A SIMPLIFIED METHOD OF DETERMINING 'EFFECTIVE' COMPOSITE LAMINA ELASTIC PROPERTIES

摘要

Traditional approaches for obtaining lamina properties include ASTM D3039 and D3518. When elastic properties derived from these test methods are used in classical lamination analysis to predict elastic properties of [0{sub}x/±45{sub}y/90{sub}z] laminates, the correlation with laminate test data is good but not great. Additional "point design" coupon testing is usually used to fully characterize specific laminate configurations. The method described herein is "reverse calculation" of the lamina properties from laminate properties. Significant improvement in prediction of laminate elastic properties was obtained using these "effective" lamina properties. Tensile test data with biaxial strain gages were obtained for seven different [0{sub}x/±45{sub}y/90{sub}z] laminate configurations of the carbon-thermoplastic composite AS4/APC-2 (PEEK). Laminate pairs that provided the best lamina property predictions include one highly directional laminate with more than forty percent 0-degree plies, and one ductile laminate with 75-percent ±45- degree plies. The reverse calculation method significantly reduces testing. Traditional methods require three types of tests: axial tension, transverse tension and diagonal tension (shear), plus additional "point design" coupons. The reverse calculation method requires only tension tests of two properly designed multi-directional laminates, and the improved prediction of laminate properties may eliminate or minimize the need for additional "point design" test coupons.