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The purpose of this study is to revise and modify the firefighter job-related performance tests from overseas to implement into the circumstances in Korea, examine its validity by analyzing the level of association between the test employed in the ongoing firefighter selection process, and propose a Korean firefighter job-related physical fitness test. Therefore, a modified version of Candidate Physical Ability Test (CPAT) from the United States firefighter selection process was conducted on 28 male firefighter officer candidates. Recorded results from VO2max, heart rate, blood lactate, anaerobic power test, and the ongoing Korean firefighter physical fitness test were analyzed to assess the validity of the modified test. IBM SPSS Statistics Ver. 27.0 was employed for the data correlation analysis in different fitness factors and the total circuit physical test time. The results revealed the proposed modified firefighter job-related physical fitness test showed significant correlation with VO2max (r = −0.450, p < 0.05), METS (r = −0.735, p < 0.01) recovery lactate over 15 min (r = −0.460, p < 0.05), peak power (r = −0.484, p < 0.05), average power (r = −0.647, p < 0.01), and in the ongoing firefighter physical fitness test, grip strength (r = −0.709, p < 0.01), lower back strength (r = −0.681, p < 0.01), standing long jump (r = −0.618, p < 0.01), sit-ups (r = −0.397, p < 0.05), and shuttle run (r = −0.523, p < 0.01). Fitness factors including VO2max, recovery lactate, anaerobic power, muscular strength, and so forth known to play a crucial role in firefighting operations were also shown to be important in the modified firefighter job-related physical fitness test. However, we suggest that studies with a larger sample size are needed in order to generalize our findings.

The mechanical properties of SiCf/SiC composites have been investigated, based on detailed analyses of their microstructure. SiCf/SiC composites were prepared from fiber preforms by a slurry infiltration technique, in which a mixture with SiC, Al2O3, and Y2O3 particles was impregnated into the fabric structure. SiCf/SiC composites were consolidated by liquid phase sintering process, associated with the creation of secondary phases by the addition of Al2O3 and Y2O3 particles. The reinforcing material was a plain weave Tyranno SA SiC fabric with a carbon interfacial layer. The sintered density and the pore volume fraction of SiCf/SiC composites were about 3.0 Mg/m3 and about 10%, respectively. These SiCf/SiC composites had an average flexural strength of about 250 MPa at room temperature. They exhibited pseudo-ductile fracture behavior, due to the carbon interfacial layer. The introduction of the carbon interfacial layer greatly improved the fracture energy of SiCf/SiC composites.

This paper dealt with the microstructure and mechanical properties of SiC based composites reinforced with different reinforcing materials. The composites were fabricated using reinforcing materials of carbon nanotubes (CNT) and Tyranno Lox-M SiC chopped fibers. The volume fraction of carbon nanotubes was also varied in this composite system. An Al2O3–Y2O3 powder mixture was used as a sintering additive in the consolidation of the SiC matrix. The characterization of the composites was investigated by means of SEM and three point bending tests. These composites showed a dense morphology of the matrix region, by the creation of a secondary phase. The composites reinforced with SiC chopped fibers possessed a flexural strength of about 400 MPa at room temperature. The flexural strength of the carbon nanotubes composites had a tendency to decrease with increased volume fraction of the reinforcing material.

TiNi shape memory alloy was used to recover the shape of transformed objects using its shape memory effect. This shape memory effect plays an important role inside metal matrix composite. A composite using shape memory alloy has a large advantage that can control crack initiation and propagation, when compared with other composites due to the shape memory effect of shape memory alloy under high temperature. In this study, TiNi/Al6061 and TiNi/2024 shape memory composites were fabricated by the hot press method, and a fatigue test was performed to evaluate the fatigue damage for the shape memory composites under room temperature and high temperature. The relationship of the crack growth rate and the stress intensity factor for these shape memory composites were clarified at both temperature conditions. The delay effect of crack propagation due to shape memory alloy was also evaluated under high temperature. In addition, an acoustic emission technique was used to evaluate the crack initiation and the control of crack propagation by shape memory effect under fatigue test nondestructively. The relationship between AE parameter and the degree of fatigue damage of the shape memory composites was discussed.

