Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. This project was aimed at developing analytical approaches to improving and better understanding the dimensional stability of composite space structures under thermal environments and changing material behavior due to microscopic damage. A comprehensive review of the literature on damage modeling of polymer matrix composite laminates was conducted. Damage due to matrix cracking was characterized using micromechanics. Aspects of predicting and utilizing degraded properties at the fiber and matrix level were studied. A computational approach to optimization of structure dimensional stability by introduction of "anti-distortion appliqués" was developed for minimizing thermally induced instability. The concept involves adding material to offset and eliminate measured instabilities. The concept was demonstrated but the approach is limited by the current lack of precision measurement systems for large structures. Unclassified b. ABSTRACT Unclassified c. THIS PAGE Unclassified UU 19b. TELEPHONE NUMBER (include area code) 703-696-7259 Standard Form 298 (Re. 8-98) v Prescribed by ANSI Std. Z39.18 def node_swap(nt , xt , yt , zt) : ## this subroutine detects the center nodes, corner nodes, edge nodes and face nodes. global tem, tm global c_1, c_2, c_3, c_4, c_1_1, c_1_2, bodyc, bc2, bc3 global c135, c136, c146, c145, c235, c236, c246, c245 global c146_2, c236_2, c145_2, c235_2 global ct_35, ct_36, ct_45, ct_46 global e_35, e_36, e_45, e_46 global e_15, e_16, e_25, e_26 global e_13, e_14, e_23, e_24 global f_1, f_2, f_3, f_4, shf global c_6_x, c_6_y, c_14m, c_23m global c_11, c_12, c_21, c_22, c_21 global ck_z_1, ck_z_2, ck_z_3, ck_z_4 global e_15c_11, e_15c_22, e_16c_11, e_16c_22 global e_25c_11, e_25c_22, e_26c_11, e_26c_22 global c146_2, c236_2, c145_2, c235_2 global ct_35, ct_36, ct_45, ct_46 global e_35, e_36, e_45, e_46 global e_15, e_16, e_25, e_26 global e_13, e_14, e_23, e_24 global f_1, f_2, f_3, f_4, shf global c_6_x, c_6_y, c_14m, c_23m global c_11, c_12, c_21, c_22, c_21, c_61, c_62, c_51, c_52 global ck_z_1, ck_z_2, ck_z_3, ck_z_4 global e_15c_11, e_15c_22, e_16c_11, e_16c_22 global e_25c_11, e_25c_22, e_26c_11,...

No abstract

Thermal expansion measurements of composlte systems containing hard dispersions embedded in brittle and semibrittle matrices indicate the importance of (1) the magnitude of the stress developed in the matrix and (2) the crack propagation behavior of the matrix. The thermal expansion of these composites can be predicted if the residual stress developed as a result of the difference in the expansions of the components does not exceed a critical value defined by the modified Griffith equation. This critical stress varied considerably with the nature (brittle, semibrittle, or ductile) of the matrix.

A study was conducted to characterize the solid phases of cadmium-sulfur-selenium red pigments. Continuous solid solution of CdS and CdSe and obedience to Vegard's law were confirmed by X-ray diffraction analysis. An increased rate of color formation was realized by using smaller reactant particles. Thermal decomposition of the CdS-CdSe solid solution involved t h e reappearance of the CdS-CdSe mixtures with subsequent transformation of these resulting compounds.

HE crystallization behavior of two lead borate glasses was studied by the differential thermal analysis method,' and the T therrnal effects were interpreted with the aid of supplementary information obtained from measurements of viscosity, thermal expansion, and microstructure The compositions P-0-A and P-0-B correspond to the specific cotnpounds found by Geller and BuntingZ in their determination of the phase relations in the systeni PbO-BZOs. Both of these glasses were found to nucleate readily at the air-glass interface; thus a powdered ( -60 +lOO-mesh) sample of these glasses heated at i.5OC pcr minute in the DTA apparatus developed a large quantity of crystals and similar heating of a bulk sample resulted in very few crystals. The third glass examined was a solder glass3 which exhibited no measurable degree of crystallization despite prolonged heat treatments of fine particles.The thertnogranis of these glasses are shown in Figs. 1 ( A ) , (C), and (D). Each glass exhibited an initial endotherm during heating and a corresponding exotherm during cooling; this reversible effect ( Fig. 1(B)) was indicative of the glass transformation range and was accompanied by an abrupt change in specific heat and in thermal expansion. This correlation agrees with similar results obtained by Bair4 with lead silicate glasses. A second, large endotherm was observed during the heating of powdered samples of all three glasses and occurred a t approximately 50" to 80°C above the transformation temperature. This endotherm occurred only during the heating of powdered samples and was followed by a crystal-growth exotherin in glasses P-0-A and P-0-B but not in the solder glass in which no detectable growth occurred. Microsections of the DTA samples were made a t various temperatures by interrupting the run and abruptly quenching the samples. 9 microsection of t h e sample and holder heated to this second endotherm (point 1 of Fig. l ( A ) ) revealed that the glass particles had partly coalesced and had drawn away from the container walls, thus introducing an air gap or temporaryThe glass compositions investigated are given in Table I.