface. When HLEBI cut the chemical bonds and generated active terminated atoms with dangling bonds at cross-linked PDMS and PTFE polymers, strengthening the bonding force of cross-linking polymers was induced by the chemical bonding and intermolecular attractive force. (doi:10.2320/matertrans.MBW201411)

Cost Cut with High Impact Value of Sandwich Structure with Inexpensive ABS Core between High Strength CFRP Laminate Plies

Sandwich structural composites (CFRP/ABS/CFRP) of inexpensive acrylonitrile butadiene styrene (ABS) cores (2.0 mm thickness) between carbon fiber reinforced epoxy (CFRP) laminate plies (2.5 mm thickness) were suggested and prepared, since the materials cost of ABS resin was about 8% that of CFRP. Although Young’s modulus of CFRP/ABS/ CFRP is slightly smaller than that of CFRP, Charpy impact value (auc) of the CFRP/ABS/CFRP approximately corresponded to that of CFRP composite. Furthermore, applying homogeneous low voltage electron beam irradiation (HLEBI) to both side surfaces improved the auc of CFRP/ABS/CFRP. Since the irradiated depth estimated is about 119 ± 23 μm, the irradiation effects mostly acted within the CFRP sheet. The Charpy impact value (auc) of CFRP/ABS/CFRP at mid-fracture probability (Pf ) after irradiation at 0.30 MGy (kJg_1) was approximately 25 % higher than that before treatment. It was approximately equal to that for irradiated CFRP and was also about 20% higher than that of the CFRP before treatment. Although the use of ABS resin as the core reduced other mechanical properties of tensile and bending, the materials cost of CFRP/ABS/CFRP was approximately 25 % that of CFRP. Thus, the sandwich structural composites of CFRP/ABS/CFRP could be utilized for daily articles.

EB-Irradiation Induced Strengthening of Carbon Fiber Reinforced Thermoplastic Polymers

Carbon fiber reinforced polymers (CFRP), which are typical composite materials, and have been applied as light structural materials with high strength [1, 2]. The further strengthening has been always expected to develop high speed transports with small energy consumption. Although influences of electron beam (EB) irradiation with high energy on the fracture toughness of carbon cross of carbon fibers in thermo-hardened epoxy resin matrix (thermo-hardened CFRP) have been often reported [3], no one has succeeded the strengthening of CFRP irradiated by electron beam. On the other hand, the homogeneous low voltage electron beam irradiation (HLEBI) often induces not only the hardening, high wear resistance and sterilization for practical use of polymer, but also the mist resistance [4–6]. In addition, the irradiation has improved not only the bending fracture strain of carbon fiber [7, 8], but also the deformation resistivity, strength and fracture strain on static tensile test [9]. In our recent research, it has succeeded that the EB-irradiation also enhances the fracture stress and fracture strain of static bending test of thermo-hardened CFRP [10]. Furthermore, the improvement of impact value of thermo-hardened CFRP by EB-irradiation has been also reported to apply to high-speed transports [11]. However, the production rate of thermo-hardened CFRP has been serious problem in mass production.

Improvement of Bending Modulus and Impact Value in Injection-Molded Short Carbon Fiber Reinforced Polyetheretherketone with Homogeneous Low-Voltage Electron Beam Irradiation

In short carbon fiber reinforced polyetheretherketone (SCFRP-PEEK) composites, carbon fibers and PEEK matrix typically exhibit a weak adhesive force at the interface. However, applying 0.43MGy dose of homogeneous low-voltage electron beam irradiation (HLEBI) was apparently shown to improve not only the bending modulus (Ef) 65.5% at the median-ranked cumulative probability evaluated as a distribution function (PE = 0.50) from 6.7 to 11.1GPa, but also Charpy impact fracture value (auc) 17.5% at median-ranked cumulative probability (Pf = 0.50) from 16.6 to 19.5kJm ¹2 . The 0.43MGy HLEBI dose also remarkably improved the statistically lowest Charpy impact value as at Pf = 0 calculated by 3-parameter Weibull equation 80.0% from 8.0 to 14.4kJm ¹2 . Penetration depth, Dp of the HLEBI was calculated to be 153 to 226µm (3­11%) into both side surfaces. SEM results of the HLEBI-treated Charpy impact sample fracture surfaces show more matrix sticking to the fibers and more matrix being held between fibers than the untreated increasing pullout resistance. The HLEBI appears to assist in strengthening the typically weak bonding between the carbon fiber and PEEK matrix improving mechanical properties. [doi:10.2320/matertrans.M2013455]

