Single Scarf Research Articles

Effects of repair techniques and scarf angles on mechanical performance of composite materials

Today, composite materials, which have the advantage of strength and lightness ratio, have gained great importance especially in the aeronautical industry and automotive sector. With widespread use of composites, the repair of damages caused by external factors has also become an important research topic. In this study, the effects of different repair methods and scarf angles on the mechanical performance of the material were investigated. Scarf angles of 20°, 30°, and 45° have been selected in order not to create too many scarf areas and to find a quick repair method. Also, a comparison of single scarf and double scarf repair was made to find a more robust solution. The samples were produced from carbon fiber prepreg and with the [45/0/90/0/45]2s fiber orientation. Tensile, compression, and flexural (3-point bending) tests according to ASTM standards were applied to composite samples prepared with single scarf and double scarf repair configurations at different angles. The stress–strain curves obtained as a result of the tests showed that the specimens repaired at 20° had the highest strength. In addition, it has been determined that the samples repaired with double scarf withstand higher forces compared to the samples repaired with single scarf at the same angle.

Transfer of abductor hallucis tendon combined with scarf osteotomy versus single scarf osteotomy in moderate to severe hallux valgus deformity: a comparative retrospective cohort study

BackgroundScarf osteotomy (SO) was broadly applied in moderate to severe hallux valgus (MSHV), and the results were satisfactory. However, due to the complicated pathologic changes in hallux valgus, the ideal surgical treatment is still controversial. Transfer of the abductor hallucis tendon combined with Scarf osteotomy (TAHTCSO) was an innovative alternative technique. This retrospective cohort study aimed to define if TAHTCSO mode resulted in improved outcomes as compared with the single SO in MSHV.MethodsOf 73 patients (92 ft) with MSHV, 36 (45 ft) were treated through TAHTCSO and 37 ones (47 ft) through SO. The patients were assessed clinically and radiographically with a 24-month follow-up. They were assessed pre-operatively and post-operatively with intermetatarsal angle (IMA), hallux valgus angle (HVA), distal metatarsal articular angle (DMAA), first metatarsophalangeal joint range of motion (1#MTP ROM), as well as American Orthopaedic Foot and Ankle Society (AOFAS) forefoot scores and postoperative complications of surgery.ResultsBoth cohorts had the same baseline feathures. All patients were followed up from 24 to 40 months, with a mean of 28.3 months. Patients in the TAHTCSO cohort had significantly decreased HVA at 6 months (p < 0.0001), 12 months (p < 0.0001), and 24 months (p < 0.0001) after surgery. 1#MTP had been increased slightly with non-statistic sense (p>0.05). IMA, DMAA and AOFAS also had not significantly difference at all followed time after surgery as compared with the SO cohort. The healing of osteotomies was observed within 8 weeks in the two cohorts. Two cases of hallus varus had been found in SO cohort and there were no cases of delayed healing and bone non-union in both cohorts.ConclusionIn this retrospective cohort study, TAHTCSO had sufficient maintenance of the correction and improved functional performance thereby was a good alternative for MSHV, though it did not display a better result for MSHV compared to SO.

Infield composites repair techniques for combat aircraft: research and development perspective

Combat aircraft that are damaged and reside on the ground are completely ineffectual to air component commanders. Aircraft battle damage repair (ABDR) aims to rapidly restore these damaged aircraft to some level of combat capability. To be effective, the repairs must allow the aircraft to return to combat in time to affect the outcome of the battle. The Composite Group at Department of Materials, Queen Mary College, University of London, has worked on various aspects of the rapid repair concept for composite materials. In the present paper in particular, the vacuum infusion method is highlighted as an alternative reliable bonded infield repair approach for composite monolithic skins. The study identifies certain technical challenges that the repair technique must address to be viable. Results are presented from a novel toughening method developed by incorporating polyester and carbon veils at the infused bondline, while single scarf coupons as well as full scale testing data demonstrate the effectiveness of the vacuum infusion repair technology in accordance with the ABDR specifications.