Residual Stresses in Intrinsic UD-CFRP-Steel-Laminates - Experimental Determination, Identification of Sources, Effects and Modification Approaches

Abstract:

This paper focuses on the reduction of process-related thermal residual stress in fiber metal laminates and its impact on the mechanical properties. Different modifications during fabrication of co-cure bonded steel/carbon epoxy composite hybrid structures were investigated. Specific examinations are conducted on UD-CFRP-Steel specimens, modifying temperature, pressure or using a thermal expansion clamp during manufacturing. The impact of these parameters is then measured on the deflection of asymmetrical specimens or due yield-strength measurements of symmetrical specimens. The tensile strength is recorded to investigate the effect of thermal residual stress on the mechanical properties. Impact tests are performed to determine the influence on resulting damage areas at specific impact energies. The experiments revealed that the investigated modifications during processing of UD-CFRP-Steel specimens can significantly lower the thermal residual stress and thereby improve the tensile strength.

References

[1] H.S. Kim, S.W. Park, D.G. Lee, Smart cure cycle with cooling and reheating for co-cure bonded steel/carbon epoxy composite hybrid structures for reducing thermal residual stress, Composites Part A: Applied Science and Manufacturing. 37 (2006).

DOI: 10.1016/j.compositesa.2005.09.015

[2] D. Stefaniak, E. Kappel, B. Kolesnikov, C. Hühne, Improving the mechanical performance of unidirectional CFRP by metal-hybridization, in: ECCM15 - 15th European Conference on Composite Materials, Venice, (2012).

[3] A. Fink, Lokale Metall-Hybridisierung zur Effizienzsteigerung von Hochlastfügestellen in Faserverbundstrukturen, Deutsches Zentrum für Luft- und Raumfahrt, Institut für Faserverbundleichtbau und Adaptronik, Braunschweig, (2010).

DOI: 10.1002/stab.201590105

[4] D. Stefaniak, E. Kappel, M. Kolotylo, C. Hühne, Experimental identification of sources and mechanisms inducing residual stresses in multi-layered fiber-metal-lamiates, in: Euro Hybrid Materials and Structures, Stade, (2014).

[5] Y. Yu, I.A. Ashcroft, and G. Swallow An experimental investigation of residual stresses in an epoxy-steel laminate, International Journal of Adhesion and Adhesives. 26 (2006) 511–519.

DOI: 10.1016/j.ijadhadh.2005.07.006

[6] S. S. Kim, H. Murayama, K. Kageyama, K. Uzawa, M. Kanai, Study on the curing process for carbon/epoxy composites to reduce thermal residual stress, Composites Part A: Applied Science and Manufacturing. 43 (2012) 1197–1202.

DOI: 10.1016/j.compositesa.2012.02.023

[7] M. Mulle, F. Collombet, P. Olivier, and Y. -H. Grunevald, Assessment of cure residual strains through the thickness of carbon–epoxy laminates using FBGs, Part I: Elementary specimen, Composites Part A: Applied Science and Manufacturing. 40 (2009).

DOI: 10.1016/j.compositesa.2008.10.008

[8] Hexcel, HexPly 8552 Epoxy Matrix - Product Data, (2008).

[9] J. Xue, W. -X. Wang, Y. Takao, and T. Matsubara, Reduction of thermal residual stress in carbon fiber aluminum laminates using a thermal expansion clamp, Composite Part A: Science and Manufacturing. 42 (2011) 986–992.

DOI: 10.1016/j.compositesa.2011.04.001

[10] G.D. Angel and G. Haritos, An Immediate Formula for the Radius of Curvature of a Bi-metallic Strip, International Journal of Engineering Research & Technology. 2 (2013) 1312–1319.

[11] E.J. Barbero, Introduction to Composite Materials Design, 2nd ed., CRC Press Taylor & Francis Group, Boca Raton, (2011).