Adhesive Resistance to Peeling Force of PTFE/PDMS Laminated Sheet Assisted by Homogeneous Low Voltage Electron Beam Irradiation at 77 K

The effects of homogeneous low voltage electron beam irradiation (HLEBI) under liquid nitrogen on the adhesive force of peeling ( o Fp )a t accumulative probability of peeling (Pp) of laminated PTFE/PDMS sheets of polytetrafluoroethylene (PTFE) and polydimethylsiloxane (PDMS) at 77K were investigated without glue. o Fp values at each Pp of PTFE/PDMS laminated sheets irradiated of 0.04 to 0.43MGy at both 77 and 298K exceed the corresponding values of the untreated samples. Although 298K-HLEBI with 0.04MGy improves o Fp value at low Pp (0.06), 77K-HLEBI didn’t improve it. On the contrary, the 77K-HLEBI with 0.22MGy apparently enhanced the o Fp at low-Pp of 0.06. It is higher than that of 298K-HLEBI with 0.22MGy. Furthermore, the operation dose range at high o Fp value of more than 1.5Nm ¹1 at low Pp (0.06) at 77K, indicator of high industrial reliability of production process, was 0.33MGy, which was more than 3.7 times broader than that at 298K. Based on the 3-parameter Weibull equation, the lowest o Fp value at Pp of zero (Fs) could be estimated. The 0.22MGy-HLEBI at 77K apparently improves the Fs, which was higher than that 0.22MGy-HLEBI at 298K. Decreasing the irradiation temperature from 298 to 77K controlled the rapid adhesion and rapid decay of adhesion at low-Pp, which were mainly caused by the low forming ability of dangling bonds induced by strong apparent bonding force, which is related to decreasing atoms vibration energy. Since the 0.22MGy-HLEBI at 77K controlled the recovery of dangling bonds and generated the chemical bonds, the strong adhesive force of PTFE/PDMS treated by 0.22MGy-HLEBI at 77K could be explained. Therefore, HLEBI under liquid nitrogen was useful tool for quick strong PTFE/PDMS lamination with sterilization for bio-adaptable application. [doi:10.2320/matertrans.MAW201416]

J045021 電子線照射処理による厚肉フッ素樹脂と異種高分子の接着([J045-02]知的材料・構造システム(2))

Fluororesin, which exhibits high wear resistance as well as high strength and fracture toughness, can be applied to artificial blood vessel. However, the fluororesin is difficult to glue. To laminate the fluororesin and different polymers of polydimethylsiloxane (PDMS) and polyethylene (PE), the new treatment of hot-press after homogeneous low voltage electron beam irradiation (HLEBI) was innovated without glue. The adhesive force (^oF_p) of peeling resistance of laminated sheets of fluororesin and different polymers of PDMS and PE was evaluated. In order to evaluate the influence of the hot- pressing after HLEBI on ^oF_p, electron spin resonance (ESR) signals related to dangling bonds were observed. When HLEBI cut the chemical bonds and generated dangling bonds with nonbonding electrons at terminated atoms in monomers of fluororesin, PDMS and PE, the nonbonding electrons induced not only the intermolecular attractive force but also chemical bonding. Therefore, the hot- pressing after HLEBI was a useful tool for quick lamination of fluororesin and different polymers of PDMS and PE without glue.

Electrical Conductivity Enhancement of PTFE (Teflon) Induced by Homogeneous Low Voltage Electron Beam Irradiation (HLEBI)

Electrical conductivity (·) enhancement, control, aging stability, and linear relation between · and reciprocal temperature (1/T) in PTFE (Teflon) had been examined by homogeneous low potential electron beam irradiation (HLEBI). Irradiations up to 0.432MGy were found to raise the · of PTFE more than two orders of magnitude. In addition, control of electron movement or Fermi level by HLEBI on polymers seems possible since at low HLEBI levels up to 0.216MGy, a strong dependence on · was observed. Aging stability investigation showed the saturated conductivities at 10 6 s( ·s) (2.5 © 10 ¹16 and 3.6 © 10 ¹15 Sm ¹1 ) obtained at EB doses of 0.0432 and 0.432MGy, respectively were approximately 4.9 and 70.6 times higher than · of untreated PTFE (5.1 © 10 ¹17 Sm ¹1 ). Although the aging initially reduced the · of irradiated samples, ·s were remarkably higher than the untreated. For example, the lower dose 0.0432MGy samples decayed significantly, but its ·s value (2.5 © 10 ¹16 Sm ¹1 ) was still about 490% above untreated condition at 5.1 © 10 ¹17 Sm ¹1 . ESR (electron spin resonance) measurements showed aging for 10 6 s only slightly reduced the peak intensity of irradiated PTFE. This indicated the charge carriers generated did not easily decay. Results agree with the literature where PTFE was irradiated with VUVand radicals such as CF3 + did not substantially decay with aging. Since the slopes of linear relationships between logarithmic electrical conductivity (ln·) and reciprocal temperature (1/T) of all PTFE samples irradiated were approximately equal to that before treatment from 303 to 375K, HLEBI didn’t convert the · system. The small irradiation dose of 0.0432MGy raised the electrical conductivity at room temperature. At higher temperatures above ³375K, the 0.0432 and 0.432MGy-HLEBI generated drops in conductivity ·. When unstable dangling bonds with isolated radicals at terminated sites are assumed to be formed in irradiated PTFE, the · recovery by heating to 424K as well as high · of irradiated PTFE could be explained. HLEBI probably generated dangling bonds in the form of radicals acting as acceptors to carry charge. Since a chemical dopant was not needed to act as a charge carrier, HLEBI could probably be an attractive method to attain homogeneous doping of organic films. [doi:10.2320/matertrans.M2011273]

