Fabrication of composite fan blades using PMR A-type polyimide resin and graphite fiber reinforcement

PMR polyimides are safe, easy to handle, can be processed with relatively wide process controls, and offer excellent mechanical properties, with thermo-oxidative stability. Procedures, staging and cure schedules fully dense, crackfree, dimensionally controlled, complex structure: high tip speed fan blades 1.27 cm (0.5 in) thick

PMR polyimide/graphite fiber composite fan blades

Ultrahigh speed fan blades, designed in accordance with the requirements of an ultrahigh tip speed blade axial flow compressor, were fabricated from a high strength graphite fiber tow and a PMR polyimide resin. The PMR matrix was prepared by combining three monomeric reactants in methyl alcohol, and the solution was applied directly to the reinforcing fiber for subsequent in situ polymerization. Some of the molded blades were completely finished by secondary bonding of root pressure pads and an electroformed nickel leading edge sheath prior to final machining. The results of the spin testing of nine PMR fan blades are given. Prior to blade fabrication, heat resin tensile properties of the PMR resin were examined at four formulated molecular weight levels. Additionally, three formulated molecular weight levels were investigated in composite form with both a high modulus and a high strength fiber, both as-molded and postcured, in room temperature and 232 C transverse tensile, flexure and short beam shear. Mixed fiber orientation panels simulating potential blade constructions were also evaluated. Flexure tests, short beam shear tests, and tensile tests were conducted on these angle-plied laminates

Fiber reinforced PMR polyimide composites

Commercially obtained PMR-15 polyimide prepregs with S-glass and graphite fiber reinforcements were evaluated along with in-house prepared glass and graphite cloth PMR 2 materials. A novel autoclave approach was conceived and used to demonstrate that both the PMR systems respond to 1.4 MPa (200 psi) autoclave pressures to produce void free composites equivalent to die molded laminates. Isothermal gravimetric analysis and subsequent mechanical property tests indicated that the PMR 2 system was significantly superior in thermo-oxidative stability, and that S-glass reinforcements may contribute to the accelerated degradation of composites at 316 C (600 F) when compared to graphite fiber reinforced composites. Fully reversed bending fatigue experiments were conducted with a type of fixture unused for organic matrix composites. These studies indicated that the graphite fiber composites were clearly superior in fatigue resistance to the glass fiber reinforced material and that PMR matrix composite systems yield performance of the same order as composite materials employing other families of matrices

Composite impact strength improvement through a fiber/matrix interphase

Research was conducted to improve the impact strength and toughness of fiber/resin composites by means of a fiber coating interphase. Graphite fiber/epoxy resin composites were fabricated with four different fiber coating systems introduced in a matrix-fiber interphase. Two graphite fibers, a high strength and a high modulus type, were studied with the following coating systems: chemical vapor deposited boron, electroless nickel, a polyamide-imide resin and a thermoplastic polysulfone resin. Evaluation methods included the following tests: Izod, flexure, shear fracture toughness, longitudinal and transverse tensile, and transverse and longitudinal compression. No desirable changes could be effected with the high strength fiber, but significant improvements in impact performance were observed with the polyamide-imide resin coated high modulus fiber with no loss in composite modulus

An investigation of changing concerns toward instructional computer use during student teaching

This study investigated hypothesized change in the concerns of student teachers toward instructional computer use during an eight week student teaching experience. In Phase 1, information concerning seven variables which have the potential to influence teacher computer utilization was collected from student teachers and their cooperating teachers. In addition, seven dimensions of concern toward employment of instructional computer use were examined by administering the Stages of Concern Questionnaire (SoCQ) before and after the student teaching experience. Multiple regression analysis indicated that change in only one of the seven stages of concern (concerns toward collaboration) could be predicted by any of the independent variables. Post hoc partitioning of data resulted in construction of a 2 x 2 matrix. SoCQ profiles, constructed for each cell, revealed that change patterns differed greatly depending on the relative level of the two independent variables: (a) student teacher computer competence and (b) instructional computer use by the cooperating teacher. Phases 2 and 3 of the study employed focus group discussions with student teachers and cooperating teachers. Phase Two data yielded a picture of student teachers with modest technical computer knowledge and high concerns for the role of the computer in the classroom. Students teachers looked to their cooperating teachers and university evaluation criteria for direction in establishing a priority of competing concerns. Neither source appeared to place a high priority on competence with instructional computer use. However, the opposite was true for student teachers when they underwent job interviews with school district administrators. Cooperating teachers, aware of the gap between their own university preparation and the computer capabilities they find themselves increasingly expected to utilize, looked to their student teachers to arrive with more up-to-date computer backgrounds. Based on the post hoc partitioning of data, it was concluded that changes in the concerns of student teachers toward instructional computer use do differ as a function of (a) the prior computer competency of student teachers and (b) the amount of instructional computer use employed by cooperating teachers. Focus group discussions revealed that expectations for computer use play a critical role in student teaching experiences and that computer use may present a role reversal within some student teaching triads, as student teachers share personal computer competence

Social Cognitive and Affective Neural Substrates of Adolescent Transdiagnostic Symptoms

Indiana University-Purdue University Indianapolis (IUPUI)The social cognitive ability to identify another’s internal state and social affective ability to share another’s emotional experience, known as empathy, are integral to healthy social functioning. During tasks, neural systems active when adolescents empathize include cognitive (medial prefrontal cortex and posterior cingulate cortex with the dorsolateral prefrontal cortex) and affective (anterior insula and anterior cingulate cortex) regions that are consistent with the adult task-based literature implicating the default mode, salience, and frontoparietal networks. However, task-based studies are limited to examining neural regions probed by the task; thus, do not capture broader patterns of information processing associated with complex processes, such as empathy. Methods of functional connectivity capture broader patterns of information processing at the level of network connectivity. Although it has clear advantages in identifying neural vulnerabilities to disorder, functional connectivity has yet to be used in adolescent investigations of empathy. Via parent- and self-report, deficits in either cognitive or affective processes central to empathy associate with the most widely agreed on classifications of behavioral disorders in adolescents – transdiagnostic symptoms of internalizing and externalizing. However, this evidence relies exclusively on self-report measures and research has yet to examine the neural connectivity underlying transdiagnostic symptoms in relation to cognitive and affective empathy. What has yet to be known is (1) how the social cognitive and affective processes of empathy are functionally connected across a heterogeneous sample of adolescents and (2) the association of cognitive, affective, and imbalanced empathy with transdiagnostic symptoms. Addressing these gaps in knowledge is an important incremental step for specifying vulnerabilities not fully captured via subjective report alone. This information can be used to improve prevention and intervention strategies. The present study will examine the functional connectivity of neural networks underlying empathy in early to mid-adolescents and their association with transdiagnostic symptoms