PEEK/carbon fiber composites: Experimental evaluation of unidirectional laminates and theoretical prediction of their properties

Abstract

Comparison of tensile characteristics (modulus, strength) measured for bought-in laminates and also laminates manufactured in-house with published data has proved the testing procedure to be sound and compression molding to give composites of good quality. In the theoretical domain, the micromechanical approach was used to predict engineering constants such as the longitudinal, transverse and shear moduli that characterize the laminate in its principal directions. For the off-axis loading, macromechanical abstraction was applied and the angular dependencies of the above composite parameters were further supplemented by those for the Poisson ratio and the ultimate strength. Regardless of the theoretical approach used, the error of the predictions relative to the experimental data does not exceed 1 0 percent.

Modelling of Behaviour of Laminates Based on a Thermoplastic Matrix

“…All our results have been reported either in tabular or graphical form in the previous communications [1][2][3][4], each of them devoted to the theory/experiment correlation for a particular laminate construction. The aim of this section is thus to discuss them in a manner allowing identification of the most important generic features governing performance of the PEEK/carbon fibre material.…”

“…Stacking of eight plies was done in such a sequence that the final laminate was symmetrical and conformed to the regular alternating construction, e.g., + 30/ ― 30/ + 30/ ― 30 ~ ,ym . Compression moulding on Bucher presses (Bucher-Guyer, Niederweningen, Switzerland) was used as the manufacturing route with all the experimental variables (time, temperature, pressure) for each manufacturing step (contact, consolidation and cooling) set at the same level as given in Reference [1]. Thin aluminum foil was used instead of a chemical agent for quick release.…”

“…The cutting operation of coupons to be loaded in a direction 0 ought to be conducted in such a way that a &dquo;stiffer&dquo; ply constitutes the coupon surface [2], that is, plies 1 and 8 satisfy cp -a, < 0 -ce, with i = 1 and 8 and j = 4 and 5. Instead of gluing tapered aluminum or epoxy end-tabs, the load was exerted on a specimen by gripping between two sheets of sandpaper [1].…”

“…INTRODUCTION UR PREVIOUS COMMUNICATIONS [1][2][3][4] reported behaviour of APC-2 (carbon fibres reinforced polyether ether ketone [PEEK] laminates being the best known representative of the material class having a thermoplastic matrix. The general approach we adopted has been to compare experimental findings with theoretical predictions and to identify some of the fundamental principles that control the mechanical performance of this type of composite.…”

“…In the first contribution [1], the uniaxial laminates were used in order to establish the fabrication route (compression moulding), to develop testing methods and to characterise PEEK/carbon lamina. The second study [2] was concerned with the case of cross-ply laminates and formulation of a model that relates E( cP) and a( cP) to the material properties of the lamina and construction characteristics of the laminate.…”