Effects of Electron Beam Irradiation on Adhesive Force of Laminated Sheet of High Strength Polytetrafluoroethylene (PTFE) and Bio-Adaptable Polydimethylsiloxane (PDMS)

The effects of homogeneous low voltage electron beam irradiation (HLEBI) on the adhesive force of peeling ( o Fp) and peeling resistance energy ( o Ep) at each peeling probability (Pp) of laminated sheets of bio-adaptable polydimethylsiloxane (PDMS) with transparency and high strength polytetrafluoroethylene (PTFE) with sterilization were investigated without glue. Although both o Fp and o Ep of peeling at low Pp of 0.06 were 0.2N·m ¹1 and 4.0 © 10 ¹2 J·m ¹1 before treatment, HLEBI enhanced the o Fp and o Ep up to the largest values of 11N·m ¹1 and 2.2J·m ¹1 of the laminated sheets irradiated at 0.13MGy, respectively. They were more than 55 times larger that those before treatment. On the other hand, additional HLEBI reduced the o Fp and o Ep of laminated sheets irradiated at more than 0.22 to 0.86MGy, although they were apparently larger than those before treatment. In order to investigate the influence of EB irradiation on o Fp and o Ep, electron spin resonance (ESR) signals related to dangling bonds were observed. When HLEBI cut the chemical bonds and generated dangling bonds with nonbonding electrons in PTFE and PDMS, the electrons induced the chemical bonding and intermolecular attractive force. HLEBI induced strong adhesive force of laminated sheets was explained by the discussion. Therefore, it was concluded that HLEBI was a useful tool for quick lamination of bio-adaptable PDMS and high strength PTFE. [doi:10.2320/matertrans.M2012124]

Tensile Properties of Optical Fiber Irradiated by Low Voltage Electron Beam Homogeneously

Homogeneous low voltage electron beam irradiation (HLEBI) with small dose of 0.30 to 1.17 MGy enhanced the elasticity indicated by the initial and maximum slope values of stress–strain curves ((dσ/dε)i and (dσ/dε)max) of 250 µm diameter optical fiber (OF), which was constructed with both core (10 µm diameter) and clad (125 µm diameter) silica glasses covered with acryl-urethane sheath (62.5 µm thickness). The highest (dσ/dε)i and (dσ/dε)max values of 5.3 and 5.9 GPa, which were about 10 and 20% higher than those (4.8 and 4.9 GPa) before irradiation, were found at 0.104 MGy, respectively. Moreover, remarkable effects of HLEBI of 0.65 MGy on both tensile strength (σf) and fracture strain (εf) of OF were obtained at each fracture probability (Pf) value. Since HLEBI also enhanced the density of dangling bonds of each material of OF, effects of compressive stress on pull-out resistance and elasticity enhancements of fiber and sheath probably occurred. Thus, 0.64 MGy-HLEBI enhanced the (dσ/dε)i and (dσ/dε)max as well as εf, resulting in enhancement of σf of OF.

