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A goniometer for measuring small angle X‐ray scattering pole figures by using synchrotron radiation has been constructed. In order to obtain the scattering in a large range of scattering angles, position‐sensitive detectors (Gabriel counter and vidicon system) are applied. The integrated intensity as well as the position and the half width of the maximum are determined as functions of the angle between the incident beam and the normal to the film surface of the sample. The time necessary to determine a pole figure was approximately 3 hours. Samples of poly(ethylene terephthalate) were drawn under different conditions: uniaxially and biaxially at 92°C under homogeneous deformation, and uniaxially at 40°C by necking. The influence of the drawing conditions on the orientation of the crystal lamellae was determined. The results of the small angle scattering are compared with pole figures obtained by wide angle scattering. In addition some results with polypropylene were obtained. The small angle X‐ray scattering is strongly affected by the limited size of the crystals and by the incomplete regular arrangement of the crystals. This gives rise to difficulties in the interpretation of the results. The problem will be discussed.

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IntroductionThe possibility of using synchrotron radiation as a source of X-rays for scattering experiments has considerably improved the methods of the characterisation of the molecular orientation and molecular order in polymers. In another publication [1], it has been shown that the morphology of ultra highly drawn polyethylene is correlated to the kinetics of isothermal melting, as determined by X- ray scattering employing synchrotron radiation. In this paper we present some results on chain orientation and orientation of crystal lamellae surfaces in uniaxially and biaxially drawn films of polyethyleneterephthalate (PET). These results were obtained by inserting a pole figure goniometer into the synchrotron radiation beam and measuring the wide angle X-ray scattering (WAXS) and small angle X- ray scattering (SAXS) with different angles of incidence of the primary beam onto the sample.

SYNOPSISThe X-ray absorption coefficients of carbon fibers, different polymeric matrix materials, and composites were measured and the fiber contents in the composites were calculated from the measured absorption. In addition the fiber content determinations were performed by means of acid digestion of the polymeric matrix and weighing. Good agreement was found between the results obtained by the two different methods. The experimental error in the fiber content measurements was determined as a function of the difference in the absorption coefficient of the matrix material and the fiber. I NTRODUCTIO NThe fiber content is one of the most important parameters in establishing the composite's strength and stiffness characteristic^.'-^ Due to different effects, like bleeding out of fibers in the case of thermosets, the fiber content cannot be completely controlled by processing. Therefore, it is important to have available nondestructive methods for the determination of the amount of fibers present in the composites.Up to now the most commonly used techniques for determining the fiber content were density measurement or acid digestion of the polymer m a t r i~.~.~ In the present paper we want to present a new method based on X-ray absorption measurement. This method is nondestructive and yields good results provided the difference between the absorption coefficients of the fiber and the matrix is sufficiently large. PRINCIPLE OF MEASUREMENTWhen an X-ray beam passes through a sample of thickness d , the intensity I, is decreased by absorption to the intensity I given by