• 대한기계학회논문집A
• /
• 제26권10호
• /
• pp.2114-2121
• /
• 2002

In order to study the effects of oblique tabs on the in-plane shear properties of unidirectional carbon fiber reinforced aluminum laminate composites, the 10$^{\circ}$off-axis tensile test, the 45 $^{\circ}$off-axis tensile test and Iosipescu shear test were performed to determine the shear properties. Off-axis tension test was studied by using new oblique-shaped tabs proposed by Sun and $Chung^{(7)}$. Iosipescu shear test was studied by using modified Wyoming test fixture. The oblique tabs reduced remarkably end-constraint effects of off-axis specimens with a aspect ratio of about eight. The experimental results show that there is no significant difference between off-axis test results and those of Iosipescu shear test. The 45$^{\circ}$off-axis tensile tests are recommended for the determination of the shear properties of unidirectional carbon fiber reinforced aluminum laminated composites.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2002년도 추계학술발표대회 논문집
• /
• pp.96-99
• /
• 2002

In order to determine the in-plane shear properties of unidirectional carbon fiber reinforced aluminum laminate composites, a new Iosipescu shear test fixture was developed, by using a fixture undergoing tensile force for the specimen edge to be subjected to compressive loads assumption, under plane stress. Also, to compare the results, Iosipescu shear test method by the modified Wyoming fixture and the off-axis tensile test were performed to determine the shear properties. Off-axis tension test was performed by using new oblique-shaped tabs proposed by Sun and Chung. [5] The oblique tabs reduced remarkably end-constraint effects of off-axis specimens with a aspect ratio of about eight. It is observed through the experimental results show that there is no significant difference between off-axis test results and those of Iosipescu shear test.

• Advanced Composite Materials
• /
• 제16권2호
• /
• pp.167-180
• /
• 2007

The tensile strength of unidirectional carbon fiber reinforced plastics under a high strain rate was experimentally investigated. A high-strain-rate test was performed using the tension-type split Hopkinson bar technique. In order to obtain the tensile stress-strain relations, a special fixture was used for the impact tensile specimen. The experimental results demonstrated that the tensile modulus and strength in the longitudinal direction are independent of the strain rate. In contrast, the tensile properties in the transverse direction and the shear properties increase with the strain rate. Moreover, it was observed that the strain-rate dependence of the shear strength is much stronger than that of the transverse strength. The tensile strength of off-axis specimens was measured using an oblique tab, and the experimental results were compared with the tensile strength predicted based on the Tsai-Hill failure criterion. It was concluded that the tensile strength can be characterized quite well using the above failure criterion under dynamic loading conditions.

• Composites Research
• /
• 제12권2호
• /
• pp.82-90
• /
• 1999

일반적 직교이방성 복합재료의 기계적 성질을 측정하기 위한 간단한 실험방법으로 편축시험편에 대한 인장시험 또는 굽힘시험이 흔히 사용된다. 이때 재료의 특성상 인장시험편에서는 전단변형이 발생될 수밖에 없으며, 굽힘시험편에서는 비틀림변형을 피할 수 없다. 그러나, 시험장치의 그림 또는 지지대에서의 구속은 커플링에 의한 변형을 수용할 수 없고, 따라서 이에 따른 응력집중을 유발한다. 결과적으로 불균일한 변형장과 응력장을 낳게되어 측정값의 정확도를 저하시키며, 조기 파손으로 인한 복합재료 강도의 과소평가를 가져오게 된다. 본 연구에서는 이를 완화하기 위한 방안으로 시험편 경계면 형상의 변화를 제안한다. 이를 위하여 경사좌표계에서의 적층이론을 유도하며, 각 시험조건에 대한 특성방정식을 구한다. 유한요소해석을 수행하여 특정방정식을 이용하여 수정된 시험편 형상의 유용성을 보인다.

• 대한조선학회지
• /
• 제25권4호
• /
• pp.58-68
• /
• 1988

$[0^{\circ}]_{8T},\;[90^{\circ}]_{8T},\;[+45^{\circ}]_{8T}$의 단축방향과 $[{\pm}15^{\circ}]_{2S},\;[{\pm}30^{\circ}]_{2S},\;[{\pm}45^{\circ}]2_{2S},\;[{\pm}60^{\circ}]_{2S},\;[{\pm}75^{\circ}]_{2S}$ Angle Ply 그리고 $0^{\circ},\;{\pm}45^{\circ},\;90^{\circ}$로 조합된 다방향 복합적층판의 기계적 성질에 대하여 스트레인 게이지를 이용하여 측정 수록하였다. 메트릭스의 특성이 잘 나타나는 $[10^{\circ}]$ Off-Axis와 $[{\pm}45^{\circ}]$ Angle Ply를 이용하여 전단탄성계수를 측정하였다. 복합재료 인장시험시 발생하는 Acoustic Emission 특성과 파괴거동을 비교 검토하고, 이것을 통하여 Acoustic Emission법의 유용성과 파손 메카니즘을 규명하고자 하였다.