Effects of Electron Beam Irradiation on Charpy Impact Value of Short Glass Fiber (GFRP) Samples with Random Distribution of Solidification Texture Angles from Zero to 90 Degrees

Compression-molded short-fiber GFRP-BMC panels have random distribution of solidification texture angles from zero to 90 degrees in the center of the mother panels. Hence, there is significantly lower impact strength in the panel center than in the outside. However, experimental results showed homogeneous low voltage electron beam irradiation (HLEBI) applied to the center region apparently enhances the Charpy impact values (auc) 5 to 25%. Fracture mechanism was observed to convert at auc > ³5.4­6.7kJ·m ¹2 from clean to secondary microcrack proliferation and/or bends near the main crack, with increasing fracture surface area as auc increased. SEM observation revealed 0.86MGy HLEBI treated GFRP had much more polymer adhering to fibers than the untreated. This increased matrix adhesion can be explained by electron spin resonance (ESR) peaks indicating dangling bonds are generated creating repulsive forces between outer shell electrons in the polymer matrix, apparently exhibiting increased compressive stress on the fibers increasing adhesion force. Moreover, the lone pair electrons generated in the matrix may have bonded with the fibers more efficiently. For these reasons, increased fiber-matrix adhesion seen in the 0.86MGy samples appears to assist for more internal cracking, increasing resilience to impact of the GFRP-BMC, raising the auc. [doi:10.2320/matertrans.M2012145]

Effects of Electron Beam Irradiation on Peeling Resistance of Laminated Sheet of High Strength Polypropylene (PP) and Bio-Adaptable Polydimethylsiloxane (PDMS)

The effects of homogeneous low voltage electron beam irradiation (HLEBI) on the adhesive force (maxFp, oFp and minFp) and its energy (oEp) of peeling resistance of laminated sheets of bio-adaptable polydimethylsiloxane (PDMS) with transparency and high strength polypropylene (PP) without glue but with sterilization were investigated. Although both maxFp and oEp were 14 N·m−1 and 0.21 J·m−1 before treatment, HLEBI enhanced the maxFp and oEp up to the maximum values of 34 N·m−1 and 0.89 J·m−1 of the laminated sheets irradiated at 0.30 MGy, respectively. On the other hand, additional HLEBI reduces the maxFp, oFp, minFp and oEp of laminated sheets irradiated at more than 0.22 to 0.65 MGy, although they were apparently larger than those before treatment. In order to investigate the influence of EB irradiation on maxFp, oFp, minFp and oEp, electron spin resonance (ESR) signals related to dangling bonds were observed. When HLEBI generated dangling bonds in PP and PDMS, the dangling bonds probably served as reactive and bonding sites for each polymer at the interface. Consequently, HLEBI from 0.22 to 0.65 MGy reinforced the maxFp, oFp, minFp and oEp of the laminated sheets. Therefore, it was concluded that HLEBI was probably a useful tool for quick lamination of bio-adaptable PDMS and high strength PP.

Effects of Electron Beam Irradiation on Elasticity of CFRTP (CF/PEEK)

Homogeneous low voltage electron beam irradiation (HLEBI) improved the elasticity indicated by both flexural modulus (Ef ) and the maximum slope value (ðd�= dÞmax) of the bending stress–strain curve of carbon fiber reinforced thermoplastic polyetheretherketone (CFRTP) composite sheets with 0.50 mm thickness, although the penetration depth estimated was from 0.14 to 0.21 mm on both side surfaces. HLEBI remarkably enhanced both Ef and ðd�= dÞmax. The Ef at middle cumulative probability (PE) of 0.50 for CFRTP irradiated at 0.30 MGy (kJg � 1 ) was 3.3 GPa, which was 27% higher (2.6 GPa) than for CFRTP before irradiation. Moreover, ðd�= dÞmax at middle cumulative probability (PE ¼ 0:50) was more than 4.9 GPa for CFRTP irradiated at 0.30 MGy. The interfacial friction force, as well as the strengthening of both carbon fiber and polyetheretherketone probably contributed to the HLEBI effects to enhance both Ef and ðd�= dÞmax in the CFRTP. [doi:10.2320/matertrans.MBW201005]

High Impact Value of CFRP/ABS/CFRP Sandwich Structural Composite Homogeneously Irradiated with Low Voltage Electron Beam

Homogeneous low voltage electron beam irradiation (HLEBI) improves the Charpy impact value (auc) of sandwich structural composite (CFRP/ABS/CFRP) of acrylonitrile butadiene styrene (ABS) resins cores (2 mm thickness) covered with carbon fiber reinforced epoxy polymers (CFRP) with 250 mm thickness at both side surfaces. The auc values of CFRP/ABS/CFRP at low (0.06) and mid (0.50) fracture probability (Pf ) after irradiation at 0.30 MGy (kJg � 1 ) were 35.9 and 53.0 kJm � 2 , which were approximately 20.3 and 25.2% higher than those (28.6 and 39.7 kJm � 2 ) before treatment, respectively. Although the maximum auc value at mid Pf (0.50) after 0.30 MGy irradiation for the CFRP/ABS/CFRP is approximately equal to that for CFRP, it is also about 21.4% higher than that (41.7 kJm � 2 ) of these CFRP before treatment. Although the use of ABS resin as the core reduced other mechanical properties of tensile and bending, the price of CFRP was apparently higher than that of ABS polymer. Thus, it is possible that the sandwich structural composites of CFRP/ABS/CFRP could be used for daily articles. Since the irradiated depth estimated is about 119 � 23 mm at their both sides surface, the irradiation effects mostly was acted within the CFRP sheet. [doi:10.2320/matertrans.M2010187]