The high temperature property of SiC/SiC composites fabricated by the melt infiltration (MI) process has been investigated. SiC/SiC composites reinforced with BN/SiC double coated Hi-Nicalon SiC fibers were fabricated by infiltrating molten silicon into a braiding fibric preform containing C and SiC particles. The mechanical properties of MI- SiC/SiC composites were carried out at the elevated temperatures using the three point bending test. The microstructure of MI- SiC/SiC composites was examined by means of SEM and EDS. The matrix region of MI- SiC/SiC composites represented the chemical fluctuation depending on the composition ratio of Si and C elements. The flexural strength of MI- SiC/SiC composites greatly decreased at the temperatures higher than 1100 °C, due to microstructural instabilities such as interfacial debonding and matrix oxidation.

A new series of thermotropic polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate, with 4,4□-bis(9-hydroxynonoxy)biphenyl (BP9). Structures of the monomer and the corresponding polymers were identified using FT-IR and 1 H NMR spectroscopic methods. BP9 exhibited a smectic type mesophase, however, nematic phase was found for all synthesized liquid crystalline polyurethanes except for 1,4-phenylene diisocyanate/BP9 based polyurethane. Their phase transition temperatures and thermal stability were investigated by differential scanning calorimetry (DSC), optical polarizing microscopy, and X-ray scattering. The infrared study indicated that the hydrogen bonding among urethane linkages attributed to the mesomorphism. Thermal gravimetric analysis (TGA) of synthesized polyurethanes showed that no weight loss of the polymers observed up to 280°C.

High-molecular-weight para-type homopolyurethanes prepared by polyaddition of 2,5-tolylene diisocyanate with 4,4‘-bis(ω-hydroxyalkoxy)biphenyls showed monotropic liquid crystallinity, when measurements were performed under shearing. For example, a polyurethane PU6T having [η] 0.82 which was obtained from 4,4‘-bis(6-hydroxyhexyloxy)biphenyl showed TI-LC of 201 °C and TLC-K of 181 °C. In addition, thermotropic liquid-crystalline para-type copolyurethanes PUmnT (m and n denoting carbon number in alkylene moiety: 2, 6, 8, and 11) were synthesized by polyaddition of the diisocyanate with two 4,4‘-bis(ω-hydroxyalkoxy)biphenyls having different alkylene lengths. For example, PU68T(75/25) had TI-LC of 188 °C and TLC-K of 173 °C. Blends of two para-type homopolyurethanes also exhibited monotropic liquid crystallinity. The liquid crystallinity was examined by differential scanning calorimetry measurement, polarized optical microscope observation, and X-ray diffractometry.

Synthesis and Thermotropic Properties of Polyurethanes Prepared from 2,5-Tolylene Diisocyanate and 2,6-Bis(ω-hydroxyalkoxy)naphthalenes

Thermotropic liquid-crystalline polyurethanes were synthesized by the polyaddition reaction of para-substituted 2,5-tolylene diisocyanate (2,5-TDI) with 1,4-bis(ω-hydroxyalkoxy)benzenes (BHBm : HO(CH 2 ) m OC 6 H 4 O(CH 2 ) m OH ; m is the carbon number of the hydroxyalkoxy group). Intrinsic viscosities of the polymers were in the range of 0.22-0.41 dL/g. Polyurethanes 2,5-TDI/BHBm's (m = 3, 5, 6, 8) prepared from BHBm and 2,5-TDI, exhibited monotropic liquid crystallinity, although these polyurethanes contained no mesogenic core unit. For example, polyurethane 2,5-TDI/BHB5 with [η] = 0.33 prepared from 1,4-bis(5-hydroxypentoxy)benzene (BHB5) and 2,5-TDI exhibited an anisotropic phase from 119 to 51 °C. In contrast, for the series of 1,4-PDI/BHBm (m = 2, 3, 5, 6, 8, 11) having no substituent in a phenylene unit, no explicit mesomorphic behavior was observed by DSC measurement and polarized microscopic observation.

Thermotropic polyurethanes [O(CH 2 ) m OPHPhO(CH 2 ) m OCONHPh(R)NHCO] n (m= 2-6,8,11; R= H, Me) with intrinsic viscosities in the range of 0.41-0.99 dL/g were synthesized. DSC thermograms for these polymers exhibited two endothermic peaks corresponding to phase transitions of melting and isotropization. IR study indicated that the hydrogen bonding between urethane linkages affected the mesomorphism.