Effect of Moisture Absorption on Hot/Wet Compressive Strength of T800HIPMR-15 Carbon/Polyimide

Kakuta

Hamaguchi

et al. 2008

Self Cite

The objective of this study was to investigate the static and fatigue strengths of a G40-800/5260 carbon fiber/bismaleimide composite material, a type of high temperature CFRP, at room temperature (RT) and 150°C and to evaluate the practicality of this material. The stacking sequence of the material is quasi-isotropic, 32 plies [+45/0/-45/90]4s. Static tensile and compressive tests were performed at RT and high temperatures for non-hole (NH) and open-hole (OH) specimens. In addition, the effectiveness of notched strength criteria was discussed on the basis of test results. Fatigue tests yielded the S-N relationships of OH specimens for three kinds of stress ratio R (=minimum stress/maximum stress), R=0.1 (tension), 10 (compression), and -1 (tension-compression) at RT and 150°C. This study laid emphasis on investigating the static and fatigue strengths at 150°C and the role of compression load repetition in tension-compression fatigue. Major findings are as follows. (1) Static NH and OH compressive strengths, OH compression fatigue strength, and OH tension-compression fatigue strength were temperature-dependent and classified as matrix-dominant properties. These fatigue strengths decreased with increasing load cycles. (2) An open hole greatly reduced static tensile and compressive strengths at both RT and 150°C. (3) The ratio of compression strength to tension strength under static or fatigue loading was fairly low for both NH and OH specimens at RT and 150°C, except for the case of NH static strength at RT. (4) The compression stress range mostly controlled fatigue lives in tension-compression fatigue tests at RT and 150°C. (5) The material tested showed no large static and fatigue strength reduction at 150°C except for NH compressive strength; however, it should be used with care when structures have open holes and encounter compression loading, especially at high temperatures.

Section: Material Specimens and Testing Proceduresmentioning

confidence: 99%

Static and Fatigue Strengths of a G40-800/5260 Carbon Fiber/Bismaleimide Composite Material at Room Temperature and 150°C

Kakuta

Hamaguchi

et al. 2008

Self Cite

“…The cross head or actuator speed of a testing machine was 1 mm/min for tension tests and 1.3 mm/min for compression tests. Four test temperatures were used, room temperature (RT, i.e., 25 C), 70, 90, and 110 C. For compression tests an NAL type compression-test fixture [9,10] was used at RT and above. An Instron 4500 material testing machine and an Instron 8500 digitally controlled servo-hydraulic material-testing machine were used.…”

Section: Static Test Proceduresmentioning

confidence: 99%

Carbon Plain-Weave Fabric Low-Temperature Vacuum Cure Epoxy Composite: Static and Fatigue Strength at Room and High Temperatures and Practicality Evaluation

Kakuta

Saeki

et al. 2007

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The high cost of carbon fiber composite materials is a large barrier to their increased application. Low-temperature vacuum cure epoxy resins were developed as one way to break through this barrier. This kind of epoxy is initially cured at low-temperature in a vacuum bag and post-cured at high temperature in an air-circulating oven. This study investigated the static and fatigue mechanical properties of a low-price CFRP of this kind and evaluated its practical utility. The material tested was TRK180M carbon plain-weave-fabric/1053 low-temperature vacuum cure epoxy laminate with quasi-isotropic lay up. Static tests provided tensile and compressive strength of non-hole and open-hole specimens at room and high temperatures up to 110°C. Tension, compression, and tension—compression fatigue tests determined S—N relationships of open-hole specimens at room temperature and 110°C. Static tensile and compressive damage in non-hole specimens and fatigue damage in open-hole specimens for three kinds of fatigue tests were observed with a CCD microscope and a micro X-ray CT scanner. Test results are compared with other published results and discussed from a practical viewpoint. The tests pointed out the evaluation of the strength related to compression loading and sensitive to matrix damage to be very important and demonstrated the sufficient practical utility of this material.

“…The specimens for static compression tests were removed from the testing chamber at the scheduled cycles. Details of the compression test method used in this study were previously given in [7] and [8] and are not repeated here. Static compression tests were conducted at room temperature (RT) after dehumidifying the specimens, because testing was not necessarily possible immediately after removing the specimens from the testing chamber.…”

Section: Materials Specimens and Testing Proceduresmentioning

confidence: 99%

Effect of Thermal Cycling on Microcracking and Strength Degradation of High-Temperature Polymer Composite Materials for Use in Next-Generation SST Structures

Katoh²,

Hamaguchi³

et al. 2002

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The objective of this study was to investigate the effect of thermal cycles encountered by an SST in service on the cumulative frequency of microcracks and degradation of open-hole-compressive (OHC) strength in high-temperature polymer-matrix composite materials. One cycle of thermal cycling was designated as the sequence from room temperature (RT) to 54C, up to +177C, and back to RT. Thermal-cycling tests were conducted up to 10,000 cycles on two kinds of carbonfiber/thermoplastic polyimide composite material: IM7/PIXA, IM7/K3B, and up to 1000 cycles on G40-800/5260 carbon fiber/bismaleimide composite material. At scheduled thermal cycles, transverse microcracks initiated on the sectional surface of the laminates were observed and counted using an optical microscope. Static mechanical tests at RT provided OHC strength before and after thermal cycles. In addition, a simple and approximate finite element model (FEM) analysis using basic lamina data of the T800H/PMR-15 carbon fiber/polyimide composite was conducted to estimate the thermal stresses generated in the laminate. Major results obtained by the tests and FEM analysis are as follows: A fairly large number of microcracks were initiated, though the number as a function of thermal cycles varied according to the material; OHC strength before and after thermal cycles did not change during the course of this study; thermal cycles and transverse microcracks did not affect OHC strength; the calculated thermal-stress level in layers generated by one thermal-cycle of 231C temperature difference was under the limit for crack initiation of the T800H/PMR-15.