Effects of Electron Beam Irradiation on Impact Value of Novolak-Type Phenol CFRTP

Homogeneous low voltage electron beam irradiation (HLEBI) improved the Charpy impact value (a uc ) of carbon fiber reinforced thermoplastic novolak-type phenol polymers (CFRTP) composite sheets with 2 mm thickness, although the irradiated depth estimated was 182.5 ± 33.5 μm on both side surfaces. The a uc values at low fracture probability (P f ) of 0.06 for CFRTP irradiated at 0.30 MGy (kJg ―1 ) was 60 kJm ―2 , which was 32% higher (46 kJm ―2 ) than for CFRTP before irradiation. Although the lowest impact values (a s ) estimated by three-parameter Weibull equation was zero for CFRTP before irradiation, HLEBI enhanced the a s value. The highest a s value was more than 59 kJm ―2 for CFRTP irradiated at 0.30 MGy. Thus, HLEBI remarkably enhanced the a s value, as well as the a uc value at low P f value. Since HLEBI enhanced the Weibull coefficient (n), it also enhanced the reproducibility of CFRTP samples. The maximum n value was found at 0.22 MGy HLEBI dose. The interfacial friction force, as well as the strengthening of both carbon fiber and novolak-type phenol resin probably contributed to the HLEBI effects to enhance the a s value of CFRTP, as well as enhancement of reproducibility.

Effects of Homogeneous Low Voltage Electron Beam Irradiation on Adhesive Strength of Polycarbonate (PC) Sheet Covered with Nylon6 Film

The effects of homogeneous low voltage electron beam irradiation (HLEBI) on the adhesive strength of different polymers without glue but with sterilization were investigated. HLEBI at more than 0.043 MGy generated adhesive force and enhanced fracture strain at the interface in polycarbonate (PC) composites covered with nylon6 film. HLEBI at less than 0.130 MGy increased the elasticity (d�= d) and fracture stress of the composites. Although it was far below that of commercial pure metal, the elasticity (2 GPa) of composites irradiated from 0.130 to 0.216 MGy was very close to that of nylon6. HLEBI from 0.216 to 0.432 MGy increased the fracture strain of the composites, whereas it decreased elasticity (d�= d). Based on the results, HLEBI from 0.130 to 0.432 MGy apparently maintained the high fracture strength of the composites. To investigate the influence of EB irradiation on adhesive strength, electron spin resonance (ESR) signals related to dangling bonds were observed. Since HLEBI generated dangling bonds in both PC and nylon6, the dangling bonds probably served as reactive and bonding sites for each polymer at the interface. Results indicated that HLEBI enhanced the adhesive strength of the composites, therefore, it was concluded that HLEBI was probably a useful tool for quickly joining the different polymers. [doi:10.2320/matertrans.MRA2008489]

Effects of Electron Beam Irradiation on Impact Value of Carbon Fiber Reinforced Thermoplastic Polyetheretherketone

Homogeneous low voltage electron beam irradiation (HLEBI) improves the Charpy impact value (auc) of composites sheets of carbon fiber reinforced thermoplastic polyetheretherketone (CFRTP) with 2 mm thickness, although the irradiated depth estimated is 177 � 32 mm at their both sides surface. The auc values at low fracture probability (Pf) of 0.13 for CFRTP irradiated at 0.43 MGy (kJg � 1 ) is 78 kJm � 2 , which is 56% higher than that (50 kJm � 2 ) for CFRTP before irradiation. Although the lowest impact values (as) estimated by three parameters Weibull equation is zero for CFRTP before irradiation, HLEBI enhances the as value. The highest as value is more than 55 kJm � 2 for CFRTP irradiated from 0.43 to 0.65 MGy. Thus, HIEBL remarkably enhances the as value, as well as the auc value at low Pf value. Since HLEBI enhances the Weibull coefficient (n), it also enhances the reproducibility of CFRTP samples. The maximum n value is found at 0.43 MGy of HLEBI dose. The interfacial friction force, as well as the strengthening of both carbon fiber and polyetheretherketone probably contributes the HLEBI effects to enhance the as value of CFRTP, as well as enhancement of reproducibility. [doi:10.2320/matertrans.M2009210]